Production performance of cows raised with different postweaning growth patterns.

Abstract

The period of heifer development is a relatively small fraction of a cow's life; however, her pattern of growth may have permanent effects on her productivity as a cow. We hypothesized that altering the growth pattern during the peri-pubertal period would increase life-time productivity across genetic types of Bos taurus cows. The objective was to determine the stayability, calf production, and weight of calf weaned across six calf crops. Heifers (n = 685) were placed on one of two developmental programs at 256 ± 1 d of age. Control heifers received a diet that provided 228 kcal ME·(body weight [BW], kg) -0.75 daily, and stair-step heifers were allocated 157 kcal ME·(BW, kg)-0.75 daily for 84 or 85 d, and then the daily allocation was increased to 277 kcal ME·(BW, kg)-0.75. Stair-step heifers (0.33 ± 0.02 kg/d) had a lower average daily gain (ADG) than control heifers (0.78 ± 0.02 kg/d; P < 0.001) during Period 1, and stair-step heifers (0.93 ± 0.03 kg/d) had a greater ADG than controls (0.70 ± 0.03 kg/d; P < 0.001) during Period 2. There were no treatment (P = 0.28) or breed type differences (P = 0.42) for the proportion of cows weaning a calf; however, the proportion of cows weaning a calf decreased with cow age (P < 0.001). Calves from stair-step dams had heavier weaning weights (193 ± 1 kg) compared to control calves (191 ± 1 kg; P = 0.007). There was not a treatment (P = 0.25) or breed type differences in cumulative BW weaned (P = 0.59). A diverse genetic population of cattle within B. taurus was tested and responses in calf production did not differ between stair-step growth pattern and a more constant nonobese growth pattern.