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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    Varying pasture growth and commodity prices change the value of traits in sheep breeding objectives
    Rose, I.J. ; Mulder, H.A. ; Thompson, P.N. ; Werf, J.H.J. van der; Arendonk, J.A.M. van - \ 2014
    Agricultural Systems 131 (2014). - ISSN 0308-521X - p. 94 - 104.
    multiple rearing ability - economic values - mediterranean environment - bioeconomic approach - functional traits - wool production - fleece weight - merino ewes - model - reproduction
    Breeding programs for livestock require economic weights for traits that reflect the most profitable animal in a given production system. Economic weights are commonly based on average conditions. In pasture based livestock production systems the cost of feed is an important profit driver, but availability of feed from pasture can vary greatly within and between years. Additionally, the price of supplementary feed during periods of feed shortage and the prices for meat and wool vary between years. Varying prices and pasture growth can change the optimal management of the flock affecting profitability. This paper investigates how variation in commodity prices and pasture growth affect the economic values of traits in the breeding objective. We modelled a sheep farm with a self-replacing Merino flock bred for wool and meat in a Mediterranean environment. We optimised management decisions across 5 years using dynamic recursive analysis to maximise profit when commodity prices and pasture growth varied annually. Actual pasture growth and wool, meat, and grain prices from 2005 to 2009 were used. Management could adapt to varying pasture growth and commodity prices by changing sheep numbers, age structure of the flock and amount of grain fed to sheep. The economic value of seven traits in the breeding objective were compared for a scenario with average pasture growth and commodity prices over years and a scenario with varying pasture growth and commodity prices over years. Variation in pasture growth and commodity prices decreased average profit and increased the economic value of all breeding goal traits compared to the average scenario. The order of importance of traits stayed the same between varying and average scenarios but the relative importance of traits changed. The economic values that increased the most were for traits that had increased profit with the smallest impact on energy requirements such as yearling live weight, longevity and fibre diameter. Our results showed that it is important to account for variation in feed availability and commodity prices when determining the expected profit and economic values for traits. The results also suggest that whereas variation in pasture growth and commodity prices between years makes the farming operations less profitable, these changing conditions increase the genetic variation in profitability of sheep. Therefore, genetic improvement has more value relative to scenarios where pasture feed supply and prices are constant.
    Genetic correlations between bodyweight change and reproduction traits in Merino ewes depend on age
    Rose, I.J. ; Mulder, H.A. ; Werf, J.H.J. van der; Thompson, A.N. ; Arendonk, J.A.M. van - \ 2014
    Journal of Animal Science 92 (2014)8. - ISSN 0021-8812 - p. 3249 - 3257.
    wool production - liveweight - nutrition - sheep - parameters - pregnancy - survival - components - lactation - variance
    Merino sheep in Australia experience periods of variable feed supply. Merino sheep can be bred to be more resilient to this variation by losing less bodyweight when grazing poor quality pasture and gaining more bodyweight when grazing good quality pasture. Therefore, selection on bodyweight change might be economically attractive but correlations with other traits in the breeding objective need to be known. The genetic correlations (rg) between bodyweight, bodyweight change, and reproduction were estimated using records from ~7350 fully pedigreed Merino ewes managed at Katanning in Western Australia. Number of lambs and total weight of lambs born and weaned were measured on ~5300 2-year-old ewes, ~4900 3-year-old ewes and ~3600 4-year-old ewes. On a proportion of these ewes bodyweight change was measured: ~1950 two-year-old ewes, ~1500 three old ewes and ~1100 four-year-old ewes. The bodyweight measurements were for three periods. The first period was during mating period over 42 days on poor pasture. The second period was during pregnancy over 90 days for ewes that got pregnant on poor and medium quality pasture. The third period was during lactation over 130 days for ewes that weaned a lamb on good quality pasture. Genetic correlations between weight change and reproduction were estimated within age classes. Genetic correlations were tested to be significantly greater magnitude than zero using likelihood ratio tests. Nearly all bodyweights had significant positive genetic correlations with all reproduction traits. In two-year old ewes, bodyweight change during the mating period had a positive genetic correlation with number of lambs weaned (rg = 0.58); bodyweight change during pregnancy had a positive genetic correlation with total weight of lambs born (rg = 0.33) and a negative genetic correlation with number of lambs weaned (rg = - 0.49). All other genetic correlations were not significantly greater magnitude than zero but estimates of genetic correlations for three-year-old ewes were generally consistent with these findings. The direction of the genetic correlations mostly coincided with the energy requirements of the ewes, and the stage of maturity of the ewes. In conclusion, optimized selection strategies on bodyweight changes to increase resilience will depend on the genetic correlations with reproduction, and are dependent on age.
