Beef Cattle Browsing
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
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 MARKET COW & BULL BEEF QUALITY AUDIT
Cow and bull quality audits were conducted in 1994 and 1999. A third audit was conducted in 2007 at 23 packing plants in six regions. Key findings and comparisons to earlier audits were:
- there were fewer lame cows and almost no cattle that were injured and could not walk
- all truck and trailer loads met American Meat Institute guidelines for spacing
- unnecessary use of electric prods needs improvement
- cattle slipping during unloading can be a problem
- cattle should be separated by gender
- there were fewer cattle with mud or manure problems, cancer eye, horns, or brands
- most had some form of identification
- there were more shoulder/neck knots, indicating need to observe labels for injectables
- no buckshot or birdshot was found in carcasses
- there were fewer bruises, arthritic joints, or injection-site lesions
- fewer cows were pregnant
- more heads and livers were condemned
- carcass weights were heavier
- fat thickness was lower, fat color was more desirable, and muscle scores were higher.
Regarding carcass weight, cows increased from 540 lb in 1999 to 635 lb in 2007 but fat thickness was less, further evidence that the genetic size of cattle in this country is still increasing. However, bulls increased only 15 lb, so the future rate of increase in size may slow. Or maybe producers culled their “small” bulls last year. (Executive Summary of the National Market Cow and Bull Beef Quality Audit – Beef Cattle Edition, published by the National Cattlemen’s Beef Association and funded by the Beef Checkoff.)
Ohio State University researchers studied three methods of weaning. A total of 280 spring-born calves (from three locations over two consecutive years) were weaned either: at trucking (TR); in drylot for 30 days before trucking (DL); or on pasture allowing fence-line contact with dams 30 days before trucking (FL). All calves were shipped on the same day each year, at which time average weight was 557 lb, with a range of only 2 lb between the averages of the three groups. Shrink during shipping was 3.6% for TR, 2.9% for DL, and 3.6% for FL. Sickness levels during the four weeks were 28% for TR, 38% for DL, and 15% for FL. Average daily gain for the first four weeks on feed was 3.1 lb for TR, 2.0 for DL, and 2.9 for FL. The DL calves actually lost weight during the first week on feed, possibly due to highest sickness. Drylot weaning resulted in lower overall gain for the first month on feed, and fence-line weaning resulted in lowest levels of sickness. (Prof. An. Sci. 23:637)
NIR PREDICTION OF BEEF TENDERNESS
Of the three primary beef steak and roast palatability factors (tenderness, flavor, juiciness), tenderness is by far the most variable. The industry needs to be able to quickly and easily predict tenderness. Objective methods to accurately predict tenderness have existed for some time. However, they are generally not feasible for large-scale commercial implementation because of the cost or time required. Oklahoma State University researchers studied near-infrared reflectance (NIR) spectroscopy to predict tenderness.
Ribeye rolls from 768 carcasses were evaluated. Approximately one-half of the samples came from carcasses grading USDA Select and one-half from carcasses grading Choice (ranging from low Select to average Prime). Average USDA Yield Grade was 2.5 (ranging from 0.6 to 4.6) and carcass weight averaged 759 lb (ranging from 519 lb to 999 lb).
One-inch thick steaks were cut and NIR measurements taken 72 hours after slaughter. Steaks were then aged for 14 days and frozen for subsequent cooking slice shear force testing. As was true for carcass factors, shear force measurements also varied considerably and 6.9 % of the samples were classified as tough (9.3% for Select and 4.5% for Choice). Steaks certified as tender by NIR were statistically significantly lower in shear force than those certified as tough. The authors concluded that “the NIR system did not predict exact tenderness with high accuracy.” But “the system was able to successfully sort tough from tender samples to 70% certification levels” and “NIR offers in-plant opportunity to sort carcasses into tenderness outcome groups for guaranteed-tender branded beef programs.” (J. Animal Sci. 86:211)
In another report, 100 of the above 768 carcasses were randomly selected for further study. NIR predicted 27 of those 100 carcasses to be tender, 45 to be intermediate, and 28 to be tough. Only two of those 28 predicted to be tough were not classified the same by shear force testing (93% accuracy). (J. Animal Sci. 86:413)
PREWEANING GAIN, MILK PRODUCTION, & UDDER CONFORMATION
Milk production has been shown to be a major factor affecting calf gain from birth to weaning. USDA researchers at Miles City, Montana, studied factors affecting gain and relationships among those factors in Line 1 Herefords. This line was closed to outside genetics in 1935, with male and female replacements selected from within the line based on heaviest yearling weight. In this report, 6835 records of preweaning gain(PG) from 2172 dams were analyzed. Milk production (MP) was estimated using the weigh-suckle-weigh method. Udder score (US) was the nine-point system of the American Hereford Association.
