The effects of varying the dietary calorie: protein ratios on the performance characteristics and carcass quality of growing pigs in the tropics

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Abstract
SUMMARY Two trials were carried out to investigate the effects of increasing calorie: protein (C:P) ratios of high iso-nitrogenous diets on the performance characteristics, nutrient digestibility, carcass quality and organ weights of 67 growing pigs of the Yorkshire and Landrace breeds, reared in a tropical environment on concrete-floored pens from 9 to 56-8 kg live weight before slaughtering and grading. The dietary protein content was approximately 24 % of dry matter in all cases, and the C:P ratios ranged from 153 to 184 kcal digestible energy/g in both trials. Results showed no consistently significant differences in gain and feed intake due to increasing C:P ratio, but feed conversion ratios consistently improved with increasing C:P ratio. Digestible energy consumed per kg of body weight gained also increased with increasing C:P ratio. The nutrient digestion coefficients did not appear to be significantly affected by the C:P ratio. With respect to carcass quality measurements, there were nonsignificant differences in dressing percentage and average backfat measurements, but significant differences in percentage trimmed fat with increase in C:P ratio. The carcass length, loin eye area, and percentage lean cuts decreased as the C:P ratios increased, the last two showing significant differences only in the second trial. The organ weights showed no significant differences due to increases in C:P ratio.