Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Animal Science

Major Professor

Richard N. Heitmann

Committee Members

James W. Bailey, Gina M. Pighetti, Kelly R. Robbins, & John C. Waller


Dairy calf weaning is associated with increases in ketone levels that exceed measured rates of utilization in adults and present a potential energy loss that may be mitigated by ionophores. Therefore, effects of weaning and ionophore supplementation on nutrient metabolism and growth in dairy calves pre- and post-weaning were examined in two experiments. The first experiment consisted of 24 Jersey bulls calves blocked in groups of two according to birth date and weight and randomly assigned to receive either a commercial pelleted starter (CON), or the same diet containing lasalocid (TRT; 83 mg/kg DM) to examine effects of weaning transition on weight (BW), gain (ADG), and blood concentrations of glucose, acetoacetate (ACAC), B-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), volatile fatty acids (VFA), lactate, pyruvate, insulin, and glucagon over 16 wk. The second experiment assessed the effects of weaning and lasalocid supplemented starter (listed above) on BW, ADG, net portal-drained viscera, hepatic, and total splanchnic fluxes of the same metabolites listed above for Experiment 1, but were measured on d 35, 56, 84, and 112 in nineteen Jersey bull calves that were equipped with catheters in portal, hepatic, and mesenteric veins and artery at wk 3-4. In Experiments 1 and 2 all calves were fed milk replacer from d 3-34. On d 35, calves began receiving either CON or TRT calf starter ad libitum plus their milk replacer ration until weaning on d 49. From d49-112 calves received only CON or TRT ad libitum. Post-weaning intake, ADG, and feed: gain did not differ between CON and TRT in either Experiment 1 and 2. Total VFA and ketones significantly increased and NEFA and glucose significantly decreased following introduction of solid feed in both experiments. Both experiments demonstrated significant effects of ionophore supplementation on ACAC, BHBA, and VFA during the early post-weaning period. In both experiments significant changes in metabolic profile of transition calves were demonstrated peri-wearning and ionophore appears to moderate alimentary output at a post-weaning period where ketone concentrations have potential to exceed whole animal capacity for utilization.

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