Pre-harvest Feeding, Feeding Duration, and Inclusion of a β-agonist on Market Dairy Cow Feedlot Performance and Carcass Characteristics
DOI:
https://doi.org/10.21423/aabppro20094255Keywords:
feeding duration, feedlot performance, supplementation, beta agonist, market dairy cow, zilpaterol hydrochlorideAbstract
The objectives of this experiment were to evaluate the effects of pre-harvest feeding, feeding duration, and use of a beta agonist (zilpaterol hydrochloride) on market dairy cow feedlot performance and carcass characteristics.
The experiment was set up in a randomized block design, with pen as the experimental unit. A total of 160 lactating market dairy cows (already culled from herds) were used for the project. Cattle were assigned to one of the following five treatments: harvest immediately on day 0 (Con), feed for 70 days without zilpaterol (70no), feed for 70 days with zilpaterol from day 4 7 to day 67 (70zil), feed for 105 days without zilpaterol (105no), and feed for 105 days with zilpaterol from day 82 to day 102 (105zil).
Cattle were fed in a commercial feedlot in southern Idaho and received a high concentrate potato by-product- based ration. There was a feeding duration length x zilpaterol interaction (P < 0.005) for final body weight (BW). The 70no, 70zil, and 105no cows had greater (P < 0.05) final BW compared to control cows, while 105zil cows had greater (P < 0.05) final BW compared to control and all other fed treatments. The effect of zilpaterol supplementation on average daily gain (ADG) was inconsistent, since 105zil cows had a greater (P < 0.05) ADG vs. 105no cows, yetADG was not different (P > 0.10) among 70no and 70zil cows. No differences were observed (P > 0.10) for the feed-to-gain ratio from the main effects of feeding length or zilpaterol supplementation. Final hot carcass weight (HCW) was greater (P < 0.0001) among fed compared to control cows, and cows receiving zilpaterol had greater (P < 0.03) HCW than cows not receiving a B-agonist. Measured ribeye area (REA) was greater among fed (P < 0.001) compared to control cows and also greater (P < 0.01) among cows receiving zilpaterol compared to no zilpaterol. The effects of feeding duration and zilpaterol supplementation on feedlot performance and carcass characteristics were inconsistent.
