Hormones and Feed Intake Regulation: Ruminant and Rat Models

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Theobjective of this mini review article was to illuminate hormones-mediated feed intake regulation in ruminant and rat models. This was to help formulate nutritional strategies to optimize metabolism and performance in food-producing animals and to improve human physiology and health. Nutrient partitioning is mediated by a variety of hormones. Hormones are involved in both short-term and long-term regulation of feed intake. The greatest fluctuations in body metabolism, nutrient partitioning, and feed intake usually occur around calving in large ruminants when levels of metabolic and reproductive hormones are highly variable in periparturient cows.

Estrogen depresses feed intake by acting primarily on the paraventricular nucleus of the hypothalamus. Insulin is another important hormone possessing both long-term and short-term effects on ruminant nutrient partitioning and feed intake. The long-term roles of insulin in feed intake control relate to pregnancy and lactation. This occurs mainly during mid- and late-lactation when the cow tends to gain weight. Insulin is involved in both up- and down-regulation of feed intake in mammals. When compared to prepartum levels, insulin secretion drops substantively shortly after parturition. Without the postpartum drop in insulin secretion rate, the cow would be unable to use body reserves and deal with insufficient Dry Matter Intake (DMI). The low postpartum insulin will additionally enable the cow to gradually increase DMI.

Theshort-term insulin effects on nutrient metabolism and partitioning, which are more relevant to the findings of dairy cattle studies, initiate upon or even shortly before feeding or nutrient ingestion. Seeing the fresh feed can cause a surge in insulin secretion in sheep and cattle. The higher postprandial insulin surge leads to greater glucose uptake by peripheral tissues.