RELATIONSHIP OF DIETARY PROTEIN LEVELS TO PERFORMANCE AND CARCASS MERIT OF MARKET SWINE

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Abstract
Three trials, involving 108 Yorkshire SPF pigs, were conducted to study the protein requirements of growing-finishing pigs. The design of each trial was a 3 × 3 × 2 factorial involving three levels of protein in the grower (19.2, 17.4 and 15.5%), three levels of protein in the finisher (17.4, 15.5 and 14.2%) and two sexes (barrows and gilts). The study was considered as one experiment conducted as a randomized complete-block design with five replications. During the growing phase there was a linear increase in growth rate and curvilinear reduction in feed required per kg gain, due to higher dietary protein levels (P = 0.05). During the finishing phase, dietary protein levels did not influence rate of gain but feed required per kg gain increased linearly as protein level in the diet decreased (P = 0.05). Feeding the lowest level of protein throughout resulted in a slower rate of gain and increased the feed required per kg gain. The efficiency of feed utilization was the same for barrows and gilts, although barrows gained faster and consumed more feed per day (P = 0.05) than gilts. There were linear increases in area of Longissimus dorsi muscle due to increased protein level in the finisher diets. An interaction between sex and protein levels (P = 0.05) was observed in the finisher period for total ham weight and weight of ham lean.