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Beef Cattle Browsing

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

January 2009

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.

COOL MARCHES ON
But to a slightly different drummer. The new COOL Rules (actually mCOOL, mandatory Country of Origin Labeling), will go into effect March 16. For producers, things appear to be even simpler than first thought. The interim rules stated that producer affidavits would suffice to document country of origin. And nothing beyond records kept “in the normal course of business” could be required for a producer to back up affidavits. Now the final mCOOL provisions, as listed on page 2707 in the U. S. Federal Register, January 15, state as follows. “In the case of cattle, producer affidavits may be based on a visual inspection of the animal to verify its origin. If no markings are found that would indicate that the animal is of foreign origin (i. e., “CAN” or “M”), the animal may be considered to be of U. S. origin.” This is essentially what some producers wanted in the beginning of COOL, that is, if it’s not imported then it’s U. S. So, it’s as simple as that, maybe. There is some thinking that lack of markings could be used only in support of records. However, the Federal Register says nothing about support. This will probably be clarified before March 16.

As for labeling in retail stores, muscle cuts (steaks, roasts, etc.) commingled during a production day from Category A (animals born, raised, and slaughtered in the U. S.) and Category B (born elsewhere but raised and slaughtered here) can be labeled as product of the U. S. plus other country or countries of birth. The same goes for cuts commingled in a day from Category B and Category C (animals imported for immediate slaughter). So, you see a lot of beef labeled “Product of U. S., Canada, Mexico” (countries can be listed in any order). However, some people, including elected officials, are unhappy with the latter process and want product of strictly U. S. origin segregated and labeled accordingly. Stay tuned.

RESPIRATORY DISEASE VS. FEEDLOT AND CARCASS PERFORMANCE
Two recent studies out of Kansas State University evaluated the effects of the bovine respiratory disease complex on feedlot performance and carcass characteristics. The first involved 665 crossbred heifers, initially averaging 495 lb, obtained from local auctions in Kansas and throughout the southeastern U. S. During a 36-day receiving period, heifers exhibiting clinical signs of apparent BRD and having a rectal temperature above 103 degrees F. were treated with antibiotics; 41% were never treated, 37% were treated once, 12% twice, and 10% three times.

After the receiving period, heifers were grazed for 136 days and then fed for 124 days in a commercial feedyard. During the receiving period, heifers treated for BRD had lower ADG, which decreased as number of antibiotic treatments increased. During the grazing phase, treated heifers tended to compensate for lower receiving-period ADG. Feedyard ADG did not significantly differ. Finished weight decreased as number of receiving-period antibiotic treatments increased. Carcass fat thickness was greatest for heifers never treated and lowest for those treated three times. Marbling score differed little except that heifers treated three times were notably lower.

The other study, using data from a single feedyard over five years, examined effects of timing of BRD treatment in over 31,000 cattle. Cattle were classified by initial weight ranges, i. e., from 500-600 lb = 5Wt, 600-700 lb = 6Wt, etc. Data were analyzed in two ways based on weeks on feed at BRD treatment or weeks from treatment to slaughter. Net returns were lower for 5Wt and 6Wt if treated during the first week on feed compared to those treated during the second through fourth weeks. However, in 7Wt and 8Wt cattle, returns were lower if treated during later weeks. As time of BRD treatment became closer to slaughter, all weight groups had lower net returns due to lower ADG and lighter carcass weight. (J. Animal Sci. 87:328, and 87:314)

ANALYZING THE 2005 NATIONAL BEEF QAULITY AUDIT
The 2005 National Beef Quality Audit surveyed 16 packing plants in 11 states, collecting data twice at each plant. Compared to previous audits (1991, 1995, 2000), some general trends were: more black-hided cattle, fewer branded hides, less Bos indicus influence, and higher carcass weights. There were no horns on 22% of the cattle, similar to the 2000 Audit but lower than the 1991 (31%) and 1995 (32%) Audits. (This trend seems contradictory in view of the increased registration numbers of Angus/Red Angus.) Bruises were found in 35% of carcasses. Over 97% were A Maturity. Overall carcass traits were as follows:

Obviously, there is still tremendous variation in the nation’s beef supply.

