Abstract #T142

# T142
Effects of feeding different amounts of milk replacer on nutrient digestibility in 2- to 4-month-old Holstein calves 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 2 × 2 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 post-weaning is affected by pre-weaning program. Fifty calves were randomly assigned to 1 of the 4 pre-weaning 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. For the 56 d grower portion of the trial, calves were grouped into 12 pens (n = 12) based on MR program, 4–5 calves per pen (3 pens/TRT). All calves received ad libitum access to water and a textured starter (42% starch and 20% CP) blended with 5% chopped grass hay. On d 66–70, d 87–91, and d 108–112, fecal samples were taken from the pen floor with care not to sample floor materials and composited by pen to estimate apparent digestibility coefficients (dC). Apparent dC of DM (P < 0.01), NDF (P = 0.01), and ADF (P < 0.01) were greater for MOD vs. HI. Apparent dC of DM (82.2, 81.3 ± 0.24; P = 0.01) and ADF (54.1, 50.5 ± 1.06; P = 0.02) were greater for GR vs. AB. There were no significant differences between OM, CP, fat, starch, or sugar dC based on treatment and no interactions were observed. Starter consumption was greater for MOD calves compared with HI calves (P < 0.01) and GR consumed more than AB (P < 0.01). These results suggest that calves receiving MOD amounts of MR pre-weaning are more adapted to consuming more complex nutrients and that a GR weaning is beneficial during transition.

Key Words: calves, digestibility, weaning