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Beef Cattle Browsing

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

September 2007

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.

COMPARING BREEDS USING ACROSS-BREED EPD
For the traits that have EPD, it is accepted as the best means of comparing genetic value of individuals within a breed. Across-breed EPD adjustments have been developed which allow comparison of individuals of different breeds, and these adjustments also can be used to compare breeds. There have been some indications that the major breeds have become similar in some traits, especially growth. Let’s compare the two most numerous British and Continental breeds (according to most recent registrations), Angus and Charolais. Using across-breed EPD adjustments and most recent breed-average EPDs, an average Charolais sire ranks in the top 1% of Angus for Weaning Weight EPD and the top 20% for Yearling Weight EPD. However, the average Charolais sire also ranks in the heaviest 2% of Angus for Birth Weight EPD and the lowest 5% for Marbling EPD. Similar contrasts exist in other comparisons of British and Continental breeds. (U. S. Meat Animal Research Center, American Angus Association, American-International Charolais Association)

EFFECTS OF CALVING SEASON & MARKETING STRATEGY ON PROFIT
Montana State University researchers evaluated several strategies of calving season/time of weaning/marketing using computer simulation. A Northern Plains, fixed-forage resource was assumed, capable of carrying around 500-600 cows, depending on the management system. Five systems were studied over an 11-year cattle price cycle: spring (SP, calving beginning March 15, wean Oct. 31); spring with 5% higher calf mortality (SP-HM); summer (SU, calve May 15, wean Dec. 15); summer with early weaning (SU-EW, wean Oct. 31); fall (FA, calve Aug. 15, wean Feb. 1).

Compared to the number of cows maintained under the SP system, about 10% more SU-EW cows and 20% more FA cows were maintained, but only slightly more SU and SP-HM. Also compared to SP, purchased feed costs increased slightly for SP-HM, about doubled for the two summer programs, and were almost five times higher for fall calving (approximately $60/cow for fall and $12/cow for spring). Average weaning weights were heavier for SP and SP-HM, followed by SU > SU-EW > FA (the range was 547 lb for SP steers to 381 lb for FA). Gross ranch margin was: SP > SP-HM and SU > SU-EW > FA. The authors concluded that, when marketing at weaning, traditional spring calving is most profitable unless calf mortality is elevated, in which case summer calving with normal weaning might be competitive.

In a companion paper, four marketing strategies were studied for the five calving scenarios: sell at weaning (SW), wean and feed (WF), background and sell yearling feeders (BG), background and feed (BF). Gross ranch margins were calculated for four periods in the cattle price cycle: peak, descending, valley, and ascending. Averaged across the entire 11-year cycle and the four marketing strategies, gross margin was lowest for SU-EW. Compared to SU-EW, increases in gross margin were: SP +18%, SP-HM +7%, SU + 2%, FA +5%. Across the entire cycle and the five calving scenarios, gross margin was lowest for SW. Compared to SW, gross margins were: WF +10%, BG +10%, BF +7%.

Returns from feeding were generally highest for fall calves. Early-weaned summer calves tended to return more from feeding than normal-weaned . At peak prices, backgrounding and feeding was generally more profitable than selling at weaning. When prices were descending, retained ownership was not profitable, except for backgrounding of spring-born calves. At the price bottom, retaining did not pay for spring-born calves, but did for fall-born. Also at the bottom, profits were made from feeding early-weaned summer calves (whether backgrounded or not) but feeding normal-weaned summer calves was profitable only when started directly after weaning. When prices were ascending, returns were positive for either backgrounding or direct feeding, but not for backgrounding and then feeding. In general, retained ownership was profitable during peak and ascending price periods. At the valley, retention generally did not pay, except for fall-born calves. Results varied when prices were descending.

NOTE: This research is an example of the interactions between production systems, marketing strategies, and cattle cycles. However, the specific findings reflect what might be applicable in a particular region of the U. S., the Northern Plains. Summer calving in hotter regions is usually not beneficial. (J. Animal Sci. 85:2314/2322.

