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RESEARCH ON THE RECORD – for Jun. 8, 2009

Influence Of Percentage Angus On Feedlot Performance And Carcass Traits

The objective of this Iowa State Univ. and Certified Angus Beef (CAB) study was to evaluate the effect of percentage Angus in feeder calves on feedlot performance and carcass traits. The total number of calves involved was 18,250. Calves were categorized into four classifications: Low Angus (L), Half Angus (), Three-quarter Angus (), and Straight Angus (S). Calves were harvested when visually evaluated to have 0.4 in of external fat. Results are summarized in the following table.

The authors concluded that feedlot performance, health, and carcass merit were positively influenced by the percentage of Angus in the calves (Busby et al. 2008. Southern Section ASAS. Abstract 19).

Predicting Beef Tenderness With Hyperspectral Imaging

In previous research, Univ. of Nebraska scientists constructed a “hyperspectral imaging apparatus” by integrating a digital video camera and a spectrograph for the purpose of predicting 14-day aged beef tenderness from 14-day scans. Compared to shear force evaluation of tenderness, the hyperspectral system was highly accurate (96.4%) in predicting 14-day tenderness. In the current study, the objective was to determine the accuracy of the system in predicting 14-day tenderness from scans done at two days postmortem. This would be important because beef typically reaches the consumer by 14 days postmortem.

A total of 314 USDA Choice and Select loin steaks were scanned at two days postmortem, aged to 14 days, and frozen. Steaks were then thawed, scanned, cooked in an oven, and slice shear force (SSF) values were obtained. The system predicted three tenderness categories (tender, intermediate, or tough) with 77.1 per cent accuracy. Because SSF intermediate values are actually “acceptable” in tenderness to consumers, the tender and intermediate groups were merged into one group, resulting in two tenderness categories (acceptable and tough). When this was done, the system correctly classified steaks with an accuracy of 93.7 per cent. The authors concluded that the hyperspectral imaging system was effective in predicting 14-day aged beef tenderness from two-day scans and that implementation of such a system may result in “guaranteed tender” premium for beef products that could benefit producers and the industry as a whole (Grimes et al. 2008. Nebraska Beef Cattle Report).

Quality Grade and Yield Grade Going the Wrong Way

USDA data reveals that during the decade from 1996 to 2006, beef carcasses declined in both quality and yield. In 1996, 62.6 per cent of federally graded carcasses were Choice or Prime compared to 59.0 per cent in 2006. During that same time period, carcasses became fatter and heavier resulting in an increase in the percentage of carcasses yield grading 4 or 5 from only 1.7 per cent in 1996 to a whopping 11.7 per cent in 2006. The quality grade decline actually began after 1986, when the percentage of carcasses grading Choice or Prime peaked at 96.9 per cent. These data clearly indicate that we are depositing more fat externally while at the same time depositing less intramuscular fat (marbling) in the ribeye (Source: USDA).

Estrogenic Implants Limit the Benefits of Feeding MGA

Colorado State and Kansas State Univ. scientists conducted an extensive review of 18 research trials to evaluate the effects of feeding melengestrol acetate (MGA) to feedlot heifers implanted with an estrogenic compound (EST), trenbolone acetate (TBA), or a combination of EST and TBA. Following is a partial summary of results:

EST implants increased dry matter intake (P<0.01) and ribeye area (P=0.08).

EST implants or MGA had no effect on the percentage of carcasses grading Low Choice or higher.

Heifers implanted with TBA had greater (P<0.05) avg. daily gain, final body wt., hot carcass wt., lower feed:gain ratio, and lower numerical yield grade.

For heifers not implanted with EST, MGA improved (P<0.01) feed:gain, and increased avg. daily gain, final body wt., and hot carcass wt.

For heifers implanted with EST, MGA had no effect on live animal performance.

Regardless of implant status, heifers fed MGA had greater (P<0.05) dry matter intake, and increased (P<0.01) fat depth, numerical yield grade, and percentage yield grade four and five carcasses.

The authors concluded that in the absence of EST, MGA is effective in improving performance; however, when EST implants are used, there appears to be little performance benefit from feeding MGA (Wagner et al. 2007. Prof. Animal Sci. 23:625).

The authors are animal scientists at Michigan State University in East Lansing, Michigan, U. S. A.

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