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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    Effects of a single glucocorticoid injection on propylene glycol-treated cows with clinical ketosis
    Drift, S.G.A. van der; Houweling, M. ; Bouman, Marina ; Koets, A.P. ; Tielens, A.G.M. ; Nielen, M. ; Jorritsma, R. - \ 2015
    The Veterinary Journal 204 (2015)2. - ISSN 1090-0233 - p. 144 - 149.
    This study investigated the metabolic effects of glucocorticoids when administered to propylene glycol-treated cows with clinical ketosis. Clinical ketosis was defined by depressed feed intake and milk production, and a maximal score for acetoacetate in urine. All cows received 250 mL oral propylene glycol twice daily for 3 days and were randomly assigned to a single intramuscular injection with sterile isotonic saline solution (n = 14) or dexamethasone-21-isonicotinate (n = 17). Metabolic blood variables were monitored for 6 days and adipose tissue variables for 3 days. β-Hydroxybutyrate (BHBA) concentrations in blood decreased in all cows during treatment, but were lower in glucocorticoid-treated cows. Cows treated with glucocorticoids had higher plasma glucose and insulin concentrations, whereas concentrations of non-esterified fatty acids, 3-methylhistidine and growth hormone were unaffected. mRNA expression of hormone-sensitive lipase, BHBA receptor and peroxisome proliferator-activated receptor type γ in adipose tissue was not affected. This shows that lipolytic effects do not appear to be important in ketotic cows when glucocorticoids are combined with PG. Plasma 3-methyl histidine concentrations were similar in both groups, suggesting that glucocorticoids did not increase muscle breakdown and that the greater rise in plasma glucose in glucocorticoid-treated cows may not be due to increased supply of glucogenic amino acids from muscle.
    Real time operational support in young stock rearing
    Ipema, A.H. ; Mol, R.M. de; Hogewerf, P.H. ; Prins, Bram ; Sijbrandij, Fedde ; Winden, R.P.J. ; Hanenberg, M.J.A. ; Jorritsma, R. - \ 2015
    In: Precision Livestock Farming 2015 - Papers Presented at the 7th European Conference on Precision Livestock Farming, ECPLF 2015. - Milan : Precision Livestock Farming '15 - ISBN 9788890975325 - p. 301 - 308.
    The aim of the Dutch Smart Dairy Farming project is to develop decision support models for operational support in farm management. This project started in 2012 and involves collaboration between several institutions and companies in the dairy chain. The project has three focus areas: animal health, fertility and feeding. The objective of the 'animal health' focus area is to optimise young stock rearing as a basis for extending the life of cows. Lowering the annual replacement rate, which is currently about 30%, has a significant positive impact on financial results. The main objectives of this young stock rearing project were to develop state-of-the-art tools which would help the farmer to optimise growth and development of young stock. Milk feeders and water drinkers combined with weighing scales were used for data collection at individual calf level. Daily data about milk intake, milk feeder visits, water intake and body weight were used to build detection models that generate alerts when measured values deviate and indicate a possible health problem. Body weight measurements were also used to determine the growth rate of a calf and to produce an alert if this deviated too much from a desired growth rate. All alerts were translated into messages with work instructions for the farmer. Weekly feedback from the farmer indicated that almost 60% of the messages were correct. It is suggested that the large number of wrong messages (false positives) can be reduced by applying more advanced analysis techniques.
    Application of multivariate analysis of sensor data for the detection of metabolic disorders in dairy cows
    Mol, R.M. de; Troost, Mirjam ; Sterk, A. ; Winden, R. van; Jorritsma, R. ; Sijbrandij, F.D. ; Hennes, N. ; Lankhorst, E.J. ; Hogewerf, P.H. - \ 2015
    In: Precision Livestock Farming 2015 - Papers Presented at the 7th European Conference on Precision Livestock Farming, ECPLF 2015. - Milan : Precision Livestock Farming '15 - ISBN 9788890975325 - p. 341 - 350.
