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Objectives: The objectives of this study were to investigate calf mortality rates, the average daily weight gain till weaning and factors associated with the risk of mortality and of poor growth in young dairy replacement heifers in Germany on a herd-level bases.
Materials and Methods: A case-control study was performed in 50 herds, which were selected based on acceptance to participate in the study and were located in northeast Germany. The experimental unit was the herd. Each herd was visited once between 2012 and 2014. A questionnaire on farm management practices, morbidity and calf mortality was completed by in-person interview. Furthermore colostral, blood und faecal samples were collected to check for colostral quality, failure of passive transfer
(FPT), nutritional status and faecal pathogens causing neonatal calf diarrhea. Heart girth measurements were conducted around weaning (12th week) to assume average daily weight gain (ADG). Additionally a score concerning calf welfare was determined. The epidemiological associations between these factors with calf mortality and with poor growth were estimated by using two logistic regression models. In the first step all candidate variables were screened in univariable analysis and those associated with the outcome variable at p≤0.20 (n=14/23) qualified for multivariable analysis, but just 7 candidate variables each were selected. The initial multivariable models were reduced using a manual stepwise backward procedure, with p<0.1 as criterion for retention. Variables excluded during the reduction were re-entered one by one after all remaining variables were significant (p<0.05). Results: The median calf mortality risk in calves 1–6 month of age was 5.0% (Range: 0.0–17.7%). The factors significantly associated with high calf mortality (>5.0%) were the application of Halofuginon (p<0.05, OR: 6.7) and the access to hay in the first week of life compared to those offered no hay before weaning (p<0.05, OR: 0.2). In the multivariable logistic regression model the factors application of Halofuginon (p<0.01, OR: 10.0) and a high rate of calves with FPT (p<0.05, OR: 8.1) explained 37.6% of the variation between herds with high and low calf mortality. On herd-level the median ADG in calves 3 month of age was 675 grams per day (Range: 414-1027 g). The risk factors significantly associated with poor growth were offering hay before weaning (p< 0.05, -142 g), collecting first colostrum later than two hours after parturition (p<0.05, -142 g), the amount of concentrates consumed at weaning (p<0.01, +130 g per kg concentrates), changing the bedding in the calf pen at least once every two weeks (p<0.05, -96 g), relocating calves more than twice from birth till weaning (p<0.01, -93g), feeding less than 3.0 liters of first colostrum (p<0.05, -88 g) and leaving the maternity pen more than two hours per day unattended (p<0.05, -84 g). In the multivariable logistic regression model the factors amount of concentrates consumed at weaning (p<0.001, +160 g per kg concentrates), relocating calves more than twice from birth till weaning (p<0.001, -119g) and having an incidence of milk fever under 5% (p<0.01, -115 g) explained 72.8% of the variation in growth of calves around weaning.
Conclusions: These results indicate that management practices in dairy farms rearing their own replacement heifers have an impact on calf mortality and on poor growth till weaning. They should be taken seriously concerning calf health and animal welfare.