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NON-GENETIC FACTORS CAN AFFECT QUALITY GRADE OF CATTLE

Overland Park, Kansas
-- Dr. Pete Anderson, vice president of sales and technical services for VetLife, told the attendees at the Beef Improvement Federation (BIF) Annual Research Symposium in Fort Collins, Colorado that there are a number of factors besides genetics that impact beef marbling and quality grades. Anderson said, “Since approximately fifty percent of the US fed cattle are marketed on a value-based system that is largely driven by marbling scores and resulting quality grades, it is important that we understand all the factors that beef quality grades.

“Marbling is a complex biological trait that is not well understood. Research shows that once an animal's genetic marbling capability has been determined, there are still numerous factors that can negatively and positively impact quality grade. These factors include placement factors, pre-feedyard nutrition and health, feedyard nutrition and health and endpoint selection.”

Placement factors and demographics of the animals

Carcass data from more than 20 million animals in VetLife's Benchmark database shows that sex of the animal, placement age and weight as well as the season of the year have an impact on quality grade. The data indicate that overall, heifers grade higher than steers with more premium quality grades, fewer penalty grades and greater carcass value. Benchmark data also indicates that steers and heifers placed on feed at lighter weights graded better than animals placed on feed at heavier weights. Anderson said, “We cannot directly correlate placement weight with an animal's age, but, on average, a population of 400 lb animals will be younger than a population of 800 lb animals. This data disproves the myth that calves don't grade as well. In fact, research has shown that calves reach subcutaneous fatness endpoints at lighter weights and younger ages than yearlings.”

Seasonality also has significant effect on quality grade. The Benchmark database shows a very predictable seasonal trend. Quality grade is highest in January and February and lowest for cattle harvested in September and October. There are two seasonal factors that are likely to influence quality grades – photoperiods (the amount of daylight) and the less obvious factor, variation in pre-feedyard nutrition.

Pre-feedyard nutrition impacts quality grade

Cattle harvested during the low grading months likely spent time on lush pastures prior to being placed in a feedyard. Recent research has shown that the high levels of Vitamin A in grass inhibit the animal's ability to deposit fat for marbling. Since it takes the first 100 days on feed for beef animals to deplete these high levels of stored Vitamin A, cattle that consumed fresh green pasture have a more difficult time marbling and achieving higher quality grades.

Consuming high levels of Vitamin A is not the only pre-feedyard nutritional factor that impacts marbling. In fact, any nutritional insult anytime during the animal's life will reduce marbling. Nutritional insults include drought, cows that produce insufficient quantities of milk and a number of other factors. Research has shown that marbling of calves from poor- milking cows can be improved with a corn-based creep feed. To have an impact on marbling, feedstuffs must preferentially make glucose available to the muscle.

Health has a significant impact on quality grade

One of the strongest statistical relationships in the Benchmark database is a negative correlation between either death loss or medicine use and the percentage of animals grading Choice or better. Those lots of cattle that have high morbidity and mortality invariably grade poorly, relative to the rest of the population. Many Benchmark members assess the health risk of incoming feeder cattle as low, medium or high. The data show that the higher the risk score the poorer the quality grade, even when the cattle get straightened out and achieve carcass weights equal to or greater than the lower risk cattle.

Effect of feed intake on quality grade

Researchers have conducted studies to determine if limiting feed intake would decrease marbling scores or quality grades. The theory being that to express their genetic potential to marble, cattle must have daily caloric intakes adequate to sustain normal levels of growth. An analysis of Benchmark carcass results and performance parameters – average daily gain, daily intake, feed conversion, final weight and percentage of Yield Grade 4's – showed that it is very difficult to find a correlation between these basic feedyard parameters and the percentage of cattle grading choice. As managers of a diverse population, we have to manage for the worst in the population to make sure the best in the population can express their genetic potential.

Effects of implants and other growth promotants on quality grade

The VetLife research data base contains 325 published implant studies. The studies show that implanted animals have a 16.2 percent increase in ADG over non-implanted controls and than implants, on average, reduce the percentage grading Choice by 10.8 percentage points (65 percent to 54.2 percent). However, these averages can be misleading for a variety of reasons.

One of the primary reasons is that many of the studies did not employ management practice currently used to counter the impact of more potent implant programs, such as altering nutrition programs, extending the feeding program and feeding the animals to greater weights.

Anderson says, “Implant potency should be matched to the genetic capability of the animal to deposit muscle and to energy consumption levels. Energy consumption should always be above maintenance levels if implants are used. Moderate potency implants should be used for low consuming cattle or with cattle that have high maintenance requirements due to disease, weather or other stress-creating situations.”

Summary

“Many factors contribute to an animal's ability to express marbling and the quality grades that result. The current feeding environment includes high grain and roughage prices, volatile markets, strong consumer demand for high quality products but slowing demand for mid and low quality products. In this kind of environment, producers and managers have to be aware of all the factors affect the beef business as a whole. Since marbling occurs over the entire lifetime of the animal, all segments of the industry will need focus on improving quality grades if we are to make significant progress,” Anderson concluded.

A complete copy of Dr. Anderson's paper may be found at www.bifconference.com and click on the Symposia papers section.

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