Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Breeding strategies for sustainable intensification of developing smallholder dairy cattle production systems
    Kariuki, Charles Mbogo - \ 2017
    Wageningen University. Promotor(en): J. Komen, co-promotor(en): J.A.M. Arendonk; A.K. Kahi. - Wageningen : Wageningen University - ISBN 9789463430951 - 134
    dairy cattle - small businesses - sustainable animal husbandry - intensification - breeding programmes - progeny testing - genetic improvement - dairy performance - developing countries - melkvee - kleine bedrijven - duurzame veehouderij - intensivering - veredelingsprogramma's - nakomelingenonderzoek - genetische verbetering - melkresultaten - ontwikkelingslanden

    Smallholder dairy cattle production systems in Africa are intensifying production through importation of germplasm from breeding programs conducted in temperate regions to improve commercial cow populations. Presence of genotype by environment interaction results in unfavorable correlated responses. The aim this thesis was to develop strategies for breeding programs in developing countries that can support sustainable intensification of these systems. Specific objectives were (a) to determine desired gains for breeding objective traits, (b) compare progeny testing (PT) and genomic selection (GS) selection strategies, (c) evaluate the economic performance of PT and GS selection strategies and (d) compare genetic gains for economic and non-economic breeding objectives; the Kenya dairy cattle sector was used as a working example. To account for the limited pedigree and performance recording, a five-trait breeding objective and small-sized breeding program were studied. Breeding objective traits, determined based on producer preferences, were milk yield (MY), production lifetime (PLT), calving interval (CI), fat yield (FY) and mature body weight (MBW). Producers were categorized into high intensive group, who placed highest preference on PLT and MY, and low intensity group that placed highest preferences on CI and PLT. MY and FY were the most important traits for processors. Consensus desired gains, based on weighted goal programming, were 2.51, 2.42, 0.22, 0.87 and 0.15% for PLT, MY, CI, FY and MBW, respectively. Comparison of breeding schemes shows that GS schemes had lower accuracies but gave higher responses per year due to shorter generation intervals. Besides genetic gains, economic performance underpins the adoption of selection strategies. GS schemes had between 3.2 and 5.2-fold higher cumulated genetic gain in the commercial cow population and higher gross margins compared to PT schemes. Semen storage made PT schemes more profitable but less so than GS schemes. Functional traits can increase the sustainability of resource poor smallholder systems under harsh environments. Economic breeding objectives yielded undesirable responses in functional traits. Breeding objectives based on desired gains or non-market objectives improved response in functional traits but at a monetary cost. It is concluded that sustainable productivity of smallholder systems can be improved by implementation of local breeding program based on GS, but this requires more emphasis on functional traits, which can be achieved by use of non-economic objectives.

    Optimization of breeding schemes for Nile tilapia (Oreochromis niloticus) in smallholder production systems in Kenya
    Omasaki, Simion Kipkemboi - \ 2017
    Wageningen University. Promotor(en): J. Komen, co-promotor(en): J.A.M. Arendonk; A.K. Kahi. - Wageningen : Wageningen University - ISBN 9789463431064 - 167
    oreochromis niloticus - tilapia - breeding programmes - selective breeding - genetic improvement - small farms - sustainability - fish culture - aquaculture - kenya - oreochromis niloticus - tilapia - veredelingsprogramma's - selectief fokken - genetische verbetering - kleine landbouwbedrijven - duurzaamheid (sustainability) - visteelt - aquacultuur - kenya

    The aim of this thesis was to develop a sustainable low cost breeding program for Nile tilapia that addresses both genetic and economic aspects of smallholder fish farmers in Kenya. First, Analytical Hierarchy Process Technique was used to define a breeding goal based on farmer’s preferences for traits. Farmers’ preferences for traits differed significantly depending on income and market orientation. Low and medium income farmers preferred harvest weight (HW) while high income farmers preferred growth (GR) and survival (S) traits. Grouping farmers according to market objective (fingerling production or fattening) showed that fingerling producers preferred GR and S while fattening farmers preferred HW and S. Consensus preference values were obtained using weighted goal programming and these values were used to derive desired gains for a breeding goal that takes into account farmers’ diverse backgrounds and preferences for traits. Secondly, the existence of genetic variation for traits of interest was investigated. Substantial additive genetic effects for HW, GR and shape traits were present that can be exploited through selection under low input production system. Heritability estimates for HW, GR and shape were 0.21 ± 0.03, 0.26 ± 0.04 and 0.12 ± 0.03 for mixed sex (nucleus) respectively. The calculation of economic values for breeding goal traits revealed that economic values for GR differed depending on the definition of the breeding goal and that selection for feed efficiency is the key factor to economic profitability of Nile tilapia breeding programs. A significant genotype by environment re-ranking was found for GR between the mixed sex nucleus and monosex production environments. Genotype by environment interaction (G x E) led to lower genetic gain for GR in production environment. Incorporating sib information from monosex production environment into the selection index resulted in a more accurate estimation of breeding values which increased genetic gain in growth. Using desired gain approach, weights for desired gains in harvest weight, growth rate and survival were derived that maximized genetic gains for these breeding goal traits. It is concluded that these results can be used to develop a sustainable centralized breeding program. However, a reliable well planned and organized decentralized strategy for dissemination of genetically improved fry of Nile tilapia to farmers is paramount.

    Milk progesterone measures to improve genomic selection for fertility in dairy cows
    Tenghe, Amabel Manyu Mefru - \ 2017
    Wageningen University. Promotor(en): R.F. Veerkamp; B. Berglund, co-promotor(en): D. J. de Koning; A.C. Bouwman. - Wageningen : Wageningen University - ISBN 9789463431330 - 179
    dairy cows - fertility - progesterone - milk - genomics - genetic improvement - heritability - genetic parameters - dairy performance - reproductive traits - animal genetics - animal breeding - dairy farming - melkkoeien - vruchtbaarheid - progesteron - melk - genomica - genetische verbetering - heritability - genetische parameters - melkresultaten - voortplantingskenmerken - diergenetica - dierveredeling - melkveehouderij

