Abstract

The effects of different fat inclusion methods in starter feed on performance, growth, health indices, digestibility, and blood metabolites were evaluated in Holstein dairy calves. Forty-four 3-day-old Holstein dairy calves (averaging 39 kg BW) were allocated to treatments in a completely randomized block design (11 calves per treatment; 6 females and 5 males) as follows: (1) no fat or oil supplementation to starter feed (CTR); (2) dietary starter mixed with soy oil (DMSO); (3) fat included in the form of extruded soybean seed (ESBS); and (4) fat included in the form of roasted soybean seed (RSBS). The experimental starter diets were maintained with iso-energetic, iso-nitrogenous, and ruminal iso-degradable proteins. Dietary fat content was constant in fat supplemented treatments. All calves were weaned on d 59 of age and maintained in the study until d 73 for final data records. There was no difference in starter intake among experimental treatments until d 47; however, it was reduced in the transition period as well as in the post-weaning period in fat supplemented diets compared with the CTR treatment. No changes were found for BW among treatments in either the pre- or post-weaning period. Feed efficiency was relatively constant among treatments. Regardless of the dietary fat inclusion method, wither height was lower in all calves fed a diet supplemented with fat compared with the CTR treatment (p = 0.04). The fat-supplemented calves tended to have higher fecal score than the un-supplemented ones (p = 0.08) and showed lower fecal consistency in these treatments. Blood albumin was greatest (p = 0.04) and blood cholesterol was lowest (p = 0.05) in the CTR treatment compared to the supplemented treatments. No differences were observed for other blood metabolites, liver enzymes, or insulin concentrations among treatments. Under the conditions of this experiment, it could be concluded that fat supplementation in the form of processed oilseeds rather than direct mixing of oil with the starter diet resulted in better fecal scores and fiber digestibility in dairy calves; however, fat inclusion per se is not advisable in the starter diet of dairy calves.