Beef Cattle Browsing – October 2008

Beef Cattle Browsing

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

October 2008

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.

Country of Origin Labeling is upon us. The program was implemented on September 30, with a six-month transition period. There are three categories under COOL: product born, raised, and slaughtered in the U. S.; product that is U. S. origin and/or other countries of actual or possible origin; product from animals imported for immediate slaughter and would be designated by the country from which imported. Separating domestic and foreign supply will cause some problems, certainly for the packing industry. There had been some indication that the simplest procedure would be to forget about trying to keep up with source and just label everything as multi-country origin. Some even predicted that a packer could do so by slaughtering one non-U. S. animal every day to comply with the regulations. That meant beef exclusively born, raised and slaughtered in the U. S. could be labeled as multi-country origin. This seemed to defeat the purpose of COOL so pressure, political and otherwise, has been exercised. First, Tyson Foods announced they would fully comply by labeling most of its covered product (estimated by them to be about 90 percent) as U. S. origin. Cargill Foods and JBS-Swift quickly followed. It is expected that other processors will also get on board. (, 10/16, 10/17, 10/24).

The CO-Synch + progesterone-insert protocol for timed artificial insemination (TAI) involves administration of gonadotropin-releasing hormone (GnRH). Some research had indicated that human chorionic gonadotropin (hCG) is more effective than GnRH in stimulating ovulation in dairy cattle. Researchers at Kansas State University and the University of Florida investigated effects of these two hormones on ovulation and fertility in beef cattle. In one study involving 46 purebred Angus, Hereford, or Simmental cows a standard dose of GnRH was compared to four different levels of hCG. There was no difference among groups in incidence of ovulation. A second study included 676 cows of purebred Angus, Hereford, Simmental, or Angus X Hereford breeding managed at six locations. Pregnancy was significantly reduced with hCG, especially with cycling cows. The researchers concluded that hCG was not recommended in this procedure.

Also three AI systems were compared:

  • 1 TAI followed 11 days later by cleanup bulls for 57-58 days
  • I TAI plus a second TAI 35 days after the breeding season started followed 7 to 10 days later by cleanup bulls for 25-29 days
  • 2 TAI as in B above with continuous estrus detection and insemination

Total pregnancy rates were 90%, 61%, and 74% for A, B, and C, respectively. System A resulted in less than half of calves being AI-sired. (J. Animal Sci. 86:2539)

The National Animal Identification System (NAIS) in the U. S. is a voluntary program at the federal level. Our neighbor to the north has also developed a national identification program which might be of interest. Colorado State University researchers reviewed this Canadian program. It is administered by the Canadian Cattle Identification Agency (CCIA), a subsidiary of the Canadian Cattlemen’s Association, which is owned and led by a board of directors representing all segments of the industry. CCIA started in 1998 in collaboration with the Canadian Food Inspection Agency (CFIA). CCIA began full operation on a voluntary basis in 2001 and became mandatory in 2002 under the Federal Health of Animals Act. Since CCIA is a private organization, it is not subject to laws dealing with access of public information.

Under this program, all bison, cattle, and sheep must have an official CCIA-approved RFID ear tag when they leave the herd of origin or are imported. Tags are obtained from veterinary offices, feed stores, etc. who must report assignment to the CCIA database within 24 hours. There is voluntary but not yet mandatory premises registration under this program. However, herd-of-origin information collected when tags are obtained is assumed to fulfill this need, even though geographic location is not part of that information.

While the program is run by the privately-owned CCIA, the government agency CFIA is charged with enforcement, including fines for non-compliance. This function includes on-farm audits of producers, markets, and packers. There is a separate program in the province of Quebec that is stronger in some ways, such as requiring that calves be identified no later than seven days after birth. The Quebec program operates under the national framework regarding assignment of ID numbers and traceability.