    Improved reproductive performance has a substantial benefit for the overall profitability of dairy cattle farming by decreasing insemination and veterinary treatment costs, shortening calving intervals, and lowering the rate of involuntary culling. Unfortunately, the low heritability of classical fertility traits derived from calving and insemination data makes genetic improvement by traditional animal breeding slow. Therefore, there is an interest in finding novel measures of fertility that have a higher heritability or using genomic information to aid genetic selection for fertility. The overall objective of this thesis was to explore the use of milk progesterone (P4) records and genomic information to improve selection for fertility in dairy cows. In a first step, the use of in-line milk progesterone records to define endocrine fertility traits was investigated, and genetic parameters estimated. Several defined endocrine fertility traits were heritable, and showed a reasonable repeatability. Also, the genetic correlation of milk production traits with endocrine fertility traits were considerably lower than the correlations of milk production with classical fertility traits. In the next step 17 quantitative trait loci (QTL) associated with endocrine fertility traits, were identified on Bos taurus autosomes (BTA) 2, 3, 8, 12, 15, 17, 23, and 25 in a genome-wide association study with single nucleotide polymorphisms. Further, fine-mapping of target regions on BTA 2 and 3, identified several associated variants and potential candidate genes underlying endocrine fertility traits. Subsequently, the optimal use of endocrine fertility traits in genomic evaluations was investigated; using empirical and theoretical predictions for single-trait models, I showed that endocrine fertility traits have more predictive ability than classical fertility traits. The accuracy of genomic prediction was also substantially improved when endocrine and classical fertility traits were combined in multi-trait genomic prediction. Finally, using deterministic predictions, the potential accuracy of multi-trait genomic selection when combining a cow training population measured for the endocrine trait commencement of luteal activity (C-LA), with a training population of bulls with daughter observations for a classical fertility trait was investigated. Results showed that for prediction of fertility, there is no benefit of investing in a cow training population when the breeding goal is based on classical fertility traits. However, when considering a more biological breeding goal for fertility like C-LA, accuracy is substantially improved when endocrine traits are available from a limited number of farms.

    Genetic improvement of feed intake and methane emissions of cattle
    Manzanilla Pech, Coralia I.V. - \ 2017
    Wageningen University. Promotor(en): Roel Veerkamp, co-promotor(en): Yvette de Haas. - Wageningen : Wageningen University - ISBN 9789463430692 - 199
    cattle - feed intake - methane production - genetic improvement - genetic parameters - conformation - breeding value - animal genetics - rundvee - voeropname - methaanproductie - genetische verbetering - genetische parameters - bouw (dier) - fokwaarde - diergenetica

    Feed costs represent half of the total costs of dairy production. One way to increase profitability of dairy production is to reduce feed costs by improving feed efficiency. As DMI is a trait that varies significantly during and across lactations, it is imperative to understand the underlying genetic architecture of DMI across lactation. Moreover, phenotypes of DMI are scarce, due to the difficulty of recording them (expensive and labor-intensive). Some predictor traits have been suggested to predict DMI. Examples of these predictor traits are those related to production (milk yield (MY) or milk content) or to the maintenance of the cow (body weight (BW) or conformation traits). The ability to determine when predictor traits ideally should be measured in order to achieve an accurate prediction of DMI throughout the whole lactation period is thus important. Recently, with the use of information of single nucleotide polymorphism (SNP) markers, together with phenotypic data and pedigree, genomically estimated breeding values (GEBV) of scarcely recorded traits, such as DMI, have become easier to accurately predict. This approach, combined with predictor traits, could contribute to an increased accuracy of predictions of GEBV of DMI. Methane (CH4) is the second important greenhouse gas, and enteric CH4 is the largest source of anthropogenic CH4, representing 17% of global CH4 emissions. Furthermore, methane emissions represent 2-12% of feed energy losses. Selecting for lower CH4 emitting animals and more feed-efficient animals would aid in mitigating global CH4 emissions. To identify the impact on CH4 emissions of selecting for lower DMI animals, it is important to determine the correlations between DMI and CH4 and to identify whether the same genes that control DMI affect CH4. Therefore, the general objectives of this thesis were to (1) explore the genetic architecture of DMI during lactation, (2) study the relationship of DMI to conformation, production and other related traits, (3) investigate the correlations between DMI and methane traits, and determine the SNP in common between DMI and CH4 through a genome-wide association study (GWAS), and (4) investigate the accuracy of predictions of DMI using predictor traits combined with genomic data.

    Genetic improvement of longevity in dairy cows
    Pelt, Mathijs van - \ 2017
    Wageningen University. Promotor(en): Roel Veerkamp, co-promotor(en): T.H.E. Meuwissen. - Wageningen : Wageningen University - ISBN 9789463430821 - 188
    dairy cows - longevity - genetic improvement - breeding value - genetic analysis - survival - animal models - animal genetics - melkkoeien - gebruiksduur - genetische verbetering - fokwaarde - genetische analyse - overleving - diermodellen - diergenetica

    Improving longevity helps to increase the profit of the farmer, and it is seen as an important measure of improved animal welfare and sustainability of the sector. Breeding values for longevity have been published since in 1999 in the Netherlands. For AI-companies and farmers it is necessary that breeding values are accurately estimated and will remain stable for the rest of life. However, current breeding values for longevity of bulls seem to fluctuate more than expected. The main aim of this thesis was to revisit the genetics of longevity and develop a genetic evaluation model for longevity, where breeding values reflect the true breeding value quicker during early life and therefore breeding values become more stable. Genetic parameters were estimated for survival up to 72 months after first calving with a random regression model (RRM). Survival rates were higher in early life than later in life (99 vs. 95%). Survival was genetically not the same trait across the entire lifespan, because genetic correlations differ from unity between different time intervals, especially when intervals were further apart. Survival in the first year after first calving was investigated more in depth. Survival of heifers has improved considerably in the past 25 years, initially due to the focus on a high milk production. More recently, the importance of a high milk production for survival has been reduced. Therefore functional survival was defined as survival adjusted for within-herd production level. For survival the optimum age at first calving was around 24 months, whereas for functional survival calving before 24 months resulted in a higher survival. Over years, genetic correlations between survival in different 5-yr intervals were below unity, whereas for functional survival genetic correlations did not indicate that survival changed over years. This suggested that a genetic evaluation using historical data should analyze functional survival rather than survival. A new genetic evaluation system for longevity was developed based on a RRM analyzing functional survival. Based on the correlation between the first breeding value of a bull and his later breeding values, the ranking of bulls was shown to be more stable for RRM than the current genetic evaluation. Bias in breeding value was observed, mainly for bulls with a large proportion of living daughters. Adjusting for within-herd production level reduced this bias in the breeding values greatly. Before implementing this new model for genetic evaluation, the cause of this bias needs to be further investigated.

