INFLUENCE OF STARTING RATION ENERGY–PROTEIN RATIO AND FAT CONTENT ON FINISH GRADE OF EARLY AND LATE MARKETED BROILER TOM TURKEYS

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Abstract
Commercial source broiler-type male poults were offered starting rations having energy (kcal metabolizable energy/kg)–protein (% crude) ratios either above (100) or below (90) the optimum (95). In each case, total fat comprised a high (28%) or moderate (14%) amount of dietary ME. All rations contained 30% protein from constant proportions of soybean meal, corn and corn gluten meal while energy and fat were varied with animal–vegetable tallow, starch, glucose monohydrate, and purified cellulose. Common corn–soybean meal rations were fed from 2 wk of age to slaughter at 12 and 16 wk. Statistical analysis revealed an interaction between E/P ratio and fat level for both body weight and feed conversion at 2 wk. Poults fed a diet with above optimal E/P ratio grew more rapidly when 28 rather than 14% of the ME was supplied as fat while the converse occurred when the ratio was below the optimal. The higher E/P ratio and greater percentage of dietary fat favored increased weight gains. Feed conversion was unaltered by the level of fat per se; however, rations having a greater energy concentration were utilized more efficiently than those with the lower energy (E/P ratio). Starting treatments did not influence performance after 6 wk of age. Effects of starting diets on finish were detected at 16 but not 12 wk of age. A statistically significant improvement in back finish occurred when 28% rather than 14% of the ME was provided by fat regardless of energy–protein relationship. No differences attributable to ratio or its interaction with dietary fat were apparent. Treatment effects on breast grades paralleled those on back finish but were not statistically significant.