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Effects of Dietary Protein and Energy Levels for Growing-Finishing Swine on Performance, Muscle Composition and Eating Quality of Pork¹

University of Kentucky, Lexington 40506

Abstract

Three experiments involving 232 growing-finishing swine were conducted to determine the effects of widely varying levels of dietary protein and energy levels on performance and on the relationship between muscle composition and eating quality of pork roasts. Dietary variables ranged from 12 to 20% protein and 2,900 to 3,670 kcal of metabolizable energy/kg. Protein levels were attained by adjusting the ratio of corn to soybean meal. Energy levels were attained by substituting up to 10% sand or fat for dextrose.

In general, pigs fed the higher protein level gained faster and more efficiently and had carcasses with less backfat, more longissimus area and a higher percentage of lean cuts than those fed the lower protein levels. Intramuscular fat content of the longissimus (third to seventh rib) was 14.6 and 24.5% (P<.01), and protein content was 70.4 and 61.0% (P<.01), on a dry-matter basis, for pigs fed 20 and 12% protein, respectively. Composition of the biceps femoris, semimembranosus and semitendinosus followed the same pattern but the relative differences were less. Dietary energy level did not affect muscle composition as much as did dietary protein, with pigs fed 0 and 10% fat having 18.5 and 20.6% fat, and 66.6 and 64.8% protein, respectively, in the longissimus.

Taste panel scores for loin roasts were not consistently affected by dietary treatment, though juiciness and tenderness scores tended to be higher for roasts containing greater amounts of intramuscular fat. The data indicate that levels of intramuscular fat and protein can be changed markedly by varying the dietary protein and energy level without having any major effects on the eating quality of pork roasts.

¹ Journal Paper No. 75-5-180 of the University of Kentucky Agricultural Experiment Station, Department of Animal Sciences, Lexington 40506.

² Present address: Col. Marter, Gomez 42, Chatingo, EDO, De Mexico.

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