Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2015
Publication Date: 4/1/2016
Publication URL: http://handle.nal.usda.gov/10113/61842
Citation: Foote, A.P., Tait Jr, R.G., Keisler, D.H., Hales, K.E., Freetly, H.C. 2016. Leptin concentrations in finishing beef steers and heifers and their association with dry matter intake, average daily gain, feed efficiency, and body composition. Domestic Animal Endocrinology. 55:136-141.
Interpretive Summary: Leptin is a hormone that is produced in fat cells and acts as a signal to the brain to reduce feed consumption. Leptin concentrations in blood also increase with increasing amounts of body fat. This experiment was performed to determine the changes in circulating leptin concentrations in feedlot steers and heifers and to determine the association of the circulating leptin concentrations with feed intake, growth, feed efficiency, and body composition. Leptin concentrations in blood plasma were greater in heifers than steers at the beginning of the experiment. By the end of the experiment, leptin concentrations had increased in both sexes but the two sexes were not different from one another. Leptin concentrations were positively associated with feed intake, indicating that cattle that consumed more feed tended to have greater concentrations of circulating leptin. Cattle that had greater average daily body weight gain also tended to have greater circulating leptin concentrations. Additionally, cattle with better feed efficiency measures tended to have lower circulating leptin concentrations. Leptin concentrations were also positively associated with measures of body fatness. Leptin appears to be a promising indicator of production traits in beef steers.
Technical Abstract: The objective of this experiment was to determine the association of circulating plasma leptin concentrations with production and body composition measures of finishing beef steers and heifers and to determine if multiple sampling time points improve the associations of plasma leptin concentrations with production and body composition traits. Individual DMI and ADG was determined for 84 d using steers and heifers (n = 127 steers and n = 109 heifers). Blood was collected on day 0, day 42, and day 83 for determination of plasma leptin concentration. Leptin concentration was greater in heifers than steers on day 0 (P < 0.001 for sex by day interaction) and leptin concentration increased in both sexes but was not different from each other on day 83. Leptin concentrations at all three time points and the mean were shown to be positively associated with DMI (P = 0.006) while the mean leptin concentration explaining 8.3 % of the variance of DMI. Day 42, day 83, and mean leptin concentrations were positively associated with ADG (P = 0.011). Mean leptin concentration was negatively associated with G:F and positively associated with residual feed intake (RFI), indicating that more efficient cattle had lower leptin concentrations. Leptin concentrations were positively associated with body fat measured by ultrasonography at the 12th-rib and over the rump (P < 0.001), with the mean leptin concentration explaining 21.9 % and 12.7 % of the variance in 12th rib and rump fat thickness, respectively. The same trend was observed with carcass composition where leptin concentrations were positively associated with 12th rib fat thickness, USDA calculated yield grade (YG), and marbling score (P = 0.006) and mean leptin concentration explained 16.8, 18.2, and 4.6 % of the variance for 12th rib fat thickness, YG, and marbling score, respectively. Given these and previous results, it appears that leptin physiology could be a candidate for mechanisms that contribute to feed efficiency variation in beef cattle.