Beef Cattle Browsing — July 2013


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

Beef Cattle Browsing is an electronic newsletter published by Texas A&M AgriLife Extension, Department of Animal Science at Texas A&M University. This newsletter is a free service and is available to anyone interested in beef cattle.  Media, feel free to use this information as needed and cite Texas A&M University Beef Cattle Browsing Newsletter, Dr. Steve Hammack.

The Federal Renewable Fuels Standards originated with the federal Energy Policy Act of 2005 and was extended by the Energy Independence and Security Act in 2007. Under the 2007 extension, amounts of transportation fuel from renewable sources must be continuously increased, to reach 36 billion gallons by 2022. Though a number of renewable sources are included, in practice the vast majority of renewable fuel comes from ethanol derived from corn. This places production of ethanol from corn in competition with other uses, especially livestock feeding. This is one reason, along with pressures on corn supply and export demand, that corn prices have dramatically increased in recent years.

Initially, opposition to using corn for ethanol production came largely from the livestock industry. Also, some scientists reported that production of ethanol from corn can use more energy than is produced. More recently, some consumers have joined the discussion. And the American Council of Chain Restaurants recently estimated RFS increases cost to full-service restaurants by almost $700 million a year and predicts RFS will increase corn prices by 27% by 2015. In view of reduced production due to drought, various efforts have been made to get waivers from the RFS standards, which can be allowed under the regulations. Some U. S. senators and representatives, from both farm and non-farm states, have become more active in seeking changes to RFS. Of course, corn farmers generally favor RFS. Time and the political process will tell if there are changes to RFS.

(TCFA Newsletter, 6/28/13;, downloaded 6/24/13)

Zilmax® (Z) is often fed at the end of finishing periods because of its favorable effects on performance and carcass leanness, but there are often unfavorable effects on tenderness. Supplemental Vitamin D3 has been shown to improve tenderness. A study was conducted to see if feeding D long-term (165-day finishing period) or short-term (last 13 days before slaughter) would improve tenderness with or without Z. Results were:

  • long-term D feeding had no effects on feeding performance, with or without Z;
  • short-term D without Z decreased ADG, feed efficiency, and slaughter weight;
  • long-term D without Z had no effect on carcass traits;
  • long-term D with Z tended to decrease kidney, pelvic, heart fat;
  • short-term D without Z tended to decrease carcass weight and fat cover and increase dressing percent;
  • short-term Dwith Z had no effect on carcass traits.

Unfortunately, feeding D either long-term or short-term had no effect on tenderness, except for a tendency for slight improvement when Z was fed and steaks were aged 21 days.

As expected, feeding Zilpaterol® resulted in higher feed efficiency, carcass weight, dressing percent, and ribeye area and decreased fat thickness, numerical Yield Grade, marbling, and tenderness. Across Vitamin D treatments, marbling of Z averaged Small23 and non-Z averaged Small46. This may seem like a small difference, but when the average is near the minimum of Small00 for Choice not much difference can be important. That was true in this study since Z averaged 54% Low Choice and higher and non-Z averaged 72% Low Choice and higher.

A difference of 54% versus 72% Choice is certainly large. But realize that non-Z feeding increased the percent grading Choice by18 percentage points not 100, i. e., grade could not be improved for every carcass by eliminating Z since over half fed Z graded Low Choice or higher. On the other hand, average carcass weight in this study was 856 lb for Z and 824 lb for non-Z. And that difference of 32 lb applies to the entire group. Using a Choice-Select spread of $10/cwt carcass and applying that to the 32 lb results in average total carcass value of $1673/hd for Z and $1625/hd for non-Z, even though the latter graded much better. NOTE: this does not account for any effect if some carcasses qualify for premium programs such as CAB, but also does not account for benefit from differences in feed efficiency. All variables should be accounted for, as is done by knowledgeable cattle feeders.

(J. Animal Sci. 91-3322; Purdue Univ.)

Decreasing density of steam-flaked corn (SFC) by more extreme processing can increase dietary starch availability. However, more energy is required in processing to decrease density. A study was conducted to compare SFC densities of either 22, 26, or 30 lb/bushel fed with 25% wet corn gluten feed for 163 days to 108 Continental X British steers initially averaging 807 lb and finished to weights averaging 1294 lb.

Increased SFC density seemed to negatively affect digestibility of starch; however, density had no effect on feed consumption, ADG, or feed efficiency. As SFC density increased so did dressing percentage and ribeye area by slight amounts, but there were no other carcass effects. The authors concluded that “bulk density can be increased up to 30lb/bushel on 25% WCGF rations without affecting performance or carcass traits”.

