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1307
Fatty acid composition of intramuscular lipids from Nellore and Brangus bulls fed diets supplemented with cottonseed
Finishing bulls were used in a factorial design with two breeds and two diets with contrasting fat levels to evaluate changes in marbling and fatty acid profile of intramuscular lipids. Nellore (n=20) and Brangus (n=20) bulls were randomly assigned to a low (LFD) or a high fat diet (HFD): 3.2% vs. 6.4% ether extract. The diets had similar energy and protein levels and were composed by sorghum silage (30% DM), soybean hulls, ground corn, soybean meal, urea and a mineral mixture. HFD additional fat derived from cottonseed (18% DM), in substitution to ground corn (31% vs. 52%, on HFD and LFD, respectively). The experiment lasted 71-d. All carcass were evaluated for marbling (1-18 scale) and back fat thickness (BFT). Longissimus dorsi (LD) samples were randomly selected from four animals of each treatment for fatty acid analysis by gas-chromatography. Fatty acid composition is expressed as g/100 g of total lipids. All data were analyzed using the GLM procedure of SAS (SAS, 2011) with animal as the experimental unit and genetic group, diets and the interaction between them as class variables. Back fat thickness was similar among treatments (5 mm, on average), but marbling was higher for Brangus. There was significant breed vs. diet interaction (p<0.01), mainly because marbling with LFD was much more intense for Brangus than Nellore (8.0 vs. 3.3), while for HFD it was quite similar (Brangus = 5.8 VS. Nellore = 5.3). Fatty acid composition of intramuscular lipids showed that samples from Brangus bulls had more palmitic (C16; 17.7% vs. 15.3% p<0.05), stearic (C18; 11.9% vs. 8.9% p<0.05), oleic (C181c9; 28.1% and 23.3%), and elaidic (C181t9; 0.15% and 0.12%, p<0.05) acids. They also had 20% and 18% greater saturated (SFA) and monounsaturated (MUFA) fatty acids (p<0.05), respectively. HFD diet increased the amount of stearic acid (C18; 11.5% vs. 9.3% p<0.05) and resulted in more than 20% higher (p<0.05) elaidic acid and C18:2 non conjugated isomers, whereas the content of rumenic acid (C182c9t11, mean 0.19%) was unaffected by genetic group or diet. Differences in fatty acid content among Brangus and Nellore LD are in accordance with higher marbling from the former. Cottonseed fatty acid profile may have been extensively biohydrogenated, as suggested by the higher levels of stearic acid in HFD samples. Marbling differences among breeds had more impact in intramuscular fatty acid profile than supplementation with cottonseed.
Keywords: Meat, Lipid, Zebu