Beef Cattle Browsing – June 2006

Beef Cattle Browsing

Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus

June 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.

Times have been good for cow-calf producers. How good? Cattle-Fax ® says returns from cow-calf operations have averaged $109.00/cow/year during 2001 to 2005, compared to $2.33/cow/year during 1980 to 2000. This increase has happened even though cash costs are higher, $351/cow last year compared to $315/cow in 2004, and that does not include depreciation, opportunity costs, or returns to management. So, higher calf prices are responsible for the increase and Cattle-Fax ® says that is partly due to an increase of about 25% in demand for beef over the past five years. (Cattle-Fax ® Update)

Steers were grazed in 2003 and 2004 from mid-March to mid-June on endophyte-infected fescue in west central Arkansas. Initial weights were 634 lb and 594 lb for the two years. Stocking rates were 1.2, 1.6, 2.0, or 2.4 steers per acre. Half of the steers on each rate were implanted with Synovex-S. Implanted steers gained significantly faster and produced significantly more total weight gain/acre at the lower stocking rate. But these effects decreased as stocking rate increased. In fact, at the highest stocking rate, non-implants actually gained slightly faster and had slightly more total gain. As might be expected, forage availability was highest at lowest stocking rates. This study confirms numerous previous research reports showing that response from growth implants is diminished when nutrition is limited. (J. Animal Sci. 84:1626)


Excess fat can certainly be a problem in the beef business. Most retail cuts are trimmed these days to very little outside fat. But what might happen if we select for ever leaner genetics? Maybe we can get some idea from the pork people. In the mid-1980s, selection intensified in the pork industry for increased leanness. So, Iowa researchers recently compared carcass and palatability factors of hogs sired by 1980s-era and current Duroc boars. Carcasses from current sires had significantly larger loin eyes and less backfat. But they also had significantly less marbling, lower mechanical tenderness scores, and poorer scores for lean color and flavor. The authors cautioned that selection for increased leanness should be accompanied by concurrent selection for eating quality. In addition, some research has shown that extreme leanness may adversely affect reproductive efficiency in cows. (J. Animal Sci. 84:1577)

Montana researchers studied birth weight (BW), scrotal circumference (SC), and several semen factors in 841 Hereford bulls. Heritability estimates were high for SC, moderate for BW, and low to moderate for semen factors. There was a positive genetic correlation between BW and SC, so selection for decreased BW would be expected to reduce SC also. Other genetic correlations caused the authors to note that “selection to decrease birth weight may result in undesirable correlated responses in a majority of semen characteristics.” The trend from genetic evaluation programs in most breeds indicates that, after initially increasing in the 1970s and 80s, BW EPD has stabilized over the last 15 to 20 years, during which time SC EPD has increased slightly. Therefore, it appears that seedstock breeders have been successful in overcoming the genetic relationship by concurrent selection for moderated BW and increased SC.

Iowa researchers developed half of a group of 167 Angus heifers as replacements (REP) and fed half for slaughter (SL). REP heifers gained 1.53 lb/day and SL gained 3.09 lb/day. All heifers were ultrasonically scanned three times during the development/feeding period to estimate fat thickness over the 12th rib (FT), ribeye area (REA), and intramuscular fat (IMF), an estimate of marbling. Rates of increase for SL heifers compared to REP were 19.0 times faster for FT and 8.8 times faster for REA. However, IMF increased at a rate only 2.6 times faster for SL heifers. It was concluded that IMF is least affected by energy consumption and weight gain and that, while FT and REA are related to weight, IMF is most influenced by animal age. Also, heifers being developed for replacements can be reliably evaluated for genetic ability to marble, but probably less accurately for FT and REA. (2004 Iowa St. Univ. Animal Industry Report)

Research has shown that carcass composition varies depending on whether the slaughter end-point is at the same age, weight, or some measure of fatness. U. S. Meat Animal Research Center researchers wanted to know if end-point might affect genetic factors. Studying 1664 steers of various breed crosses, they found that estimates of heritability for carcass factors differed slightly depending on end-point. Genetic correlations among factors were more affected by slaughter end-point. Of particular importance, the authors concluded that: 1) genetic selection for improved Yield Grade would be most effective at the same age or fat cover; 2) selection at the same age or same weight for less fat cover would reduce marbling; 3) selection at the same fat cover for superior Yield Grade could be done with little effect on marbling. (J. Animal Sci.83:764)

NAIS is still on schedule. According to the USDA-APHIS website, the private/state tracking databases should be operational by early 2007. Also, the following goals have been established: 1) by Jan. 1, 2007, 25 % of premises will be registered and 5% of animals born in 2006 will be tagged; 2) by Jan. 1, 2008, 70% of premises will be registered and 40% of animals born in 2007 will be tagged; 3) by Jan. 1, 2009, 100% of premises will be registered and 100% of animals born in 2008 will be tagged. However, the Texas Animal Health Commission has postponed addressing proposed regulations for premises registration until the winter or spring of 2007. (Premises can be voluntarily registered at this point by contacting Texas Animal Health Commission,

Some opposition to NAIS has surfaced, particularly from outside groups and small or non-commercial producers. Perhaps in response, USDA-APHIS has developed “The National Animal Identification System: A Guide for Small-Scale or Non-Commercial Producers”. That publication and other NAIS information can be accessed at Finally, that website says, “The NAIS is a voluntary program.”, but at least one state, Michigan, has made the program mandatory by law.

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