title: Impact of supplemental protein source offered to primiparous heifers during gestation on I. Average daily gain, feed intake, calf birth body weight, and rebreeding in pregnant beef heifers.
abstract: A 3-yr study was conducted to determine the effect of supplemental protein source on ADG, feed intake, calf birth BW, and subsequent pregnancy rate in pregnant beef heifers. Crossbred, Angus-based, AI-pregnant heifers (yr 1, n = 38; yr 2, n = 40; and yr 3, n = 36) were stratified by BW (450 ± 10 kg) and placed in a Calan Broadbent individual feeding system at approximately d 142 of gestation. Following a 25-d adaptation period, an 84-d feeding trial was conducted. Heifers were offered ad libitum grass hay (8 to 11% CP, DM basis) and no supplement (CON), 0.83 kg/d distillers-based supplement (HI), or 0.83 kg/d dried corn gluten-based supplement (LO). Supplements were formulated to be isocaloric, isonitrogenous (28% CP, DM basis), and equal in lipid content but differed in RUP, with HI (59% RUP) having greater levels of RUP than LO (34% RUP). Dry matter intake was also calculated based on feed NE values to account for different energy levels of the supplement compared with the control diet. Control heifers tended (P = 0.09) to consume less total DM than either supplement treatment. However, forage-only DMI was greater (P < 0.01) for CON heifers (9.94 ± 0.12 kg) compared with HI or LO heifers (8.50 and 8.34 ± 0.12 kg, respectively). Net energy DMI was less (P < 0.01) for CON heifers (4.98 ± 0.23 kg) compared with HI or LO heifers (5.43 and 5.35 ± 0.23 kg, respectively). Control heifers gained less (P < 0.01; 0.59 ± 0.14 kg/d) than either HI (0.82 ± 0.14 kg/d) or LO heifers (0.78 ± 0.14 kg/d), resulting in lower (501 ± 9 kg) BW (P < 0.01) than HI (519 ± 9 kg) heifers at the end of the feeding period. Calf birth BW was similar (P = 0.99) among treatments. At prebreeding, CON heifers weighed less (P < 0.03) than LO heifers. Cow BW was similar (P = 0.48) among treatments at pregnancy diagnosis, and final pregnancy rate was also similar (87%; P = 0.22). Protein supplementation increased ADG in pregnant heifers; however, calf birth BW and subsequent pregnancy rates were similar.
authors.forename: A F
authors.initials: AF
authors.lastname: Summers
authors.forename: T L
authors.initials: TL
authors.lastname: Meyer
authors.forename: R N
authors.initials: RN
authors.lastname: Funston
mesh_terms: D000821:Animal Feed; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000502:physiology; D001724:Birth Weight / Q000187:drug effects* / Q000502:physiology; D001835:Body Weight / Q000187:drug effects* / Q000502:physiology; D001947:Breeding / Q000379:methods; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000494:pharmacology*; D019587:Dietary Supplements; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D005260:Female; D008297:Male; D039382:Maternal Nutritional Physiological Phenomena / Q000502:physiology; D010298:Parity / Q000187:drug effects; D006109:Poaceae; D011247:Pregnancy; D018873:Pregnancy Rate; D011270:Pregnancy, Animal / Q000187:drug effects* / Q000502:physiology; D012621:Seasons; D003313:Zea mays
chemical_list: D004044:Dietary Proteins