POSTPARTUM INTERVAL & ESTROUS CYCLE LENGTH vs. FERTILITY
Researchers at the U.S. Meat Animal Research Center hypothesized that pregnancy rate is higher  with more and/or longer estrous cycles before breeding. Over 500 2- to 4-year-old females of various combinations of British-Continental breeding were studied. Females containing breeds noted for higher milking ability tended to have shorter postpartum intervals to estrus. Increase in body condition resulted in longer estrous cycles (19.2 days for BCS 4 up to 21.3 days for BCS 8). There was no significant relationship between number of observed estrous cycles before breeding and conception rate. However, conception rate decreased as length of cycle before breeding increased, which the authors speculated might be due to “a persistent follicle with greater potential for a lower quality oocyte”. (J. Animal Sci. 85:2156)

GENETIC SELECTION FOR GROWTH & HEAT RESISTANCE
Some earlier Australian research had suggested that positive response to selection for growth in tropical locales resulted from increased resistance to environmental stresses and not from genetics for growth. This prompted later work to see if direct selection for stress reduction might increase growth more than direct selection for growth. Cattle consisting of half British and half tropical breeds were used to investigate this possibility. Work was conducted in central Queensland, an environment described as “dry tropical with a variable and unreliable wet season”. Closed lines included two lines selected on increased growth to 600 days of age, one line selected on reduced rectal  temperature (based on repeated measurements under conditions of heat stress), and controls. Selection was practiced over about two generations.

Weights increased in the growth lines, though not consistently at maturity. In the growth lines, there was some improvement in resistance to heat, ticks, and worms. Selection for growth resulted in no changes in male or female fertility, feed efficiency, or carcass/meat factors. Selection for reduced rectal temperature was effective and was accompanied by increased carcass marbling and small correlated resistance to ticks and worms. Selection for increased growth also reduced rectal temperature but selection for reduced rectal temperature did not increase growth. The authors concluded that selection for reduced rectal temperature may involve factors other than heat resistance. (Livestock Prod. Sci 86:143)

EARLY WEANING & CREEP FEEDING vs. GROWTH, CARCASS, & PROFIT
University of Illinois researchers assigned Simmental X Angus steer calves to four groups: weaned at 63 days of age (EW), high-concentrate creep (HC), high-fiber creep (HF), and controls (CO). Except for EW, calves were weaned at 189 days of age.

CO gained less from 63 to 189 days of age, with HF intermediate. At 189 days all calves were adjusted for 22 days to full feed on a high-concentrate ration. During the adjustment period, EW gained more and CO less than HC or HF. On full feed, EW gained less. During the entire finishing period gain did not differ, but from 63 days of age to slaughter CO gained less. During all feeding periods, feed efficiency tended to be positively related to gain.

CO were fed for about two weeks longer than the other groups, but still produced carcasses weighing 30 lb to 50 lb lighter. Average Yield Grades did not differ, but there tended to be more YG4 in EW and less in CO. But EW had higher marbling scores and tended to have more Choice and Prime Quality Grade. Economic values were:

1) Not including cow costs, forage costs, or milk consumed by normal-weaned calves
(2) Carcass value minus Total costs

Early weaning increased marbling and carcass quality, but the cost of doing so reduced profit. (Prof. Anim. Sci. 23:325)

THE OTHER GUY’S RESIDUES ARE NOT MY PROBLEM
Maybe they are. Let’s say you buy some cows and then sell them to a packer. If antibiotic residues turn up, are you responsible? Yes, according to a recent federal court decision in Wisconsin. A seller claimed he bought some cows and had never medicated them. But the court ruled the seller should have required records on the cattle he bought. It should be noted that regulatory officials had previously sent the guilty party several notices to keep records of purchased cattle. (Summarized from La Crosse, WI Tribune, 8/27/07)