title: Influence of pregnancy on body weight, ruminal characteristics, and visceral organ mass in beef heifers.
abstract: Crossbred heifers (initially 24 mo, approximate age and 378 +/- 32.1 kg BW) were used to evaluate the influence of pregnancy and advancing gestation on 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 diets formulated to provide 0.45 kg of ADG. Treatments were pregnancy and nonpregnancy; pregnant and nonpregnant heifers were slaughtered on d 40, 120, 200, and 270. Live weight at slaughter and BW change throughout the trial were 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 eviscerated BW (EvBW; P < 0.1), with the pregnant heifers having greater live weights, carcass weights, and EvBW at the d-200 slaughter period. Ruminal fluid fill and total fill (g/kg BW) declined as slaughter period advanced, resulting in the pregnant heifers having less fill at d 270 (P< 0.07). However, ME intake was not different between pregnant and nonpregnant heifers (P > 0.1) at any of the slaughter periods. Heart mass responded differently when nonpregnant and pregnant were analyzed over time and an interaction was detected as slaughter period advanced (P < 0.1). Liver, duodenum, jejunum, and large intestinal mass were not responsive to pregnancy (P > 0.1). Data indicate that ruminal fill is altered by pregnancy but visceral organ mass is not greatly changed by treatment.
authors.affiliation: North Dakota State University, Fargo 58105, USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Scheaffer
authors.forename: J S
authors.initials: JS
authors.lastname: Caton
authors.forename: M L
authors.initials: ML
authors.lastname: Bauer
authors.forename: L P
authors.initials: LP
authors.lastname: Reynolds
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology*; D002417:Cattle / Q000033:anatomy & histology / Q000502:physiology*; D002149:Energy Intake; D005260:Female; D005285:Fermentation; D009929:Organ Size / Q000502:physiology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism / Q000502:physiology*; D012417:Rumen / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014781:Viscera / Q000033:anatomy & histology* / Q000502:physiology