    Early detection of metobolic disorders in dairy cows by using sensor data
    Mol, R.M. de; Dijk, J. ; Troost, M.H. ; Jorritsma, R. ; Hogewerf, P.H. - \ 2014
    In: Book of abstracts of the 65th Annual Meeting of the European Federation of Animal Science. - Wageningen : - ISBN 9789086862481 - p. 159 - 159.
    An exploratory study of the relation of pH data from pens boluses with othe sensor data
    Mol, R.M. de; Roosmalen, Y.A.H.M. ; Troost, M.H. ; Sterk, A. ; Jorritsma, R. ; Hogewerf, P.H. - \ 2014
    In: Book of abstracts 65th Annual Meeting of the European Federation of Animal Science. - Wageningen : Wageningen Academic Publishers - ISBN 9789086862481 - p. 107 - 107.
    In the Dutch Smart Dairy Farming project, automated measurements of the pH in the rumen of dairy cows were used to analyze processes during the transition period. The pH data can be used to monitor the developments during the end of the dry period and the start of the lactation. If these pH values are related with other sensor data (like activity and feed intake), then monitoring these other data might results in possibilities to detect metabolic problems. On two practical dairy farms (farm 1: 300 cows, automatic milking system; farm 2: conventional milking, 110 cows), in total 70 cows were fitted with Smaxtec pH bolus a few weeks before calving. Valid measurements were available per bolus over two months. Other sensors were used to measure milk yield, activity, rumination, concentrates intake, visits to concentrate feeder (and milk robot on farm 1) and body weight. This resulted in a data set to be used to explore the relation between pH value and other traits. The first results show: (1) no clear relation between pH and concentrates intake; (2) great fluctuations in pH on the day of calving (caused by changes in feeding?); (3) that an increase in rumination might be correlated with a decrease in pH The pH data were aggregated by logistic regression; making it possible to convert the pH data of one day in an average level and a slope describing the variance within a day. More results will be included in the presentation.
    Use and interpretation of mastitis alerts by farmers
    Hogeveen, H. ; Buma, K.J. ; Jorritsma, R. - \ 2013
    In: Proceedings of the 6th European Conference on Precision Livestock Farming. - - p. 313 - 319.
    Genetic and nongenetic variation in plasma and milk ß-hydroxybutyrate and milk acetone concentrations of early-lactation dairy cows
    Drift, S.G.A. van der; Hulzen, K.J.E. van; Teweldemedhn, T.G. ; Jorritsma, R. ; Nielen, M. ; Heuven, H.C.M. - \ 2012
    Journal of Dairy Science 95 (2012)11. - ISSN 0022-0302 - p. 6781 - 6787.
    holstein cows - subclinical ketosis - metabolic predictors - health disorders - energy-balance - body-weight - feed-intake - cattle - parameters - yield
    This study assessed genetic variation, heritability estimates, and genetic correlations for concentrations of plasma ß-hydroxybutyrate (BHBA), milk BHBA, and milk acetone in early lactation to investigate differences between cows in susceptibility to hyperketonemia and possibilities to use test-day milk ketone bodies for genetic improvement. Blood and test-day milk samples were collected on randomly selected dairy farms in the Netherlands from cows of various parities between 5 and 60 d in milk. Plasma samples were analyzed for BHBA (reference test for hyperketonemia) and test-day milk samples were analyzed for BHBA and acetone using Fourier-transform infrared spectroscopy. The final data set consisted of plasma BHBA concentrations of 1,615 cows from 122 herds. Milk BHBA and milk acetone concentrations were determined for 1,565 cows. Genetic variation, heritability, and proportion of phenotypic variation attributable to the herd were estimated using an animal model with fixed effects for parity and season, a covariate for days in milk, and random effects for herd, animal, and error. Genetic correlations for plasma BHBA, milk BHBA, and milk acetone were estimated using bivariate analyses. The heritability estimate for plasma BHBA concentrations in early lactation was 0.17, whereas heritability estimates for milk BHBA and milk acetone were 0.16 and 0.10, respectively. This indicates that selective breeding may contribute to a lower incidence of hyperketonemia in early lactation. For the 3 traits, the proportion of variance attributable to herd was larger than the additive genetic variance, underlining the importance of on-farm feeding and management in the etiology of hyperketonemia in fresh cows. Prevention strategies for hyperketonemia can, therefore, include both feeding and management strategies at dairy farms (short-term) and genetic improvement through breeding programs (long-term). Genetic correlations between concentrations of plasma BHBA and milk BHBA (0.52) or milk acetone (0.52) were moderate. As milk ketone bodies can be routinely analyzed at test days, this may provide a practical alternative for breeding programs aimed at reducing hyperketonemia in early lactation.
