Short- and long-term effects of initial serum total protein, average starter feed intake during the last week of the preweaning period, and rearing body gain on primiparous dairy heifers' performance

The aim of this study was to evaluate the short- and long-term effects initial serum total protein (STP) concentration, average starter feed intake (SI) during last week preweaning period, daily gain (ADG) on growth, fertility, performance Holstein heifers their first lactation. Eighty-four female dairy calves were weaned at d 56 age then continued until end Growth performance, including body weight, ADG, withers height, its change analyzed monthly from 3 450 life, reproduction data in lactation primiparous over a 4-yr period (2015 2019) recorded. In 24 h received 4 L colostrum (<2 <12 after birth); 2 3: feedings/d transition milk; 49: 6 L/d milk replacer (150 g powder/L as-fed) feedings; 50 56: 1 feeding. fed pelleted 56, that 8 wk mo age, dry mixed ration with an 85:15 ratio weaning straw. From 7 calving, contained 16.9% ~14.0% crude protein, respectively, matter basis ~2.40 Mcal metabolizable energy/kg basis. results current showed STP concentration associated improved growth especially greater weight height. addition, increasing levels estrus, artificial insemination (AI) service, pregnancy, calving decreased by 16, 18, 25, 25 d, respectively. Initial positively correlated production increased yield energy-corrected about 1,558 kg 1,149 Calves higher had better which turn fertility parameters, accelerated estrus (by 17 d), reduced AI service 13 d). Preweaning ADG favorably heifers, faster occurrence reduction calving. Also, yield, milk, 4% fat-corrected 305 DIM 829, 754, 763 heifers. These indicate rearing particular attention should be paid SI increase