Beef Cattle Browsing – October 2006

Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus October 2006 This newsletter is published by Texas AgriLife Extension – Animal Science. Media, feel free to use this information as needed and cite Texas A&M University Beef Cattle Browsing Newsletter, Dr. Steve Hammack.TIGHTER CAB SPECS? Certified Angus Beef has changed some of their carcass specifications. Carcasses over 1000 lb and those with ribeye area less than 10 sq in or over 16 sq in will not be certified. CAB estimates this will eliminate at least 6 percent of carcasses that currently qualify. However, Yield Grade specifications have been relaxed, so little effect is predicted on total number certifying. While the upper limit on carcass weight is a restriction, 1000 lb equates to almost 1600 lb live weight, so we’re still dealing with very large/heavy cattle on the upper end. CAB would probably like to tighten weight and ribeye specifications even more. However, currently only about 15 percent of cattle that pre-qualify live (51 % or greater black hide) meet the carcass requirements, and demand exceeds supply. GROWTH PROMOTANTS FOR FINISHING In a group of four papers presented at the recent American Society of Animal Science Annual Meeting, Kansas researchers evaluated ractopamine and several implants in separate trials. Ractopamine (RAC, Optaflexx™ ) was fed for the final 28 days before cattle were harvested and compared to controls. In steer calves (2060 head, British X Continental, initial weight 554 lb), RAC increased total ADG 2.7%, final weight 15 lb, and percentage Yield Grade 1 by 6 percentage units, but decreased percent Choice by 8 percentage units. In yearling heifers (2252 head, British X Continental, initial weight 629 lb), RAC increased final weight 19 lb and feed efficiency by 2% with no significant effects on carcass factors, except that carcass weight and ribeye area tended to increase. In yearling steers (2252 head, initial weight 691 lb), RAC increased ADG, carcass weight, ribeye area, and feed efficiency, with no effect on Quality Grade or Yield Grade.Finally, in three trials with a total of 2417 heifers (initial group weights averaging from 546 lb to 623 lb) a single initial implant of Revalor-200TM was compared to an initial Revalor-IH TM followed by reimplant with Finaplix-HTM . There was no significant difference in feeding performance or Yield Grade, but the single implant program reduced Quality Grade. The latter confirms results from some other studies indicating that less aggressive implant programs can result in similar feeding performance without adverse effects on carcass quality. (J. Animal Sci. 84:Supple.1, pp. 419-420) RESIDUAL FEED INTAKE (NET FEED EFFICIENCY) Residual feed intake (RFI) is defined as the difference between actual feed intake and predicted feed requirements for body maintenance and growth. So, more efficient animals have a low RFI value. Canadian researchers have reviewed existing research reports and concluded that genetic selection for low RFI could: