Effect of Compensatory Growth on Puberty of Nellore Heifers

The objective in this study was to determine the effect of growth rates and compensatory growth on age and BW at puberty of heifers. One hundred and twenty Nellore (Bos indicus) heifers, weaned at 8 ± 0.75 mo of age, born from 6 bulls (block effect), were assigned to 40 feedlot pens according to initial BW (180 ± 8.6 kg) to receive one of 4 treatments: 1) HG: high gain - heifers submitted to high ADG, ad libitum DMI; 2) MG: medium ADG (0.6 kg); 3) RG: restricted gain - feed restriction for 4 mo (0.2 kg), followed by ad libitum DMI with compensatory growth; 4) AG: alternate gain - ad libitum DMI for 2 mo, alternated with 2 mo of feed restriction (ADG = 0.2 kg) during 10 mo. The experimental period lasted 10 mo. All heifers received the same diet composed of ground corn (70%), sugarcane bagasse (12%), soybean meal (16%), mineral mixture (1%) and urea (1%). The lower gain was attained by restriction of DMI. Transrectal ultrasonography and progesterone concentration was assessed weekly to determine puberty onset. At 18 mo of age, heifers that did not reach puberty were submitted to a puberty induction with a progesterone inset by 9 d. The continuous variables were analyzed by the MIXED procedure and the binomial variables evaluated by GLIMMIX procedure (SAS 9.3). There was no effect of treatments in the percentage of pubertal heifers at 18 mo of age (HG: 66, MG: 40, RG: 69 and AG: 51%, P = 0.17), BW (HG: 351, MG: 339, RG: 339, AG: 337 ± 15 kg; P = 0.74) and age at puberty (HG: 17.4, MG: 18.2, RG: 18.7, AG: 18.1 ± 0.35 mo; P = 0.15). However, the ADG during the total experimental period (0.771^a, 0.607^c, 0.630^c, 0.688^b ± 0.05 kg; P<0.01) and ADG until the puberty (0.836^a, 0.725^b, 0.667^b, 0.727^b ± 0.04 kg; P<0.01) was greater in heifers submitted to HG compared to heifers from the other treatments. Moreover, heifers submitted to HG had greater (P<0.01) DMI than the RG (HG: 5.9^a, MG: 4.7^c, RG: 4.6^c, AG: 5.4^b ± 0.12 kg/d). About 80% of the heifers responded to induction, and there was no difference (P = 0.90) among treatments. Compensatory growth was an efficient nutritional strategy to reduce DMI, and did not affect puberty in Nellore heifers until 18 mo of age.