Abstract #T141

# T141
Effects of feeding different amounts of milk replacer on nutrient digestibility in Holstein calves to 2 months of age using different weaning transition strategies.
R. N. Klopp*1, T. M. Hill2, F. X. Suarez-Mena2, R. L. Schlotterbeck2, G. J. Lascano1, 1Clemson University, Clemson, SC, 2Nurture Research Center, Provimi, Brookville, OH.

Growth and the digestibility of nutrients can be greatly affected by diet pre-weaning and the rate at which calves are weaned. A 2x2 factorial design (moderate (MOD) or high (HI) milk replacer (MR) feeding rates and abrupt (AB) or gradual (GR) weaning) was utilized to compare how nutrient digestibility pre-weaning is affected. Calves (n = 50) were randomly assigned to one of 4 treatments (13 for MOD-AB and MOD-GR, 12 for HI-AB and HI-GR). Data were analyzed as a completely randomized design with repeated measures when applicable by PROC MIXED in SAS. Calves assigned to MOD-AB were fed 0.66 kg (DM basis) MR for first 42 d then 0.33 kg for last 7 d, MOD-GR were fed 0.66 kg MR for 28 d, 0.33 kg for 14 d, and 0.17 kg for the last 7 d, HI-AB were fed 0.66 kg MR for 7 d, 0.82 kg for 7 d, 1.1 kg for 28 d, and 0.66 kg for the last 7 d, HI-GR were fed 0.66 kg MR for 7 d, 0.82 kg for 7 d, 1.1 kg for 14 d, 0.66 kg for 14 d, and 0.33 kg for the last 7 d. All calves received the same MR (25% CP, 17% fat DM basis) and were given ad libitum access to water and a textured starter (42% starch and 20% CP). On d 26–30 and d 45–49, a fecal sample was taken from 5 calves in each treatment via the rectum to estimate apparent digestibility coefficients (dC). Apparent dC of DM (P = 0.01), OM (P = 0.01), and fat (P = 0.04) were greater for HI vs. MOD calves. Apparent dC of NDF (P < 0.01), ADF (P < 0.01), and sugar (P = 0.02) were greater for MOD vs. HI. Apparent dC of DM (90.9, 89.0 ± 0.5384; P = 0.05) was greater for AB vs. GR and the apparent dC of ADF (39.5, 32.3 ± 1.67; P = 0.01) was greater for GR vs. AB. There were no significant differences between CP or starch dC based on treatment and no interactions were observed. Starter intake was greater for MOD calves compared with HI (P < 0.01) and GR consumed more than AB (P < 0.01). These results suggest that calves receiving HI MR pre-weaning digest readily available nutrients more efficiently but MOD MR results in increased fibrous fractions dC. Accordingly, AB weaning strategy had higher dC for DM and OM but there was a depression in fiber dC.

Key Words: calves, digestibility, weaning