Initial reaction to mandatory identification was often negative. However, this largely dissipated when the first case of indigenous BSE was discovered in May, 2003, less than a year after the program became mandatory. The CCIA estimates that current compliance on a national level is somewhere between 97 and 100 percent. (Prof. Anim. Sci. 24:277)

It has been well established that marbling can be increased by selection of high-marbling sires. Pennsylvania State University researchers wanted to know if this might be influenced by management. In one study, they included calves from Angus sires that averaged either high (HM) or low (LM) for marbling EPD, used on Simmental-Angus crossbred cows. Calves were weaned at 212 days of age and fed to endpoints of estimated fat cover of 0.4 inch (LF) or 0.6 inch (HF). The HF group was significantly heavier (52 lb) at slaughter, but there was no significant effect due to fat endpoint on either ADG or feed conversion. There were no significant differences due to marbling-EPD sire group in weight at birth, weaning, or slaughter, or in ADG or feed conversion. The HM sire group had significantly higher average marbling (Small 57 versus Small 23) leading to 79% Choice, versus 70% for LM, but fat thickness, ribeye area, and Yield Grade did not significantly differ. Comparing fat endpoints, HF had 79% Choice and 3.20 Yield Grade, compared to 70% Choice and 2.56 Yield Grade for LF. There were no significant differences due to marbling-EPD sire group or fat endpoint in meat juiciness, flavor, or overall acceptability, but HF were slightly more tender.

In a second study, calves of the same breeding as above and by HM sires were either:

  • weaned at 170 days of age and fed
  • weaned at 170 days of age, backgrounded 40 days on corn silage, and then fed
  • weaned at 212 days of age and fed
  • weaned at 212 days of age, backgrounded 40 days on corn silage, and then fed

Marbling scores were: backgrounded = Modest 04; unbackgrounded = Small 59; early weaned = 543; normal weaned = Modest 20. This led to the highest overall marbling score (Modest 62) and percent Choice (100%) for calves that were both normal-weaned and backgrounded. (Some other research has shown early weaning resulted in highest marbling when calves were immediately placed on rations higher in energy than used in this study.) There were no significant differences in final weight, fat thickness, or ribeye area.

In both studies, cattle were 12-13 months of age and weighed 1100-1200 pounds at slaughter. The authors concluded that such progeny from high-marbling EPD sires “will express at least some of their marbling potential” with similar live performance and meat quality. (Prof. Anim Sci. 23:349)

The number of beef cows in the U. S. continues a steady decline. According to the USDA, beef cows decreased from 34.5 million head in 1997 to 32.6 million head in 2008. However, beef production per cow increased almost 12 percent over that period, so total production was over five percent higher in 2008 than in 1997.Why? Cattle are simply getting bigger. This can be seen in several ways. Genetic trend for yearling weight, as measured by breed association genetic programs, is trending steadily upward (even as frame size has stabilized). Average slaughter weights are following the same trend. Does higher production per cow by increasing cattle size mean greater efficiency? To answer that you must consider the amount and cost of the inputs required to increase size. How much longer will cattle continue to get bigger? That’s anybody’s guess.

Exposure of susceptible pregnant females to bovine viral diarrhea (BVD) can result in the birth of calves that are persistently infected (PI). These PI-BVD cattle can be a source of BVD transmission to susceptible cattle in the feedlot. New Mexico State University and Kansas State University collaborated to study the likelihood of such transmission using 296 beef heifers, averaging 497 lb, from 12 different sources obtained from a “Calf Special” auction in southwest Oklahoma. These heifers had been vaccinated for the BRD viral complex (including BVD), 7-way clostridial, M. hemolytica, and H. somni. Cattle were fed at the Clayton, NM, Livestock Research Center. Upon arrival there they were vaccinated for the BRD complex and 7-way clostridial, given antibiotics, and de-wormed.

Two types of experimental treatments were included in the study, direct and spatially exposed. Direct exposure involved commingling in a pen with a PI animal. Spatially exposed treatments involved placing a PI animal in an adjacent pen. For both direct and adjacent treatments there were pens with: negative control with no exposure; exposure for 60 hours; or exposure for the duration of the study. There were no significant differences among pens in feed consumption, average daily gain, feed efficiency, or any carcass traits. The authors concluded that exposing previously vaccinated, freshly-weaned, transported calves to PI-BVD calves resulted in “little, if any, marked effects on health, performance or carcass characteristics”. They cautioned that more research was needed to determine possible consequences in cattle with different management background than that implemented in this study. (J. Animal Sci. 86:1917)

According to recent breed association figures of the two most numerous beef breeds in the U. S., 53% of registered Angus calves were AI-sired, compared to 19% of Herefords. (Seedstock Digest, Oct. 6) 

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