Effect of timing of feeding a high-concentrate diet on growth and attainment of puberty in early-weaned heifers

Precocious puberty ( HC; CH > CC). Body weights in HC and CH treatments differed from a mean age of 169 through 238 d, after which BW did not differ between these treatments. The ADG over the entire experimental period was greatest for the HH treatment (1.2 ± 0.04 kg/d; P < 0.05), followed by the HC and CH treatments (1.0 ± 0.03 and 1.0 ± 0.02 kg/d, respectively), which were not different, and the CC treatment gained the least (0.7 ± 0.04 kg/d; P < 0.05). Precocious puberty occurred in 67, 47, 47, and 20% of heifers in the HH, HC, CH, and CC treatments, respectively (HH > CC; P < 0.05). Mean age at puberty for the HH and HC treatments (271 ± 17 and 283 ± 17 d of age, respectively) was earlier (P < 0.05) than for the CC treatment (331 ± 11 d of age). Age at puberty in the CH treatment (304 ± 13 d of age) was intermediate to and not different from the other treatments. Heifers fed the H diet during phase 1 attained puberty earlier (P < 0.05) than heifers fed the C diet during phase 1. In conclusion, increasing dietary energy intake in early-weaned heifers, through feeding a high-concentrate diet from 126 to 196 d of age, decreased age at puberty regardless of the diet fed after 196 d of age.