Heritabilities were: PG direct effect = 0.13; PG maternal effect = 0.25; MP = 0.25; US = 0.23. Phenotypic correlations were: PG and MP = +0.37; PG and US = -0.07; MP and US = -0.09. MP was highly correlated genetically with PG (+0.80), however the genetic correlation between MP and US was -0.36.
Udder score essentially had no effect on either milk production or calf gain. (However, udder structure and integrity can be a factor in longevity.) As has been shown in other research, milk production was highly related to overall maternal effects on preweaning gain. So, the authors noted that direct selection for milk production is probably not justified if estimates are available of the maternal genetic component for preweaning gain. (NOTE: Expected Progeny Difference for “Milk” is an estimate of this maternal genetic component.) Also, the authors noted that some consideration should given to udder quality or it may be degraded by selection for increased milk production. (J. Animal Sci. 84:1639)
FORAGE SELECTIVITY BY GRAZING CATTLE
University of Nebraska and USDA researchers studied grazing selectivity of three grass species. Monoculture pastures were evaluated, one cool-season, smooth bromegrass (SB), and two warm-season, switchgrass (SG), and big bluestem (BB). Three rumen-fistulated steers averaging 649 lb were used to sample grazing intake, during a 45-minute period after rumen evacuation, of four stages of plant growth: vegetative, elongation, early reproductive, and regrowth. Forage availability to the steers was always more than adequate, essentially representing a light stocking rate. Clipped forage samples were also taken.
Crude protein selected by the steers was higher than in clipped samples, about four percentage points higher in SG and BB and six percentage points higher in SB. Selected CP was about two percentage points higher at vegetative stage (when CP was considerably higher than at all other stages) and was six points higher at the other stages. Selected CP was never below the steers’ minimum requirement. Selected fiber content was always lower than clipped, ranging from about four percentage points less at the vegetative stage to almost 10 points less for regrowth. Selected content of lignin, which impairs digestibility, was never higher than four percent but was as high as seven percent in clipped samples. Cattle effectively selected a higher-quality diet, especially when forage quality was low.
The authors indicated that a scheme to maintain animal performance could involve heavy-stocking warm-season grasses early in the summer when quality is high and reduced stocking later when there is less opportunity for cattle to selectively graze. In fact, such a system has found favor in some of the traditional summer-grazing areas of the Central Plains. (Prof. An. Sci. 23:672)
WHICH BEEF IS GREENER?
Much has been said about adverse effects on the environment from using grain to feed livestock. This is challenged by a recent report from the Hudson Institute Center for Global Food Issues. The Center used an Iowa State University beef production model (cowherd to carcass) and greenhouse gas emissions estimates from the United Nations Intergovernmental Panel on Climate Change. Based on the analysis, beef produced under the prevailing method in the U. S. (grain finishing, with growth promotants) required two-thirds less land and produced 40% less greenhouse gas emissions than organic grass-fed beef. Also, the use of growth promotants required about 20% less land than grain finishing without growth promotants. The report notes that growth promotants have been found to be safe and produce a wholesome product by the Food and Drug Administrations of both the U. S. and Canada, the World Trade Organization, the Food and Agriculture Organization of the United Nations, the World Health Organization, and the European Agriculture Commission. The full report can be viewed at http://www.cgfi.org/pdfs/nofollow/beef-eco-benefits-paper.pdf