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.

Keywords: development; heifer; production.

Figure 1.

Breeding weight as cows age: treatment (T), P = 0.06; breed type (B), P = 0.03; age (A), P < 0.001; T × B, P = 0.81; T × A, P = 0.05; B × A, P < 0.001.

Figure 2.

Cumulative weaning weight weaned: treatment (T), P = 0.25; breed type (B), P = 0.59; age (A), P < 0.001; T × B, P = 0.98; T × A, P = 0.51; B × A, P = 0.98.

Figure 3.

Decay curves for the percent of original heifers present at each breeding. The probability (P < 0.01) is that treatment specific curves fit the data better than a pooled curve. Percent of cows present was a function of breeding age in years, f(breeding age) = 100e^{(k(breeding age – 1))}. Control ( – – –– –) k = −0.1291 ± 0.0062 and stair-step ( – – –– –) −0.1090 ± 0.0033.