Beef Cattle Browsing – February 2010

Beef Cattle Browsing

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

March 2010

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.

The Secretary of Agriculture announced on February 5 some changes in the National Animal Identification System. A new framework will be developed by a partnership of Federal, State, and Tribal Nation representatives. It is intended that the new program:

  • apply ONLY to animals moving interstate
  • achieve basic animal disease traceability without overburdening producers
  • be led by States and Tribal Nations with federal support
  • allow maximum flexibility to meet local needs
  • encourage use of low-cost technology
  • insure data are owned and maintained under control of States and Tribal Nations
  • reduce Federal role and operate on principles of personal accountability
  • reduce concern expressed to this point in NAIS.

The program will be mandatory only in traceability of animals shipped interstate. However, each State and Tribal Nation will determine specific approaches to accomplish this traceability. (USDA – APHIS Veterinary Services Fact Sheet, Feb, 2010)

This newsletter is generally confined to items involving only beef cattle. However, sometimes we can gain some insight from research on other species. A study was designed to examine effects of genetic selection for increased intramuscular fat (IMF) in swine. Animals were divided into a selection line and a control line. The study was conducted over two generations.

As has been found in numerous studies on cattle, both IMF and carcass marbling were moderately heritable. IMF was favorably related to both tenderness and flavor. However, selection for higher IMF resulted in decreased loineye area and increased backfat. In swine, as well as cattle, in selecting for higher IMF or marbling some attention should also be given to muscling and external fat. (Iowa State Univ.; J. Animal Sci. 88:69)

Research has shown a nutritional requirement in cattle for both rumen degradable intake protein (DIP) and rumen undegradable intake protein (UIP). Feeds vary in content of these two proteins; for example, alfalfa hay is over 80% DIP while corn is less than 50% DIP. A group of 432 heavy feeder yearling steers, initially averaging 869 lb, was used to evaluate effects of DIP and UIP on feedlot performance and carcass merit using rations based on steam-flaked corn. Rations contained crude protein (CP) starting at 10.5% (dry basis) with incremental increases of 1.0% to 14.5% CP. DIP was increased in 1.0% increments (from 5.4% to 9.4%) as CP increased. UIP was included at a constant level of 5.1%. An additional group at the 14.5% CP level had increased UIP (6.1%) and 8.4% DIP.

Increased DIP and CP were associated with higher ADG, heavier final weight, higher fat thickness, and numerically higher Yield Grade (lower lean to fat ratio, resulting in fewer YG 1 and 2). Higher DIP in the 14.5% CP ration resulted in lower marbling; there were no other significant effects on carcass traits. The 6.1% level of UIP did not increase ADG or final weight above the 5.1% level. However, for maximum performance, it appears that UIP should be more than 7.4% but not as high as 8.4%. In summary, for heavy yearling steers the requirement on a dry matter basis should be 13.5% CP (equivalent to about 12.2% air-dry basis) with about 62% from DIP. (Colorado State Univ.; J. Animal Sci. 88:1073)

A review was conducted of 21 studies involving the diets over periods of 5 to 23 years of almost 350,000 people. The study, recently reported in the American Journal of Clinical Nutrition, was conducted by researchers at the Harvard University School of Public Health and Children’s Hospital Oakland Research Institute. Their conclusion was “there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of coronary heart disease or cardiovascular disease.”

Six cow herds with long calving seasons were converted to a short season. Average calving season was reduced from 273 days to 85 days. This resulted in 92% of cows calving in the desired season compared to 46% before the season was shortened. The average time taken to arrive at the shorter season was 3.8 years. One objection raised by some to shortening the calving season is that cows have fewer opportunities to breed and therefore fewer will calve over a year with a short season. However, in these herds the average of cows calving after the short season had been attained was 89%, compared to 87% for the last year before the change was initiated. Averaged over the six herds, cost of production was reduced and income increased with a shorter calving season. (Univ. of Arkansas; Beef Cattle Research Update, March, 2010)

Even though fertilization, by natural service or AI, occurs in over 90% of beef cows, less than 70% of single services result in conception. So, there is 20% to 30% embryonic loss. Some research indicated that treatment with a prostaglandin inhibitor might reduce this loss. One such material is flunixin meglumine. Three experiments were conducted to evaluate this possibility. In all three studies, females were either injected with the material 10 to 15 days after AI or not injected to serve as controls. (This is an experimental treatment not cleared for general use.)

In one study involving 1,221 beef heifers, treatment significantly reduced pregnancy, 66% versus 72% for controls. In a second study of 719 suckling beef cows, pregnancy rates did not significantly differ, being 57% for treated and 59% for control. In a third study of 247 beef heifers and 335 suckled beef cows, pregnancy rate did not significantly differ, being 56% for treated heifers versus 55% for controls and 45% for treated cows versus 42% for controls. The authors concluded that the treatment did not improve pregnancy establishment. (Montana State Univ.; J. Animal Sci. 88:943)

Genetic relationships were calculated among body weight (BW), scrotal circumference (SC), and various carcass traits in a group of 2,590 Nelore cattle. Data were collected over seven years, resulting in almost 23,000 weights and almost 5,700 scrotal measurements. Weights were taken and adjusted to120, 210, 365, 450, and 550 days of age. Scrotal circumference was measured and adjusted to 365, 450, and 550 days. Body weight, hip height (HH), and ultrasound measurements for ribeye area (REA), fat thickness at the 12th-13th rib (FT), and fat thickness over the rump (RF) were taken from 450 to 599 days of age.

REA was very lowly correlated with FT and HH, moderately to highly positively correlated with BW, and not correlated with SC. FT was highly positively correlated with RF. Both FT and RF were lowly correlated with BW and SC and moderately negatively correlated with HH. The authors concluded that selection by ultrasound for carcass traits should not interfere with selection to increase body weight and scrotal circumference. (Sao Paulo State Univ., Univ. of Sao Paulo, and Univ. of Calif. at Davis; J. Animal Sci. 88:52)

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