Correlation of fatty acid composition and iodine value (IV) among 3 fat depots in pork carcasses

Abstract Text: F Feeding diets containing high inclusion (>40%) of DDGS reduces fat quality in pork. Pork processors often determine fatty acid composition of jowl as a predictor of fat composition in other higher value cuts. However, the differences in fatty acid composition among fat depots have not been studied extensively. Thus, the objective was to evaluate differences in fatty acid composition among fat depots and evaluate their correlation. Mixed sex pigs (n = 216; initial BW = 24 ± 4 kg) were blocked by BW and allotted to 1 of 3 diets: a basal corn-soybean meal diet with 40% DDGS (dietary fat = 4.8%); basal diet plus 5% cottonseed oil (dietary fat = 10.3%); or basal diet plus 8% crude glycerol (dietary fat = 6.6%) for the last 6 wk before harvest. Although diets were not isocaloric, AA to ME ratios were equal among diets within each of the 3 feeding phases. At slaughter, 48 gilts (16 from each treatment harvested on one day) had all layers of fat sampled from the tip of the jowl, backfat at the 10^th rib, and belly from the caudal end at the ventral midline. Fatty acid composition of fat samples was analyzed using gas chromatography and IV was calculated according to AOCS (1998). A split-plot analysis was used to analyze IV and linoleic acid (C18:2) concentrations among fat depots. No differences (P = 0.07) were observed for IV (78.2, 79.5, and 78.1; SE = 2.66) of jowl, backfat, and belly fat, respectively. Concentration of C18:2 was greater (P < 0.01) for backfat (28.4% ± 3.9) than for jowl (25.6% ± 3.9) and belly (26.7% ± 3.9). Iodine values of jowl and belly (r = 0.60), jowl and backfat (r = 0.84), and belly and backfat (r = 0.63) were correlated (P < 0.0001). Similarly, C18:2 concentrations of jowl and belly (r = 0.66), jowl and backfat (r = 0.94), and belly and backfat (r = 0.67) were correlated (P< 0.0001). Although all correlations were highly significant, IV and C18:2 composition of jowl only explained about 40% of the variation in IV and C18:2 concentration of belly. However, jowl was a more reliable predictor of IV and C18:2 composition of backfat. In conclusion, IV and C18:2 concentration of jowl can be used to predict IV and C18:2 concentration of backfat but is less reliable for predicting composition of belly fat. 

Keywords: fat depot, iodine value, pigs