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.
GRAIN-FED OR GRASS-FED GROUND BEEF: WHICH IS HEALTHIER?
Angus steers were divided into three management groups: grazed and supplemented with hay to 20 months of age; fed corn-based ration to estimated Choice grade; fed corn-based ration to estimated Prime grade. Ground beef containing 24 percent fat was prepared from carcasses of each group. Male humans ate 0.45 lb ground beef patties five days a week for five weeks and then rotated among samples from the three management groups for additional five-week periods. Blood samples were collected from the participants at the start and end of each period.
Consuming ground beef from the Prime group resulted in higher levels of HDL cholesterol and larger LDL cholesterol particles, both beneficial in protecting against cardiovascular disease. The pasture-group beef resulted in higher levels of saturated trans-fat, which is detrimental to cardiovascular health. Other blood parameters were not significantly affected. (AgriLife News, Texas A&M System, 5/27/2010)
HOW DO CATTLE CHANGE DURING FEEDING?
In three studies involving 920 steers conducted over three years, data were collected on body weight, ADG, dry matter intake, and feed efficiency on both a shrunk body weight and carcass weight basis. Dry matter intake increased during the feeding period. Live ADG decreased as feeding progressed but carcass ADG did not; so, for cattle fed for the same length of time, marketing based on carcass weight could result in higher financial return than live marketing. Feed efficiency decreased over time on both a live and carcass weight basis. However, the decline in efficiency based on carcass weight was only one-fourth as much as live basis; so, cattle to be marketed as carcasses could be fed longer before cost of weight gain exceeds the value of that gain. (J. Animal Sci. 85, Supple. 2:124, Univ. of Nebraska)
VARIABLES AFFECTING OVARIAN STATUS
A sample of 72 slaughtered and 333 necropsied beef cows was used to study effects of stage of estrous, female age, and birth weight on follicle count. There was no significant effect due to stage of estrous. Calf birth weight had a small positive effect, but only explained 5% of the count. Follicle count increased up to five years of age but decreased thereafter. In a group of 406 heifers ranging from 353 to 463 days of age, ovarian ultrasonography was used to classify as low count (<15 follicles) or high count (<24 follicles). Stage of estrous did not significantly affect follicle count. Low-count heifers had smaller ovaries (P<.001), lighter birth weight (P<.003), and lower first pregnancy rate (P<.05). The authors concluded that lowered fertility due to ovarian decline may begin earlier than thought.
(Note: this study was conducted in Nebraska, so the experimental animals were almost surely of British and, possibly, Continental breeding. Ovarian decline may differ in later-maturing types such as Brahman and Brahman-influenced.) (J. Animal Sci. 87:1971, U. S. Meat Animal Res. Ctr., and Univ. of Nebraska)
BREED EFFECTS ON LIVE PERFORMANCE AND CARCASS MERIT
An analysis was conducted of results of crossbreeding studies published from 1976 to 1996. Depending on the trait, the number of studies analyzed ranged from 31 to 78 and the number of breed averages ranged from 352 to 646. Sufficient data were available for Angus, Hereford, Shorthorn, Charolais, Limousin, Gelbvieh, Simmental, and Brahman breed effects. Results for direct and maternal genetic effects on birth and weaning weight and direct genetic effects for postweaning gain, stated in relation to Angus, were:
|Birth Wt direct, lb||Birth Wt maternal, lb||Weaning Wt direct, lb||Weaning Wt maternal, lb||PW gain direct, lb|
The British differences are slight, except for low maternal effect on weaning weight in Hereford. Based on these results, Continental breeds and Brahman would be predicted to sire calves heavier at birth. Maternal effects on birth weight were slight, except for the depressing effect with Brahman dams. Charolais, Limousin, and Simmental had the highest direct effect on weaning weight with Limousin intermediate. Gelbvieh had the largest maternal effect on weaning weight with Simmental, Charolais, and Brahman intermediate. Charolais and Simmental had the largest effect on postweaning gain, Gelbvieh and Hereford were intermediate, and Brahman was lowest of all . Recent comparisons using Across-Breed EPD indicate that Angus have increased in direct effect for weaning weight and postweaning gain relative to the other breeds. Results for direct genetic effects on carcass traits were:
|Carcass Wt, lb||Ribeye area, sq in||Fat thickness, in||Marbling score|
The Continental breeds produced heavier carcasses. They also produced larger ribeyes and less fat cover, which would result in lower numerical Yield Grades (higher percent lean). Angus and Shorthorn were higher in marbling (and therefore in Quality Grade), Hereford were intermediate, and Continental and Brahman were lowest. (J. Animal Sci. 88:460; Univ. of Georgia, National Institute of Livestock Research-Uruguay)
USDA YIELD GRADE: PROBLEMS AND SHORTCOMINGS?
