What is an optimal body condition profile for reproduction in dairy cows?
Résumé
The relationships between body condition score (BCS) and reproductive performance of dairy cows exist. A BCS of 3.0 at calving and a maximum loss of 0.5 points at the beginning of lactation are recommended. However, individual profiles of BCS vary between cows. This work aimed to study the relationships between reproductive performance and different BCS profiles. Data from 6 French experimental farms with Holstein or Normande cows were used. Only lactations of cows inseminated at least once and with enough BCS records to estimate a BCS profile were used, i.e. 1,685 lactations of Holstein cows and 482 lactations of Normande cows. Artificial insemination (AI) and successive calving dates, total and maximum milk yield, average fat plus protein, and sanitary events related to reproduction (metritis, calving difficulty, etc.) were recorded. For 721 lactations, ovarian cyclicity status, determined using milk progesterone profile were available. BCS profiles were established by breed using a PCA on 9 variables: 5 BCS variables at fixed stages (calving, then 28 d, 56 d, 98 d, and 210 d postpartum) and 4 variables of BCS variation between these stages. Then, variance analyses were performed to identify differences between BCS profiles for reproductive performance. Total milk yield averaged 7,500 kg (±1,816 kg) and the total calving rate averaged 73% (from 55% to 88%). Four BCS profiles were identified in the Holstein breed and 3 in the Normande breed. In the Holstein breed, a ‘lean’ profile was identified with a total calving rate lower than for the other three profiles. In the Normande breed, a ‘fat’ profile was identified with a lower calving rate at first AI than the other two profiles. In conclusion, the profiles identified were consistent with the literature. Cows that were too thin or too fat were more likely to fail at breeding. However, the differences in calving rate at successive AI, days open, and ovarian cyclicity were small between BCS profiles and showed that reproductive failure is multifactorial and difficult to attribute solely to one BCS profile.
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