Estimated copper requirements of angus and simmental heifers.
In Exp. 1, Simmental (n = 21) and Angus (n = 21) heifers, approximately 9 mo of age, were used in a 160-d study to determine the effect of dietary Cu on growth and Cu status. Two- or three-yr-old first-calf heifers (21 Angus and 21 Simmental) entering into their last trimester of pregnancy were used in Exp. 2 to estimate Cu requirements of the two breeds during gestation and early lactation. Treatments in both studies consisted of 0 (control), 7, or 14 mg of supplemental Cu (as CuSO4)/kg of DM. The control corn silage-based diets contained 6.4 and 4.4 mg of Cu/kg of DM in Exp. 1 and 2, respectively, and 1.2 mg of Mo/kg. Dietary Cu did not affect performance in either breed in Exp. 1. Copper supplementation generally did not affect plasma Cu concentrations in Angus heifers, but increased (P < 0.05) plasma Cu in Simmental heifers from d 37 until the end of Exp. 1. Final liver Cu concentrations were lower (P < 0.05) than initial concentrations in control Angus and Simmental heifers; however, liver Cu increased (P < 0.01) in Cu-supplemented heifers. In Exp. 2, Cu supplementation of the control diet increased (P < 0.05) plasma Cu during gestation and greatly increased (P < 0.01) liver Cu in both breeds. Calves born to cows not supplemented with Cu also had lower plasma Cu concentrations than Cu-supplemented calves by 73 d of age. In both studies, control Simmental heifers had lower (P < 0.05) plasma Cu concentrations than Angus on most sampling dates. When Cu was supplemented at 7 or 14 mg/kg of DM,few differences in plasma Cu concentrations were observed between breeds. Results suggest that Angus heifers have a lower minimal Cu requirement than Simmental. Based on liver Cu, the control diets containing 4.4 or 6.4 mg of Cu/kg of DM did not meet the Cu requirement of either breed during gestation and lactation or growth. Addition of 7 mg of Cu/kg of DM to the control diets met Cu requirements of both breeds.
Department of Animal Science and Interdepartmental Nutrition Program, North Carolina State University, Raleigh 27695-7621, USA.
L A
LA
Mullis
J W
JW
Spears
R L
RL
McCraw
D000818:Animals; D001947:Breeding; D002417:Cattle / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D003300:Copper / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D005260:Female; D007774:Lactation / Q000378:metabolism / Q000502:physiology*; D008099:Liver / Q000737:chemistry; D009751:Nutritional Requirements; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism / Q000502:physiology*; D011897:Random Allocation
D003300:Copper