Effects of Feeding Rate and Concentrations of Protein and Fat of Milk Replacers Fed to Neonatal Calves

Three trials were conducted to examine the effects of feeding rate and concentration of CP and fat in the milk replacer (MR) on calf performance. In all trials, Holstein bull calves (41 to 42 kg average initial BW; less than 7-d old) were randomly assigned to MR treatments and fed fixed amounts of MR with free-choice starter and water for 6 wk. Calves were fed starter and water after 6 wk. Calves were weighed initially and weekly. Starter intake was measured and fecal scores and medical treatments recorded daily. In all trials, a conventional 20% CP, 20% fat MR fed at 0.45 kg daily served as the control treatment. Trial 1 included CP concentrations ranging from 22 to 28% in MR fed at 0.68 kg daily. Trial 2 included fat concentrations from 11 to 17% in MR fed at 0.68 kg daily. Calves were weaned at 42 d and measurements were recorded through 56 d. In each trial, calves fed the control MR gained the slowest. When 0.68 kg daily of a 13% fat MR was fed with CP concentrations from 22 to 28%, BW gains increased linearly (optimum of 26%) and starter intake was no different from the control. When 0.68 kg daily of a 24% CP MR was fed with fat concentrations between 11 and 17%, BW gains increased linearly and starter intake was not different from the control. Trial 3 was conducted with MR of 26 and 28% CP and 17 and 20% fat fed at 0.68 or 0.77 kg daily. Calf BW gains did not differ among MR fed at 0.68 and 0.77 kg daily. Performance data from these trials indicate that a MR fed at 0.68 kg daily should contain approximately 26% CP and 17% fat, with no results suggesting that starter intake or efficiency would be reduced or scouring would be increased compared to a conventional 20% CP, 20% fat MR fed at 0.45 kg.