Effects of Feeding Different Amounts of Milk Replacer on Growth Performance and Nutrient Digestibility in Holstein Calves to 4 Months of Age Using Different Weaning Strategies

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 calf performance and nutrient digestibility is affected pre and post-weaning. The 112 d study consisted of a 56 d nursery and a 56 d grower phase. Calves (n=50) were randomly assigned to one of four pre-weaning treatments. 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) MR for first 42 d then 0.33 kg for 7 d, MOD-GR were fed 0.66 kg MR for 28 d, 0.33 kg for 14 d, and 0.17 kg for 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 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 7 d. All calves received the same MR (25% CP, 17% fat) and were given ad libitum access to water and starter (42% starch and 20% CP) during the nursery phase. For the 56 d grower portion of the experiment, calves were grouped into 12 pens based on MR program, 4-5 calves per pen. All calves received ad libitum access to water and the same textured starter blended with 5% chopped grass hay. The results of the nursery phase indicated that HI MR promoted greater BW and FE, GR weaning lead to more starter consumption and lower HH, and HI MR digested readily available nutrients more efficiently but MOD MR resulted in increased fibrous fraction digestibility. The results of the grower phase indicated that HI calves lost their growth advantage over MOD calves after weaning, calves receiving MOD amounts of MR are more adapted to consuming complex nutrients, and GR weaning is beneficial during the weaning transition