Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
April 2007
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.
NATIONAL BEEF QUALITY AUDIT – WHAT HAS CHANGED?
National Beef Quality Audits have been conducted about every five years since 1991, the last in 2005. Some interesting changes occurred since 1991. Condemnations of major organs are higher, but held relatively steady compared to the 2000 Audit. Brands, horns, and bruises decreased slightly. Cattle called “Bos indicus-type”, defined as having a hump in the carcass greater than 4 inches, decreased from 7.3% to 0.8%. (Note: Many cattle with some Bos indicus genetics have humps of less than 4 inches, so the NBQA classification is for higher percentage.) Carcass quality grade is essentially unchanged, the percent of Low Choice and higher going from 55% to 57%.
In 2005 there was a slight difference between genders in quality grade, with about 3% more steers than heifers grading Low Choice or higher. Hide color was: black – 56%, red – 19%, “Holstein” – 8%, gray – 6%, yellow – 5%, other – 6%. Interestingly, when asked what changes they would like from their supplier, the cow-calf, stocker/backgrounder, and feeder operators all ranked as highest “improve/change genetics”. (2005 National Beef Quality Audit)
PROTEIN SUPPLEMENTATION – WHAT’S REALLY NEEDED?
At one time, figuring how to supplement protein was pretty simple. Crude protein (CP) was the universal standard, even though it’s not a direct measure. (CP is determined by the relatively simple procedure of analyzing for percent nitrogen, factoring in the average percentage of nitrogen in proteins, and then calculating “protein”.) Then nutritionists decided that metabolizable protein (MP), true protein absorbed by the intestine, was what needed to be addressed. In ruminants, two things can happen to protein consumed by the animal. It can pass through the rumen intact (undegraded intake protein, UIP) or be broken down (degraded intake protein, DIP) and used by rumen microbes in synthesizing protein. Considerations of both UIP and DIP have proven to be important in growing animals, especially when feeding high-concentrate rations. But the situation is less clear in grazing animals, especially mature cows.
North Dakota State University researchers studied steers weighing about 1100 lb that had been fitted with rumen and duodenal cannula for extracting samples. Steers were fed low-quality (6.0% CP) grass hay ad lib supplemented with three levels of UIP. Each supplement provided the same amount of DIP and net energy. There was also an unsupplemented control. As expected with forage of this quality, digestibility was lower with no supplementation. However, among the three supplemental UIP levels, there was no difference in digestibility, total ruminal volatile fatty acids, or synthesis of microbial protein. The authors concluded that “under conditions in this study, supplementation with additional UIP, when DIP requirements are met, provided little added benefit”. (J. Animal Sci. 85:1092)
EFFECTS OF ESTROUS CYCLE MANIPULATION ON FERTILITY
Fixed-time artificial insemination programs involve manipulation of the estrous cycle to synchronize estrus. Such programs are based on a sequence of inducing ovulation, resetting follicular growth, development of mature follicles, and synchronized ovulation. Ohio State University researchers investigated the effects of this process on ovulation, luteal function, and fertility. They used both lactating and dry Angus X Simmental cows averaging 4.6 years of age, all of which had calved at least once. Lactating cows averaged 74 days postpartum. Estrus was synchronized. Then when adequate follicle development occurred, part of both the lactating and dry cows were treated with gonadotrophin-releasing hormone (GnRH) and inseminated 12 hours after treatment. The other cows were not treated and were inseminated 12 hours after onset of estrus.
Compared to the non-treated group, GnRH averaged ovulating almost 1 day earlier and produced smaller follicles. All of the non-treated group were diagnosed pregnant 30 days after AI, compared to 76% of the GnRH group. All of these effects were statistically significant (P<.05). The authors concluded that “premature ovulation of a dominant follicle with GnRH reduced the size of follicles, reduced fertility, and decreased subsequent luteal function” and that “timed AI synchronization programs must be structured in a manner to ensure that mature follicles are present when treatments are administered to synchronize ovulation”. (J. Animal Sci. 85:937)
VALIDATING COMMERCIAL DNA TESTS FOR BEEF QUALITY
It seems new commercially marketed genetic markers are being announced with increasing frequency. Producers understandably would like to know if marketing claims for these tools are valid. Ideally this requires independent third-party validation, which has a number of barriers. In particular, you need large numbers of animals with enough data on phenotypic traits in order to evaluate their relationship to genetic markers. Researchers from six land-grant institutions and the U. S. Meat Animal Research Center, under the auspices of the National Beef Cattle Evaluation Consortium, studied three commercially available marker panels: GeneSTAR Quality Grade, GeneSTAR Tenderness, and Igenity TenderGENE.
GeneSTAR Quality Grade was not found to be associated with marbling score. However, there was an association with USDA Quality Grade. In the GeneSTAR procedure each favorable allele is called a “star”. (This paper evaluated the two stars included in the panel at the time. There are now four stars in GeneStar Quality Grade.) The average effect of a star was an increase of 6.2% more carcasses grading Low Choice or higher. The authors theorized this effect on grade was probably because of a high proportion of cattle near the line between Select and Choice.
Both tenderness tests were significantly related to Warner-Bratzler shear force measurement, resulting in improvement of from 0.33 lb to 0.75 lb for various alleles. Because of the similarity of results for the two tenderness tests, the authors speculated both probably involve the same region of the genome. Combining the effects of GeneSTAR Tenderness and Igenity TenderGENE yielded a difference of over 2 lb shear force between the most tender and toughest genotypes.
The authors concluded that “tenderness could be markedly improved by selecting for favorable genotypes included in the GeneSTAR Tenderness and Igenity TenderGENE marker panels” and that “using GeneSTAR Quality Grade may increase percentage of Choice and Prime carcasses”. They cautioned that, as more tests are marketed, it will become important and probably harder to find suitable test populations. (J. Animal Sci. 85:891)
BUILDING FLEXIBILITY INTO YOUR BEEF SYSTEM
At the recent Southwest Beef Symposium in Amarillo, my colleague Dr. Ron Gill discussed ways to make a cow-calf operation more flexible. Briefly summarized from the Proceedings they are: http://spectre.nmsu.edu/dept/docs/animal/2007%20SW%20Beef%20Symposium%20Proceedings.pdf
1) Stocking rate – for cow-calf operations, stocking at no more than 75% of normal forage production potential. Otherwise, in poor years you must reduce numbers or buy feed.
2) Enterprise selection/diversification – by utilizing any excess forage with stock cows or yearlings. In doing so, you should exercise good biosecurity to protect the base cow herd.
3) Genetics of the cow herd – to fit your conditions. This generally means British-base cows, with needed levels of Bos indicus influence when dictated by the environment. Calf genetics can be tailored for particular markets through choice of sire breeds, and individuals within breeds.
4) Counter cyclical management – especially by selling cows when everybody is dying to get in the business and being able to buy cows when nobody else is. This uses the cattle cycle to your advantage, although it seems to be getting harder to predict cycles than was once true.
5) Outside investment opportunities – in other segments of the industry. If they’re “stealing your calves” then keep them, maybe even to the rail so you get what your cattle are “really worth”. If you think packers are going to get more than “their share”, consider buying their stock.
6) Emergency reserves – especially of cash. Don’t spend money just to save on taxes. When times are good, don’t make “investments” in things like equipment you “really need” or for a vacation you “really deserve”. Proper stocking yields forage reserves that can be used or marketed.