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Beef Cattle Browsing

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

July 2007

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.

HUMP HEIGHT vs. QUALITY
High quality beef programs typically exclude carcasses with humps measuring over some prescribed maximum, often two inches. A paper summarized here last month addressed growth and carcass traits of purebred Brahman steers and also looked at hump height. These steers averaged Slight90 marbling (MS), Select77 USDA Quality Grade (QG), and 7.62 inches hump height (HH). (So, if purebred Brahman average about 8 inches hump height, then it appears 2 inches should probably be the average of about 1/4 Brahman.) Genetic correlations with HH were 0.17 for MS and 0.04 for QG. Phenotypic correlations were 0.21 for MS and 0.17 for QG. Correlations between HH and tenderness were near zero or positive. (Also of interest, the genetic correlation between HH and ADG was -0.41 but the phenotypic correlation was 0.23. These cattle were fed from April through August in South Texas. Under those conditions, cattle with greater hump height actually tended to gain more.)

Correlations with quality traits were low, and certainly did not indicate that greater hump height was either genetically or phenotypically related to reduced marbling, Quality Grade, or tenderness. Perhaps hump height should be re-evaluated in high-quality programs? (J. Animal Sci.85:1377)

EFFECT OF EXTERNAL STIMULI ON BREEDING PERFORMANCE OF COWS
Montana State University researchers studied the effects on AI breeding performance of cows exposed to bulls, bull urine, or across a fence from bulls. Compared to controls, all three types of exposure resulted in higher percentages of cows showing estrus after treatment with prostaglandin. In cows exposed to bulls, AI pregnancy rate was 84.6% vs. 60.0% for unexposed controls. In cows continuously exposed to bull urine, pregnancy was 89.5% vs. 55.0% for cows exposed to steer urine. But in cows maintained across a fence from bulls, pregnancy was 57.7% vs. 77.0% for controls. The authors concluded that “a novel urinary pheromone of bulls” may be related to higher fertility in cows. (J. Animal Sci. 85:1669)

PROTEIN EFFECTS ON FEEDLOT PERFORMANCE, ODOR, & EMISSIONS
USDA-ARS researchers at Clay Center, NB and Bushland, TX fed Charolais-crossbred steers (initial weight 667 lb) for either 185 or 212 days to final weights of approximately 1250 lb. Treatment groups were: low protein (LP, 9.1% Crude Protein), medium protein (MP, 11.8% CP), high protein (HP, 14.9% CP), or low and high alternated every 48 hours (AP). LP tended to eat less feed than MP or AP but not HP. LP gained about 30% slower than the other treatments, which did not differ. LP carcasses also had less fat thickness, numerically lower Yield Grades, and tended to have less marbling. LP had lower Crude Protein in a slurry of feces, feedlot soil, urine, and water. Slurries from HP and AP had higher concentration of total aromatics and ammonia than LP or MP. While feeding lower levels of protein reduced nitrogen losses, odor, and emissions, the tradeoff was drastically lower rate of gain. (J. Animal Sci. 85:1487)

EFFECT OF FEEDING FATS ON MEAT COMPOSITION AND QAULITY
The health and performance benefits from weaning and preconditioning calves has been well documented by several sources, including Texas A&M Ranch to Rail. Also, data from video auctions show that buyers will pay for such management. More evidence is found in a report from the Iowa Beef Center. Data were collected on over 20,000 head from 105 sales at nine auction markets throughout Iowa in the fall/winter of 2005-06. Compared to calves that were neither weaned nor vaccinated (or no claim was made) the following average bonuses ($/cwt) were paid:

Bonuses can be had, but the most benefit comes from following a prescribed program that is certified by some disinterested third part. (http://www.iowabeefcenter.org/content/activities.htm)

FACTORS AFFECTING PRICE OF CALVES
The same Iowa Beef Center report from above evaluated other factors affecting price. The following prices are deviations from the base of heifer, polled/dehorned, non-black, not fleshy, healthy, clean:

The median lot size was 5 head. Above that size, price steadily increased to a bonus of almost $13/cwt at 78 head (about a truck load).

GENETIC FACTORS IN STAYABILITY
Stayability has been defined as the probability of a female remaining in the herd to some specific age, given the opportunity to do so. As such it is thought to be an indirect measure of fertility, since open individuals tend to be culled. Several U. S. breed associations currently calculate Stayability EPD. Brazilian researchers evaluated data from about 17,000 Nellore cows born from 1987 to 2003 managed in 15 herds owned by the same corporation. All open cows were culled and stayability was evaluated at 5, 6, and 7 years of age. Heritabilities of stayability were similar at all three ages, ranging from 0.22 to 0.28, and the genetic trend for stayability was positive at all three ages. There was sufficient variation in stayability to indicate that selection over time could be effective. Little evidence was found that selection on 7-year stayability would yield much more response than on 5-year. The authors therefore concluded that selection using the 5-year trait would be most effective, rather than 6- or 7-year, because heritabilities are similar, there are more records involved, and it is obtained earlier in life. (J. Animal Sci. 85:1780)

TEXAS A&M BEEF CATTLE SHORT COURSE
The 53rd Annual Texas A&M Beef Cattle Short Course will be held in College Station on August 6-8. A variety of topics affecting beef cattle production will be discussed. Full details are available at http://beef.tamu.edu.