| Body condition score at
calving is the single most important trait determining when a cow resumes
heat cycles and therefore when she is likely to re-conceive for the next
calf crop. However, it is also very important to avoid condition
loss between calving and the breeding season to maintain excellent rebreeding
performance.
Fig. 1. Winter weight and body condition change and rebreeding percentage
for cows allowed to maintain or lose condition after calving (Wettemann,
et al. , 1987 JAS, Suppl. 1:63).
A two-year Oklahoma State University study (Figure 1) shows the impact
of losing body condition in the period from calving to the start of the
breeding season. Seventy-five cows in year 1 and seventy cows in
year two were randomly alloted to receive either 2 pounds (LOSE) of cottonseed
meal from calving (beginning February 11) until mid April or 5 pounds (MAINTAIN)
of cottonseed meal daily. All cows had free choice access to grass
hay during February and March. Cows were exposed to fertile bulls
for 90 days each year starting May 1. Pregnancy rate was determined
at 70 days after the breeding season. Cows that were fed to maintain
body condition from calving until the beginning of the breeding season
averaged 94% pregnant, while those that calved in similar body condition
but lost nearly a full condition score were 73% rebred. The body
condition that was maintained throughout the winter until calving time
must be maintained until rebreeding to accomplish high rebreeding rates.
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