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Beef Cattle Browsing

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

April 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.

UNITED NATIONS REPORT ON LIVESTOCK EMISSIONS OF GREENHOUSE GAS FOUND FAULTY
In 2006, the United Nations Food and Agriculture Organization issued “Livestock’s Long Shadow.” The report stated that meat and milk production caused 18 percent of greenhouse gas emissions (GHG), more than that from transportation. However, a recent analysis of the UN report was published “Clearing the Air: Livestock’s Contribution to Climate Change”, led by Dr. Frank Mitloehner of the University of California – Davis. This study found that the UN report had included all factors involving livestock gases including everything necessary to grow feed, digestive emissions, and processing animals into food. But transportation gases included only fossil fuels used in driving. Cited in the report was a finding by the U. S. Environmental Protection Agency that, in the United States, livestock production is responsible for only 3% of GHG, compared to 26% from transportation. A spokesman for UN-FAO has admitted the inconsistency and said a more thorough analysis would be completed. (Texas Cattle Feeders Association Newsletter, 3/26/10)

In a related matter, the Science Museum in England has changed the name of their Climate Change Gallery to Climate Science Gallery in order to “respect and welcome all views on the subject.” Perhaps some balance is being introduced into the discussion regarding climate change, global warming, and related topics. (Source: various news reports)

NORMAL VS. LATE WEANING
A group of 158 fall-calving, mostly Angus cows were divided into two groups and studied for four years. In one group, calves were weaned in mid-April at approximately 210 days of age (NW). In the other group, weaning age, in mid-July, was approximately 300 days (LW). Cow weight and Body Condition Score in mid-April did not significantly differ between the two groups. But just before calving began in late August, NW cows averaged 1287 lb compared to 1236 lb (P<.01) for LW cows; BCS did not significantly differ at this time. However, NW cows lost more weight and BCS postpartum so there was no significant difference in either weight or condition when breeding began in late November.

NW calves tended to be heavier (P < .008) than LW at birth (80.1 lb vs. 74.8 lb) and were also heavier (P < .003) in mid-April (431 lb vs. 414 lb). (The authors stated the latter may have been partly due to NW cows higher (P < .05) daily milk production of 1.3 lb measured in February; milk yield did not significantly differ in November or April.) After weaning, NW calves were placed on native grass pasture. When LW calves were weaned in mid-July, they tended to be heavier (P < .06), 620 lb vs. 585 lb for NW at the same time.

Pregnancy rate was compared for young (2- and 3-year-old) and older females of both weaning ages. The two mature groups did not differ. Young NW females had significantly higher pregnancy rate than both NW-mature and LW-young females. LW-mature had significantly higher rate than LW-young. The authors concluded that, at least in fall-born calves, late weaning may increase calf weight without adversely affecting reproductive performance, except in young females. (Oklahoma State Univ.; J. Animal Sci. 88:1577)

HERITABILITY OF BOVINE RESPIRATORY DISEASE
Groups of 1519 preweaned and 3277 feedlot cattle were used to study heritability of bovine respiratory disease (BRD). Across both groups, the sire of individuals was known. Preweaned calves came from one herd. All calves were vaccinated for Clostridia, Haemophilus, IBR, BVD, BRSV, and PI₃ by 200 days of age. Feedlot cattle were those consigned to the Tri-County Steer Carcass Futurity in Iowa and fed in several feedlots. Health treatment varied across feedlots.

As has been found in several studies, incidence of BRD adversely affected weight gain and carcass merit, and these effects were more severe as the number of treatments for BRD increased. However, heritability of BRD resistance and number of treatments was only 0.11 and 0.08, respectively, for preweaned calves and 0.07 and 0.02 for feedlot cattle. In spite of these low heritabilities, the authors concluded that, because of high economic cost of BRD, “selection for BRD resistance should be considered for incorporation into beef cattle breeding programs.” (Iowa State University; J. Animal Sci. 88:1220)

EFFECT OF BIOLOGICAL TYPE ON POSTPARTUM ACTIVITY
Postpartum activity was studied in three biological types of cows: Charolais (CH, beef type), Normande (NO, dual-purpose type), and Holstein (HO, dairy type). Twice daily, NO and HO cows were milked and CH were suckled. By 30 days post partum, CH resumed ovarian activity significantly slower, 32% vs. 57% for HO and 63% for NO. By 50 days, all three groups differed significantly from each other, being 68% for CH, 79% for HO, and 92% for NO. However, though CH resumed ovarian activity slower their subsequent activity was good and without abnormal cycles. In all types, activity was less by 50 days in first-calving females compared to those calving at least twice.

