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Growth, Reproductive Performance and Nitrogen Balance of Gilts as Affected by Protein Intake and Stage of Gestation^1,2,

Oklahoma Agricultural Experiment Station, Stillwater 74078

Abstract

The effects of four levels of crude protein (CP) and stage of gestation on the growth, reproductive performance and N balance of 64 crossbred gilts were examined in two trials. Gilts were fed 147, 256, 309 or 369 g of CP daily in trial 1 and 119, 227, 275 or 326 g/d in trial 2. Total body weight gain and average daily gain (ADG) were not significantly affected by protein intake, although the quadratic effect on ADG approached significance (P<.1). Both total body weight gain and ADG increased linearly (P<.01) as stage of gestation progressed. Gilts were slaughtered at 30, 60 or 90 d of gestation and reproductive performance was evaluated. Protein intake did not significantly affect numbers of corpora lutea or live embryos, survival rate or embryo length. But survival rate (P<.05), number of corpora lutea (P<.05) and live embryo numbers (P<.01) declined linearly as gestation stage progressed. Embryo length increased linearly (P<.05) as stage of gestation progressed. Nitrogen balance studies were conducted before breeding and in early, mid and late gestation. Significant trial x protein level x collection period interactions existed. In trial 1, N retention increased linearly (P<.01) as dietary protein increased. Retention increased (P<.01) by 4.1 g/d from prebreeding to early pregnancy. Stage of gestation had a quadratic effect on retained N; retention was higher in early and late gestation than in mid-gestation. In trial 2, mean N retention during pregnancy was –1.7 g/d. Retention was not significantly affected by protein intake but retained N declined quadratically (P<.05) with stage of gestation to a –16.3 g/d at d 90. In contrast with trial 1, pregnancy did not result in an increase in retention of N. A relationship between protein intake and N balance data and resulting reproductive performance could not be established. The lowest levels of protein intake (147 and 119 g/d in trials 1 and 2, respectively) appeared to be adequate for the first 90 d of gestation in the gilt. However, N retention was not maximized at this protein intake.

¹ Journal Article 3196 of the Oklahoma Agr. Exp. Sta., Oklahoma State Univ., Stillwater 74078.

² The authors wish to express appreciation to Rex Vencl for his care of experimental animals and R. K. Johnson for assistance with statistical analysis.

³ Present address: Extension Anim. Sci. Dept., Univ. of Georgia, Athens 30602.

⁴ Dept. of Anim. Sci. and Ind.