Influence of pregnancy on body weight, ruminal characteristics, and visceral organ mass in beef heifers

Crossbred heifers (initially 24 me, approximate age and 378 +/- 32.1 kg BW) were used to evaluate the influence of pregnancy and advancing gestation o n DMI, BW, carcass weight, ruminal characteristics, and visceral organ mass . Heifers (naturally serviced (n = 22; nonpregnant controls, n = 17), were grouped in common pens. Heifers were provided corn silage and hay-based die ts formulated to provide 0.45 kg of ADG. Treatments were pregnancy and nonp regnancy; pregnant and nonpregnant heifers were slaughtered on d 40, 120, 2 00, and 270. Live weight at slaughter and BW change throughout the trial we re not influenced by pregnancy (P > 0.1). Carcass weight per unit of BW was decreased due to pregnancy (P < 0.05) and an interaction was found in evis cerated BW (EvBW; P < 0.1), with the pregnant heifers having greater live w eights, carcass weights, and EvBW at the d-200 slaughter period. Ruminal fl uid fill and total fill (g/kg BW) declined as slaughter period advanced, re sulting in the pregnant heifers having less fill at d 270 P < 0.07). Howeve r, ME intake was not different between pregnant and nonpregnant heifers T > 0.1) at any of the slaughter periods. Heart mass responded differently whe n nonpregnant and pregnant were analyzed over time and an interaction was d etected as slaughter period advanced (P < 0.1). Liver, duodenum, jejunum, a nd large intestinal mass were not responsive to pregnancy (P > 0.1). Data i ndicate that ruminal fill is altered by pregnancy but visceral organ mass i s not greatly changed by treatment.