By Gregor Dike
We are in the midst of calving season: eight on the ground and sixteen more (if the bulls did their work) to come by year’s end. All healthy, all good sized, all the right color patterns….but did I use the right bull? How did I match my bulls with the cows I own? I used four criteria:
- Maximizing genetic distance based on the pedigree of the specific cow and bull under consideration
- Hopeful resultant coat color pattern
- Hopeful increase in size of offspring
- Hopeful improvements in specific areas of conformation
- Also, I will sometimes select the bull by, “Last year’s calf was great, might as well do it again.”
Look at my list. Other than the first two criteria the rest are just “hopes” at best. Is this anyway to run a business seeking to develop increasingly higher quality yaks? And, what is “higher quality”?
Take a moment to read what was being done back in the late 1980’s in the Chinese yak herds.
From Chapter 3 of “The Yak” 2nd edition revised by Gerald Wiener, Han Jianlin and Long Ruijun:
“In general, there are no clearly defined breeding objectives and no developed breed structure among herdsmen. Chinese animal scientists, however, decided towards the end of the 1980’s to develop breeding objectives for the principal yak breeds. The intention was to provide technical assistance for a more systematic approach to yak breeding and to aim:
- For earlier maturity
- To improve the animal’s shape for meat production
- To develop strains for either milk or meat, or for meat and hair production
The criteria to be adopted therefore stressed:
- Body size
- Growth rate
- dressing and meat percentages
- milk yield and fat percentage
- as well as the yield of hair – both coarse and down, but with an emphasis on the down
- This is what the scientists were thinking about thirty years ago in terms of yak breeding programs
- Look at what the herdsmen were looking at thirty years ago
- “Selection of yak by the herdsmen in the Jiulong area is relatively systematic. Herdsmen pay more attention to choice of yak bulls for breeding than they do to the cows.
The guiding principle for the herdsmen is to:
- Check the ancestors (the parents) first and the bull second
- Selection of replacement males starts in the herd with calves from cows that have good conformation and high milk yield over two parities of calving
- The herdsmen require that the sire of the males being chosen as replacement bulls should have copious hair and a large number of progeny
- The bulls being selected should have good conformation. In particular, the herdsmen require that the horns of the selected bulls stretch outward from a rough base and that there is a long distance between the horns. The forehead, head, muzzle and mouth have to be broad; the neck thick and the lips thin and long; withers should be high and brisket wide; the back, loin and rump should be wide and flat; the tail hairy; forelimbs straight and hind legs curved; the scrotum should be shrunken
- Acceptable coat colors are black or black with some white specks on the forehead and at the extremities of the body (e.g. legs or tail), but not on the body itself
It is not just the criteria that the herdsmen used (and scientists proposed), but think about the detailed record keeping and monitoring involved.
Did I use the right bull? I don’t even have criteria for “right”. Am I measuring birth weights for each bull? Am I recording weaning weights? Am I recording yearling weights? Am I measuring milk output? Am I weighing down collected? Right bull? …. only in terms of a color pattern I like and whose is not related to who.
Take a look at the following article by Dr. Stephen B. Blezinger entitled “PERFORMANCE TESTING PUREBRED BULLS IS IMPORTANT”.
These criteria may vary somewhat depending on the purchaser’s goals and the type of operation he or she has (i.e. commercial, vs. purebred). Basic attributes we want to know in a bull include:
- Structural Soundness
- Libido
- EPD’s – (defined below)
- Scrotal Circumference
- Semen Quality
- For purebred purposes producers also look at bloodlines and genetics to determine what sire and dam he may be from as well as family groups of which he may be a member.
- Additionally we may also look at how well he has performed on the show circuit.
- Commercial cattle producers may look at all this information to some degree, especially that information pertaining to reproductive performance. However, in most cases they are concerned to a large degree on what type of effect the bull he is considering may have on the subsequent performance of the calf crop. Depending on his marketing program, his concern may be on the bull’s effect on weaning weights if he sells at weaning or possibly on yearling weights if he retains ownership into the growing or finishing phase.
