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Influence of Protein Intake, Energy Intake and Stage of Gestation on Growth, Reproductive Performance, Nitrogen Balance and Carcass Composition in Gestating Gilts¹

Oklahoma State University, Stillwater 74078

Abstract

Thrity-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P<.01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P<.05 and linear effect, P<.01, respectively). Nitrogen retention (P<.01), efficiency of N retention (P<.05) and dry matter digestibility (P<.01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P<.01), liver weight (linear effect P<.01) SM weight (quadratic effect, P<.05) and SM percentage N (linear effect P<.10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P<.10, P<.05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.

¹ Oklahoma Agr. Exp. Sta. Journal Article No. 4230.

² Current address: Ralston Purina, Checkerboard Sq., St. Louis, MO 63164.

³ Dept. of Anim. Sci.