Compared to the 2000 Audit, average Quality Grade was exactly the same and Yield Grade was only 0.1 lower. There were 3% Prime, 52% Choice, 40% Select, and 4% Standard carcasses; 15% were YG1, 39% YG 2, 33% YG 3, 11% YG 4, and 2% YG5. As Quality Grade improved, Yield Grade became less desirable (Yield Grades were Prime 3.5, Choice 3.2, Select 2.6, Standard 2.0). Quality grade increased significantly as fat thickness increased from less than 0.2 to 0.6 inches. However, little change in Quality Grade was seen if fat exceeded 0.6 inch. As carcass weight increased, Quality Grade improved and Yield Grade declined (increased numerically). There were no significant differences between steers and heifers for any factors except that both lean and skeletal maturity score was slightly higher for heifers. (J. Animal Sci. 86:3533)

LONG-TERM GENETIC SELECTION RESPONSE
New Zealand researchers studied effects of selection over 17 years in a herd of Angus cattle, involving almost 4,000 cows. Replacements were selected on an index incorporating weaning weight, yearling weight, cow fertility, and mature cow weight. After the 17 years of the study, 3.21 generations of selection had occurred. Over that period, significant genetic increases occurred equal to or greater than predicted in postweaning ADG, yearling weight, and slaughter weight. However, this was not true for dressing percent, which decreased slightly, and mature weight. Genetic change in mature weight was predicted to increase 64.5 lb over the seventeen years, but the increase was only 2.2 lb. Based on the results of this study, weaning and yearling weights can be increased without affecting cow weight. (J. Animal Sci. 86:3348)

IMPLANTS VS. GENETIC POTENTIAL
Growth implants have been shown in numerous studies to increase weight gain but decrease marbling. Montana State University researchers wanted to know if the effects were similar in cattle with differing genetic potential for growth, muscling, and marbling. In one study Angus steers sired by bulls high in EPD for retail product yield but near breed average for marbling and other traits were compared to steers sired by bulls high for marbling but near average for retail product and other traits. Half of both sire groups received a combination implant when placed on feed. As expected, calves from high retail-product sires were higher in that trait and calves from high-marbling sires were higher for that trait. Implanting increased carcass weight and reduced both marbling and tenderness, but did not affect Yield Grade. Response to implanting did not differ for the two sire groups.

In a second study, half of groups of British-sired (BS) and Continental-sired (CS) steers and heifers received combination implants. CS had heavier carcasses, superior Yield Grades, and lower tenderness, but marbling did not differ. Implanting effects were the same as the first study, except that implanted cattle had superior Yield Grade. There were no significant interactions between implanting and sire type, though CS-implanted tended to be less tender than CS-nonimplant or either of the BS groups. (J. Animal Sci. 87:269)

SO, YOU WANT A BULL TO ADD 10 POUNDS OF WEANING WEIGHT?
Sounds like that shouldn’t be very hard to do. The best predictor of change in weaning weight is EPD. Let’s look at the most recent genetic evaluation of the most numerous breed, Angus. The current breed average for Weaning Weight EPD is +44 lb. Let’s say you want to find bulls that are predicted to sire calves 10 lb heavier than that average, that is, a +54 EPD. Part of a breed’s genetic evaluation report is a distribution of EPD, presented as a chart of percentile breakdown or percentile ranking. Breed average is at the 50th percentile, in this case that’s +44. Where is +54? It’s at the 10th percentile. So, to find an Angus bull expected to sire calves 10 lb heavier than a breed-average bull you’d have to go up to the 10th percentile.

What about some of the other more numerous breeds? In Herefords, Limousin, Red Angus, and Simmental the 10th percentile is also 10 lb above breed average. In Brangus it’s 12 lb. In Charolais it’s 11 lb. In Gelbvieh it’s 9 lb. The distribution is essentially the same in all. Finding such bulls is not going to be as easy as it might seem. However, it’s easy to find such sires for artificial insemination. But whether or not to use AI is up to each producer. (Source: breed association websites)