Performance of and Digestion in Calves fed Conventional, Moderate, and Aggressive Milk Replacer Programs

Abstract Text: Calves fed large amounts of milk replacer (MR) gain more BW pre-weaning than calves fed less MR; however, post-weaning growth may be reduced.  Limited research suggests that impaired nutrient digestion may depress growth post-weaning.  We compared growth and post-weaning digestion in 3-d old male Holstein calves fed 1 of 3 MR programs.  Programs were Conventional (C, 0.45 kg/d of powder containing 21% CP, 21% fat (DM basis), fed for 42 d), Moderate (M, 0.68 kg/d of powder containing 27% CP, 17% fat (DM basis), fed for 42 d), and Aggressive (A, up to 0.91 kg/d of powder containing 27% CP, 17% fat, fed for 49 d).  All calves were fed a 20% CP (DM basis) textured starter and water ad libitum for 56 d.  The trial used 96 calves (initial BW = 41.4 ± 1.86 kg) received 5 wk apart in 2 replicates of 48 calves.  During d 51 to 55, fecal samples were collected from 5 calves per treatment randomly selected from calves in the first replicate.  Selected nutrients and acid insoluble ash (used as an internal marker) were analyzed in starter and feces to estimate nutrient digestibility.  Data were analyzed as a randomized complete block design with replicate as block.  Repeated measures analysis was performed on overall (0 to 56 d) data.  Means were separated with a protected LSD test.  Pen was the experimental unit.  Calves fed C had lower (P < 0.05) average daily BW gain (0.35, 0.51, and 0.55 kg/day, respectively, for C, M, and A; SEM = 0.018), gain/feed (0.35, 0.49, and 0.48; SEM = 0.016), and change in hip width (3.3, 4.1, and 4.1 cm; SEM = 0.20) compared to other calves.  Calves fed A had greater (P < 0.05) change in body condition score and lower (P < 0.05) starter intake compared to other calves.  Digestibility of OM was 79, 78, and 68% and NDF digestibility was 54, 51, and 26% for calves fed C, M, and A, respectively, and were lower (P < 0.05) in calves fed A.  Results are similar to previous published results in calves and suggest that depressed post-weaning digestion may be related to reduced starter intake and impaired rumen development.

Keywords: Calves, Milk Replacer, Digestion