A study was conducted using 801 beef-type steers and 235 calf-fed Holstein steers. Both types were fed Zilmax ® for 0, 20, 30, or 40 days before slaughter. The cattle were slaughtered, USDA Yield Grades (YG) were calculated, and carcasses were fabricated into boneless, closely-trimmed cuts. There was no significant difference in YG among the three levels of Zilmax feeding, so their data were combined for analyses.
Overall, Zilmax feeding reduced numerical YG and increased total red-meat yield percent. Using the average YG of 2.9 as found in the 2005 National Beef Quality Audit, extrapolating from the current findings from beef-type steers would result in red-meat yield of 69.4% for non-Zilmax controls compared to 70.7% for Zilmax feeding. With an 880 lb carcass, this would equal 11.4 lb more red meat. The authors noted that the estimate of overall muscling in the YG equation is based on one muscle measurement, ribeye area, but that Zilmax increases musculature disproportionately higher in the hindquarter. They speculated this may be one reason for the discrepancy between YG and actual percentage of red meat.
In the calf-fed Holstein data there was essentially no correlation found between YG and total red-meat yield. The authors attributed this at least partially to the fact that the YG equation does not include percent bone. In this study the beef-type carcasses averaged 16.3% bone with a red-meat yield to bone ratio of 4.32:1. The Holstein carcasses averaged 21.2% bone and a ratio of 3.22:1.
In summary, the authors suggested new methods to estimate red meat yield in Zilmax-fed cattle and inclusion of bone in estimates for Holsteins. (J. Animal Sci. 88:2139; West Texas A&M Univ., New Mexico St. Univ., Texas Tech Univ., Oklahoma St. Univ., Univ. of Illinois, Private consultants in Canyon, TX. and Derby, KS, Texas A&M Univ., California Poly. St. Univ., Intervet/Schering-Plough Animal Health)
EFFECT OF HIDE COLOR ON CALF PRICE
Data were collected in 2005-2006 at three North Dakota auctions on over 31,000 calves (average 537 lb) in November-December and almost 30,000 calves (average 627 lb) in January. Average price was $1.30/cwt for black, $1.29/cwt for Charolais-cross, $1.27/cwt for red, and $1.26 for mixed color. (J. Animal Sci. 85 Supple. 2: 53, North Dakota St. Univ.)
AN INDEX TO ASSESS ENVIRONMENTAL STRESS IN ANIMALS
The temperature-humidity index is often used to estimate environmental effects during summer. It does not include the effect of wind. The wind-chill index is used in winter. It includes wind and temperature, but not humidity. A study was conducted to develop a comprehensive index to adjust temperature to include humidity, wind speed, and radiation across both hot and cold conditions. The results indicated that humidity has a large positive effect on the index at high temperatures but a slight negative effect at low temperatures. (At very high temperatures, high humidity drastically elevates the effective temperature, but at very low temperatures the effective temperature is slightly lower.) Changes in wind speed at slower levels lowered the wind speed more than changes at higher levels of wind. (For example, a 30 mph wind does not lower the effective temperature 3 times as much as a 10 mph wind.) Radiation (both direct solar and ground surface) was found to have a linear positive effect. The authors indicated use of this index could allow more effective management techniques to improve animal comfort and performance. (J. Animal Sci. 88:2153; Univ. of Nebraska, Univ. of Queensland-Australia)