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Beef Cattle Browsing

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

May 2008

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.

CORN-BASED DISTILLERS GRAINS – WHAT IS THE FUTURE?
The Center for Agricultural and Rural Development at Iowa State University projects the production of corn-based distillers grains to reach between 40 and 88 million metric tons in less than 10 years. Large volumes of these products would need to be used in livestock production, especially beef, to prevent surpluses. The Center has prepared a review and report that addresses this issue.

The primary nutrient content problems with these products in beef rations are excessive and highly variable levels of sulfur, fat, and phosphorous. Excess levels of distillers grains will reduce weight gains and somewhat impact carcass merit (reducing carcass quality grade and percentage of red meat). The paper concludes that the maximum level of distillers grains in finishing rations is no more than 50%, being highest in rations using dry-rolled corn, lower with high-moisture corn, and lowest with steam-flaked corn. Feedyards in the Southern Plains tend to use more steam-flaked corn than those farther north. This could affect how much distillers grain can be used in feeding cattle in the different regions. Finally, it is noted that changes in processing techniques in ethanol plants could improve nutritional content and reduce variability of distillers grains, but that economics will drive such decisions. The full report can be seen at www.card.iastate.edu 

EFFECT OF BODY CONDITION ON REPRODUCTION
Numerous research studies have shown a relationship in beef cows between reproduction and body fatness at calving, measured by Body Condition Score (BCS, where 1=emaciated to 9=obese). South Dakota State University researchers confirmed this, finding post partum intervals as follows: BCS3 = 88 days; BCS 4 = 70 days; BCS 5 = 59 days; BCS 6 = 52 days; BCS 7 = 31 days. The authors noted that, for best efficiency, post partum intervals to first heat should not exceed 60 days and the minimum BCS at calving should be BCS 5 for mature cows or BCS 6 for heifers calving first at two years of age. (Proc. 2007 Range Beef Cow Symposium, Ft. Collins, CO)

FORECASTING HEAT STRESS IN CATTLE
Summer will soon be here, and some cattle will have trouble coping. The U. S. Meat Animal Research Center (MARC) at Clay Center, NB, has developed a system to forecast heat stress. Factors include not only temperature and humidity (used in calculating the Temperature-Humidity Index heard on weather forecasts) but also wind speed and solar radiation. Data used are seven-day forecasts of the four weather factors from the National Weather Service.

MARC has determined that breathing rate (breaths/minute) is a good predictor of heat stress as follows: 90 = normal; 90-110 = be alert; 110-130 = danger; above 130 = emergency. Increased risk factors are: exclusively British/European breeding, dark color, excitable disposition, bad health and/or history of health problems, newly arrived, recent transfer from northern regions, and full-finished cattle. One of the most effective ways of minimizing heat stress is through some Bos indicus or other tropically-adapted genetics. More detailed information on heat stress can be accessed at http://www.ars.usda.gov/Main/docs.htm?docid=16750

CALVING SEASON & WEANING AGE vs. MATERNAL PERFORMANCE
USDA-Miles City, MT researchers studied over two years the effects of calving season and age at which replacement females were weaned on first-calving lactation and calf gain. Calves were born during three periods, averaging Feb 4 (late winter, LW), March 30 (early spring, ES), or May 26 (late spring, LS). (Dams of these calves had been born in the same period as their calves.)  LW and ES dams had been weaned at either 190 or 240 days of age. (ES weaned at 190 days is most typical of historical production systems in this locale.) LS dams had been weaned at either 140 or 190 days. The 140-day-weaned LS heifers gained 0.63 lb/day from weaning to 190-days of age. This was significantly less than the 190-day-weaned LS heifers (1.21 lb/day) over that same time period, when the latter were still nursing.

Calving Season.  There were no clear trends in total milk yield as results varied significantly for the two years. LW and ES were similar in both years, but LS were higher in the first year and lower in the second. Cow weight and BCS at calving tended to be lower for ES but at weaning was lower for LS. From breeding to weaning, LS lost weight and BCS in both years. Calf weaning weight tended to be on the order of LW>ES>LS, with LS varying more between years. Pregnancy rates did not differ significantly among the three groups.