    Antibodies and longevity of dairy cattle : genetic analysis
    Klerk, B. de - \ 2016
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Jan van der Poel; Bart Ducro. - Wageningen : Wageningen University - ISBN 9789462577589 - 134
    dairy cattle - dairy cows - antibodies - longevity - genetic analysis - breeding value - genomes - genetic improvement - animal genetics - melkvee - melkkoeien - antilichamen - gebruiksduur - genetische analyse - fokwaarde - genomen - genetische verbetering - diergenetica

    The dairy sector has a big impact on food production for the growing world population and contributes substantially to the world economy. In order to produce food in a sustainable way, dairy cows need to be able to produce milk without problems and as long as possible. Therefore, breeding programs focuses on improvement of important traits for dairy cows. In order to improve desirable traits and obtain genetic gain there is a constant need for optimization of breeding programs and search for useful parameters to include within breeding programs. Over the last several decades, breeding in dairy cattle mainly focused on production and fertility traits, with less emphasis on health traits. Health problems, however, can cause substantial economic losses to the dairy industry. The economic losses, together with the rising awareness of animal welfare, increased herd size, and less attention for individual animals, have led to an increased need to focus more on health traits. Longevity is strongly related to disease resistance, since a more healthy cow will live a longer productive life (longevity). The identification of biomarkers and the detection of genes controlling health and longevity, would not only greatly enhance the understanding of such traits but also offer the opportunity to improve breeding schemes. The objectives of this thesis therefore were 1) to find an easy measurable disease resistance related biomarker in dairy cows, 2) identify the relation between antibodies and longevity, 3) identify genomic regions that are involved with antibody production/expression. In this thesis antibodies are investigated as parameter for longevity. Antibodies might be a novel parameter that enables selection of cows with an improved ability to stay healthy and to remain productive over a longer period of time. In this thesis antibodies bindiging the naive antigen keyhole limpet hemocyanin (KLH) were assumed to be natural antibodies. Antibodies binding bacteria-derived antigens lipoteichoic acid (LTA), lipopolysaccharide (LPS) and peptidoglycan (PGN) were assumed to be specific antibodies. In chapter 2 it was shown that levels of antibodies are heritable (up to h2 = 0.23). Additionally, antibody levels measured in milk and blood are genetically highly correlated (± 0.80) for the two studied isotypes (IgG and IgM). On the other hand, phenotypically, natural antibodies (from both IgG and IgM isotype) measured in milk cannot be interpreted as the same trait (phenotypic correlation = ± 0.40). In chapter 3 and 4 it was shown that levels of antibodies (both natural-and specific antibodies) showed a negative relation with longevity: first lactation cows with low IgM or IgG levels were found to have a longer productive life. When using estimated breeding values for longevity, only a significant relation was found between natural antibody level (IgM binding KLH) and longevity. Lastly chapter 5 reports on a genome-wide-association study (GWAS), to detect genes contributing to genetic variation in natural antibody level. For natural antibody isotype IgG, genomic regions with a significant association were found on chromosome 21 (BTA). These regions included genes have impact on in isotype class switching (from IgM to IgG). The gained knowledge on relations between antibodies and longevity and the gained insight on genes responsible for natural antibodies level make antibodies potential interesting biomarkers for longevity.

    Multi-population genomic prediction
    Wientjes, Y.C.J. - \ 2016
    Wageningen University. Promotor(en): Roel Veerkamp; Mario Calus. - Wageningen : Wageningen University - ISBN 9789462576193 - 267
    cum laude - dairy cattle - genomics - prediction - quantitative trait loci - genetic improvement - breeding value - selective breeding - animal breeding - animal genetics - melkvee - genomica - voorspelling - loci voor kwantitatief kenmerk - genetische verbetering - fokwaarde - selectief fokken - dierveredeling - diergenetica
    Cum laude graduation
    Genomic selection for improved crossbred performance
    Lopes, Marcos Soares - \ 2016
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis; John Bastiaansen; E.F. Knol. - Wageningen : Wageningen University - ISBN 9789462576315 - 202
    pigs - crossbreds - genomics - selective breeding - performance - genetic improvement - pig breeding - varkens - kruising - genomica - selectief fokken - prestatieniveau - genetische verbetering - varkensfokkerij

    Lopes, M.S. (2016). Genomic selection for improved crossbred performance. PhD thesis, Wageningen University, the Netherlands

    With the implementation of genomic selection in pig breeding, the genetic progress in purebred populations is expected to increase up to 55% compared to traditional selection based on pedigree information. However, as most of the animals in the pork production system are crossbreds, the increase in genetic progress in purebreds will only be observed on production farms if this progress is expressed in the performance of crossbreds. The main aim of this thesis was to evaluate different models based on genomic information which can be applied to improve performance of crossbred animals. Another aim was to gain insight into genetic architecture of (complex) traits and to investigate how selection history has influenced haplotype patterns of current commercial pigs. This thesis shows that by going beyond traditional genomic selection models, phenotypes can be predicted more accurately. Therefore, these improved models should be considered to improve crossbred performance. Further, this thesis provides important insights into the genetic architecture of the evaluated (complex) traits and also shows evidence that human-driven introgression and selection have shaped the genome of current commercial pig breeds. The research presented in this thesis was performed using data from pigs and the discussion on the practical application of results was focused on pig breeding. The results are relevant for all livestock species where crossbreeding is applied.