    Improved knowledge about Conception Rates Influences the Decision to Stop Insemination in Dairy Cows
    Inchaisri, C. ; Vries, A. de; Jorritsma, R. ; Hogeveen, Henk - \ 2012
    Reproduction in Domestic Animals 47 (2012)5. - ISSN 0936-6768 - p. 820 - 826.
    replacement policies - milk-production - economic value - cattle - yield - model - stage - 1st - pregnancy - fertility
    The conception rate in dairy cows is dependent on a number of cow factors such as days in milk and insemination number. Unfortunately, some of these factors were not accounted for in optimal insemination and replacement decision models. By using wrong estimates of the conception rate, the calculated optimal insemination and replacement policy might differ from the real optimal insemination and replacement policy. The objective of this study was to evaluate different sets of conception rates with an increasing level of accuracy to determine the insemination policy. An existing dynamic program for optimal insemination and replacement was used to compare three different scenarios in the estimation of conception rates, based on the reproductive performance of Dutch dairy cattle: (i) constant conception rate throughout lactation, (ii) conception rate dependent on parity and months in milk, and (iii) conception rate dependent on parity, months in milk and insemination number. The time step of the model was 30.4 days (1 month). The discounted future cash flow of culling a cow at each time step (replace a heifer immediately) was compared with keeping that cow under optimal future decisions. The difference between immediate culling and optimal decisions is defined as the retention pay-off. The insemination value was calculated as the difference between the future cash flow between immediate insemination of a cow and waiting one time-step. The results show that the difference in the insemination values and the optimal time to stop insemination depend on parity, lactation stage and the relative milk yield. In older cows with equal milk yields and at the same months in milk, the insemination value was lower than in younger cows. Within a parity, the insemination value was higher for cows with a higher milk yield. On individual cow level, using more accurate conception rate as input in the optimal insemination and replacement model might reduce miscalculation of the economic consequences for at least of €20–€38 per cow per year. Basing insemination decisions on less accurate input of the probabilities of conception, however, did not have an economic consequence at the herd level. In conclusion, using the appropriate conception rate as input in the optimal insemination and replacement model would increase the precise decision for the optimal time to stop insemination and hence improve the reproductive management efficacy.
    Analysis of the economically optimal voluntary waiting period
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2011
    Journal of Dairy Science 94 (2011)8. - ISSN 0022-0302 - p. 3811 - 3823.