    Quantitative trait loci associated with pre-weaning growth in South African Angora goats
    Visser, C. ; Marle-Koster, E. van; Snyman, M.A. ; Bovenhuis, H. ; Crooijmans, R.P.M.A. - \ 2013
    Small Ruminant Research 112 (2013)1-3. - ISSN 0921-4488 - p. 15 - 20.
    genome-wide association - microsatellite markers - genetic-parameters - parentage verification - conformation traits - carcass composition - wool production - fleece traits - merino sheep - beef-cattle
    This study aimed to identify chromosomal regions associated with genetic variation in pre-weaning growth traits in Angora goats. A genome-wide scan was performed by genotyping 1042 offspring from 12 half-sib families using 88 microsatellite caprine markers covering 1368cM. Phenotypes were recorded at birth (BW) and weaning (WW) and analysed using GridQTL software. A total of six putative QTL were detected on six different chromosomes, all at chromosome-wide significance level. Four QTL were identified for BW on CHI 4, 8, 17 and 27 and two QTL for WW on CHI 16 and 19. QTL effects ranged from -0.32 to 0.25 in units of residual standard deviation in different families. Some of these QTL correspond to chromosomes where QTL associated with growth have been identified in other species. These chromosomal segments hold potential to influence weight gain in young goats.
    QTL for mohair traits in South African Angora goats
    Visser, C. ; Marle-Koester, E. van; Bovenhuis, H. - \ 2011
    Small Ruminant Research 100 (2011)1. - ISSN 0921-4488 - p. 8 - 14.
    fiber diameter - merino sheep - wool production - fleece traits - dairy-cattle - body-weight - loci - linkage - genes - parameters
    The aim of this study was to identify QTL associated with mohair production and quality traits in South African Angora goats. Limited research has been performed on QTL influencing the economically important mohair traits of Angora goats. Twelve half-sib Angora goat families with an average of 58 offspring per sire were genotyped for 88 microsatellites covering 22 autosomes. Phenotypic data was collected at second and third shearing for males and females respectively. A linkage analysis was performed under the half-sib model using the least squared regression approach of GridQTL. Three putative QTL were detected for fleece weight on CHI 2, 5 and 24, which corresponds with the locations of keratin and keratin-associated proteins. This study detected two putative QTL associated with mohair fibre diameter (on CHI 4 and 24, respectively), which is the most important price-determining trait. Four QTL were detected on CHI 8, 13, 18 and 20 which influence both comfort factor and spinning fineness. The variance explained by the QTL ranged between 6.9% for fibre diameter and 33.6% for standard deviation along the length of the staple. These results reveal segregation of QTL influencing mohair production and quality, and contribute to the understanding of the genetic variation of mohair traits.
    PH bufferanalyse 2009. Bepaling zuurbindende waarde volgens het KIWA keur minerale wolproducten
    Blok, C. ; Winkel, A. van; Berg, C.C. van den - \ 2010
    zuur-base-evenwicht - wolproductie - zuurgraad - methodologie - oefening - milieu-analyse - acid base equilibrium - wool production - acidity - methodology - practice - environmental analysis
    Poster over de PH bufferanalyse 2009, een bepaling van de zuurbindende waarde volgens het KIWA keur minerale wolproducten. De methode voldoet in de praktische uitvoering. De auteurs stellen dat het valt te overwegen de methode niet te gebruiken voor standaard-steekproeven maar uitsluitend voor te schrijven als methode bij geschillen.
