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.
Editor: Dr. Stephen Hammack, Professor & Extension Beef Cattle Specialist Emeritus
This month’s edition includes summaries of some presentations at the Beef Improvement Federation National Meeting in Houston last month. More detailed information on presentations can be accessed at http://www.bifconference.com/bif2012/newsroom.html. The next BIF meeting will be in Oklahoma City on June 12-15, 2013.
FITTING CATTLE TO THE ENVIRONMENT
By Dr. David Riley, Texas A&M University
Riley stated that Bos indicus-type cattle are better adapted to subtropical production conditions, as in the U. S. South and Southwest, accounting for the fact that about 40% of the nations’ cow herd has some Bos indicus genetics. Due to a combination of adaptability and heterosis, the Bos indicus-Bos taurus F1 crossbred cow has been shown to be most productive and efficient in the subtropics. However, the majority of cattle feedyards are in the Texas High Plains and northward. Half-Bos indicus cattle can be stressed
in these feedyards during winter, but quarter-bloods generally perform acceptably. Consequently, many part-Bos indicus cowherds in the subtropical U. S. use Bos taurus sires, resulting in an adapted cow producing a calf that is adapted to the areas where most feedyards are located.
ECONOMICALLY RELEVANT TRAITS FOR COMMERCIAL COW HERDS – LONGEVITY
By Jim Sanders, Texas A&M University
“Longevity is mostly a lack of problems,” said Sanders. He discussed the major reasons for a cow leaving the herd:
- Age – While some producers cull strictly on age, age should be considered in concert with other factors.
- Lost or worn teeth – Crossbred cows and those with Bos indicus genetics tend to retain effective dentition longer.
- Udders – Primary problems are pendulous udders and/or large teats. Generally, cows should be culled based on whether calves can nurse, not on udder visual appearance.
- Eyes – Culling is mostly due to cancer eye, which is more prevalent in animals with white pigment around the eye.
- Reproduction – Reproduction is lowly heritable (i. e., most of the variation is due to non-genetic factors, especially nutrition) but heterosis can improve reproduction as well as survivability.
Sanders indicated that some genetic improvement in longevity should be possible by selecting young herd sires out of older cows that have survived for whatever reason.
ECONOMICALLY RELEVANT TRAITS FOR COMMERCIAL COW HERDS – REPRODUCTION
By Milt Thomas, Colorado State University
Thomas, formerly of New Mexico State University, used long-term research conducted in the Chihuahuan desert of New Mexico using Brangus cows. The study involved selection of herd replacements for increased weight. Over time, reproduction declined slightly as cows became larger. Highest reproduction was seen in cows somewhat below average in size. Thomas suggested that, especially in marginal environments, more attention should be paid to selecting females that mature early.
ECONOMICALLY RELEVANT TRAITS FOR COMMERCIAL COW HERDS – TEMPERAMENT
By Dr. Ron Randel, Texas A&M
Randel defined temperament as reactivity or fear response to humans and noted that it has a heritable component. Temperamental cattle are more easily stressed in handling, leading to reduced feed composition, lower ADG, lower carcass quality grade, poorer response to vaccination, and therefore lower profit. Also, temperamental cattle can be more dangerous to handlers. Randel said that the object should not be to look for the most docile animals but to eliminate the crazy ones. Methods of objectively evaluating behavior include chute docility score, pen scoring with other animals, and chute exit velocity (how fast they cover a distance of six feet upon being released). Of these, if only one method is used he recommended some form of pen scoring, preferably at or as near weaning as feasible.
ECONOMICALLY RELEVANT TRAITS FOR COMMERCIAL COW HERDS – WEIGHT AND CARCASS MERIT
By Bob Weaber, Kansas State University
Weaber said a commercial cow-calf producer should ask themselves three questions: What is my source of replacement females? How do I sell calves? How do I generate revenue? The answer to these questions should determine genetic selection emphasis because traits have different value to different producers. A producer selling all calves at weaning and bringing in replacement females from outside should primarily emphasize moderate calving ease and growth when selecting sires. If the producer sells at weaning but saves heifers for replacements, some emphasis should be given to maternal traits. But if a producer retains ownership all the way through selling carcasses on a value-based grid, then carcass value should be a part of sire selection. Weaber said Dollar Value Index EPDs can be useful if the index applicable to a particular herd is used. But important single-trait EPDs should still be evaluated because sires with the same Dollar Value EPD can vary significantly in those traits. He also reminded the audience that reproduction and longevity are the most important traits in profitability of a cow herd.
