Beef Cattle Browsing – February 2005

Beef Cattle Browsing

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

February 2005

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.

U.S.D.A. beef carcass standards estimate maturity based on skeletal shape and appearance and on lean color and texture. These standards indicate that A maturity classification corresponds to cattle less than 30 months of age. Eruption of permanent incisors is related to chronological age. Based on 16 research studies, the first pair of incisors averages erupting at 23.8 months (range across studies was from 22.5 to 27.0 months), and the second pair at 30.4 months. Researchers at West Texas A&M compared dentition and estimates of carcass maturity. Two studies were conducted, one involving 1,264 Mexican-origin steers and the other a sample from a four-day kill of 11,136 steers and heifers. In general, there was little relationship between teeth and estimates of carcass maturity. For example, even for cattle with four pairs of incisors, 40 percent were classified as A maturity by U. S. D. A. graders. Based on this and other research, it appears that dentition, not “maturity”, might be a more accurate predictor of chronological age. (J. Animal Sci. 79:1683)

The majority of beef cow herds are small. Average herd size in the U. S. is 41.6 cows. (Connecticut has the lowest at 7.5 cows/herd, Nevada the largest at 175, Texas averages 41.2) Over 78% of herds have less than 50 cows, and less than 1% have over 500 cows. However, herds of less than 50 head have only about 29% of the total cows, and herds over 500 head have almost 15 % of the cows. These distributions have not changed much over the years and, barring unforeseen drastic economic changes, probably will not. (USDA – National Agricultural Statistics Service – Report on Livestock Operations, April, 2004)

U.S. Meat Animal Research Center and Florida researchers evaluated five genetic markers, known to be associated with some production traits in Bos taurus cattle, for possible application in Bos indicus, in this case purebred Brahman. Relationships were assessed between the five markers and 13 production and carcass traits. Of the 65 relationships, only six were statistically significant. One marker was significantly related to fat and ribeye area, another to tenderness, and three markers to hump height. (Hump height is a limiting factor in some “high-quality” branded-beef programs.) There was no association between any of the markers and rate of gain, hip height, final weight, carcass weight, marbling, kidney-pelvic-heart fat, yield grade, retail yield, or shear force (mechanical tenderness estimate). Breeders of cattle containing Bos indicus should perhaps be cautious in using genetic markers validated in Bos taurus breeds. (J. Animal Sci. 83:13)


Texas A&M researchers studied the effects of time of castration on production and profit in stockers grazed on native range in the Rolling Plains of Texas. The study included 279 calves (average initial weight of 475 lb) in five loads from Central, North, and West Texas auctions; 49% were bulls, which were castrated within 24 hours of arrival. Cattle were received in December, preconditioned for 35 days, and then grazed until July-August. Sickness in newly-castrated calves was 60%, compared to 25% for steers already castrated. New-castrates gained significantly less (1.42 lb/day vs. 1.64 lb/day) and had lower gross returns ($192.19/hd vs. $216.04/hd). Steers already castrated that did not get sick gained 1.69 lb/day and grossed $227.50/hd, compared to 1.28 lb/day and $178.98 for new-castrates that got sick. This study confirms that price discounts for bulls are justified. (J. Animal Sci. 82:2773)

Canadian researchers (on Prince Edward Island) used ultrasound to estimate fat cover (FT), ribeye area (REA), and intramuscular fat (IMF, predictor of marbling) in 487 feeder calves from eight feedlots. After finishing, 34% graded Canadian AAA (U.S. Choice), 57% AA (Select), and 9% A (Standard). All three ultrasound estimates were significantly related to carcass quality grade. The highest relationship was with IMF, followed by FT, and then REA. Higher carcass grade was associated with greater IMF, more FT, and smaller REA. Other significant predictors of quality grade were feedlot of origin, days on feed, and carcass weight. (Can. J. Animal Sci. 84:165)

It depends, on what is “engineered”. What about in plants that have been genetically modified for resistance to herbicides? Researchers in Denmark compared sugar beets, beet fodder, and beet pulp from conventional and Roundup Ready (glyphosate-tolerant) varieties, fed to sheep. Quoting their conclusions, “Digestibilities and feeding values of Roundup Ready materials were not influenced by the introduction of the Roundup Ready trait compared with conventional varieties of beets. (J. Animal Sci. 83:400)

Prof. Ed Huston, after a lifetime of service with the Texas Agricultural Experiment Station, summarized the results of 17-years of studies on native range in the 20-inch average annual rainfall area of West Texas. He found that unsupplemented cows lost 18.4% of their fall weight (including reproductive tissues) before beginning breeding April 1, and conceived at a rate of 81%. Cows supplemented with about one-half of their total daily protein requirement in a concentrated supplement lost 12.9% of fall weight and conceived at 91%. Body weight and condition generally did not differ whether the weekly total of supplement (14 lb) was fed daily (2 lb/feeding), three times a week (5 lb/feeding), or once a week (14 lb/feeding). Cows fed once a week were less variable in forage consumption and body weight change. Optimum supplementation pays, and you may be able to feed less often than you might think. (J. Animal Sci. 81 Suppl. 1: 125)

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