Paweł Górka, Waldemar Budziński
Both whey and skim milk are considered valuable sources of protein in calf milk replacer (MR). However, it is still unclear which source is more beneficial for performance of calves. This study evaluated the effects of whey-based MR and MRs containing 25% or 50% inclusion of skim milk on the growth performance of dairy calves. Ninety Holstein calves (10 d old; 57 females and 33 males; 44.9 ± 4.9 kg) were semi-randomly assigned to one of 3 groups (n = 30/group): 0% skim milk in MR (on as-fed basis; G0), 25% skim milk in MR (G25), and 50% skim milk in MR (G50). Allocation was performed to maintain a balanced distribution of calf sex and calves born to primiparous and multiparous cows among groups. Milk replacers were formulated to contain a similar concentration of protein, fat, and essential amino acids. Calves were fed 7.5 L daily of MR (1200 g of MR powder) in 3 feedings (3 × 2.5 L) and starter ad libitum. Data were analyzed using mixed models, with treatment, calf sex, and dam parity included as fixed effects, and initial BW as a covariate for BW, ADG, starter intake, and feed efficiency. Results were expressed as adjusted least squares means. When justified, means between groups were separated using Tukey's test. Passive immunity and initial BW did not differ between groups. Cumulative MR and starter intake did not differ between groups. Final BW, ADG, and feed efficiency were higher in G25 compared with G50, but did not differ between G0 and G25 or G0 and G50. Fecal scores and health treatments did not differ between groups. In the current study, growth performance of calves fed whey-based MR did not differ from those fed MR containing skim milk powder. Overall, no statistical evidence of a difference was detected between G0 and the skim-milk-containing treatments under the conditions of this study. However, calves fed MR containing 50% skim milk had 8.5% lower ADG and 4% lower final BW than those fed MR containing 25% skim milk.