Dietary effects on fat deposition and fatty acid profiles in muscle and fat depots of Friesian bull calves
1995
Aharoni, Y. | Nachtomi, E. | Holstein, P. | Brosh, A. | Holzer, Z. | Nitsan, Z.
Dietary effects on fat deposition, cholesterol level, and fatty acid profiles of muscle and fat depots in Friesian bull calves were evaluated in two trials. In Trial 1 (eight pens of seven Friesian bull calves), three levels of ME (10.4, 10.9, 11.7 MJ/kg of DM; diets L, M and H, respectively) were offered to three groups of calves throughout the entire experimental period. Calves of the fourth group were fed diet M for the first 80 d and diet L thereafter (Treatment ML). Calves were 185 +/- 15 d of age and 215 +/- 18 kg BW at the start of the trial and were slaughtered when they reached a predetermined equal degree of fatness, in a BW range of 480 to 580 kg, and an age range of 417 to 548 d. In Trial 2, four groups of calves (eight pens of seven Friesian bull calves) had free access to diets of the same ME (11.7 MJ/kg of DM) but that differed in either CP content (11.3 vs 13.4%) or had poultry litter substituted for part of soybean meal at the equivalent CP. Calves were 180 +/- 13 d of age and 240 +/- 19 kg BW at the start of the trial and were slaughtered after 232 +/- 11 d, at 508 +/- 22 kg BW. In both trials, dressing percentages and carcass percentages of kidney, pelvic, and cod fat depots were recorded at slaughter, and samples of the 12th rib longissimus muscle with its subcutaneous fat were obtained for lipid analyses. Increasing the ME concentration shortened the growing period and tended to increase carcass depot fat percentage. Saturated fatty acid (SFA) content was negatively correlated to energy level in both depot and muscle fats (P < .05). Increasing the CP from 11.3 to 13.5% had no effect on depot fat accumulation or cholesterol and fatty acid profiles. Substitution of soybean protein by poultry litter protein increased myristic acid contents in muscle (P = .055) and decreased palmitic acid in muscle and subcutaneous fat (P < .05). Oleic acid content of subcutaneous fat tended to increase (P = .07) and SFA of muscle to decrease (P = .08) by this substitution. The results indicate the possibility of manipulating beef fat composition by dietary means.
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