Performance testing, in many situations, focuses on how a bull performs in terms of average daily gain as well as feed conversion – how much feed it takes to put on a pound of gain. When you step back and consider that we are in the business to produce beef, or more specifically – red meat – at the best cost possible, we begin to see the inherent value of testing these parameters and determining how a given bull or sire group performs. In other words, when a given bull is used to produce calves that will go into the production pipeline, will his influence improve performance and economics or reduce that performance? In the market and economy we currently enjoy, a producer CANNOT afford to utilize bulls that don’t enhance his program.
Likewise, purebred or seed stock producers need to focus on the collection of this data so they can effectively market their product to the commercial cattleman. Within a given breed, purebred producers have a tremendous need to develop a sound commercial market. In other words, the purebred cattleman has to develop an outlet for his cattle to go to the commercial producers and therefore affects production economics to at least some degree in the industry. Purebred operators have to remember that they can only sell to one another for so long and then they have to go outside to develop their market. This is the only consistently sound means of maintaining cash flow and profitability. For this reason the need for performance testing in purebred bulls is imperative. Purposes for Performance Testing As alluded to above, performance testing is used primarily to evaluate gains and feed conversions in a given animal or possibly in a sire group (group of bulls from the same sire). Technically, the purposes of testing include: 1) To observe and compare gain ability of individual bulls (and sire groups when feasible), as well as pen feed conversion. 2) To encourage and assist in the use of performance records as a means to more efficient beef production. 3) To encourage herd improvement through the use of performance tested bulls.
What are EPDs?
[From the paper “What Are EPDs and How Are They Calculated” Michigan State University Extension, Joel Cowley, Extension Beef Specialist, Department of Animal Science, July 22, 1998] “Expected Progeny Differences (EPDs) are the most current and accurate means to select cattle for the traits for which they are calculated. It has been suggested that selection based upon EPDs is five to nine times more accurate than selection based upon performance indexes and ratios.
EPDs are estimates of how a bull or cow’s future progeny will perform, on average, for a given trait. The words ‘on average’ are italicized, as this is a very important concept to keep in mind. A parent contributes only a sample half of its genes to each offspring. That sample, being random, might contain a large number of genes that have a positive effect on the trait in question (a good sample) or it could contain many genes that have a negative effect (a poor sample). This can be likened to a deck of cards in a poker game. Some hands are winners and some are losers, but they all come from the same deck. Therefore, EPDs do not predict the absolute performance of an animal’s offspring, but the average performance.
How are EPDs calculated?
EPDs are usually calculated twice a year when a breed association gathers performance and pedigree information for their breed. The information is sent to an educational institution where a National Cattle Evaluation (NCE) is performed. Most NCEs currently utilize a multiple trait animal model to statistically analyze the data and generate EPDs. An animal model produces an EPD for every animal in the analysis, parent or non-parent, male or female. Animal models take into account all genetic relationships within a data set so that an animal’s own performance is combined and properly weighted with the performance of relatives (progeny, parents, grandparents, full and half-siblings, etc.) in order to generate an EPD. Multiple trait animal models take into account the genetic relationships that may exist between two or more traits and utilize these relationships as another source of information on a trait. As an example, weaning weight information can be used to help calculate Yearling Weight EPDs, as some of the same genes that affect weaning weight also have an influence on yearling weight. This can help to compensate for biases that might occur as a result of sequential culling (culling a sire’s offspring at weaning so that they have no yearling weight data) or selective reporting of yearling data.
The animal model approach also adjusts for the merit of mates. If a sire was mated to only the best cows, his EPD is adjusted to account for this so that he does not receive all of the credit for a superior set of calves.
The genetic change within a breed is also accounted for in an NCE. Therefore, comparisons may be made across generations of cattle. Based upon the available information, young bulls with no progeny can be directly compared with older bulls with a large number of progeny, meaning that more conservative estimates of an animal’s genetic worth are made when information is limited.
The animal model also separates out the maternal component of a trait. As an example, weaning weight is partitioned into the genetics for growth to weaning age (weaning weight direct) and the influence of mild (the maternal component of weaning weight).
It is important to remember that the EPDs generated by any NCE are only directly comparable with EPDs from the same evaluation (within the same breed).
