Utilization of Supplemental Triglycerides or Free Fatty Acids by Calves from 4 to 10 Weeks of Age

Our objectives were 1) to determine the effects of increased availability of 2-monoglycerides from triglyceride digestion on absorption of free fatty acids (FFA) and utilization of nutrients by calves of weaning age and 2) to determine whether absorption of FFA increased with age. Thirty-two male Holstein calves were fed milk replacer until d 28 of age and then were assigned to one of four treatments: 1) control, 80 g/d of whey protein concentrate in 2 L of water; 2) control plus 120 g/d of lard triglycerides; 3) control plus 90 g/d of lard triglycerides plus 30 g/d of lard FFA (low FFA); and 4) control plus 60 g/d of triglycerides plus 60 g/d of lard FFA (high FFA). Treatments were fed by nipple pail twice daily to maintain closure of the esophageal groove. Intake of calf starter (available continuously) was decreased by supplemental fats and tended to be lower for calves fed high FFA than for those fed low FFA. Digestibilities of total C₁₈ fatty acids and total fatty acids were lower for calves fed triglycerides than for calves fed FFA, but digestibilities were not affected by age. Energy digestibility was greater for fat treatments than for controls and was greater for FFA treatments than for triglycerides, but intakes of digestible energy and metabolizable energy did not differ. Absorbed N was greater for calves on the control treatment than for those on the fat treatments, but retained N and average daily gain did not differ. Digestibility of fatty acids was greater for calves fed mixtures of triglycerides and FFA than for those fed triglycerides alone, but digestibility did not change during wk 6 to 10 of age.