Abstract #T200

# T200
Effects of milk replacer feeding rate and age at weaning on calf performance and digestion through 8 weeks of age.
T. S. Dennis*1, F. X. Suarez-Mena1, T. M. Hill1, J. D. Quigley1, W. Hu1, R. L. Schlotterbeck1, 1Nurture Research Center, Provimi North America, Brookville, OH.

The objectives of this study were to evaluate calf performance and diet digestibility over time of calves fed moderate (MOD) or high (HIGH) milk replacer (MR) feeding programs and weaned at 2 ages. Male Holstein calves (n = 96; 43 ± 1.2 kg of BW) were housed in individual pens in a naturally ventilated barn with no added heat for 56 d. Calves were fed a common MR (25% CP, 17% fat on DM basis) using 4 feeding programs. Program MOD6 was 0.66 kg/d MR weaned from d 39 to 42, HIGH6 was up to 1.09 kg/d MR weaned from d 35 to 42, HIGH8 was up to 1.09 kg/d MR weaned from d 46 to 53, and GRAD8 was up to 1.09 kg/d and gradually weaned from d 35 to 53. All calves were fed a textured starter with 20% CP and 37% starch on DM basis. Fecal scores and medical treatments were recorded daily. Calves were weighed initially and weekly thereafter. Hip width and body condition score (BCS) were measured initially and every 2 wk thereafter. Fecal samples were collected between d 31–35, 45–49 (MOD6 and HIGH6 only), and 56–60 from 5 calves/treatment to estimate digestion coefficients (dC). Data were analyzed as a randomized complete block design with repeated measures. Pre-planned contrasts of MOD6 vs. others, HIGH6 vs. HIGH8, and HIGH8 vs. STEP8 were used to separate the means. Calves fed MOD6 tended to be 3.4 kg lighter at 56 d (P = 0.08) than calves fed other treatments. Starter intake was significantly greater for MOD6 compared with other treatments (P < 0.01), averaging 0.78 kg/d compared with 0.43 kg/d from 0 to 56 d. Feed efficiency (gain/feed) was greatest for calves fed GRAD8 (P = 0.01). Hip width, BCS, and fecal scores were similar among treatments. At d 35, dC of DM, OM, CP, and fat were least for calves fed MOD6 vs. HIGH6 (P ≤ 0.01). In contrast, dC of NDF and starch were greatest for MOD6 at d 35 (P ≤ 0.02). At d 49 and 60, dC of ADF and NDF were greater for MOD6 vs. other treatments (P ≤ 0.02). In this study, calves fed high MR rates gained more BW but not frame size over 56 d. Additionally, fiber digestibility was depressed around weaning for calves fed high MR rates and was not improved with gradual weaning.

Key Words: weaning age, feeding rate, digestion