For what traits are EPDs calculated?
EPDs are calculated for a number of, but not all, economically important traits. Most breeds report EPDs for Birth, Weaning and Yearling Weight as well as Milk. The following is a list of traits for which EPDs are calculated.
Birth Weight– Birth Weight EPDs are expressed in pounds and predict the average difference that can be expected in an animal’s offspring when compared with another animal in the same genetic evaluation. Birth weight EPDs are primarily used as an indicator of calving ease, with the age and size of the females to be bred usually dictating how much birth weight can be tolerated.
Weaning Weight– Weaning Weight EPDs are expressed in pounds and predict the average differences in weight that can be expected between the progeny of animals in the same genetic evaluation at 205 days of age. Weaning Weight EPDs do not account for differences in weaning weight that are due to milk.
Yearling Weight– Like Birth and Weaning Weight EPDs, Yearling Weight EPDs are expressed in pounds and predict the average differences that can be expected between the progeny of animals at one year of age.
Milk– Milk EPDs are expressed as pounds of calf weaned by a bull’s daughters. They reflect the average differences in weaning weight that can be expected in grandprogeny due to the milking ability of a bull’s daughters. Available feed resources will dictate the extent to which milking ability should be selected.
Total Maternal (Maternal Weaning Weight)- Like Milk EPD, Total Maternal EPDs are also measured in pounds of calf weaned by an animal’s daughters. They account for average differences that can be expected from both weaning weight direct as well as from milk, and measure a sire’s ability to transmit milk production and growth rate through his daughters. They are calculated by adding an animal’s Milk EPD to one-half of its Weaning Weight EPD.
Yearling Hip Height– Reported in inches. Predict the average difference in progeny hip height that can be expected at one year of age. (Angus).
Calving Ease Direct– Predict the average difference in ease with which a sire’s calves will be born when bred to first-calf heifers. Expressed as percentage of unassisted births with a higher value indicating greater calving ease (Gelbvieh, Simmental, Tarentaise).
Calving Ease Maternal– Predict the average ease with which a sire’s daughters will calve as first-calf heifers when compared to the daughters of another sire in the same evaluation. Expressed as percentage of unassisted births (Gelbvieh, Simmenal, Tarentaise).
Scrotal Circumference– Estimate the average differences that can be expected in scrotal circumference in male progeny. Expressed in centimeters. Of interest as larger scrotal circumference is favorably associated with fertility and age at puberty in a sire’s daughters (Limousin, Angus, Hereford).
Gestation Length– Predict average differences in gestation length. Expressed in days. Shorter gestation lengths are associated with less dystocia and longer post-partum intervals (Limousin and Gelbvieh).
Stayability– Expressed as the probability that an animal’s daughters will remain in production to at lease six years of age when compared to the daughters of another animal. A measure of sustained fertility that probably reflects traits such as fleshing ability and structural soundness. Expressed as deviations from a 50% probability, a higher value indicates increased stayability (Red Angus, Limousin).
Mature Daughter Height and Weight– Predict the average differences that can be expected in mature daughter size in inches and pounds, respectively. These EPDs can be used to match mature cow size to forage resources (Angus).
Carcass Weight– Estimate average differences in carcass weight. Expressed in pounds at a given age endpoint (Angus and Simmental).
Docility– Predict the percentage of an animal’s offspring that are expected to score favorably (1 or 2) on a five-point scoring system when compared to the offspring of another animal. Expressed as a percentage with higher values being favorable (Limousin).
Now, back to the original question.
What about you? Did you use the right bulls this past breeding season?
I have no idea. But maybe it is time to get develop a list of criteria and start collecting data so that five years from now with data in hand I can begin to have a performance based breeding program. Imagine if US YAKS developed a workable set of EPDs for its member breeders and everyone started collecting data on their animals. How would your management and sales change if you had performance based data on all of your yaks? So that when breeding season came around you would know which bulls would most likely give the result you are seeking and when a potential buyer asked about an animal you could show them the performance data and tell them the economic advantages each yak would bring. You would cull the right yaks, keep the right yaks and breed the right yaks. A lot of work? Yes. But if we want to improve our herds and really know what the species has to offer……