Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
September 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.
EFFECTS OF DIFFERENT FAT-LEVEL SLAUGHTER END-POINTS
Iowa researchers fed Angus-sired heifers to ribeye fat cover of either 0.45 in (LF) or 0.70 in (HF). HF averaged requiring 51 days longer on feed. In addition to the controlled difference in fat cover, HF had 86 lb heavier carcasses and 0.85 sq in larger ribeyes. LF had Quality Grades of 15% Select, 65% Low Choice, and 20% Average Choice or higher (qualifying for Certified Angus Beef, CAB). HF had 2% Select, 52% Low Choice, and 46% Average Choice or higher (including 19% Prime). LF had 74% Yield Grade 1 or 2 (mostly 2) and no YG 4. HF had only 23% YG 1 or 2 but 17% YG 4. Heifers were marketed on a carcass grid with the following $/cwt price variations from the base price for Choice YG 3: Select -12.41; CAB +3.50; Prime +6.00; YG 1 +4.00; YG 2 +3.00; YG 4 -20.00. There were no Standards, YG 5, heavy (>950 lb) or light (<550 lb) carcasses, or dark cutters, all of which would have received substantial discounts. Primarily because the discount for YG 4 was higher than for Select, the average value for HF carcasses was $2.47/cwt less than LF. However, because of the heavier carcass weight, HF averaged $110.57/hd higher than LF. The grid used had relatively low premiums for CAB and Prime, compared to recent grids. Using recent grids, the advantage for HF would have been even higher. The decision on whether or not to feed longer must consider such things as relative prices for quality grade, yield grade, and outlying carcass weights, as well as the reduced feed efficiency from feeding longer to higher levels of fat. The latter was not measured in this study and would probably have reduced the total advantage of the HF group. However, carcass weight is usually the most important factor influencing returns from feeding cattle that are sold on a grid. (2006 Iowa State University Animal Industry Report, Leaflet R2071)
POULTRY FAT IN BEEF CATTLE RATIONS
Fat is often added to high-concentrate feedyard rations, especially to reduce feed costs, usually in the form of tallow. Arkansas, Kansas, and Wyoming researchers wondered if poultry fat could be used. They compared feeding no added fat (N), 4% tallow (T), or 4% poultry fat (P) to Angus-crossbred steers initially weighing 904 lb and fed for 112 days. There were no significant differences in average daily gain. (All differences herein are at P<.05.) Feed consumption was lower for T than N; P was intermediate and did not significantly differ from T or N. However, feed efficiency was greater for P over N, while T was intermediate and not different from P or N. There were no significant differences in carcass characteristics among the three diets, except that N had slightly, and significantly lower, shear-force (higher tenderness). Of seven lean color measurements, the only significant finding was that T and P were slightly darker than N. Also, there were some slight differences among treatments in fatty acid composition of carcass lean and fat. It was concluded that feeding poultry fat rather than tallow could reduce feed costs without adverse effects on performance, carcass characteristics, or palatability. (J. Animal Sci. 84:2426)
HEAT TOLERANCE EPD?
There are currently EPDs for around 30 traits reported by some breed associations. In a paper presented at the recent Beef Improvement Federation Annual Meeting, the author presented a case for developing EPD for heat tolerance in Bos taurus breeds, in order to more effectively utilize their superiority in some traits, especially carcass quality, in tropical/subtropical regions. (An alternate approach is to genetically improve carcass quality of heat-tolerant breeds, and this is also being actively pursued.) In the paper, “heat-tolerant animal” was defined as “having the ability to maintain a normal body temperature under high ambient temperatures, often considered to be above 75 deg. F.” (That definition in itself indicates that Bos taurus breeds originated in areas where temperatures do not often exceed that level.) After reviewing the factors involved in heat tolerance, the author concluded that slick hair and light color are of major importance. Finally, the author cautioned that development of any heat-tolerant EPD should “be clearly separate from predictions for carcass traits and milk yield since deficiencies in these traits are often characteristics of heat-tolerant cattle.” Time will tell if we get Heat Tolerant EPD. (Proceedings of Beef Improvement Federation Annual Meeting, 2006, p. 91)
FACTORS AFFECTING BRD IN THE FEEDLOT
Researchers at the U. S. Meat Animal Research Center, Clay Center, Nebraska, evaluated incidence and effects of the bovine respiratory disease complex (BRD) in over 18,000 calves fed at the Center from 1987 to 2001. The study included Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental and three composite populations created from various percentages of those breeds. Spring-born calves were vaccinated (clostridial and leptospiral) at about 6-weeks of age, vaccinated for major viral and bacterial diseases three weeks before weaning, weaned (with booster vaccinations) around six months of age, backgrounded for an average of about five weeks, adjusted to a finishing ration, and fed for an average of around 200 days. Overall incidence of BRD averaged 17%, decreasing from around 20% in early years to 14% later (viral vaccines were changed from killed to modified live over the 15 years). Incidence “increased dramatically after 5 days on feed and remained high until approximately 80 days on feed.” There was a higher incidence in steers than heifers. There were few breed effects, although “Herefords were generally more susceptible” and “mortality associated with BRD was greatest in Red Poll.” Surprisingly, heterosis, evaluated by comparing composites and their purebred constituents, did not seem to decrease incidence of BRD. As had been reported by other researchers, heritability of resistance to BRD was low (<.2). Economic loss in the feedyard due to BRD was estimated at an average of $13.90/hd, not including labor and handling costs. (J. Animal Sci. 84:1999)
CALVES SIRED/BULL IN MULTIPLE-SIRE BREEDING GROUPS
Washington researchers studied 19 Wagyu sires running with 420 Angus-crossbred heifers in a 3000 ac pasture in western Montana. The breeding season was 45 days. DNA was used to determine the sire of the 392 calves produced. The five most prolific bulls sired 42.6% of the calves, while the five least prolific sired only 12.4 %. Other studies have shown similar wide variation within multiple-sire groups. There was no correlation between scrotal circumference and number of calves sired. Scrotal circumference is a good measure of sperm production potential, but not of sexual activity. (J. Animal Sci. 84, Supple. 1, p. 418)