    extended calving intervals - cystic ovarian disease - dairy-cattle - milk-yield - energy-balance - reproductive-performance - bovine somatotropin - body condition - cows - progesterone
    The voluntary waiting period (VWP) is defined as the time between parturition and the time at which the cow is first eligible for insemination. Determining the optimal VWP from field data is difficult and unlikely to happen. Therefore, a Monte-Carlo dynamic-stochastic simulation model was created to calculate the economic effects of different VWP. The model is dynamic and uses time steps of 1 wk to simulate the reproductive cycle (ovulation, estrous detection, and conception), the occurrence of postpartum disorders, and the lactation curve. Inputs of the model were chosen to reflect the situation of Dutch dairy cows. In the model, we initially created a cow of a randomly selected breed, parity, month of calving, calf status of last calving, and expected 305-d milk yield. The randomly varied variables were based upon relevant distributions and adjusted for cow statuses. The lactation curve was modeled by Wood's function. The economic input values in the analysis included: cost of milk production (€0.07 to €0.20 per kg), calf price (€35 to €150 per calf), AI cost (€7 to €24 per AI), calving management cost (€137 to €167 per calving), and culling cost, expressed as the retention pay-off (€118 to €1,117). A partial budget approach was used to calculate the economic effect of varying the VWP from 7 to 15 wk postpartum, using a VWP of 6 wk as reference. Per iteration, the VWP with either the lowest economic loss or the maximum profit was determined as the optimal VWP. The optimal VWP of most cows (90%) was less than 10 wk. On average, every VWP longer than 6 wk gave economic losses. Longer VWP were in particular optimal for the first parity of breeds other than Holstein-Friesian, cows calving in winter with low milk production, high milk persistency, delayed peak milk yield time, a delayed time of first ovulation, or occurrence of a postpartum disorder, and while costs of milk production are low and costs for AI are high
    Cow Effects and Estimation of Success of First and Following Inseminations in Dutch Dairy Cows
    Inchaisri, C. ; Jorritsma, R. ; Vernooij, J.C.M. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2011
    Reproduction in Domestic Animals 46 (2011)6. - ISSN 0936-6768 - p. 1043 - 1049.
    timed artificial-insemination - body condition score - milk-production - reproductive-performance - pregnancy risk - energy-balance - united-states - cattle - conception - lactation
    The objective of this research was to determine the contribution of cow factors to the probability of successful insemination accounting for the serial number of inseminations in analysis. The investigation was performed with 101 297 insemination records in 51 525 lactations of different cows from 1368 herds obtained from the Dutch milk production recording database. Cows that had a first insemination (AI) between 40 and 150 days post-partum with one or more inseminations (=6 inseminations) were selected. An insemination was defined successful when not followed by another insemination and when the cow calved between 267 and 295 days after insemination, or when the cow was culled between 135 and 295 days after the last insemination. Breed, parity, days in milk, lactation curve characteristics, milk production traits, moment of AI related to peak milk yield time (before or after peak milk yield), the last calf (female, male, twin or stillbirth) and season of insemination were selected as independent parameters for a model with successful rate of insemination as dependent parameter. A multivariable logistic regression model was used within cow and farm as a random effect. The probability of successful insemination was the highest in the first insemination and decreased in the following inseminations. However, the success rate of all inseminations increased in a later stage of lactation. The improvement in the successful inseminations in a later stage of lactation was better in multiparous cows than in first parity cows. Insemination in summer and before peak milk yield time reduced the success of insemination. The success rate was the lowest in 100% Holstein Friesian cows compared with other breeds and was the highest when the last calf was a female calf compared to a male calf, twin or stillbirth. In conclusion, the success of first and following inseminations depended on parity, breed, season of insemination, last calf status, daily milk yield at insemination date, serial insemination number and days in milk at insemination date
    Diurnal variation of glucose, non-esterified fatty acids and insulin in plasma after a restricted feeding challange in dairy cows in early lactation
    Jorritsma, R. ; Drift, S.G.A. van der; Roos, C.A.J. ; Knegsel, A.T.M. van - \ 2010