    Exploiting genomic information on purebred and crossbred pigs
    Hidalgo, A.M. - \ 2015
    Wageningen University. Promotor(en): Martien Groenen, co-promotor(en): D.J. de Koning; John Bastiaansen. - Wageningen : Wageningen University - ISBN 9789462576018 - 202
    varkens - genomica - kruising - inteeltlijnen - genetische verbetering - fokwaarde - drachtigheidsperiode - androstenon - prestatieniveau - varkensfokkerij - diergenetica - pigs - genomics - crossbreds - inbred lines - genetic improvement - breeding value - gestation period - androstenone - performance - pig breeding - animal genetics
    Genetic improvement in indigenous chicken of Ethiopia
    Woldegiorgiss, W.E. - \ 2015
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Liesbeth van der Waaij; T. Dessie. - Wageningen : Wageningen University - ISBN 9789462573161 - 130
    kippen - pluimvee - inheems vee - genetische verbetering - houding van boeren - perceptie - kippenrassen - prestatieniveau - dierveredeling - ethiopië - fowls - poultry - native livestock - genetic improvement - farmers' attitudes - perception - fowl breeds - performance - animal breeding - ethiopia

    Abstract

    Wondmeneh Esatu Woldegiorgiss (2015). Genetic improvement in indigenous chicken of Ethiopia. PhD thesis, Wageningen University, the Netherlands

    This thesis considered various approaches to study the potential for improvement of village poultry production system using improved indigenous chicken. The approaches were structured survey questionnaire, village poultry simulation model (VIPOSIM), Heckman two-step model (econometric model), and experiments involving laboratory and field. First factors that determine the probability and intensity of adoption of exotic chickens were assessed. The probability of adopting exotic chickens was found to be positively affected by access to an off-farm income and negatively by livestock income. The intensity of adoption was negatively affected by being male household head, having a larger farm size, and having livestock income. Then, perceptions of farmers towards village poultry and impacts of interventions on flock and economic performance were assessed. Farmers’ perceptions affected their decisions about implementation of interventions, and interventions increased productivity but only in a few cases the increased revenues outweighed the additional costs. Subsequently, the evaluation of the breeds was conducted by comparing the natural antibody and productivity of improved indigenous chicken with crossbred, commercial and unimproved indigenous chickens. The results revealed that not only the NAb levels but also the effect of NAbs on survival differ between indigenous and improved breeds. NAb levels are associated with survival in commercial layer breed, but reduced survival in indigenous chickens placed in confinement. Improved indigenous chickens showed higher performance than unimproved one for all traits measured on-station, but remains lighter and developed more into a laying type than meat through the short-term selective breeding program. Overall, the present studies indicate that interventions need to be tailored towards the local situation to ensure that they lead not only to improved productivity but also to improved income.

    Breeding program for indigenous chicken in Kenya
    Ngeno, K. - \ 2015
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Liesbeth van der Waaij; A.K. Kahi. - Wageningen : Wageningen University - ISBN 9789462572775 - 154
    kippen - pluimvee - inheems vee - dierveredeling - veredelingsprogramma's - genetische diversiteit - ecotypen - genomen - genetische verbetering - kenya - fowls - poultry - native livestock - animal breeding - breeding programmes - genetic diversity - ecotypes - genomes - genetic improvement - kenya

    Abstract

    Ngeno, K. (2015). Breeding program for indigenous chicken in Kenya. Analysis of diversity in indigenous chicken populations. PhD thesis, Wageningen University, the Netherlands

    The objective of this research was to generate knowledge required for the development of an indigenous chicken (IC) breeding program for enhanced productivity and improved human livelihood in Kenya. The initial step was to review five questions; what, why and how should we conserve IC in an effective and sustainable way, who are the stakeholders and what are their roles in the IC breeding program. The next step of the research focused on detecting distinctive IC ecotypes through morphological and genomic characterization. Indigenous chicken ecotypes were found to be populations with huge variability in the morphological features. Molecular characterization was carried out using microsatellite markers and whole genome re-sequenced data. The studied IC ecotypes are genetically distinct groups. The MHC-linked microsatellite markers divided the eight IC ecotypes studied into three mixed clusters, composing of individuals from the different ecotypes whereas non-MHC markers grouped ICs into two groups. Analysis revealed high genetic variation within the ecotype with highly diverse MHC-linked alleles which are known to be involved in disease resistance. Whole genome re-sequencing revealed genomic variability, regions affected by selection, candidate genes and mutations that can explain partially the phenotypic divergence between IC and commercial layers. Unlike commercial chickens, IC preserved a high genomic variability that may be important in addressing present and future challenges associated with environmental adaptation and farmers’ breeding goals. Lastly, this study showed that there is an opportunity to improve IC through selection within the population. Genetic improvement utilizing within IC selection requires setting up a breeding program. The study described the systematic and logical steps in designing a breeding program by focusing on farmers’ need, how to improve IC to fit the farming conditions, and management regimes.

    Cooperative and uniform fish? : social interactions and variability in live body weight in the GIFT strain (Nile tilapia, Oreochromic niloticus) in Malaysia
    Khaw, H.L. - \ 2015
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Piter Bijma; R.W. Ponzoni. - Wageningen : Wageningen University - ISBN 9789462572157 - 161
    oreochromis niloticus - sociaal gedrag - lichaamsgewicht - variatie - genetische effecten - inteelt - kenmerken - heritability - genotype-milieu interactie - genotypische variatie - genetische verbetering - veredelingsprogramma's - visteelt - maleisië - oreochromis niloticus - social behaviour - body weight - variation - genetic effects - inbreeding - traits - heritability - genotype environment interaction - genetic variance - genetic improvement - breeding programmes - fish culture - malaysia

    Abstract

    Khaw, HL. (2014). Cooperative and uniform fish? Social interactions and variability in live body weight in the GIFT strain (Nile tilapia, Oreochromic niloticus) in Malaysia. PhD thesis, Wageningen University, the Netherlands.

