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Energy requeriments, proteic metabolism and meat quality of Nellore cattle (Bos indicus) as a function of their residual feed intake


Since knowledge about biological basis, which drive variation in zebuins residual feed intake (RFI), is not complete, studies are need to evaluate consequences of selection for this parameter in meat quality traits. Our hypothesis is that more efficient animals have lower mantenance energy requeriments since they have lower muscle protein degradation rates as function of higher calpain inhibitors enzimatic activity. So, selection for RFI could have negative effects on meat tenderness. Animals selection for RFI will be done at FZEA/USP, in Pirassununga, SP. Seventy-two Nellore steers will be fed in individuals pens for a 84-day period. Predict dry matter intake will be estimated by multiple regression on mid-test metabolic live weight and average daily gain. Twelve of those more efficient animals and twelve of those less efficient will be carried to Veterinary School of UFMG, in Belo Horizonte, MG, where animals mantenance energy requeriments will be determined by indirect calorimetry. Total urine produced will be collected and concentration of the amino acid 3-methil-histidin (miofibrilar degration rate marker)will be determined. Then, animals will return to FZEA/USP, where will be killed and Longissimus dorsi muscle samples will be collected to measure activity of calpain-system components and meat tenderness for objective measures. (AU)

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