Growth and reproductive performance of beef replacement heifers fed development diets containing soybean meal or wet distillers grains

Abstract

ABSTRACT Our objective was to evaluate the effects of replacing soybean meal with wet distillers grains plus solubles (WDG) in beef heifer development diets on growth and reproductive performance. Weaned heifers (n = 172; initial BW 319 ± 2 kg; age 282 ± 1 d) were stratified by BW and age and assigned randomly to be fed development diets using soybean meal (CON) or WDG as the primary source of CP in the diet. Heifers were allotted equally to 8 pens, adapted to diets for 14 d, and fed for ad libitum intake for 94 d. Heifer BW was measured on d 28, 56, and 84 relative to the beginning of the experiment and at breeding; paired serum samples were collected at these times to define puberty status. After 94 d, treatments were combined in a native short- grass rangeland pasture. Heifers from each treatment were exposed to ovulation synchronization and fixed-time AI 23 or 51 d after diets ended. Total DM delivered was 4,695 kg less (P 0.10). Conception to fixed-time AI and overall pregnancy rates were not different (P > 0.60) between treatments. Under the conditions of our study, developing replacement heifer diets using WDG as the primary source of CP had negative temporal effects on growth performance and age at puberty; however, these effects were nullified when heifers were allowed to graze native range for at least 23 d before breeding.