    Social interactions are present everywhere in the living world. Such social interactions may lead to indirect genetic effects (IGE), which are heritable effects of an individual on trait values of the other individuals its interacts with. IGEs may affect the direction and magnitude of response to selection in breeding programs. Moreover, social interactions may affect variability of traits. In aquaculture, competition for resources inflates size variation within populations. In this thesis, we used the Genetically Improved Farmed Tilapia (GIFT; Oreochromis niloticus) strain to investigate the genetic basis for social interactions and variability in harvest weight for tropical finfish. Social interaction experiments were established for quantifying the genetic and non-genetic indirect effects on harvest weight in the GIFT strain. We found evidence for IGEs on harvest weight, and a negative direct-indirect genetic correlation, which suggesting heritable competitive interactions for harvest weight in GIFT. Hence, breeding schemes may need to be adapted to avoid an increase in competition. A stochastic simulation study was conducted to examine the effect of BLUP selection on the rate of inbreeding for socially affected traits. The rates of inbreeding for scenarios with IGEs were greater than for scenarios without IGE. Therefore, with IGEs there is a greater need for a selection algorithm that restricts the increase of mean kinship. In aquaculture industry, there is a wide range of commercial production environments, which may leads to genotype by environment (GxE) interaction, for example due to differential social interactions. The GIFT fish were tested in ponds and cages to study the GxE interaction. The genetic correlations between environments (0.73 to 0.85, for harvest weight and body measurements) indicate little GxE-interaction. The data collected from the social interaction experiments were also used to investigate the presence of genetic variation in uniformity for harvest weight. The genetic coefficient of variation for standard deviation of harvest weight (0.17) shows that uniformity of harvest weight is heritable and can be increased by selective breeding. In the General Discussion of this thesis, the uniformity study was extended to incorporate IGE. The result indicates that more cooperative fish are not necessary more uniform for harvest weight. Overall, our results suggest that genetic improvement in fish breeding programs can be increased by accounting for social interactions.

    JATROPT (Jatropha curcas: Applied and Technological Research on Plant Traits) : Final report EU FP7 Grant 245236 (2010-2013)
    Loo, E.N. van; Jongschaap, R.E.E. - \ 2014
    Plant Research International - 31
    jatropha curcas - fuel crops - plant breeding - new crops - genetic improvement - yield increases - biofuels - biobased economy - jatropha curcas - brandstofgewassen - plantenveredeling - nieuwe cultuurgewassen - genetische verbetering - oogsttoename - biobrandstoffen - biobased economy
    JATROPT aimed to improve jatropha production systems through developing advanced genetics tools for breeding and for development of jatropha agro-systems.
    Optimizing genomic selection for scarcely recorded traits
    Pszczola, M.J. - \ 2013
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Mario Calus; T. Strabel. - Wageningen : Wageningen UR - ISBN 9789461737663 - 158
    melkvee - genomen - selectief fokken - genetische verbetering - fokwaarde - fenotypen - genotypen - kenmerken - voeropname - dierveredeling - dairy cattle - genomes - selective breeding - genetic improvement - breeding value - phenotypes - genotypes - traits - feed intake - animal breeding

    Animal breeding aims to genetically improve animal populations by selecting the best individuals as parents of the next generation. New traits are being introduced to breeding goals to satisfy new demands faced by livestock production. Selecting for novel traits is especially challenging when recording is laborious and expensive and large scale recording is not possible. Genetic improvement of novel traits may be thus limited due to the small number of observations. New breeding tools, such as genomic selection, are therefore needed to enable the genetic improvement of novel traits. Using the limited available data optimally may, however, require alternative approaches and methodologies than currently used for conventional breeding goal traits. The overall objective of this thesis was to investigate different options for optimizing genomic selection for scarcely recorded novel traits. The investigated options were: (1) genotype imputation for ungenotyped but phenotyped animals to be used to enlarge the reference population; (2) optimization of the design of the reference population with respect to the relationships among the animals included in it; (3) prioritizing genotyping of the reference population or the selection candidates; and (4) using easily recordable predictor traits to improve the accuracy of breeding values for scarcely recorded traits. Results showed that: (1) including ungenotyped animals to the reference population can lead to a limited increase in the breeding values accuracy; (2) the reference population is designed optimally when the relationship within the reference are minimized and between reference population and potential selection candidates maximized; (3) the main gain in accuracy when moving from traditional to genomic selection is due to genotyping the selection candidates, but preferably both reference population and selection candidates should be genotyped; and (4) including the predictor traits in the analysis when it is recorded on both reference population and selection candidates can lead to a significant increase in the selection accuracy. The key factors for successful implementation of selection for a novel trait in a breeding scheme are: (1) maximizing accuracy of genotype prediction for ungenotyped animals to be used for updating the reference population; (2) optimizing the design of the reference population; (3) determining easy to record indicator traits that are also available on the selection candidates (4) developing large scale phenotyping techniques; and (5) establishing strategies and policies for increasing the engagement of farmers in the recording of novel traits.

    The role of reproductive technologies in breeding schemes for livestock populations in developing countries
    Arendonk, J.A.M. van - \ 2011
    Livestock Science 136 (2011)1. - ISSN 1871-1413 - p. 29 - 37.
    fokkerijmethoden - dierveredeling - ontwikkelingslanden - vee - genetische bronnen van diersoorten - genetische diversiteit - veredelingsprogramma's - kunstmatige inseminatie - inteelt - genetische verbetering - animal breeding methods - animal breeding - developing countries - livestock - animal genetic resources - genetic diversity - breeding programmes - artificial insemination - inbreeding - genetic improvement - dairy-cattle - genetic-variation - embryo transfer - predefined rate - selection - programs - impact - rates - prediction - sheep
    The world is faced with the challenge to meet the increasing demand for livestock products while conserving animal genetic resource diversity and maintaining environmental integrity. Genetic improvement of local breeds can help to improve the livelihood of the livestock keepers, to increase the production of animal products and to conserve genetic diversity. Implementing breeding schemes in developing countries has proven to be very difficult. The objective of this paper is to discuss the role of reproductive technologies for the creation and dissemination of genetic improvement in livestock populations in developing countries. In the paper opportunities are discussed for implementing breeding schemes which minimize the need for extensive pedigree and performance recording. It is shown that genetic progress can be generated in a small population. Community-based breeding schemes offer a good starting point for involving farmers in improving local breeds. Artificial insemination to exchange genetic material between communities offers an opportunity to increase the rate of genetic improvement while restricting the rate of inbreeding. Furthermore, artificial insemination is a promising technique for dissemination of genetic gain to producers at a relatively low cost. Opportunities to use semen sexing in a crossbreeding scheme are presented. It is concluded that tailor-made solutions and long-term commitment are needed in order to meet the needs of farmers to increase their livelihoods and to meet the needs of the growing population of consumers.
    Breeding programs for indigenous chicken in Ethiopia : analysis of diversity in production systems and chicken populations
    Dana, N.M. - \ 2011
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Liesbeth van der Waaij; T. Dessie. - [S.l. : S.n. - ISBN 9789085858720 - 149
    kippen - veredelingsprogramma's - genetische verbetering - prestatiekenmerken - dorpen - ecotypen - karakterisering - moleculaire genetica - genetische diversiteit - genetische parameters - agrarische productiesystemen - ethiopië - fowls - breeding programmes - genetic improvement - performance traits - villages - ecotypes - characterization - molecular genetics - genetic diversity - genetic parameters - agricultural production systems - ethiopia
    The aim of this research was to generate information required to establish a sustainable breeding program for improving the productivity of locally adapted chickens to enhance the livelihood of rural farmers in Ethiopia. The first step was to characterize village poultry production environments and farmers’ objectives for keeping chickens, and to identify factors affecting the choice of genetic stock used in villages. This was achieved by carrying out a questionnaire survey and a participatory group discussion with village farmers in different geographic regions of Ethiopia. The low input nature of village environments, the prevalence of disease and predators, and other factors such as the use of chickens both as sources of eggs and meat, and income determined the choice of chicken breed used by farmers, and thus, should be considered carefully before initiating new breeding programs. The highest importance attached to adaptation traits and the existence of particular preferences for chickens of certain plumage colours and comb shapes were also found to have effects on developing new breeds for village systems.
    The next part of the thesis focused on identifying important and unique gene pools in local populations. This was achieved by characterizing the local chicken ecotypes both morphologically and molecular genetically. This way the genetic difference between the local populations and the level of genetic diversity within the populations was determined. Attributes important in breeding for tropical conditions such as the pea comb gene, and the naked neck gene have been identified. It was also revealed that the variability found within a single population could explain most of the genetic diversity (97%) in Ethiopian chicken populations. The result of this work is important both from conservation and utilization perspective and assists in maintaining indigenous genetic diversity for current and future generations.
    Finally, the pedigreed Horro population that was kept on station was used for estimating genetic parameters for the production traits, monthly and cumulative part period egg numbers and growth to 16 weeks of age. Because the pedigreed population was established only recently, data of only 2 generations were available for estimating these genetic parameters. The results are promising but inaccurate due to insufficient amount of data. They would need to be re-estimated when more generations have been produced and thus more data has been generated.

