Beef Cattle Browsing – February 2010

Beef Cattle Browsing

Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus

February 2010

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.

Pending federal legislation would encourage farmers to lower their “carbon footprint” by planting more trees and implementing low-carbon production methods. Recent computer modeling by the Environmental Protection Agency has shown up to 59 million acres could be converted to trees, possibly resulting in less food production than needed. The Secretary of Agriculture has asked that the models be reviewed. (, 1/20/10)

The effects of bovine respiratory disease (BRD) and overall incidence of pathogenic diseases (IPD) on carcass traits were investigated. Two groups were studied. The first (GP1) included 642 crossbred steers involving seven British and Continental breeds. The second (GP2) included 621 crossbred steers involving tropically-adapted Bos taurus and Bos indicus-influenced breeds as well as British breeds. Treatment incidence for BRD was 20% in GP1 and 24% in GP2. In both groups, cattle treated for BRD or IPD had significantly lower fat cover and numerical Yield Grade. There was a tendency for treatment in GP1 to lower percent Choice. Mechanical estimate of tenderness was significantly lower in GP2 treated for BRD, but not in GP1. These results agree with most previous research that respiratory and other sickness results in adverse effects on carcass merit. (U. S. Meat Animal Research Center; J. Animal Sci. 88:491)

Scientists at 15 research entities from around the world collaborated on a study of 48 breeds of cattle using genomic techniques. It was concluded that European cattle arose in the Fertile Crescent, sometimes called the Cradle of Civilization, in parts of what is now Israel, Iraq, Iran, Jordan, Lebanon, and Syria. From there movement was through Turkey, the Balkans, and Italy, dispersing through Central Europe and France and then to the British Isles. A second route appeared to be from Africa or the Fertile Crescent across the sea to the Iberian Peninsula. The authors speculated that knowledge of the evolution of breeds could lead to a better understanding of their genetic relationships. For instance, it would be helpful to know if breeds that excel in marbling are closely related or not. If not, different approaches could be needed in using genomic methods to improve marbling in all cattle. (Proc. of Nat. Acad. of Sciences 106:44 and Univ. of Missouri press release)

Pre-slaughter stress has been shown to adversely affect beef quality. Some studies in sheep and swine have indicated dietary magnesium supplementation could reduce the effect of stress. Groups of 72 steers and 72 heifers were fed three levels of magnesium for the final 14 days before slaughter. All cattle were commingled 1 day before slaughter to induce stress from mixing unfamiliar animals. Heifers produced carcasses with significantly higher marbling, greater tenderness, and lower incidence of dark cutting carcasses. There was no significant effect on lean quality due to any level of magnesium supplementation. (Colorado State Univ.; J. Animal Sci. 88:349)

The Wye Plantation Angus herd in Maryland was started in 1937 with 18 yearling heifers and 2 bulls. One of the bulls had an inbreeding coefficient of 2% and an average relationship of 2% to the foundation heifers. The other bull had an inbreeding coefficient of 16% but was essentially unrelated to the heifers. Over the next two decades 19 imported bulls (average inbreeding of 3%), unrelated to the foundation animals, were used. The herd was then closed to outside breeding, so some increase in inbreeding was inevitable. In recent years, approximately 170 females are bred each year. Records from almost 11,000 animals were analyzed to determine level of inbreeding and effects on production traits.

Average inbreeding was 7% over the period from 1939 to 2005 and 12% for the last year. Inbreeding depression was found for birth weight, actual weaning weight, 205-day adjusted weight, and scrotal circumference at weaning. Individual inbreeding level resulted in greater effects than from maternal inbreeding. The authors indicated that genetic selection can counteract the effects of inbreeding depression and estimated that 1 generation of selection could offset 7 generations of the level of increase in inbreeding in this herd. So, mild inbreeding appears to have minor depressing effects. However, it has been well documented that heterosis from crossbreeding, the opposite of inbreeding, offers benefits too large to ignore in many traits. (Univ. of Maryland; J. Animal Sci. 88:87).

Residual feed intake (RFI) is the difference between actual and expected feed requirements for body maintenance and weight gain. So, a negative RFI indicates lower than expected feed intake and, therefore, higher feed efficiency. RFI has been found to be independent of body weight or average daily gain. In this study, data were collected on 60 head of Angus X Hereford steers. Results were then compared of the 15 highest RFI and 15 lowest RFI individuals.

Low RFI steers had significantly lower dry matter intake and higher gain to feed ratio. There were no significant differences in dry matter digestibility, days on feed, slaughter weight, carcass weight, ribeye area, fat thickness, percent carcass fat, or USDA quality grade. However, gain to feed ratio accounted for 98% of the variation in cost of weight gain, while RFI accounted for only 18% of that variation. The authors concluded that “RFI is less useful than gain to feed ratio as an indicator of feedlot efficiency and profitability. (Univ. of California; J. Animal Sci. 88:324)

Reports in the popular press periodically link consumption of red meat with various cancers in humans. A recent summary of research was published, “Red Meat and Processed Meat Consumption and Cancer: A Technical Summary of the Epidemiologic Evidence.” The report found no evidence of an independent positive association between red or processed meat consumption and common cancers. An Executive Summary of the report can be viewed here and accessed at . The full report can be obtained from the National Cattleman’s Beef Association, (303) 368-3138.

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