Beef Cattle Browsing – June 2005

Beef Cattle Browsing

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

June 2005

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.

BSE (Bovine Spongiform Encephalopathy, also known as “mad cow disease”) is one of a number of TSE (Transmissible Spongiform Encephalopathy) diseases. The first report of a TSE was in 1732 involving scrapie in sheep. BSE was first observed in the United Kingdom in 1984 and was specifically diagnosed in 1987. A recent review by Illinois researchers of 217 references summarized the current state of knowledge. The major findings of the review were: TSEs are thought to be caused by an abnormal prion protein; effects are primarily neurological (behavior changes, impaired coordination, muscle spasms, etc.); transmission is by exposure to infected tissue or residue, and the primary method for BSE seems to have been through meat and bone meal from infected animals; most mammals are potentially susceptible to TSEs; transmission between species is rare, but BSE may have arisen from transmission of scrapie from sheep to cattle; there is evidence that TSEs can develop spontaneously at very low levels (possibly 1 in 1 million), so they probably can not be eradicated; and because of the low probability of transmission between species and the low levels of prion in non-nervous tissue, there is minimum risk to humans from consumption of conventional animals. While the biological risk of BSE may be minimal, the political and potential economic risk is not. If for no other reason, protection and development of export markets will be highly influenced by continued concerns about BSE. (J. Animal Sci. 83:1455)

Researchers at the U. S. Meat Animal Research Center, Clay Center, Nebraska, analyzed over 110,000 records from various breeds and crosses collected over a 20-year period to study possible genetic effects on incidence of Bovine Respiratory Disease (BRD) in beef calves, whether from viral, bacterial, or mycoplasmal causes. Spring-born calves were vaccinated with 8-way clostridial and 5-way leptospirial vaccines at average age of 42 days and boostered with those vaccines at average age of 165 days (about 30 days before weaning), along with a modified-live viral vaccine at that time. Average incidence of BRD was 10.5% (ranging from 3.3% for the lowest year to 23.6% for the highest) of which 13.1% died (so, there was 1.4% overall death loss due to BRD). There were two peaks in incidence, from birth to 20 days of age and again from 70 to 100 days of age. Difficult birth resulted in more BRD. Overall, British crosses had lower incidence than purebreds, and British X Continental or tropically-adapted breed crosses were lower than British crosses. Based on heritability estimates, it was stated that “selection for BRD could be effective provided all animals are challenged adequately with the disease”. That is, it might be possible to increase genetic resistance in a population over time but only by exposing every animal, even those not resistant, a mixed blessing at best. Interestingly, there was a negative genetic correlation between direct and maternal effects. The authors speculated that dams superior for providing resistance to their calves may delay development of their calf’s immune system. (J. Animal Sci. 83:1247)

Evidence continues to accumulate that health problems adversely affect feeding performance and carcass merit. These effects were evaluated in 6618 calves fed in eight Iowa feedlots in the Iowa Tri-County Steer Carcass Futurity. About 70% of the calves were from “Southeast” origin (Alabama, Georgia, South Carolina, Virginia) and the remainder from “Midwest” (Indiana, Iowa, Minnesota, Missouri). There were 83.1% of the calves that did not require health treatment (0T), 8.7% required one treatment (1T), and 8.2% required two treatments (2T). (In the following comparisons, any stated differences were statistically significant at the 5% level.) ADG and feed conversion were superior for 0T (3.06 lb/da and 7.11 lb feed/lb gain) compared to either 1T (2.93 lb/da and 7.23 lb feed/lb gain) or 2T (2.87 lb/da and 7.26 lb feed/lb gain), which did not differ from each other. All three groups differed from each other in carcass quality: 0T had 72.1% Low Choice or higher; 1T had 63.9%; and 2T had 58.9%. Among the calves that were provisionally eligible (black hair color > 50%) for Certified Angus Beef (CAB), 0T had 27.1% qualify on CAB carcass factors, 1T had 24.2%, and 2T had 18.7%. Midwest calves had numerically small but statistically significant advantages in gain, efficiency, and quality grade over Southeast calves. Steers, compared to heifers, gained faster and more efficiently, but had lower quality grade. Heifers had 29.0% CAB, compared to only 17.7% for steers. (Ia. St. Univ. 2004 Animal Industry Rpt. R1885)


Some, but maybe not for what might be thought, at least according to a report out of Kansas State. Data were analyzed from 60 Angus bull sales with 8285 bulls from 11 Midwest, Rocky Mountain, and Northwest states. Among the many types of information usually found in a bull sale catalog, it was concluded that “buyers seem to pay particular attention to birth weight EPD, adjusted yearling weight, and ultrasound ribeye EPD”. The authors speculated that adjusted yearling weight was given more importance by buyers than yearling EPD because the yearling EPD of these young bulls “is based solely on records of related animals (parents, grandparents, and siblings)”. It was also found that “buyers recognize the reputations of breeders and are willing to pay premiums or discounts for comparable animals sold at different sales”. (Kan. St. An. Sci. Dept. Prog. Rpt. 943)

If you ever worked out back at the local sale barn, you know how dusty it can get under that roof. And that’s probably unhealthy. How unhealthy? Well, somebody has compared health effects of working in covered and open facilities. Colorado, Pennsylvania, and North Carolina researchers surveyed 900 certified equine instructors in the U. S. Among nonsmokers, 40.6% using covered arenas reported chronic bronchitis, compared to 25.9% in open arenas. Smokers had 63.5% for covered vs. 47.1% for open. (According to the American Lung Association, the prevalence of chronic bronchitis in the general American population is only 5.4%.) Of course, the alternative to covered pens can be mud. Take your choice. (Prof. Anim. Sci. 21:128)

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