|KEISLER, D - University Of Missouri|
|King, David - Andy|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2015
Publication Date: 9/8/2015
Publication URL: http://handle.nal.usda.gov/10113/61425
Citation: Foote, A.P., Hales, K.E., Kuehn, L.A., Keisler, D.H., King, D.A., Shackelford, S.D., Wheeler, T.L., Freetly, H.C. 2015. Relationship of leptin concentrations with feed intake, growth, and efficiency in finishing beef steers. Journal of Animal Science. 93(9):4401-4407.
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 increase with increasing amounts of body fat. This experiment was performed to determine if circulating leptin concentrations were indicative of observed feed intake, growth, and feed efficiency of genetically diverse feedlot steers. The association of leptin with feed intake appeared to be unreliable as the association would change when other factors, such as body fatness were included in the analysis. Concentrations of leptin were lower in steers that grew faster and were also reduced in steers that gained faster with less feed. There also was a slight difference in leptin concentrations between the breeds used in the experiment. This indicates that genetic factors that contribute to variations in leptin concentrations should be further evaluated. Leptin appears to be a promising indicator of feed efficiency in beef steers.
Technical Abstract: The objective of this experiment was to determine the association of serum leptin concentrations with production measures including DMI, ADG, G:F as well as carcass characteristics in genetically diverse finishing beef steers. Three cohorts of steers (n = 473 total) were individually fed a finishing ration for 92, 64, and 84 d for cohort 1, 2, and 3, respectively. Serum was collected on d 42, 22, and 19 of the experiment for cohort 1, 2, and 3, respectively. Leptin concentrations were positively correlated to DMI (r = 0.21; P < 0.01) but negatively correlated to g DMI/kg initial BW (r = -0.21; P < 0.01). Leptin concentrations were also negatively correlated to ADG and G:F (P < 0.01). Leptin concentrations were positively correlated to 12th rib fat thickness, yield grade, and marbling score (P < 0.01) and negatively correlated to LM area (P < 0.01). Using a Mixed model analysis (SAS 9.3; SAS Inc., Cary, NC) to account for breed effects, leptin concentrations were positively associated with DMI (P = 0.01) and accounted for 1.10% of the variance. However, if initial BW and yield grade were included as covariates to account for body size and fatness, leptin was negatively associated with DMI (P = 0.02), and accounted for 0.54% of the variance. Regardless of covariates included in the model, leptin was negatively associated with ADG (P < 0.01) and G:F (P < 0.01), and accounted for 2.62%, and 7.87% of the variance for ADG and G:F, respectively. Leptin concentrations were also positively associated with 12th rib fat thickness, yield grade, and marbling score (P < 0.01), and accounted for 14.74%, 12.74%, and 6.99% of the variance for 12th rib fat, yield grade, and marbling score, respectively. Leptin concentrations could be a useful physiological marker for growth and feed efficiency of finishing beef cattle. Genetic influences on the biology of leptin also need to be considered when using leptin as physiological marker for production measures.