Beef Cattle Browsing – January 2006

Beef Cattle Browsing

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

January 2006

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.

Most pharmaceuticals are prescribed to be given on a bodyweight basis. Even if the average weight of a group of cattle is known, how accurate is this? Kansas researchers looked at over 6000 stocker/feeders in 24 lots to answer this question. Individual animal weights were available. If dosing had been based on group-average weight, 15% of the animals would have received a dose at least 10% higher than prescribed, and about one-fourth of those would have been overdosed by at least 20%. On the other hand, over 13% of the animals would have received a dose at least 10% lower than prescribed, and almost one-sixth of those would have been underdosed by at least 20%. (Proc. of Kansas State University Cattleman’s Day 2003, p. 101.)

For a good many years, it was assumed that feed efficiency was positively related to feed consumption. The animal that consumed the most, in relation to their body weight, gained more and did it on less feed per pound of gain. The theory was that the more an animal ate the more was left, after taking care of body maintenance, for production. Also, there was thought to be little if any difference in efficiency of utilizing feed above maintenance. In recent years, those theories have been challenged, with the concept of residual feed intake (RFI). RFI is the difference between actual feed intake and what would be expected based on the animal’s weight and rate of gain. Positive RFI animals eat more than expected in relation to their weight and gain, so they are less efficient. Some Alberta, Canada, researchers recently reported on relationships between RFI and other factors. High, medium, and low RFI steers (average weight 1119 lb) were selected from a group of 306 that had just completed a feedlot test. The selected steers were then used in a digestion trial. During the trial, feed intake was not significantly different among the three RFI levels. However, digestibility of dry matter and of crude protein was significantly greater for the low RFI steers compared to the high RFI steers. Also, the low RFI steers produced significantly less methane than the medium or high RFI steers. Interestingly, low RFI steers made significantly fewer trips to the feed bunk and spent less time eating than medium RFI steers, which made significantly fewer trips and spent less time than high RFI steers. (J. Animal Sci. 84:145)

Paratuberculosis (Johne’s disease) is a chronic, incurable bacterial infection in the digestive tract of ruminants. Severe cases can result in extremely reduced production and even death in dairy cows. Florida researchers wondered if subclinical levels affect production in beef cows. They studied 238 cows of Angus, Brahman, and various known percentages of the two breeds. ELISA tests, a measure of antibodies toward the bacterium causing the disease, were compared to production factors. (Other research has indicated that higher levels of antibodies could mean either greater susceptibility or greater resistance to infection.) The frequency of positive tests tended to increase as percentage of Brahman breeding increased. Higher ELISA scores were associated with reduced cow weight, lighter calf birth weight, and lower calf preweaning gain. Scores tended to decrease as gestation progressed, but increased as lactation progressed. Even though the disease is chronic, scores were not higher as cow age increased. The authors concluded that the ELISA test may be useful in detecting levels of Johne’s that could adversely affect production in beef cows. (J. Animal Sci. 84:41)


The Japan market is open again, but there is a catch. Because of heightened BSE concerns in their country, the Japanese will allow import of beef only from animals that are 20 months old or younger at slaughter. Verification of age will be accepted only through USDA-approved programs. There are two USDA programs that will qualify animals for export to Japan, Process Verification and Quality System Assessment. Details of those programs can be accessed at It is possible for individual producers to have their own documentation program. But for most, this will be impractical and prohibitively costly. So, most producers will have to participate through some large approved program. There are several such programs already in place, such as through some feedyards. More opportunities of this sort will likely appear. But the cow-calf producer will have to market calves to exploit these opportunities, as is true for any value-added system.

The US Meat Animal Research Center studied the effects of slaughter end-point on marbling score (MS) and Yield Grade (YG) in Angus (An), Braunvieh (Br), Charolais (Ch), Gelbvieh (Ge), Hereford (He), Limousin (Li), Pinzgauer (Pi), Red Poll (RP), Simmental (Si), and three composites consisting of some of those breeds. Slaughter end-points were: fat thickness of 0.28 in, 0.43 in, or 0.59 in; carcass weight of 650 lb, 750 lb, or 850 lb; or age of 432 days. The basis of comparison in analyses was Angus. At the same fat thickness, An had significantly higher MS than Li or Ge but lower MS than Pi. At the same carcass weight and at the same age, A had sig. higher MS than Br, Ch, Ge, Li, and Si. At the same fat thickness, An had sig. poorer (higher numerical) YG than Br, Ch, and Li. At the same carcass weight and at the same age, An had poorer YG than all breeds but He. Using data from the composites, it was found that there was no significant heterosis for either MS or YG. Slaughter end-point changes some of the relationships among breeds in MS and YG. There is more difference among breeds slaughtered at the same weight or age than when slaughtered at the same fat thickness. In general, the British breeds are superior in MS and inferior in YG than most of the Continental breeds, especially when weight or age is the slaughter end-point. (J. Animal Sci. 84:63)

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