    The present study was performed at Utrecht University to investigate the effect of a restricted feeding challenge on the diurnal variation of glucose, non-esterified fatty acids (NEFA) and insulin concentrations in plasma of multiparous dairy cows in early lactation. Two different feeding regimes were applied, in which cows were either fed according to recommendations (n=6, CON) or ad libitum during the dry period, fasted for 8h directly after parturition and restrictedly fed for the next 5 days (n=10, RES). After this experimental period, all animals were fed the same TMR ad libitum twice a day. Blood was sampled hourly for 24 hours from all cows once in the follow-up period (between days 5 to 11 after calving). Plasma samples were analyzed for glucose, NEFA and insulin and data were analyzed using the mixed procedure (PROC MIXED, SAS 9.1) to study treatment and time effects and an Ftest to study within-day and within-cow variation. Values are presented as means ± SD. NEFA concentrations were higher in the 8 hours between feedings in both groups (p <0.05). Average diurnal NEFA concentrations were higher for RES cows (1.03 ± 0.45) than CON cows (0.49 ± 0.25) (p <0.01). In addition, the variation (SD) in the diurnal NEFA concentrations per individual cow (withincow variation) tended to be greater for RES cows (p = 0.07). Also, the range of plasma NEFA concentrations at each time point tended to be greater in RES cows (p = 0.06). Restricted feeding had no effect (p > 0.05) on average diurnal concentrations of glucose and insulin, which were similar for CON cows (2.72 ± 0.31 and 2.33 ± 1.45, respectively) and RES cows (2.48 ± 0.53 and 2.18 ± 2.09, respectively). Sampling day after calving had no effect on plasma metabolite concentrations (p > 0.05). The variation (SD) between cows in plasma glucose concentrations at each time point was greater for RES cows (p <0.01). In conclusion, cows that were restrictedly fed directly after calving had higher and more fluctuating diurnal NEFA concentrations than control cows, which implies that a suboptimal feed intake around parturition can have carry-over effects on metabolism of cows in early lactation.
    Economic consequences of reproductive performance in dairy cattle
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, B. v.d.; Hogeveen, H. - \ 2010
    IDF Animal Health Newsletter (2010)4. - p. 21 - 22.
    Determining the optimal voluntary waiting period in dairy cows
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2010
    In: Proceedings of the International Workshop Farm Animal Health Economics, Nantes, France, 14-15 January 2010. - 2010 : INRA - p. 78 - 79.
    Effect of milk yield characteristics, breed, and parity on success of the first insemination in Dutch dairy cows
    Inchaisri, C. ; Hogeveen, H. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Jorritsma, R. - \ 2010
    Journal of Dairy Science 93 (2010). - ISSN 0022-0302 - p. 5179 - 5187.
    body condition score - reproductive-performance - conception rates - genetic-relationships - energy-balance - united-states - new-york - holstein - cattle - fertility
    The objective of this study was to determine the contribution of cow factors to the probability of a successful first insemination (SFI). The investigation was performed with 51,791 lactations from 1,396 herds obtained from the Dutch dairy cow database of the Cattle Improvement Co-operative (CRV). Cows that had the first insemination (AI) between 40 and 150 d postpartum were selected. The first AI was classified as successful when cows were not reinseminated and either calved between 267 and 295 d later or were culled within 135 to 295 d after first AI. The lactation curve characteristics of individual lactations were estimated by Wilmink's curve using the test-day milk records from CRV. The lactation curve characteristics (peak milk yield, milk yield at the first-AI date, time of peak yield (PT), and milk persistency) were calculated. Breed, parity, interval from calving to first AI (CFI), lactation curve characteristics, milk production traits, moment of AI related to PT (before or after PT), calf status, month of AI, and month of calving were selected as independent variables for a model with SFI as a dependent variable. A multivariable logistic regression model was used with farm as a random effect. Overall SFI was 44%. The effect of parity on SFI depended on CFI. The first-parity cows had the greatest SFI (0.43) compared with other parities (0.32–0.39) at the same period of CFI before 60 d in milk (DIM), and cows in parity =5 had the least SFI (0.38–0.40) when AI was after 60 DIM. After 60 DIM, extending CFI did not improve SFI in the first-parity cows, but SFI was improved in multiparous cows. Holstein-Friesian cows had lesser SFI (0.37) compared with cross-breed cows (0.39–0.46). Twin and stillbirth calving reduced SFI (0.39) compared with a single female calf (0.45) or a male calf (0.43) calving. The SFI in different months of AI varied and depended on CFI. Cows that received AI before 60 DIM had a lesser SFI, especially in March, June, and July (0.18, 0.35, and 0.34, respectively). Artificial insemination before PT reduced SFI (0.39) in comparison with AI after PT (0.44). The effect of milk yield at the first-AI date on SFI varied depending on CFI. After 60 DIM at the same period of CFI, a high level of milk yield at the first-AI date reduced SFI. In conclusion, knowledge of the contribution of cow factors on SFI can be applied to support decision making on the moment of insemination of an individual cow in estrus. Key words: milk production; lactation curve; first insemination; successful calving
    Economic consequences of reproductive performance in dairy cattle
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2010
    Theriogenology 74 (2010). - ISSN 0093-691X - p. 835 - 846.