    Genomic selection in dairy cattle
    Roos, A.P.W. de - \ 2011
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): B.J. Hayes; Roel Veerkamp. - [S.l. : S.n. - ISBN 9789085858539 - 184
    melkvee - selectief fokken - genetische verbetering - veredelingsprogramma's - fokwaarde - genetische merkers - haplotypen - voorspelling - dierveredeling - genexpressieanalyse - genotyping - dairy cattle - selective breeding - genetic improvement - breeding programmes - breeding value - genetic markers - haplotypes - prediction - animal breeding - genomics - genotyping
    The objectives of this Ph.D. thesis were (1) to optimise genomic selection in dairy cattle with respect to the accuracy of predicting total genetic merit and (2) to optimise a dairy cattle breeding program using genomic selection. The study was performed using a combination of real data sets and simulations. Real data sets consisted of dense marker genotypes of progeny tested bulls that had accurate phenotypes derived from their daughters’ performance records. Through cross-validation, the reliability of genomic predictions was assessed for Bayesian models that fitted either marker genotypes, ancestral haplotypes or genomic relationships. Haplotype-based methods gave the most reliable predictions and provided opportunities to limit computer requirements for analysing very large data sets. The reliability of genomic predictions across breeds was studied using simulated marker data. The data was simulated such that it showed the same the patterns of linkage disequilibrium (LD) as observed within and between Holstein, Angus, and Jersey cattle from the Netherlands, Australia, and New Zealand. It was concluded that the most reliable genomic predictions can be obtained when the reference populations of each breed are combined, whereas for diverged breeds at least 300,000 markers are required to ensure that the LD between markers and QTL persists across breeds. Using a simulated genomic selection scheme, it was shown that the annual rate of genetic gain in dairy cattle may double compared to current progeny test schemes, without compromising the rate of inbreeding. To achieve such a high rate of genetic gain, the generation interval needs to be reduced significantly, as young bulls will prove to be superior to progeny tested bulls. It is expected that in the near future many animals will be genotyped and very high marker densities will be inferred by imputation techniques. This may result in genomic predictions that are persistent across breeds and generations. Large scale genotyping of cows may enable genomic selection for novel traits and the integration of genomic information in herd management processes.
    Genen in bedrijf
    Smits, M.A. - \ 2008
    Wageningen : Wageningen Universiteit - 30
    vee - veehouderij - dierveredeling - genen - genexpressie - dierziekten - genetische verbetering - functionele genomica - dna microarrays - eiwitexpressieanalyse - livestock - livestock farming - animal breeding - genes - gene expression - animal diseases - genetic improvement - functional genomics - dna microarrays - proteomics
    Inaugurele rede van prof. dr. Mari A. Smits. Hij geeft een overzicht van de wetenschappelijke ontwikkelingen op het gebied van de functionele genomica bij dieren en de perspectieven die dat biedt voor toekomstige innovaties in de veehouderij
    Paving the way for genetic improvement of zinc accumulation in Brassica rapa
    Wu, J. - \ 2007
    Wageningen University. Promotor(en): Maarten Koornneef, co-promotor(en): Mark Aarts; Xiaowu Wang. - [S.l.] : S.n. - ISBN 9789085047667 - 130
    brassica campestris - zinc - genetic improvement - germplasm - quantitative trait loci - genes - gene expression - brassica campestris - zink - genetische verbetering - germplasm - loci voor kwantitatief kenmerk - genen - genexpressie
    Brassica rapa L. comprises several vegetable crops, some of which are among the most important vegetables in China, serving as one of the main resources of mineral nutrition for Chinese people. However, the knowledge on the genetics of micronutrient accumulation, including Zn, Fe and Mn, is lacking in B. rapa. By exploring the genetic potential for the improvement of Zn accumulation in B. rapa vegetables I expect to contribute to the reduction of micronutrient malnutrition in China. To characterize the natural variation of Zn accumulation and Zn response upon exposure to different Zn concentrations, I screened a large collection of germplasm representing nine cultivar groups covering the geographic distribution of B. rapa vegetables in China (Chapter 2). The result revealed that there was marked variation in accumulation of Zn (23.2-159.9 µg g-1), Fe (60.3-350.1 µg g-1) and Mn (20.9-53.3 µg g-1) in B. rapa. Zn accumulation correlated with Fe or Mn accumulation both under normal and deficient Zn supply. No significant correlation was detected for the accumulation of these three elements with cultivar groups. A two-fold variation was found for dry-biomass based tolerance to Zn deficiency or excessive Zn. The wide natural variation provides a base for the genetic dissection by quantitative trait locus (QTL) analysis or for developing breeding programs for improved mineral content. QTL analysis is a powerful tool in dissection of complex genetic traits. A doubled haploid (DH) population developed from two Chinese cabbage (B. rapa. ssp. pekinesis) varieties was used for QTL analysis of the accumulation of 11 minerals in leaves and for tolerance to deficient or toxic Zn supplies (Chapter 3). The trait analysis showed significantly positive correlations between the leaf concentrations of the tested minerals, indicating that this must be taken into consideration in breeding programs, especially when toxic minerals (Cd, As) are involved. Seven QTLs were detected for Na, Mg, P, Mn, Zn and Sr leaf concentrations, with an explained variance ranging from 11.1 % to 18.2 % . The tolerance to Zn stress was evaluated by dry shoot biomass of plants grown under different Zn supplies. One common QTL was found affecting Shoot Dry Biomass (SDB) under normal, deficient and excessive Zn supply conditions. An additional QTL was detected for SDB only under Zn excess stress, with an explained variance of 13.0 %. The fact that no major QTL was detected indicates the complexity of the genetic control of the traits, probably involving many loci, each with a limited contribution to mineral accumulation in B. rapa. Furthermore this indicates that the genetic improvement of these traits by classical breeding will be very complicated, as it will require a combination of favourable alleles at many of the genes contributing to the traits. Screening additional populations for larger effect QTLs may provide an alternative. Metal transporters play important roles in maintaining metal homeostasis in plants and are involved in processes of metal uptake, internal transport and storage. Thlaspi caerulescens J&C Presl. is a Zn/Cd/Ni hyperaccumulator, which has been used as a model for plant metal homeostasis research. It has been proposed that the hyperaccumulation is most likely due to the different regulation of the metal homeostasis genes rather than involving genes with novel functions (Van de Mortel et al., 2006). I cloned four metal transporter full-length cDNAs by screening T. caerulescens cDNA libraries, encoding two ZIP transporters (TcZNT5 and TcZNT6, in Chapter 4) and two so-called NRAMP transporters (TcNRAMP3 and TcNRAMP4, in Chapter 5). These four genes showed strongly increased expression in T. caerulescens, as compared to the non-accumulator Arabidopsis thaliana in a wide range of Zn supplies or in the presence of Cd, indicated that these genes were involved in metal hyperaccumulation or tolerance in T. caerulescens. Expression analysis in two T. caerulescens accessions with contrasting Cd accumulation (La Calamine and Ganges) further revealed that their difference in Cd accumulation ability was associated with differences in the regulation of the expression of ZNTs and NRAMPs . Loss of function of the AtZIP5 gene in Arabidopsis increased its tolerance to Cd as measured by reduced root growth, but overexpression of the T. caerulescens orthologue TcZNT5 in Arabidopsis did not lead to any change in phenotype. In contrast, loss of function of AtZIP6 in Arabidopsis did not change its phenotype, but overexpression of the T. caerulescens orthologue TcZNT6 in Arabidopsis increased Cd sensitivity. The Arabidopsis double mutant nramp3 nramp4 showed hypersensitivity to Cd and toxic Zn, in addition to its previously reported hypersensitivity to Fe deficiency. Our study did not reveal functional differences between the T. caerulescens and A. thaliana NRAMPs, which transport the same metals when heterologously expressed in yeast and all four are localized at the vacuolar membrane in plants. Furthermore the phenotype caused by the inactivation of the AtNRAMP3 and AtNRAMP4 genes in Arabidopsis can be rescued by expression of TcNRAMP3. Nevertheless, neither nramp3 nramp4 plants expressing TcNRAMP3, nor wild-type plants expressing TcNRAMP4 at high levels show enhanced Zn or Cd tolerance compared to wild type Arabidopsis. The data presented in this thesis indicate that enhanced Zn accumulation, Zn tolerance or Cd tolerance probably requires elevated and controlled expression of a set of genes, rather than only single metal transporter genes.
    Natural mating in Nile tilapia (Oreochromis niloticus L.) : implications for reproductive success, inbreeding and cannibalism
    Fessehaye, Y. - \ 2006
    Wageningen University. Promotor(en): Johan Verreth; Johan van Arendonk, co-promotor(en): Hans Komen; Henk Bovenhuis. - [S.l.] : S.n. - ISBN 9789085045403 - 149
    oreochromis niloticus - tilapia - natuurlijke paring - voortplantingsefficiëntie - inteelt - kannibalisme - genetische verbetering - visteelt - oreochromis niloticus - tilapia - natural mating - reproductive efficiency - inbreeding - cannibalism - genetic improvement - fish culture
    Niletilapia ( Oreochromis niloticus L.) is one of the most important species among the commercially farmed tilapias. Both small-scale and commercial production of tilapia is rapidly expanding in many countries of the world because tilapias meet many of the desirable characteristics for an ideal species for aquaculture: fast growth, high acceptability to consumers and tolerance of a wide range of culture conditions. Fry production inNiletilapia, Oreochromis niloticus is typically achieved by mass-spawning of males and females stocked in large hapas, earthen ponds or tanks. Territorial behaviour and reproductive competition in such spawning setup together with the asynchronous spawning nature in tilapia could have serious implications for breeding plans that employ mass spawning for seed production. The aims of this thesis were to gain thorough understanding into the natural mating systems in O. niloticus ; the genetic consequences of the mating system (reproductive success, effective population size and inbreeding); as well as non-genetic variations (size heterogeneity and cannibalism) among fish as a result of asynchronous reproduction. 

