EFFECTS OF DIETARY-PROTEIN CONCENTRATION (CORN-SOYBEAN MEAL RATIO) ONTHE PERFORMANCE AND CARCASS CHARACTERISTICS OF GROWING BOARS, BARROWS, AND GILTS - MATHEMATICAL DESCRIPTIONS

Three split-plot trials using completely randomized whole-plot designs were conducted to determine the effect of dietary CP level (corn: soy bean meal ratio) on daily feed intake, rate and efficiency of gain, an d carcass characteristics of growing boars, barrows, and gilts. One hu ndred eighty-nine pigs were assigned to seven corn-soybean meal diets ranging from 11 to 23% CP in two-percentage-unit increments. The pigs were penned individually and had ad libitum access to feed and water. The average initial weight was 19 kg and the average final weight was 105 kg. Regression analysis revealed that maximal rates and efficienci es of gain were attained by all sexes when animals consumed diets that contained 17 to 19% CP. Average daily gain increased linearly as diet ary lysine intake increased from 5 g/d to approximately 25 g/d. Carcas s leanness increased at a greater rate for boars than for barrows and gilts (P < .05) as CP levels increased from 11 to 19% CP. The results indicated that both inadequate and excess dietary CP concentrations ar e detrimental to the rate and efficiency of gain and carcass quality o f growing-finishing boars, barrows, and gilts. Interactions between se x and CP level indicated that inadequate CP concentrations were more d etrimental to boars than to barrows and gilts.