Duration of cycles was related to milking potential, averaging 20.2 days for CH, 21.4 days for NO, and 22.6 for HO. HO had more cyclic abnormality as evidenced by a higher level of prolonged luteal phase. The authors indicated this may partially explain poor reproductive performance in the Holstein breed. (Three French research organizations: J. Animal Sci. 87 Suppl. 2:498)

FERTILIZE, SUPPLEMENT, OR NEITHER?
Yearling crossbred, predominantly Angus steers initially averaging 726 lb were divided into three treatments groups for grazing on smooth bromegrass managed as follows:

• fertilized with 80 lb N/acre, stocked at 4.0 animal unit months (AUM)/acre;
• non-fertilized, supplemented with 5 lb/day (approximately 0.5% of mid-point body weight) of distillers grains plus solubles (DDGS), stocked at 4.0 AUM/acre;
• non-fertilized, non-supplemented control, stocked at 2.75 AUM/acre.

All pastures had been fertilized with 80 lb/acre N yearly during the 10 years before the study. The experiment was conducted from 2005 through 2007 in an area where annual precipitation averages 27 inches.

Crude protein percent of the fertilized pasture was higher, but digestibility did not differ. Cattle were grazed from late April through September and then fed for 109 days. Performance was as follows:

So, the advantage in gain for supplementation during grazing was maintained through feeding, and marbling score was higher. However, fat thickness was also higher, so USDA Yield Grade probably would have been poorer (numerically higher). Unfortunately, economic factors were not addressed in this report. (Univ. of Nebraska; J. Animal Sci. 87:3639)

IS FEEDING BEHAVIOR RELATED TO EFFICIENCY?
A group of 115 weaned Brangus heifers was fed a growing ration for 70 days. There were six heifers/pen equipped with Calangate feeders to measure individual feed intake. From day 28 to day 56, video cameras constantly recorded activity at all feeders. After the feeding period was concluded, the 18 most efficient individuals (lowest Residual Feed Intake) and 18 least efficient individual (highest RFI) were determined and feeding behavior of those 36 heifers was evaluated by examining the video. Several feeding behaviors were studied:

• A head-down feeding event (FE) began when a heifer lowered her head to eat and ended when the heifer raised her head above the feed (a new feeding event occurred when the heifer lowered her head again to eat).
• Head-down feeding duration (FD) was the sum of the duration of individual FEs.
• Head-down eating rate (ER) was average daily dry matter intake (DMI) for a week ÷ FD.
• A meal event (ME) was all FEs separated by less than 5 minutes (a new meal occurred when the time between FEs exceeded 5 minutes).
• Head-down feeding frequency (FF) was no. ME/day.
• Meal duration (MD), in minutes/day, was the sum of the duration of each ME.
• Meal frequency (MF) was number of ME/day.
• Meal eating rate (MR) was average daily DMI for a week ÷ MD.

The 18 high-efficiency heifers averaged -1.03 RFI and the low-efficiency averaged +1.00 RFI. The high RFI group averaged eating 22% more (P< .0001) dry matter but ADG did not significantly differ from the low RFI group. High RFI had lower FD (124 vs. 152 minutes/day, P< .001), higher ER (102 vs. 63 gm/minute, P< .001), higher FF (119 vs. 90 FE/day, P< .001), and higher MR (50 vs. 42 gm/minute, P< .001). However, MD and MF did not significantly differ. The authors concluded that “feeding behavior of head-down feeding events may be more useful than the number of meal events as an indicator of RFI. (Texas A&M Univ.; J. Animal Sci. 87:2009)

WHEN IS THE BEST TIME TO INSEMINATE COWS?
A recent review of research on factors involved in artificial insemination has been published. Some studies had found that once-daily insemination equaled the “AM-PM rule” in pregnancy rate. Other reports indicated single, timed insemination coupled with administration of gonadotrophin-releasing hormone to induce ovulation 30 hours later resulted in pregnancy rates similar to breeding after detection of estrus. These findings questioned whether the range of time for successful AI may be longer than previously thought.

The author of the recent review examined results of work where electronic devices were used to determine exactly when estrus occurred relative to time of AI. Based on fertilization rate, embryo quality, and pregnancy rates, the author concluded the AM-PM rule, whereby cows are bred 12 hours after estrus is detected, “still represents the optimum timing for AI.” (Virginia Polytechnic Institute; Proc. 2009 Beef Improvement Federation Ann. Res. Symposium, p. 71)

NEW ANIMAL CARE AND HANDLING GUIDELINES
The American Meat Institute Foundation has released the “2010 Animal Care & Handling Guidelines and Audit Guide: A Systematic Approach to Animal Welfare.” A new transportation audit has been added addressing truck arrival and unloading at packing plants. These guidelines, first published in 1991, are reviewed and revised every two years. They can be accessed at http://www.animalhandling.org.