Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2014
Publication Date: 11/21/2014
Publication URL: http://handle.nal.usda.gov/10113/59901
Citation: Foote, A.P., Hales, K.E., Lents, C.A., Freetly, H.C. 2014. Association of circulating active and total ghrelin concentrations with dry matter intake, growth, and carcass characteristics of finishing beef cattle. Journal of Animal Science. 92(12):5651-5658.
Interpretive Summary: The regulation of feed intake in cattle given unlimited access to feed is still largely unknown. Measurement of factors that are involved in the control of feed intake could be used to select cattle for desirable production traits such as feed intake and efficiency of feed conversion to meat. This experiment was performed to determine if ghrelin, a hormone produced in the gut of cattle, is associated with feed intake. An increase in the amount of the active form of ghrelin was associated with an increase in feed intake but an increase in total (active and inactive together) ghrelin was associated with a decrease in feed intake. There is also a difference in the concentration of ghrelin in cattle bred from bulls of different breeds. This indicates that genetics contribute to ghrelin concentrations in cattle. Ghrelin appears to be a promising candidate for a marker for feed intake in beef cattle.
Technical Abstract: Ghrelin is a gut peptide that when acylated is thought to stimulate appetite. Circulating ghrelin concentrations could potentially be used as a predictor of DMI in cattle. The objective of this experiment was to determine the association of circulating ghrelin concentrations with DMI and other production traits. Steers and heifers were fed a finishing diet and individual intake was recorded for 84 d. Blood samples were collected via jugular venipuncture following the DMI and ADG measurement period. Plasma active ghrelin and total ghrelin were quantified using commercial RIA. Active ghrelin was not correlated to DMI (P = 0.36), but when DMI was modeled using a multivariate analysis including plasma metabolites and sex, active ghrelin was shown to be positively associated with DMI (P < 0.01) and contributed for 6.2% of the variation accounted for by the regression model (R2 = 0.33). Total ghrelin was negatively correlated to DMI (P < 0.01), but was not significant in a multivariate regression analysis (P = 0.13). The ratio of active:total ghrelin was positively associated with DMI (P < 0.01), and accounted for 10.2% of the variation in the model (R2 = 0.35). Active ghrelin was positively associated with ADG (P < 0.05), while total ghrelin was negatively associated with ADG (P < 0.01), and the ratio of active:total ghrelin was positively associated with ADG (P < 0.01). Active ghrelin was not associated with G:F (P = 0.88), but total ghrelin concentrations were negatively associated with G:F (P < 0.01) and accounted for 10.24% of the variation (R2 = 0.25). Heifers consumed less feed than steers (P < 0.01), tended to have greater active ghrelin concentrations (P = 0.06), and had greater total ghrelin concentrations than steers (P = 0.04). Total ghrelin concentrations were not different between sire breeds (P = 0.80), but active ghrelin concentrations and the ratio of active:total ghrelin differed between breeds (P < 0.01), indicating that genetics have an effect on the amount and form of circulating ghrelin. Total ghrelin concentrations tended (P = 0.08) to be correlated with HCW, but no other carcass characteristics were correlated with active or total ghrelin concentrations (P > 0.10). Results indicated that ghrelin concentrations are associated with DMI in beef cattle and that there is genetic variation that leads to differences in the amount and form of circulating ghrelin which could contribute to variation observed in DMI of beef cattle.