|Rouquette, Jr, F.|
Submitted to: Texas Beef Cattle Research
Publication Type: Experiment Station
Publication Acceptance Date: 5/1/2003
Publication Date: 9/1/2003
Citation: Aiken, G.E., Rouquette, Jr, F.M., Miller, R.K. 2003. Stocking rate effects on ultrasound measures of 12th to 13th rib fat thickness and ribeye area. Texas Beef Cattle Research. p 9-12. Interpretive Summary: Beef cattle production and marketing in the U.S. is presently changing to improve product quality and meet consumer needs. A current trend in cattle marketing is to retain ownership of cattle from pasture to feedyard; thereby generating less emphasis on body weight and more on body condition. Measurements of fat and lean tissue deposition in grazing research can provide useful information to cattlemen who retain ownership of their cattle through the feedyard and therefore must consider body condition in making management decisions. A grazing experiment used ultrasound technology to determine grazing treatment effects on carcass-related traits for stocker steers. Influence of average daily weight gain on 12th and 13th rib backfat thickness and ribeye area was determined for steers grazing a mixture of 'Maton' rye and 'TAM90' ryegrass. Ribeye area increased proportionately over the range of average daily weights, but backfat thickness increased at an increasing rate as daily weight gains increased beyond 2 lb/calf/day. Cattle that are backgrounded on pasture and managed to achieve high daily weight gain would likely require less time on costly finishing rations in the feedyard.
Technical Abstract: Management of stocker cattle could have carry-over effects on eventual carcass characteristics, but these effects have not been sufficiently documented. Yearling steers were ultrasonically scanned at the start and finish of grazing experiment with a 'Maton' rye and 'TAM90' ryegrass pasture mixture to determine the influence of stocking rate (1.5, 2.1, and 2.7 steers/ac) on 12th and 13th rib fat thickness and ribeye area, and to evaluate trends in the two ultrasound measures over a range of average daily weight gains. Fat thickness decreased nonlinearly and ribeye area declined linearly as stocking rate increased. Conversely, ribeye area increased linearly and fat thickness increased at an increasing rate as average daily gain increased above 2 lb/calf/day. Results of the experiment indicated that ribeye area and external fat thickness will be greater than that of ribeye area as higher planes of nutrition are reached with reduced stocking.