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Abstract

ABSTRACT


The objective of the study was to determine if pharmacological supplies of nicotinic acid could reduce lipolysis in cattle. Six ruminally cannulated steers 225 kg were used. In an initial study, steers received abomasal infusion of nicotinic acid at 0, 8, or 16 g day-1 then were challenged with a pulse dose of isoproterenol. Nicotinic acid at 16 g day-1 inhibited isoproterenol-stimulated increases in plasma free fatty acid concentrations, whereas 8 g day-1 did not. All 6 steers were then fed 60 mg day-1 zilpaterol-HCl and 3 were continuously abomasally infused with water and 3 with 16 g day-1 nicotinic acid. Steers receiving 16 g day-1 nicotinic acid demonstrated reductions in feed intake and nicotinic acid infusions were terminated after 3.2 days. Plasma glucose and insulin were elevated in response to the nicotinic acid infusion but glucagon was largely unaffected. Elevations in plasma free fatty acids in response to nicotinic acid were observed when feed intake was reduced, suggesting that 16 g day-1 nicotinic acid did not completely block mobilization of fatty acids. Temporal patterns for free fatty acids and insulin did not suggest that elevated free fatty acids were causatively related to insulin resistance during nicotinic acid treatment. Reductions in feed intake of cattle given pharmacological amounts of nicotinic acid indicate there may be risks associated with over-consumption of nicotinic acid.

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