Ultrasound and Carcass Measures of Different Biological Types of Beef Cattle Developed under a Rotational Management-Intensive Grazing System

摘要

Yearling beef steers (n = 33) representing four biological types, typical of commercial cattle in northwest Arkansas, were evaluated for muscle and fat deposition using real-time ultrasound measurements and carcass traits. Biological types included large-framed, late maturing (LL; n = 6), medium-framed, late maturing (ML; n = 9), medium-framed, intermediate maturing (MI; n = 9) and medium-framed, early maturing (ME; n = 9) steers. Steers grazed cool-season and warm-season forages, using a rotationalmanagement-intensive grazing system. Steers were rotated to new paddocks daily. Target BW and body condition score at harvest were 1,000 Ib and 6.0 (1 to 9 scale), respectively. Average number of days before harvest was 300 +- 13 with a mean harvest BW of 1,020 +- 17 Ib and a 5.9 +- 0.5 body condition score. Overall BW gain was 489 Ib +- 22 at a rate of 1.6 Ib/d +- 0.05. Generally, carcass data were correlated with the final ultrasound readings. Marbling score was greater (P < 0.05) for ME than LL steers (Slight 46 vs. Trace 39), but there was no difference (P > 0.05) in marbling score for MI and ML steers. There was an interaction (P < 0.05) between biological types and days on grass until harvest for ribeye area. Days on grass did not affect (P > 0.05) other carcass traits. Based on marbling scores, ME steers best match the all-forage diet utilizing a rotational management-intensive grazing system.