    In order to establish captive breeding programmes that maximize genetic gain without compromising the long-term genetic diversity of stocks, understanding of the natural mating systems is a crucial step. In Chapter 2 , we analyzed parentage and quantified male reproductive success of O. niloticus under commercial hatchery conditions in two breeding hapas each stocked with 12 males and 25 females by sampling offspring from individual mass-spawning events. Eleven highly polymorphic microsatellite markers were used to genetically characterize the mating systems in O. niloticus and quantify the reproductive success of individual males and females. In total, 760 offspring from 76 spawnings were included in the paternity analysis. Mating system inNiletilapia ranged from single pair to promiscuous mating. Multiplepaternitywas detected in 46% of the broods, with up to 4 males fertilizing a single clutch. Multiple maternity was also detected in over 8% of the clutches analyzed. There was a very high variance in male reproductive success, with one third of males siring more than 70% of the offspring. Male condition factor had a significant effect on reproductive success with better conditioned males siring a large proportion of offspring. The high reproductive variance resulted in a N e of around 16 for hapas A and B, and a low N e / N ratio, 0.43 and 0.45 for hapas A and B respectively. The rate of inbreeding, ∆F , for each hapa, was estimated to be around 3.0% per generation, which is about twice the inbreeding expected in an idealized population of the same census size. When designing of fish breeding programmes based on mass-spawning, the higher inbreeding and lower effective population size should be taken into consideration.

