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Effects of milk replacer feeding rate and frequency on basal metabolism and abomasal emptying of dairy calves during summer and winter.

R. M. Orellana Rivas

Abstract:

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Effects of milk replacer feeding rate and frequency on basal metabolism and abomasal emptying of dairy calves during summer and winter.
R. M. Orellana Rivas*, T. Rodrigues, J. Silveira, V. Lacerda, J. Gao, D. Ferreira de Ara�jo, J. Souza, T. N. Marins, J. K. Bernard, S. Tao. University of Georgia Tifton, GA.

To examine the effect of milk replacer (MR) feeding rate (FR) and frequency (FF) on abomasal emptying and metabolism, Holstein calves (n = 48/season) were enrolled at 7 d of age during summer (June to Aug, BW = 40.64 � 0.65) and winter (Nov to Jan, BW = 41.86 � 0.75). Within season, calves were randomly assigned to 1 of 4 treatments in a 2 � 2 factorial arrangement including 2 FR (0.68 [LOW] or 0.79 kg of solid/d [HIGH] of a 26% CP and 17% fat MR), and 2 FF (2 � [0700 and 1600 h] or 3 � [0700, 1600 and 2200 h] daily). Calves were managed similarly and housed in polyethylene hutches using sand bedding. Milk replacer (12.5%) was fed until d 42 when FR was reduced by 50% and fed 1 � /d (0700 h) for 7 d. The ambient temperature averaged 23.3 � 2.4�C for summer and 10.5 � 5.5�C for winter. Plasma was collected weekly at 1400 h to analyze metabolites and insulin. Acetaminophen (ACE, 50 mg/kg of BW) mixed with MR were fed to a subset of calves (0700 h, n = 10/treatment/season) on d 21. Plasma was collected at −15, 15, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 420, and 480 min relative to feeding to analyze ACE. The time for plasma ACE to reach maximum (Tmax) was used to evaluate the abomasum emptying rate. Data were analyzed using the mixed procedure of SAS. During summer, feeding HIGH increased plasma glucose and decreased β-hydroxybutyrate (BHB) compared with LOW (P ≤ 0.03), and feeding 3 � decreased plasma insulin but increased BHB compared with 2 � (P ≤ 0.02). In the winter, feeding HIGH increased plasma glucose concentration compared with LOW (P = 0.04) and feeding 3 � reduced plasma insulin and nonesterified fatty acids concentrations (P ≤ 0.01) relative to 2 � . Tmax of calves fed 2 � was longer (P < 0.01) than 3 � during summer (233 vs.172 min) and winter (252 vs. 188 min). In conclusion, increasing FF accelerated abomasal emptying and reduced insulin release in both seasons, but FF affected basal metabolites inconsistently between seasons. Feeding higher amounts of MR consistently increased plasma glucose but only decreased BHB during summer.

Keywords: calf, metabolites, season.