The objective of this presentation is to discuss and review research on lipid and fatty acid metabolism in growing calves and heifers. The majority of research related to fat metabolism in dairy cattle has been conducted with lactating or transition cows evaluating the effects of diet on milk fat synthesis, energy status, and reproduction. Despite the biological activities of lipids beyond serving as an energy source and their importance in maintaining normal biological function, there is limited understanding of how they are utilized by developing dairy calves and heifers. Additionally, there is limited understanding on the potential impacts of changes in blood concentrations on development and performance of the growing replacements. In recent research studies we have observed that concentrations of circulating lipid metabolites and plasma fatty acids change as calves and heifers develop and mature. Some of these changes are related to the dietary transitions that occur during the first year of life as a calf moves from milk to a concentrate-based diet, followed by a more forage-based diet at several months of age. Additionally, there are major shifts in lipid metabolism as a calf transitions through key developmental changes such as from a pre-ruminant to ruminant and through the critical reproductive stage around the onset of puberty. A better understanding of lipid metabolism and the impacts of supplementation of dietary fats or manipulations of energy sources may offer new ways to enhance development and improve performance of growing replacement heifers through nutritional strategies.

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