    timed artificial-insemination - cystic ovarian disease - milk-production - risk-factors - calving intervals - herd environment - conception rate - energy-balance - estrous cycles - body condition
    The net economic value of reproductive efficiency in dairy cattle was estimated using a stochastic dynamic simulation model. The objective was to compare the economic consequences of reproductive performance scenarios (“average” and “poor”) of a cow having a good reproductive performance and to explore which reproductive factors have an important impact on economic efficiency. A “good” reproductive performance scenario was defined with 1 ovulation rate (POVUi), 0.7 estrus detection rate (PEst), 0.7 conception rate (PCon), 0.03 incidence rate of postpartum disorders prolonging the ovarian cyclicity (CO), 0.2 incidence rate of postpartum disorders reducing conception (ME), 0.05 embryonic death rate (ED), and voluntary waiting period (VWP) of 9 wks pp (post partum). In the current situation of dairy cows in the Netherlands, an “average” reproductive scenario (0.95 POVUi, 0.5 PEst, 0.5 Pcon, 0.07 CO, 0.27 ME, 0.07 ED and VWP of 12 wks pp) and a “poor” reproductive scenario (0.90 POVUi, 0.3 PEst, 0.3 Pcon, 0.11 CO, 0.33 ME, 0.09 ED and VWP of 15 wks pp) were identified. A sensitivity analysis was performed by comparing changes of single effect of factors in a good and poor scenario with the average scenario. The mean net economic loss (NELi) compared with the good scenario was €34 and €231 per cow per year for the average and poor reproductive performance scenario, respectively. Increasing the calving interval resulted in greater economic loss. The important factors on the cost of reproductive efficiency were the involuntary culling cost and the return of milk production. Variation in PCon, PEst, ME, ED, and VWP had large impacts on economic benefits. Keywords: Dairy cow; Reproductive performance; Simulation model; Economics
    Effects of vitamin E supplementation on and the association of body condition score with changes in peroxidative biomarkers and antioxidants around calving in dairy heifers
    Dobbelaar, P. ; Bouwstra, R.J. ; Goselink, R.M.A. ; Jorritsma, R. ; Borne, J.J.G.C. van den; Jansen, E.H.J.M. - \ 2010
    Journal of Dairy Science 93 (2010)7. - ISSN 0022-0302 - p. 3103 - 3113.
