Beef Cattle Browsing – October 2006

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:

lower maintenance requirements of the cow herd about 10reduce feed intake 10 to 12 %have no effect on ADG or mature sizeimprove feed efficiency 9 to 15%reduce gain in body fat 4% without affecting carcass quality gradelower weight of liver and digestive tractimprove efficiency of conversion of cow feed to calf weightlower methane emissions and manure levels of nitrogen, phosphorous, and potassium

(Alberta Agriculture, Food and Rural Development Report, July 1, 2006) FEEDING CALVES vs. YEARLINGS From 1995 to 2003, Nebraska researchers purchased Spring-born calves and separated them into calf-fed (C, avg = 642 lb) or yearling (Y, avg = 526 lb) groups. C were immediately placed on feed for an average of 168 days . Y were wintered on corn residue, summer-grazed, and placed on feed weighing 840 lb for an average of 90 days. Y ate 43% more feed/day but total consumption was 23% less. Y gained 0.73lb/day more but C had 17% higher feed efficiency. Y weighed 83 lb more at harvest but had .06 in less fat cover. So, C converted feed to gain more efficiently, but required more total feed to finish. Relative economics of the two systems was not reported. (J. Animal Sci. Supple. 1, 84:121) FACTORS AFFECTING GRID VALUE Colorado researchers studied factors affecting total value of 1215 steer and 785 heifer carcasses marketed from 1998 to 2004 on simulated grids, with variable prices for Quality Grade (QG) and Yield Grade (YG). One price grid emphasized QG and the other YG. Within these two basic grids, Choice (Ch) was valued over Select (Sel) by $5, $10, or $20 per cwt. Also, three base (Ch YG3) prices were evaluated: $118, $131, and $144/cwt carcass. (Current average Ch price is about $140/cwt.) Overall, 29% of the carcasses were Ch YG3, 23 % were Ch YG2, and 21% were Sel YG2.By far the most important factor affecting total carcass value was weight, ranging from accounting for 51% with $118 base and $20 Ch-Sel spread to 93% with $144 base/$5 spread. QG accounted for a range of from 4% with $145 base/$5 spread to 45% with $118 base/$20 spread. YG accounted for only 4 to 8% of revenue variation regardless of base price, Ch-Sel spread, or grid. YG was as important as QG only at low Ch-Sel spread. At higher spreads, QG was 8 to 9 times more important than YG. While all grids severely discounted poor YG, the net discounts for Ch YG4 were relatively small at higher Ch-Sel spreads. So, under these conditions there is incentive to feed longer to heavier weights to realize more dollars from more pounds and higher QG. However, there were no discounts in this study for excessive carcass weight (often set at 950 lb in most grids). Also, cattle fed longer become fatter, so feed efficiency declines. Accounting for these factors would probably have changed results somewhat. Finally, over the course of this work (1998 to 2004), average days on feed increased by 13, carcass weight increased 32 lb, and YG4-5 increased from 1.3% to 7.7%, but percent Choice and Prime varied little, ranging from 60 to 63%. (Prof. Anim. Sci. 22:41)ANGUS vs. ROMOSINUANO In two consecutive years, winter-born purebred Angus (AN) and Romosinuano (RO, a Criollo-type, native to northern Colombia) were weaned in the fall in central Florida and shipped to central Oklahoma for wheat-pasture grazing followed by finishing. Weaning weights did not vary. AN grazing gains were 59 lb (23%) higher than RO. In the feedlot, AN were fed for 22 days less, had 9% higher ADG, and weighed 35 lb more at harvest, but feed efficiency did not differ. AN carcasses averaged low Choice compared to high Select for RO. RO had more desirable Yield Grades than AN (2.61 vs. 2.92). While RO may offer some potential in the American South/Southwest on the maternal side, as with several similar breeds developed in tropical regions, they appear to offer no advantages in postweaning performance or carcass merit. (Prof. Anim. Sci. 22:8)