(J. Animal Sci. 91:3400; Texas Tech Univ.)

On 6/28/13, the USDA approved a plant in New Mexico to again slaughter horses for human consumption. Additional plants are expected to be approved shortly. For several years, Congress prohibited funds from being spent for inspection of horse meat. Since inspection is required for meat, this effectively stopped horse slaughter. However, that prohibition was not renewed last year, so USDA-FSIS must again provide inspection for approved facilities. Various groups against slaughter of horses are expected to quickly demand legal action against the practice. FSIS requirements for horse slaughter can be accessed at

A group of 104 weaned heifers (Angus, Brahman, Romosinuano, and all 2-way crosses of the three) were grown in drylot for 70 days. Individual feed consumption was measured. At the beginning and every 14 days heifers were weighed and scored for chute behavior and chute exit velocity.  After the 70-day trial, heifers were placed on pasture until first calving as three-year-olds. 30 heifers were either culled during this period or did not calve, leaving 74 heifers to be further evaluated. On a weekly basis, as cows calved they were placed as a group in drylot. Feed consumption of cows and their calves was recorded, cows were weighed weekly, scored for Body Condition Score and temperament every 2 weeks, milk production was measured by milking machine, ultrasound was used to evaluate fat thickness and ribeye area, and calves were weighed at the start and end of the trial. As growing heifers and again as cows, individuals were divided into low, medium, and high efficiency thirds, based on Residual Feed Intake.

Body weight, ADG, and BCS did not differ among heifer efficiency groups. There was no difference among the three heifer efficiency groups in cow weight, ADG, BCS, efficiency, milk production, fat thickness, or ribeye area. Correlation of the heifer and cow efficiency groups was only 0.13. There was no effect of temperament score on efficiency, whether scored as heifers or cows. Based on these findings, immature evaluation of RFI efficiency was a poor estimate of mature RFI efficiency. Also, while poor temperament has many detriments to production and management, RFI efficiency was not one of those detriments in this study.

(J. Animal Sci. 91:2254; Univ. of Florida, USDA-ARS Brooksville, FL)

Over three years, in Florida, Minnesota, North Dakota, and Mississippi, 679 Angus or Brangus cow-calf pairs were synchronized with the 7-day CO-Synch+CIDR protocol. In one experiment, with dams averaging 68 days postpartum, one-half of the suckling calves were removed from their dams for the 72 hours before timed AI and one-half of the calves remained with their dams. In the second experiment, with dams averaging 71 days postpartum, treatments were: calves removed for 72 hours before timed AI; calves removed for 48 hours before timed AI; calves removed for 48 hours but allowed to nurse 24 hours before timed AI; controls.

Calves left with their dams lost less weight during the 3-day treatment period, as did older calves. Treatment group had no effect on calf weight 63 days after timed AI.   Follicle growth was greater when calves were removed for 72 hours. However, pregnancy rates, averaging 50%, did not differ between treatments.

(J. Animal Sci. 91:2414; Univ. of Florida, Univ. of Minnesota, North Dakota St. Univ., Mississippi St. Univ.)

An analysis was conducted on data collected over 30 years at 70 locations in 7 Brazilian states. Two types of cattle were represented, these being Nelore and Montana Tropical Composite (consisting of various combinations of zebu breeds, tropically-adapted Bos taurus breeds, British breeds, and Continental breeds). Traits analyzed were postweaning gain, yearling weight, scrotal circumference, stayability, and average annual cow production. Depending on the cattle type and trait, as many as 100,000 animals provided records. Stayability was defined as calving every year, if given the opportunity to breed, to 6 years of age. Cow production was calculated as an index which “takes into account the weight of weaned calves and the length of time necessary for their production”, i. e., a combination of production and reproduction.

Cow production and stayability were highly genetically correlated (0.99 in Nelore and 0.85 in composites). Genetic correlations between postweaning gain, yearling weight, or scrotal circumference with cow production or stayability were all low, mostly <0.10. However, estimates of annual genetic change were positive for all five traits; rate of genetic change in cow production and stayability was higher in Nelore than composites. The authors concluded that “simultaneous selection for growth, productivity, and stayability is possible”.

(J. Animal Sci. 91:2527; Univ. de Sao Paolo, Univ. Paulista Julio de Mesquita Filho)

The 59th annual Beef Cattle Short Course will be held on the campus of Texas A&M University on August 5-7. Topics on all aspects of beef production will be addressed. For more information and how to register see

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