Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
May 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.
MANAGING MARBLING
Dr. Harlan Ritchie, Michigan State University, recently summarized factors affecting marbling:
Breed – of the major breeds found in the U. S., Angus, Red Angus, and Shorthorn average highest in marbling.
Genetic selection – is possible because marbling is moderate to highly heritable. Genetic tools available include EPD, DNA, and genetic markers.
Health – as has been well documented, including through the Texas A&M Ranch to Rail feedout program, cattle that never get sick in the feedyard tend to average higher in marbling.
Disposition – ill-tempered, aggressive cattle tend to marble lower, and also have higher rates of sickness/death and gain slower.
Early weaning – calves weaned earlier than usual and continuously fed high-energy rations to typical slaughter weights tend to marble higher. But they also are more susceptible to disease.
Creep feeding – for at least 80 days on high-energy supplements tends to increase marbling.
Season – cattle slaughtered in the Fall tend to marble lower. This may be related to the fact that fall-slaughtered cattle are typically weaned in the fall and grown on lush forage such as wheat pasture before finishing. Such forage is very high in Vitamin A, of which high blood levels have been shown to decrease deposition of marbling.
High-oil corn – cattle fed high-oil varieties of corn tend to marble higher.
Restricted growth – cattle subjected to restricted rates of growth (perhaps less than 1.0 to 1.25 lb/day) for several months after weaning tend to marble lower after finishing.
Implants – if slaughtered at the same age or after the same length of feeding, implanted cattle tend to marble lower. However, they also gain faster and more efficiently to heavier weights with more desirable Yield Grades. Implanted cattle fed to the same Yield Grade/carcass fatness as non-implanted cattle tend to marble at similar levels.
Ionophores (Rumensin, Bovatec, Cattlyst), ractopamine (Optaflexx), and MGA (melangesterol acetate) – do not seem to affect marbling, when fed at recommended levels
CARCASS & MEAT TRAITS OF TROPICALLY-ADAPTED BREEDS
The U. S. Meat Animal Research Center evaluated carcass and meat traits of some tropically-adapted breeds. (In what follows, all statements are in relation to Angus-Hereford crosses.) Of the tropically-adapted breeds that are more numerous and available in the U. S., Beefmaster (BM)-, Brahman (BR)-, and Brangus (BG)-sired were similar in carcass weight, lower in fat thickness, and lower in marbling. BM and BR were similar, but BG were slightly higher, in ribeye area. BR were numerically lower in Yield Grade (higher percent lean), but BM and BG were similar. BM and BR were less tender and BG were slightly less tender. Several other less numerous tropically-adapted breeds were evaluated. Of those, the Tuli (a Sanga or Bos indicus-Bos taurus combination breed native to eastern Africa) appeared to be most likely to compare to Angus-Hereford in both marbling and tenderness, while maintaining tropical adaptability. However, Tuli-sired gain slower than AH. (Proceedings of Tropically Adapted Breeds Symposium, Southern Section Am. Soc. An. Sci. Annual Meeting, Feb. 2005)
FACTORS AFFECTING HEAT STRESS IN FEEDYARDS
The most common measure of potential heat stress in large animals is based on a combination of temperature and humidity, the Temperature Humidity Index (THI). Nebraska researchers theorized that level of wind speed and solar radiation are also important factors. The best measure of heat stress is body temperature, difficult to accomplish with large numbers of animals in feedyards. A useful alternative measure was employed in these studies, panting score, ranging from 0 for normal respiration to 4 for severe open-mouthed panting accompanied by protruding tongue and excessive salivation. It was found that adjusting THI by including wind speed and level of solar radiation resulted in higher correlation with panting score than THI alone. Also, night-time Adjusted THI was related to mid-afternoon panting score. As has been found in other studies, coat color influenced heat stress. Black-colored cattle had higher panting scores than red, which were higher than white. (J. Animal Sci. 84:712)
INCREASING CULL COW VALUE
It should not be surprising that cull cow prices in this country are lowest in the Fall, since that’s when the largest number of calves are weaned and the largest number of cows are culled. For that reason, producers often hear that cull cow value can be increased by delaying marketing until prices are higher, and by increasing slaughter grade and price. South Dakota workers studied upgrading cows from Cutter to Utility grade over periods of three to four months. Lowest returns were realized by upgrading from Fall to Winter (marketing in December to February). Highest returns came from upgrading from Winter to Spring (marketing in March to June). So, not only are cow prices lowest in the Fall, but returns are also lowest from upgrading during Fall to Winter. (Proc. Range Beef Cow Symposium XIX, Rapid City, SD, 2005)
CONSUMPTION OF CREEP FEED
Numerous studies have shown that consumption by cows of supplemental feeds of all types often varies considerably from one animal to another. Canadian researchers studied the same subject with 51 creep-fed, range-pastured suckling calves. The ration was primarily barley, with some beet pulp, high-protein oilseed meals, and minerals. On average, only 21% of calves ate on a given day, ranging from 2% to 43%. Average consumption was 2.22 lb/day, ranging from 0.15 to 7.54. (One calf ate 11.4 lb on one day.) Almost 40% of the calves never ate. The design of the creep feeder limited access to one calf at a time. The authors indicated that this, as well as small feed allowance and fear of the feeder, may have increased feeding variability. But this study appears to reinforce that there is considerable variation in feed consumption of supplements by cattle on range/pasture, regardless of the animal or feed. (Can. J. Anim. Sci. 85:401)