Document Type

Thesis - Open Access

Award Date

2023

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Warren Rusche

Keywords

Beef cattle growth, Carcass composition, Feedlot, Frame size, Urea space

Abstract

The objective of the study was to determine the influence that initial BW has on growth performance responses, efficiency of dietary net energy (NE) utilization, and carcass traits in feedlot steers. Light- and heavy-weight Charolais×Red Angus steers (n = 70) selected from a larger single-source group were used in a 209-d growing-finishing feedlot experiment at the Ruminant Nutrition Center, in Brookings, SD. On d-0 and d-1 weight and hip height (HH) measurements were collected for allotment purposes; the initial experimental weight was the average between d 0 and d 1 BW. Steers were assigned to two groups based on initial BW (light initial weight, LIW = 273kg; heavy initial weight, HIW = 356kg) and allotted into 10 pens (n = 7 steers per pen; 5 pens per experimental group). Steers were fed a common diet containing 16% roughage (13.1% CP and 23.4% NDF, DM basis) once daily. Diet included liquid supplement containing vitamins and minerals to meet or exceed 2016 NASEM requirements with monensin included at 30 g/ton. Experimental data were analyzed as a randomized complete block design with pen as the experimental unit. Treatment was included as a fixed effect and block (location) was considered a random effect in the statistical model. Observed NEm (P = 0.17) and NEg (P = 0.17) for LIW and HIW did not differ. LIW steers had a greater cumulative HH change (P = 0.04). A treatment  day interaction (P = 0.05) was observed for HH with HIW steers having a greater HH at all time points. Final BW and carcass-adjusted (HCW/0.625) BW were greater for HIW steers by 13.1% and 13.4% respectively (P ≤ 0.01). HIW steers had a greater DMI (P = 0.01) compared to LIW. Cumulative ADG was greater for HIW by 3% (P = 0.04). LIW steers had improved feed conversion (P = 0.01; 5.95 and 6.62, respectively). HIW steers had greater (P  0.05) HCW, marbling scores, and yield grade (YG), with decreased REA/HCW (P = 0.01) compared to LIW. The distribution of USDA Yield Grade was altered by initial BW (P = 0.04). No differences were detected (P  0.22) for the distribution of Quality grade nor liver abscess prevalence and severity. In conclusion, HIW steers had greater growth, but poorer feed efficiency compared to LIW steers. Steers with a HIW produced fatter carcasses with a greater degree of marbling.

Publisher

South Dakota State University

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Beef Science Commons

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Rights Statement

In Copyright