Milk components as well as milk yield are key factors driving producer milk prices. Fat supplements can increase the efficiency of milk production; therefore, their addition to diets has the potential to be economically advantageous. The set of studies in this thesis evaluated the effects of supplementing palmitic (C16:0) and stearic (C18:0) acid, as well as their interaction with other dietary and animal factors. In the first experiment C16:0 and C18:0 where supplemented at 2% of ration dry matter; compared to C18:0, supplementation with C16:0 increased milk fat concentration and yield, as well as 3.5% fat corrected milk, and the efficiency of milk production. These effects were independent of cow production level, and the increase in milk fat yield was completely accounted for by an increase in the secretion of C16:0 into milk. In the second experiment, the effect of increasing doses of supplemental C16:0 (fed at 0, 0.75, 1.50, or 2.25% of ration DM) was characterized in diets that had either a low or a high fat content (2.7% or 4.2% ether extract, respectively). C16:0 increased milk fat concentration, fat yield, 3.5% FCM yield, and the efficiency of milk production, and tended to increase the yield of milk and milk protein. These responses were maximal when C16:0 was included at 1.5% of ration DM. There was no effect of basal dietary fat content on the yield of milk or milk components, however, significant interactions between C16:0 and the basal fat content of the diet were apparent. In addition, an increased secretion of 16-carbon FA as a result of C16:0 supplementation was observed which explained the majority of the increased secretion of milk fat. Collectively, these results demonstrate the potential of C16:0 to improve cow performance and provides a framework for optimizing its use to maximize productions responses and milk income.
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