Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2003
Publication Date: 1/1/2003
Citation: GEARY, T.W., MCFADIN, E.L., MACNEIL, M.D., GRINGS, E.E., SHORT, R.E., FUNSTON, R.N., KEISLER, D.H. LEPTIN AS A PREDICTOR OF CARCASS COMPOSITION IN BEEF CATTLE. JOURNAL OF ANIMAL SCIENCE. 2003. v. 81. p. 1-8. Interpretive Summary: The opportunity to modify body composition through selection or management can help cattle producers and feeders produce beef that more consistently meets expectations of consumers. Circulating concentrations of leptin provide a strong indicator of fat content in live cattle and thus, may facilitate more appropriate feeding and marketing management strategies. However, further research is needed to discern whether serum concentration of leptin coupled with other indicators may serve as a useful predictor of carcass value that can be applied before harvest.
Technical Abstract: Our objective was to determine if serum concentrations of leptin could be used to predict carcass composition and merit in feedlot finished cattle. Two different groups of crossbred Bos taurus steers and heifers were managed under feedlot conditions near Miles City, MT. The first group (CGC) consisted of 88 ½ Red Angus, ¼ Charolais, and ¼ Tarentaise composite steers harvested at the Con Agra processing facility in Greeley, CO. The second group (LB) consisted of 91 F2 steers and heifers born to Limousin, Hereford, or Piedmontese by CGC F1 cows crossed to F1 bulls of similar genetic makeup and harvested at a local processing facility in Miles City, MT. Blood samples were collected approximately 24 h before harvest (CGC) or approximately 3 d before and at harvest (LB). Serum concentrations of leptin were greater in LB cattle (27.0 ng/mL) than CGC steers (18.7 ng/mL), but did not differ (P = 0.33) between Hereford, Limousin, or Piedmontese F2 calves. Serum leptin did not differ (P = 0.79) between LB steers and heifers. Positive correlations (P < 0.01) existed between serum leptin and marbling score (r = 0.35 and 0.50), fat depth measured between the 12th and 13th rib (r = 0.34 and 0.46), KPH (r = 0.42 and 0.46), and quality grade (r = 0.36 and 0.49) in CGC and LB cattle, respectively. Serum leptin was also positively correlated with calculated yield grade for CGC steers (r = 0.19; P = 0.07) and LB cattle (r = 0.52; P < 0.0001). Longissimus area was not correlated with serum leptin in CGC steers (r = 0.12; P = 0.29), however a negative correlation existed between longissimus area and serum leptin in the LB cattle (r = -0.45; P < 0.0001). Serum concentrations of leptin were an accurate predictor (P < 0.001) of carcass composition (marbling, back fat depth, and KPH fat) and quality grade in both groups of cattle studied. In summary, peripheral concentrations of leptin are closely associated with fat deposition in cattle and may provide an objective tool for assessing fat content in feedlot cattle.