Timing of realimentation of mature cows that were feed-restricted during pregnancy influences calf birth weights and growth rates

The objective of this study was to determine the effect of feeding strategi es in cows that allowed BW loss followed by BW gain on the efficiency of fe ed utilization for calf production. The first treatment (H-H-H) was designe d to maintain body condition score of mature cows at 5.5 from the second tr imester until the subsequent breeding season. The second treatment (L-H-H) was designed such that cows lost body condition during the second trimester and regained it during the third trimester and were equal in weight and bo dy condition scores at parturition to cows assigned to the H-H-H treatment. The third treatment (L-L-H) was designed such that cows lost body conditio n during the second trimester and gained body condition after 28 d of lacta tion so that they would be equal to the other two treatments at breeding. F orty-eight cows were assigned to each treatment. Total DMI over the entire study did not differ between the H-H-H and L-H-H treatments (P = 0.23), but intake on both were higher than the L-L-H treatment (P < 0.001). Calf birt h weight of the H-H-H treatment did not differ (P = 0.43) from those of L-H -H, but both groups were greater than those of the L-L-H (P <less than or e qual to> 0.002) treatment. At 28 d of age, H-H-H (P = 0.008) and L-H-H (P = 0.007) calves weighed more than the L-L-H calves, but at 58 d of age there was no difference in calf BW among the treatments (P = 0.81). The percenta ge of cows that were diagnosed pregnant at weaning with their next calf did not differ (P = 0.71) among treatments. We interpret the results of this s tudy to suggest that weight cycling in mature beef cows may be a viable man agement tool for decreasing food costs.