Effects of Dietary Protein Level and Feed Restriction on Performance and Carcass Characteristics of Swine

Abstract

Sixty crossbred pigs were randomly assigned to five replicates of three treatments to determine effects of dietary protein level and feed restriction on rate and efficiency of gain and quantitative and qualitative carcass characteristics. Growth rate of pigs fed 16 to 14% protein diets ad libitum was significantly faster than that of pigs fed either 12 to 10% protein diets ad libitum or 16 to 14% protein diets at a restricted level of feed intake. Significantly less feed per unit of gain was required by pigs fed high protein diets at either level of feed intake. Carcasses from pigs fed high protein diets either ad libitum or at a restricted level had significantly larger longissimus muscle areas and higher percentages of ham, loin, shoulder and lean cuts than carcasses of pigs fed low protein diets. Carcasses did not differ in backfat thickness, carcass length or dressing percent because of dietary protein or feeding level. Longissimus muscle from pigs fed high protein diets contained more protein and moisture and less ether extract and had lower marbling and juiciness scores. Cooking characteristics of the meat were not significantly different among dietary treatments. Restricted feed intake of the high protein diet resulted in an 18-day increase in age at slaughter and further improved carcass leanness as indicated by less backfat, greater longissimus muscle area, lower percent belly and higher percentages of ham, ham and loin and lean cuts. Backfat of pigs fed for equal gains contained more palmitoleic and lineoleic acids and less oleic acid when pigs were fed high protein diets at a restricted level compared to low protein diets ad libitum.