    Risicobeoordeling schapenscheren en schapenwol voor mens en dier in de Nederlandse wolproductieketen
    Elbers, A.R.W. ; Roest, H.I.J. ; Zijderveld, F.G. van - \ 2009
    Lelystad : Wageningen UR, Centraal Veterinair Instituut - 23
    schapenhouderij - wolproductie - wol - scheren - infectieziekten - risicoschatting - ziektedistributie - mens-dier relaties - maatregelen - sheep farming - wool production - wool - shearing - infectious diseases - risk assessment - disease distribution - human-animal relationships - measures
    Het doel van dit onderzoek is een risicobeoordeling van de microbiologische risico's voor mens en dier van het schapenscheren, transport en het bewerken van schapenwol in de wolproductieketen in Nederland, inclusief de opties voor eventueel noodzakelijke risicoreducerende maatregelen. De VWA wilde de volgende vragen beantwoord hebben: 1. Welke microbiologische gevaren vormen in Nederland een risico voor infectie van en verspreiding onder mensen en dieren naar aanleiding van directe en indirecte contacten met het product wol in de wolproductieketen? 2. Kunt u deze microbiologische risico's in prioritaire volgorde plaatsen (kwalitatieve of indien mogelijk semikwantitatieve risicobeoordeling)? 3. Als er risico's aanwezig zijn, die op basis van een expertmening niet verwaarloosbaar klein zijn, welke risicoreducerende maatregelen kunnen mogelijk worden toegepast in de productieketen en op welk moment?
    Effect of supplementation of Sesbania sesban on reproductive performance of sheep
    Mekoya, A. ; Oosting, S.J. ; Fernandez-Rivera, S. ; Tamminga, S. ; Tegegne, A. ; Zijpp, A.J. van der - \ 2009
    Livestock Science 121 (2009)1. - ISSN 1871-1413 - p. 117 - 125.
    ethiopian highland sheep - condensed tannins - lotus-corniculatus - menz sheep - semen characteristics - wool production - efficiency - leucaena - leaves - straw
    Two successive experiments were conducted to investigate the long-term effects of supplementation of Sesbania sesban on reproductive performance of Ethiopian Menz sheep. Forty ewes and 40 rams ranging in weight and age between 16¿20 kg and 14¿15 months respectively were fed a teff straw basal diet and supplemented with two levels of Sesbania (0, and 95% of supplementary protein provided by Sesbania and the rest being provided by concentrates) for 7 months. In experiment 1 (mating period), 4 paired female¿male groups (diet of the male with or without Sesbania, and diet of the female with or without Sesbania) consisting of 20 animals each were formed and assigned for mating. Ewes that were mated and did not return to heat in subsequent cycles during the 70 days mating period continued in experiment 2 receiving similar supplementary diets (concentrate alone or Sesbania) for the study of pregnancy and lambing. During the mating period, males and animals supplemented with Sesbania were superior (P <0.05) in daily feed nutrients intake, whereas daily body weight gain (ADG) was significantly different (P <0.05) between treatments but not between sex groups. During pregnancy a significant difference (P <0.05) was observed only in nitrogen intake, and ADG of ewes did not differ (P > 0.05) between treatments. Supplementation with Sesbania promoted an increase in testicular size by 13%. Except semen concentration, the other seminal characteristics were not significant (P <0.05) between treatments. The average oestrus cycle length was 19 ± 4.6 days. Mean progesterone profile for cycling ewes on the day of oestrus was 0.4 ± 0.04 and ranged between undetectable levels to 0.75 ng/ml followed by a rise starting on day 4 (1.7 ± 0.16 ng/ml) through day 7 (2.5 ± 0.29 ng/ml) and day 10 (3.6 ± 0.47 ng/ml) to a peak of 3.9 ± 0.45 ng/ml (plateau phase) on day 14. Supplementation with Sesbania improved the proportion of ewes conceived by 17% over supplementation with concentrates. The average birth weight of lambs, and post partum dam weight of ewes was 1.97 kg and 18.6 kg respectively and differed significantly (P <0.05) between treatments. We concluded that inclusion of Sesbania up to 30% in the diet of sheep as supplement before and during the period of mating and pregnancy improved testicular growth and semen quality in rams or reproductive performance of ewes without showing negative effects
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