SIZE, EFFICIENCY AND COMPLEMENTARITY
By Dr. Stephen Hammack, Texas AgriLife, Texas A&M System
Hammack traced the variation of cattle size over the last 200 years, from large to small and then, starting in the 1960s, back to large. At that time producers began selecting larger cattle and this continues. Today, the U. S. Meat Animal Research Center calculates that all breeds are continuing to increase in size, as estimated by genetic evaluation of yearling weight, and all of the major breeds are now similar. But research also has showed no biological advantage in efficiency due to larger size.
Emphasis on bigger cattle has been largely due to emphasizing performance of individuals as opposed to that of the total herd. (Larger cows can potentially wean heavier calves, but fewer larger cows can be maintained on the fixed forage resource of most herds.) Improved herd efficiency is possible through what is termed complementarity; this can be accomplished by breeding relatively smaller cows to larger sires, resulting in more calf weight relative to cow weight. Similarity in size among major breeds has reduced the opportunity to exploit complementarity due to size. However, complementarity due to differences in type will probably continue in the South and Southwest by using B. taurus sires on B. indicus crossbred cows.
STATE OF GENOMICS
By Dorian Garrick, Iowa State University
Garrick noted that EPDs of old, highly used sires are highly accurate and will not change much with genomic information. So, the primary benefit of genomic tools is to improve evaluation of potential breeding value of young individuals, along with evaluating traits difficult to measure or that are manifested later in life. Research has shown that genomic prediction is most effective in the population from which it is derived, so predictions developed in one breed are much more useful when restricted to cattle in that breed. In fact, predictions from one breed may be essentially useless and misleading in predicting breeding value for individuals in another breed or crossbreds. Genomic techniques are most useful when incorporated into breed EPDs to increase accuracy. Angus have produced so-called genomic-enhanced EPD for the last two years, Simmental have just begun, and Hereford will soon do so. Other breeds could follow as effective levels of genomic data are accumulated within the breed.
EPIGENETICS AND FETAL PROGRAMMING
Dr. David Threadgill, North Carolina St. University
Though not a new field of study, Threadgill noted that epigenetics is receiving increased attention. An example of an epigenetic effect is fetal programming. Stress during gestation (nutrition, heat, handling, etc.) has been shown to affect subsequent growth and efficiency of the calf. In research with sheep, ewes were overfed during gestation resulting in overweight, fatter offspring and this persisted for two generations at which time the study was concluded. In swine, males fed a methyl-supplemented diet produced offspring with a higher level of DNA methylation which is associated with greater backfat. Epigenetic changes in sires used for AI could faster amplify effects in a species. Threadgill summarized by saying, “Your calves not only inherit genes from their grandparents, but also the consequences of their diet and lifestyle.” NOTE: There is still some question among researchers in this field as to how many generations retain such effects.
ESTROUS SYNCHRONIZATION IN BOS TAURUS AND BOS INDICUS
Dr. Joel Yelich, University of Florida
Yelich said that effective estrous synchronization protocols have been developed for Bos taurus but that the same procedures have not resulted in similar pregnancy rates in Bos indicus. Slight differences in endocrine responses and follicle dynamics may be involved. Modified protocols for use in Bos indicus show potential, but require and additional step involving more handling and greater cost. However, the trouble and cost may be more than offset by the level of increase in conception rate.
SOFTWARE FOR HERD RECORDS
Dr. David Lalman, Oklahoma St. University
Lalman noted there is a variety of software available for different producers, both seedstock and commercial, currently ranging in price from less than $10 to almost $700. He stressed that producers need to choose software that works for them and indicated that most vendors offer free demonstration copies. Numerous programs have been compared in Oklahoma State University publication CR-3279, “Cow-Calf Production Record Software” available at http://www.dasnr.okstate.edu/ag-media/extension-fact-sheets-2 .