    In mating systems with skewed reproductive success, the effective population size ( N e ) of a population becomes smaller. As a result, small populations experience an increased degree of inbreeding ( ∆F ). Inbreeding depression in fish affects fitness related traits such as survival, growth, reproductive traits and other morphological traits. The effect of genetic depression on different traits in O. niloticus was investigated in Chapter 3 .Experimental fish were produced in a full-sib/half-sib mating design in which each sire was mated to two dams and each dam mated to only one sire.We mated 20 sires and 35 dams to produce35 full-sib familieswith expected inbreeding coefficients (F) of 0.0, 6.3, 9.4, 12.5 and 25%. The fry were produced and reared in hapas suspended in fertilized ponds until time of tagging. In total 1832 fish were stocked in two fertilized earthen ponds for a period of 8 months (including 3 months of over-wintering). At the end of the experiment 389 fish were harvested. Results show that level of inbreeding significantly affected early fry survival and body weight at stocking. Level of inbreeding did not have significant effect on both the pond survival and weight at harvest. Effects of pond, weight at stocking, sire and dam component significantly affected body weight at harvest and pond survival. Fluctuating asymmetry was significantly affected by the dam component and pond but not by the level of inbreeding. This suggests that FA was more influenced by environmental factors than by genetic factors. The results of this study emphasizes that inbreeding had a significant effect on survival and growth on early but not on later stage of development. The observed difference in effects of inbreeding on early and later life stages can be explained by strong natural selection on fitnessduring over-wintering.

    Inbred individuals that survive the selective pressure to adulthood might still suffer reduced adult survival and reproductive success. Chapter 4 investigated the effects of inbreeding on reproductive success inNiletilapia, O. niloticus under semi-natural conditions in breeding hapas. A total of 72 fish (27 males and 45 females) from nine full-sib families(8 fish/family)were divided into two and stocked in two hapas at a sex ratio of 1 and 3. Fish had inbreeding coefficient of F = 0.0, 6.3, 9.4 and 25%. Fry were collected from the mouth of incubating females on a weekly basis and parentage assignment was done on 1120 offspring from 56 spawnings using seven polymorphic microsatellite markers. Female reproductive output (fecundity), expressed as the total number of eggs per spawning, was significantly affected by the level of inbreeding and body weight. Per 10% increase of the level of inbreeding, egg number declined by 11% of the mean. Male reproductive success, calculated as the proportion of offspring sired per spawning, was affected by the level of inbreeding, condition factor, sex ratio and gonad weight of males. Per 10% increase in the level of inbreeding, male reproductive success declined by 40%. The decline in reproductive success was higher in sex ratio 1 compared to sex ratio 3 indicating that the inbreeding depression was magnified under higher male-male competition. Degree of relatedness between mating pairs (Kinship coefficient), however, did not have any effect on reproductive success of males. Overall, our findings show that inbred individuals have lower reproductive success and uncover a natural selective pressure that favors outbred males and that counterbalances accumulation of inbreeding.  

    Asynchronous nature of reproductive cycles of individual broodstock in O. niloticus leads to episodic fry production. This presents a problem to aquaculture in two ways: 1) massive fry losses due to size-dependent cannibalism; 2) mixed age/size populations and associated cannibalism can mask the genetic merit of individuals. Fish breeders practising mass selection might inadvertently select for cannibalism as large size, faster growth rate and robustness are those phenotypic traits which a breeder desires in the selected broodstock. Selection under such circumstances can mask genetic merit and obscure selection response in mass selection programmes. In order to develop a protocol for size grading and minimize such effects, factors influencing size-dependent cannibalism inNiletilapia,Oreochromis niloticus, were investigated in controlled conditions ( Chapter5 ). First, individual-based trials were conducted to develop a linear regression model to predict the occurrence of cannibalism based on body measurements. Oral gape (G, mm), body depth (D, mm) and weight (W, g) of 140 fish were measured and we estimated maximum prey weight (Wprey) for a given predator weight (Wpredator): Log10Wprey = 1.03Log10Wpredator1.13. This model was verified by conducting 76 single pair trials. The revised model based on observed cannibalism is: Log10Wprey= Log10Wpredator1.17. Several experiments involving a group of prey and predators were conducted to elucidate the relative importance of factors that influence cannibalism. Cannibalism was significantly affected by stocking density, age of fish and predator/prey weight ratio. Logit models of mortality data of both the individual-based and observations based on a group of predators and prey estimatedR50(the predator/prey weight ratio at which an encounter of a predator and prey resulted in a predation success of 50%) to be 14.6 and 14.8, respectively. The results obtained in this experiment can be used to derive simple management of heterogeneous fry groups (e.g. grading of fish). Grading will have implications for reducing fry losses, minimizing the non-genetic variations caused by size dependent cannibalism among fish and can improve the efficiency of mass selection.

    The results described in this thesis are discussed in Chapter 6. This study demonstrated that a thorough understanding of mating systems and reproduction parameters are crucial foroutlining strategies that ensure the maintenance of genetic diversity inbreeding schemesemploying mass spawning for fry production. With the knowledge of mating systems and the number of parents contributing to the next generation, mass selection based on mass spawning can be used as a model for low cost breeding schemes that ensure a desired level of genetic gain without compromising the genetic diversity of the stocks due to inbreeding. In addition, knowledge on mating systems and other population parameters can be used in the management of supportive breeding programmes for restoration of endangered wild fish populations.
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