Beef Cattle Browsing – December 2008

Beef Cattle Browsing

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

December 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.

Texas Tech University and USDA-ARS researchers collaborated to study this question in ground beef and strip steaks. Samples obtained on three different occasions from 15 grass-fed beef producers in 13 states were compared to control samples also obtained three times from retail stores or university meats laboratories in Ohio, South Dakota, and Texas. Grass-fed ground beef had more sodium, zinc, and vitamin B12 but less magnesium, phosphorous, and potassium. Grass-fed strip steaks were lower in fat, but both sources were considered to be lean as they had less than 4.3% fat. There was no difference in cholesterol between the two sources. Differences were found in content of some fatty acids, but the authors stated that any relationship between these differences and possible effects on human health would require further study. (J. Animal Sci. 86:3575)

Selection for increased weaning weight has been going on for many years. But weaning weight includes genetic effects of growth on the part of the calf and the maternal environment provided by the dam. At one time in selecting breeding animals for heavier weaning weight we never knew how much of those two effects might be involved. EPD changed that, with separate predictions for growth (Weaning Weight Direct EPD) and maternal (Milk EPD). The combination of those two is called Maternal Weaning Weight EPD or Total Maternal EPD.

We can see how breeders have used those EPDs by looking at genetic trends within a breed. An example appeared recently in Simbrah data. Since 1980, the breed has increased almost 20 lb in Weaning Weight Direct EPD. But Maternal Weaning Weight EPD has gone up only about half that amount. Why? Because Milk EPD is essentially unchanged. It appears that Simbrah breeders have been selecting for faster preweaning growth while maintaining, but not increasing, milking ability of dams. This would not have been possible without separate EPDs for growth and milk. (American Simbrah Magazine, Fall, 2008)

Previous research has shown that distillers grains contain high levels of some compounds capable of forming materials contributing to odor. Other work suggested a relationship between feeding distillers grains and shedding of E. coli. Researchers at the U. S. Meat Animal Research Center wanted to know how such relationships might vary with different feeding levels. Steers were fed a finishing ration of either 0%, 20%, 40%, or 60% wet distillers grains with solubles (WDGS). In manure samples analyzed immediately upon collection, levels of ammonia and hydrogen sulfide increased with increasing levels of WDGS. Also, other odor-causing compounds were lower in the 0% treatment group. Manure samples were incubated at 72 degrees F. for 2 to 28 days. In the 40% and 60% groups, methane production was higher during incubation. Also, greater numbers of E. coli survived for longer periods in the 20% and 40% groups. The authors concluded that “feeding WDGS can increase odorants in manure slurries and extend the persistence of E. coli.” (J. Animal Sci. 86:3617)

Various methods have been used over the years to estimate chronological age of cattle, including dentition, skeletal maturity (from vertebral ossification), and lean maturity (from lean color). These estimates can be affected by a number of factors, such as growth implants, gender, parity, diet, and postmortem conditions. Estimation has become of major importance in some export situations concerned with possible BSE where maximum age of cattle is prescribed. Research has shown that the eye lens grows as animals age. Lens weight and nitrogen content has been related to age in some other species.

Kansas State University researchers examined these relationships in 386 cattle varying in age from 12 to 37 months. Correlations with actual age were as follows: dentition = 0.74, USDA maturity score = 0.64, lens weight = 0.77, lens nitrogen = 0.71. Verification of age of less than 30 months was done 88% of the time by dentition and 82% by lens weight. However, for 20 months of age, a cut-off for some exporting programs, no single factor verified any higher than 20% of the time.

A prediction equation combining dentition and lens weight verified for 20 months 38% of the time. Qualification for export markets limited to 20-month-old cattle is currently based on USDA maturity score. Based on this research, the authors noted that use of their prediction equation would qualify nearly four times as many cattle for 20-month programs compared to the current method. (J. Animal Sci. 86:3557)

Recently, a report out of the Panhandle indicated that a person had contracted mad cow disease. The report apparently caused a brief decline in cattle prices. In fact, there was an unconfirmed suspect case of sporadic Creutzfeld-Jakob Disease (CJD). According to the National Institute of Health, sporadic or spontaneous CJD affects about one person in a million worldwide. The Texas Department of State Health Services says that 11 such cases were reported in Texas in 2007 with five cases reported in 2006. CJD is one of several similar brain-wasting diseases that can affect large animals, including bovine spongiform encephalopathy (BSE, so-called mad cow disease) and chronic-wasting disease in elk. According to the Centers for Disease Control and Prevention, a form in humans called variant CJD is believed to be caused primarily by consumption of cattle products contaminated with the agent of BSE. There have been three confirmed cases of variant CJD in the U. S., but authorities concluded they were due to exposure in other countries. Variant CJD can be confirmed only by analyzing brain tissue, generally by autopsy.

Genetic selection research projects in cattle rarely exceed a few generations at most. Sometimes we can get some idea of what might happen longer term from other species. Spanish researchers used rabbits selected for high weight gain from four to nine weeks of age. Animals from the 18th generation of selection were compared to those from the seventh generation of the same line, the latter produced from frozen embryos of that generation. There was no effect of selection on the relative growth of any body components. So, carcass composition at the same degree of maturity was similar over 11 generations. (J. Animal Sci. 86:3409)

People for Ethical Treatment of Animals (PETA) uses many disruptive tactics to further its agenda. One of these is purchase of minimum dollar amounts of stock in companies dealing with animal products (especially meat packers, foodservice, and groceries), thereby allowing participation in company shareholder meetings. Because of the reduced value of many such stocks, PETA has had to buy additional shares in order to meet minimum total stock valuation. (, 12/5/08)

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