Inclusion of a spray-dried fat concentrate containing tributyrin and tricaproin in milk replacer enhanced increased feed intake, growth, and elicited metabolic and endocrine responses in ad libitum-fed calves.

Fat composition of milk replacer (MR) for calves differs from that of bovine milk fat, resulting in lower levels of butyric (C4:0) and caproic acid (C6:0). These fatty acids play a critical role in the gastrointestinal and metabolic development of calves by supporting rumen epithelial growth, enhancing energy metabolism, and promoting overall gut health. The objective of this study was to evaluate the effects of inclusion of a spray-dried fat concentrate containing tributyrin (TB) and tricaproin (TC) in a high-fat MR on growth, feed intake, and metabolic profiles of ad libitum-fed calves. Forty-eight newborn Holstein calves were blocked based on arrival sequence. Within each block of 2 calves, calves were randomly assigned to a control MR (CON, n = 24) including vegetable fats from palm, coconut, and linseed fats, or to an experimental MR including the same fat blend, to which TB and TC (TRI, n = 24) was added to the same levels found in milk fat. Both MR contained 23.7% crude protein, 27.7% fat, and 35.6% lactose (DM basis) and were fed at 13.5% solids. Calves were group housed and fed ad libitum MR with automated feeders. Weaning was gradual and induced between wk 7-10, after which calves were only fed solid feeds. Starter feed, chopped straw, and water were offered ad libitum throughout the whole study period. Calves were weighed and blood was collected once weekly at 1300h. Calves fed TRI showed a ∼50% reduction in therapeutic intervention days compared with CON. In addition, calves fed TRI consumed significantly more MR and starter feed, resulting in a greater growth. Serum NEFA and plasma total cholesterol were lower, whereas the enzymatic activity of serum ALP was higher in calves fed TRI than in CON. In addition, calves fed TRI had lower serum ghrelin and higher insulin-like growth factor-I concentrations. Incorporating TB and TC is a suitable strategy to increase solid feed intake upon weaning, resulting in better growth performance in ad libitum systems, and to improve health of dairy rearing calves.