Circulating Ghrelin Concentrations During the Transition Period of Dairy Cattle and the Associated Relationship with Milk Production

The hormone ghrelin was discovered in 1999. It has a 27-28 amino acid sequence with a noctanoylation at the third serine residue. Ghrelin is expressed in most tissues throughout the body and is primarily known for its GH releasing activities. Ghrelin also has a significant role in the regulation of feed intake and energy balance and may be a potent metabolic regulator of reproduction. During this experiment, plasma ghrelin concentrations were measured in dairy cattle (n=13) biweekly from 14 days prepartum to 60 days postpartum. Circulating ghrelin concentrations did not change with stage of lactation, but were affected by level of milk production. High producing and low producing cows had expected 305-day yields of 12,923 +/- 217 and 10,332 +/- 322 kilograms of milk, respectively (P< 0.001). The high producers had lower circulating ghrelin concentrations (45.1 +/- 8.9 pg/mL) than low producers (73.3 +/- 8.5 pg/mL). These results are different than anticipated but may, be explained by prioritized nutrient partitioning in low producing and high producing dairy cows