| dc.description.abstract | Intramuscular (i.m.) adipose tissue deposition, or marbling is one of the most important traits related to meat quality and palatability in beef, but difficult to accurately predict before slaughter. This study aimed to identify plasma metabolites and hormones associated with marbling. We hypothesized that there would be greater plasma metabolite and hormone concentrations in grain-fed heifers, which would have greater percent intramuscular fat (%IMF). At 12 mo age, 7 heifers were fed a grain-based diet and 14 were fed a hay-based diet. Heifers were weighed every 28 d. Ultrasound and blood samples were taken before feeding at 0 d and 84 d of treatment. Plasma was analyzed for glucose, acetate, propionate, butyrate, insulin, ghrelin, adiponectin, and fatty acid composition. Data was analyzed using single-factor analysis of variance, simple regression, and split-plot design. Rib fat thickness and plasma ghrelin concentration was greater in grain-fed heifers than in hay-fed heifers.
There was a diet x time interaction for body weight (BW) and a weak interaction with %IMF. Plasma α-linolenic acid (18:3n-3) proportions tended to be elevated in hay-fed heifers than grain-fed heifers. There was a positive correlation between BW and %IMF and between BW and change in %IMF (weak). There were positive correlations between plasma palmitoleic acid (16:1n-7) proportions, oleic acid (18:1n-9) proportions, oleic:stearic acid (weak) ratio, and monounsaturated fatty acid (MUFA):SFA (weak) ratio and %IMF and weak, negative correlations between stearic acid (18:0) and saturated fatty acids (SFA) and %IMF. Plasma ghrelin concentrations were correlated with ADI (negative), feed:gain ratio (negative), rib fat thickness (positive), and ADG (positive). There were negative correlations between plasma myristic acid (14:0), palmitic acid (16:0) (weak) and palmitoleic acid (16:1n-7) proportions and plasma ghrelin concentrations and a positive correlation between plasma linoleic acid proportions and plasma ghrelin concentrations. In conclusion, there appears to be limitations in the sensitivity of a metabolic profile for marbling. Percent IMF was associated with body weight and plasma fatty acid concentrations. It was demonstrated that plasma ghrelin concentrations also are correlated with plasma fatty acid concentrations. Ghrelin and fatty acid composition show promise for predicting marbling. | en |