    oxidative stress - periparturient period - in-vitro - superoxide-dismutase - metabolic syndrome - follicular-fluid - immune function - oxidant stress - fatty-acids - milk-yield
    The objective of this study was to investigate the effect of vitamin E supplementation on oxidative status in blood, liver, milk, and ovarian follicular fluid in periparturient heifers. Vitamin E supplementation started 8 wk before calving and continued until 8 wk postpartum. Grass silage was the main forage fed during the experiment. In addition, supplemented heifers (n = 9) received 3,000 IU of vitamin E daily on a carrier food; control heifers (n = 9) consumed only the carrier food. Blood samples and liver biopsies were taken frequently throughout the study and ovarian follicular fluid was sampled at 8 wk postpartum. Body condition score was scored weekly and milk yield was measured daily. A marker of oxidative damage, determinable reactive oxygen metabolites (d-ROM), and a set of antioxidants were measured in blood, liver, milk, and ovarian follicular fluid. Control heifers had a low vitamin E status, and selenium status was marginal in control and supplemented heifers. Vitamin E supplementation increased vitamin E concentrations in blood, liver, and ovarian follicular fluid and increased triacylglycerol in liver. Serum d-ROM were not reduced by vitamin E supplementation. Superoxide dismutase and glutathione peroxidase activity in red blood cells and liver and glutathione peroxidase activity in ovarian follicular fluid were not affected by vitamin E supplementation and they were not increased around calving. Protein thiol groups and ratio of reduced glutathione to oxidized glutathione were also not increased around calving. These results suggest that heifers around calving experience a low level of oxidative processes. This might be caused by lower than expected milk production attributed to a low forage intake. Serum d-ROM were negatively correlated with protein thiol groups and positively correlated with the activity of glutathione peroxidase in red blood cells, oxidized glutathione, and the ratio of reduced glutathione and oxidized glutathione in serum. The lack of treatment effects allowed estimation of the effects of body condition 4 wk before calving and the loss of body condition on markers of lipid peroxidation and antioxidants. A trend that a body condition of =3 might result in more oxidative damage measured by serum d-ROM was observed, but fatter heifers had a significantly higher ratio of reduced glutathione to oxidized glutathione
    The stochastic modeling to estimate the economic consequences of reproductive performance in dairy cattle
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2009
    The optimal voluntary waiting period for insemination of postpartum dairy cows under varying circumstances
    Inchaisri, C. ; Jorritsma, R. ; Vos, P.L.A.M. ; Weijden, G.C. van der; Hogeveen, H. - \ 2009
    In: Proceedings of the Annual meeting of the Dutch Society for Veterinary :Epidemiology and Economics. - - p. 24 - 26.
    Veterinary advice for entrepreneurial Dutch dairy farmers : From curative practice to coach-consultant: what needs to be changed?
    Noordhuizen, J.P.T.M. ; Egmond, M.J. van; Jorritsma, R. ; Hogeveen, H. ; Lievaart, J.J. - \ 2008
    Tijdschrift voor Diergeneeskunde 133 (2008)1. - ISSN 0040-7453 - p. 4 - 8.
    specialisatie - consulenten - melkveehouderij - bedrijfsgrootte in de landbouw - grote landbouwbedrijven - veterinaire praktijk - veterinaire opleidingen - beroepsvaardigheden - specialization - consultants - dairy farming - farm size - large farms - veterinary practice - veterinary schools - job skills
    Dairy farms are tending to become larger, with a milk quota of more than 8 tons a year, and are managed by entrepreneurial dairy farmers with their own specific characteristics and farming style. Some Dutch veterinary practices appear unable to respond to this different style and often do not serve such farms or lose them as client. Moreover, the veterinary curriculum often focuses on traditional, family-run, smaller dairy operations and not on larger farms, which raises the question whether newly qualified veterinary practitioners are adequately trained to provide these entrepreneurial farmers with the services they require. This article addresses the characteristics of entrepreneurial dairy farmers and those of cattle practitioners, to determine whether cattle practitioners need to acquire other skills to better prepare them for their coaching-consultant tasks on larger dairy farms.
    Milk yield and survival of Holstein-Friesian dairy cattle after laparoscopic correction of left-displaced abomasum
    Jorritsma, R. ; Westerlaan, B. ; Bierma, M.P.R. ; Frankena, K. - \ 2008
    Veterinary Record 162 (2008)23. - ISSN 0042-4900 - p. 743 - 746.
    risk-factors - cows
    The milk yield and survival of 91 Holstein-Friesian dairy cows that had had a left-displaced abomasum (LDA) corrected laparoscopically were compared with those of 193 control cows matched for herd, parity and calving date. Ninety per cent of the LDA treatments were performed within four weeks after calving. The risk of being culled during the whole observational period of at least three years was 1-5 times greater for the LOA cows than for their matched herdmates (P
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