Performance of steers supplemented with copper before and during receiving at the feedlot

Abstract

The effects of supplemental Cu in the diets of beef steers grazing winter-annual pasture and(or) during receiving at a feedlot were examined. On 19 February, 84 steers (average BW = 216 ± 1.5 kg) were weighed and randomly assigned to 12 bermudagrass pastures (0.81 ha each) over-seeded with wheat, rye, and annual ryegrass (seven steers/pasture). All steers were fed 0.91 kg daily of a corn-based supplement containing a basal level of Cu (control; 21 mg of Cu d-1) while grazing winter-annual pasture until 16 April. On 16 April, the steers were weighed, bled via jugular venipuncture, and one-half of the steers were supplemented with an additional 1.5 of Cu proteinate (CuPRO; 150 mg Cu d-1), during the last 29 d of grazing before shipping to a feedlot. On 17 May, the steers were shipped to a research feedlot (14 h transit, 1.016 km). After arrival on 18 May, one-half of the groups of cattle that received each treatment during grazing received 150 mg of Cu from CuPRO daily (2 × 2 factorial) for 42 d. The supplementation of steers grazing pasture with additional Cu from CuPRO during the last 29 d of grazing tended to increase (P = 0.10) ADG and BW on day 29. The BW advantage expressed by CuPRO supplemented steers was not as apparent (P = 0.18) upon arrival at the feedlot, but at the conclusion of the receiving period, steers fed CuPRO on pasture were 6.3 kg heavier (P = 0.04). No benefit was noted (P > 0.14) when CUPRO was fed during receiving at the feedlot. During the grazing phase, additional Cu from CuPRO seemed beneficial compared to basal Cu levels.