|Hould, Byron - MONTANA AGR EXP STA|
|Phelps, Dave - MONTANA AGR EXP STA|
Submitted to: Journal of Animal Science Supplement
Publication Type: Proceedings
Publication Acceptance Date: July 6, 1995
Publication Date: N/A
Interpretive Summary: Feeding a zinc supplement to pregnant beef heifers during the last trimester of pregnancy had no effect on incidence or severity of dystocia. However, zinc supplementation had significant effects on calf birth weight and these effects were affected by the genotype of both the dam and fetus. Plasma zinc concentrations of calves at birth were increased by zinc supplementation, but the increases were affected by breed of dam. Zinc supplementation increased plasma zinc concentrations of the calf at 6 weeks of age. We conclude that results of zinc supplementation may be breed dependent and zinc supplementation during gestation affects blood levels in the calf by transfer of this element in utero plus transfer in the dam's milk following birth.
Technical Abstract: A genotype x zinc supplementation interaction study was conducted involving 85 primiparous heifers. Heifers were from three genotypes [xbred composite (XCP), Hereford (H) or Charolais (Ch) sired] bred AI to three sire breeds [H, Limousin (L) or Piedmontese (P)]. The dry lot diet was 85% corn silage, 10% alfalfa hay and 5% barley with (ZN) or without (NZN) 170 mg daily supplemental zinc fed the last trimester of gestation. Precalving data were obtained 10 ñ 4 d prior to the predicted calving date. Dystocia was recorded 0=no assistance to 4=major difficulty. Dams and calves were weighed and blood sampled within 48 hr postpartum; a calf blood sample was obtained in mid May when calves were approximately 6 wk old. Dam precalving body weight (P<.05) and pelvic area (P<.05) averages were: 469 and 260; 454 and 247; 582 kg and 308 sq. cm. for XCP, H and Ch dams, respectively. Effects of ZN on dystocia were not significant. Birth weight was affected by ZN x sire breed (P<.01; H, 38.8 vs 35.4; L, 35.6 vs 36.4; P, 38.8 vs 38.8 kg, NZN vs ZN, respectively) and ZN x dam breed (P<.01; XCP, 35.5 vs 35.6; H, 36.8 vs 36.8; Ch, 41.2 vs 38.1 kg, NZN vs ZN, respectively). Plasma zinc of calves at birth was affected by dam breed x ZN treatment interaction (P<.05): .79 vs .93, .75 vs .87 and .86 vs .80 ppm for XCP, H and Ch dams, NZN vs ZN, respectively. At 6 wks of age, plasma zinc concentrations of calves suckling dams receiving ZN during gestation (1.23 ppm) exceeded those of calves suckling control dams (1.12 ppm; P<.05). We conclude zinc requirements may be breed dependent and zinc supplementation during gestation affects plasma zinc of the calf directly in utero plus transfer in the milk postnatally.