University of Missouri (MU) food scientists have developed a two-step method that can distinguish between dead and living E. coli O157:H7 cells in ground beef.

The research uses a technique called a real-time polymerase chain reaction (PCR), a quick, reliable method for detecting and identifying pathogens in food. However, PCR can't differentiate living from dead microbial cells. But, the presence of dead cells may result in false-positive findings, while as few as 10 live cells can cause severe intestinal illness, says Azlin Mustapha, MU associate professor of food science.

To prevent this, researchers stain samples with a dye called ethidium bromide monoazide (EMA). EMA can't penetrate live cells, but can enter dead cells. In dead cells, EMA binds to DNA molecules, making them insoluble and therefore invisible to PCR tests.

The researchers have had success using the new technique on ground beef, chicken and eggs. Testing takes about 12 hours, compared with older methods, which require up to two days to generate results, Mustapha says.
University of Missouri

High levels of vitamins A and D may have a negative effect on marbling deposition, say University of Illinois researchers.

Following an extensive review of the scientific literature, the researchers concluded that intramuscular adipose tissue (marbling) is regulated by factors other than those that regulate fat deposition in other carcass adipose tissues (e.g., subcutaneous fat). The researchers noted that seasonal variation in percentage of cattle grading Choice is well-documented. In general, the percentages of carcasses grading Low Choice or higher are greater in the spring, peak in March and April, then decline in summer and early fall to reach a low in September and October. Beginning in November and December, the cycle is repeated.

Previous research has shown that excessive circulating levels of vitamins A and D tend to inhibit marbling deposition. Cattle placed in feedlots in spring or early summer are commonly grazed on lush forages such as wheat pasture, fed during the long day-length months and marketed in the fall, coinciding with seasonal lows in carcass quality grade. These cattle receive high levels of vitamin A from lush forages and are exposed to long periods of sunlight in the summer, resulting in increased synthesis of vitamin D.

The vitamin A requirement for growing and finishing cattle is 1,000 IU/lb. of dietary dry matter. A recent survey of 13 feedlot nutritionist recommendations revealed that vitamin A recommendations for finishing diets ranged from 1,500 to 3,300 IU, with an average of 2,100 IU.

It is likely that the middle to upper end of this range could have a negative impact on marbling deposition, the researchers conclude. But, the authors add, further research is needed to elucidate the influence of previous nutrition, stage of growth and development, and dietary level of vitamins A and D on the production of high-quality beef.
Pyatt and Berger. 2005. Prof. Anim. Sci. 21:174 in MSU Beef Cattle Research Update, 2005.

University of Alberta researchers say they've developed a formula to reduce methane gas production in cattle. The equations, which balance starch, sugar, cellulose, ash, fat and other elements of feed, could lessen the methane gas produced by cattle by as much as 25%, the researchers say in a recent Journal of Animal Science article.

The researchers compiled an extensive database of methane-production values measured on cattle and were able to formulate equations to predict how much methane a cow would produce based on diet. The study was jointly conducted with the Universities of Guelph and Manitoba, Agriculture and Agri-Food Canada and the International Atomic Energy Agency in Austria.

The findings build on previous work by Stephen Moore, a professor of agricultural, food and nutritional science at the University of Alberta, and his research team on genetically selecting cattle that inherently produce less methane. While further studies are needed before bringing the research into general use, the work “promises significant improvements in environmental stewardship on the farm,” Moore says.

For more information, contact Moore at stephen.moore@ualberta.ca.