Weaning Age. Within LW and ES, there were no differences in milk yield due to dam weaning age. But of the two LS groups, total milk yield of 140-day-weaned was higher in both years compared to 190-day-weaned. Also, peak milk production was considerably higher in early-weaned LS than any of the other groups. Calves from early-weaned LS dams tended to gain more and be heavier at weaning than late-weaned LS. Early-weaned LS dams tended to gain less than late-weaned LS dams from calving to breeding and to lose more weight from breeding to weaning, apparently due to their higher milk production.

Producers need to understand relationships between replacement-heifer development systems, milk production patterns, calving systems, and regional environmental differences in order to maximize cow-calf production efficiency. (J. Animal Sci. 86:768)

FACTORS AFFECTING BULL BREEDING PERFORMANCE
A study was conducted by Texas AgriLife Research (Texas A&M System) on factors affecting number of calves sired in a multi-sire herd. Six Braunvieh and six Bonsmara bulls, to be run with 305 crossbred cows that had calved at least once, were evaluated for body condition score (BCS), social dominance rank (SDR), serving capacity (services per 20 minutes), sperm motility and morphology, and fertility-associated antigen classification. BCS averaged 4.6 (ranging from 4.0 to 6.0), motility averaged 65% (ranging from 30% to 90%), normality averaged 75% (ranging from 58% to 88%), and serving capacities were all 0 to 2 (except for one bull with 7 services). All bulls were positive for fertility-associated antigen.

Pregnancy rate was 92%. Braunvieh bulls sired 69% of the calves. Close to 75% of the variation in no. calves/bull was explained by a combination of breed, normality, motility, and dominance rank, with little additional variation attributable to BCS or serving capacity. More than 60% of calves born during the first 40 days were sired by the one-third of bulls that had over 80% normal sperm. The authors concluded that number of calves sired by a particular bull, in multi-sire breeding, can be increased by implementing Breeding Soundness Exams and selecting socially-dominant individuals. (Prof. Anim. Sci. 24:184)

ROUND BALE STORAGE METHOD vs. NUTRIENT CONTENT & COST
Concerns continue with contamination of food by toxin-producing Escherichia coli, specifically E. coli O157:H7. There has been some indication that certain diets might increase shedding of E. coli by fed cattle. Kansas State University researchers fed dry-rolled corn (DR) to steers and found that fecal samples positive for E. coli O157 contained 21% more fecal starch. In a second study, heifers were stepped up to a high DR ration and then sampled after 14 days. At that time, one-third of heifers’ fecal samples were positive. This group of heifers was then divided for individual feeding, with half remaining on DR and half adjusted to SF. The SF group tended to have more heifers with positive fecal samples. Heifers fed DR had higher fecal starch levels and lower fecal pH. But there was no relationship between either fecal starch or pH and prevalence of E. coli 157. (J. Animal Sci. 86:632)

IS THE CATTLE CYCLE GONE?
North Carolina State University researchers compared five storage methods of round bale, second-cut grass hay. Hay was baled in August and stored for 7 or 15 months. Storage methods were: on ground, uncovered (GU), on pallets, uncovered (PU), on ground, covered with tarp (GC), on pallets, covered with tarp (PC), barn-stored (BS). Results were as follows:

*FUTURE OF BEEF PRODUCTION
The Food and Agricultural Policy Research Institute, University of Missouri, recently reported some projections over the next 10 years involving beef production as follows:

• 600 lb – 650 lb feeder steers average price of $116/cwt in 2007 decline to $96/cwt in 2012 and rise to $115/cwt in 2017
• 1100 lb – 1300 lb finished steers stay within $2/cwt of the 2007 average of $92/cwt through 2015, then increase to $97/cwt in 2017
• net returns/cow-calf unit decrease from $34 in 2007 to minus $52 in 2012 and up to $18 in 2017
• little change in numbers of beef cows
• U. S. per capita consumption of retail beef to change little from 2007 value of 65 lb
• retail beef price to increase from $4.16/lb in 2007 to $4.74/lb in 2017
• beef exports increase from about 5% in 2007 to 10% by 2017, essentially the same as in 2003 before the discovery of BSE in the U. S.
• ethanol supplies increase from about 10 billion to over 20 billion gallons, about three-fourths of which will come from corn. (www.fapri.missouri.edu)