Expected breeding values (EBVs- also called expected progeny differences (EPDs) in some other genetic evaluation programs) are used to accurately select rams and ewes that produce consistent and profitable progeny based on the traits selected.
EBVs estimate the genetic merit of animals for key production traits.
In doing this, we are able to remove the environmental variables (such as season of the year, forage quality (i.e. pasture vs. hay), supplemental feeding, age of dam, litter size), and across different flocks if sufficient genetic links are made between flocks.
In practical terms, this allows us to remove the effect of management (or environment) from genetic selection.
For example, if we were to select the largest lambs from each group at weaning, we are likely to be selecting the singles, which may be counterproductive to increased fertility.
It also allows us to compare different contemporary groups.
For example, if I had one group of lambs born in winter and fed grain in the barn vs. another group born on pasture and not supplemented, weaning weights between these groups would obviously be different, but the bigger winter-born lambs aren't necessarily genetically superior- they simply had more nutrients available for growth.
1. Many production traits cannot be assessed accurately by visual inspection
Key examples of this are prolificacy and milk production. When purchasing a ram, how can the maternal traits that he will pass to his offspring be assessed? EBVs can give you a view into the genetic potential of his daughters.
2. Comparing animals in different flocks or management groups.
If we have a winter-born lamb group that is fed high-quality hay and creep feed, and my 2nd lamb group is lambed on pasture with no supplemental feed, at the same age, we would expect the winter-born group to be larger.
Does this automatically make the winter-born lambs genetically superior?
We need to remove the environmental (feed) factor, and compare genetics.
EBVs can do this by taking the performance of that animal as well as the performance all relatives/ancestors of that animal in the flock, and produce numbers that reflect the true genetic potential of that animal.
EBVs can also 'even out' the effects of a lamb raised as a single vs. one raised as a triplet.
3. Visual assessment of carcass traits in live animals is not very accurate.
This has been shown time and again in shows where animals are judged live, then again on the rail.
The ranking often changes drastically.
By using objective measuring through ultrasounding and EBVs, we can improve the accuracy of selecting the animal with back fat or muscling desired by the buyer.
In short, using EBVs allow a buyer evaluate what is "under the hood"of that animal- how it will perform.
After all, when you purchase a car, do you just look at it, kick a tire, and say you will take it?
Of course not.
You ask 'performance' questions such as mileage, fuel efficiency, horsepower, etc.
We should be asking the same questions with the sheep we purchase.
The dairy, beef and swine industries use EBVs and have made great strides in genetic progress.
The sheep industry is far behind the times in this respect when you look at lack of improvement in many production traits over time.
In the selection of the K Bar K flock, we emphasize the maternal traits, as a Dorset is to be a good mother first and foremost.
We balance these traits with growth and carcass traits to produce a well-balanced animal.
These animals may not top the charts in any single trait, but we are not proponents of single trait selection.
If, for example, we selected solely on the post-weaning weight EBV (see explanation below), we would inadvertently be selecting for greater mature weights and possibly greater lambing difficulties, as well as selecting against maternal traits.
However, by balancing our traits, we have been able to increase the growth rates while at the same time decreasing mature body size.
This results in a ewe that has lower maintenance requirements but producing a higher level of production per pound of her body weight.
Number of Lambs Weaned (NLW) Animals with a positive NLW will produce daughters that wean a higher percentage of lambs. For example, a ram with an EBV of +0.1 will sire daughters that on average will wean 5% more lambs (all EBVS must be halved because the ram contributes 1/2 of the genetics).
Maternal Weaning Weight (MWWT) Animals with a positive MWWT will produce daughters that wean heavier lambs. This EBV reflects a combination of the female progeny's potential for milk production and ability to provide a better maternal environment.
Weaning Weight (WWT)Animals with a positive WWT EBV produce lambs that grow quicker to weaning. An animal with a WWT EBV of 4.0 will produce lambs that are 2 kg (or 4.4 lb) heavier than an animal with a WWT EBV of 0.
Post-Weaning Weight (PWWT) Animals with a positive PWWT EBV produce lambs that grow faster and reach target weights in a shorter time. For example, an animal with a PWWT EBV of 7.0 will produce lambs that are 3.5 kg (7.7 lb.) heavier at the same age than lambs from an animal with a PWWT EBV of 0.
Yearling Weight (YWT) We are monitoring yearling weights to be sure that selection for greater PWWT isn't also increasing mature weight. Single trait selection for early growth has been shown to increase mature size. We are striving to produce a moderate-sized, efficient animal, so we don't want to be inadvertently increasing our mature size.
Post-Weaning Eye Muscle Depth (PEMD) Animals with a positive EMD EBV will produce lambs that have more muscle, independent of weight, and a higher lean meat yield. For example, a ram with a EMD EBV of 1.0 will produce lambs that have a 0.50 mm deeper loin eye. Eye muscle depth has been shown to be highly correlated to loin eye area, and is a bit easier (less subjective) to measure than loin eye area.
We are monitoring Post-Weaning Back Fat (PFAT), although at this time we are not actively selecting based on this EBV.
Our use of EBVs can help your flock, whether you, as a buyer, look at our numbers or not.
By selecting the genetically superior animals through the use of EBVs (and other selection tools), we are able to take a lot of the guesswork out of how an animal's offspring will perform.
In this way, you only need to make decisions regarding which trait(s) is most important to you (i.e. muscling, maternal, growth) and find a ram that is phenotypically pleasing to you to produce the type of lamb you need for your market.
If you purchase a ram with a WWT (weaning weight) EBV of 4.0, this means that this ram will wean offspring that are an average of 2 kg (since only 1/2 of the ram's genetics are transmitted to his offspring, you need to divide EBVs in half) or 4.4 lb. (2 kg * 2.2 lb/kg) heavier.
If you have 50 lambs, that means you have 220 additional pounds of lamb to sell at weaning (50 lambs * 4.4 lb.= 220 lb.).
Let's say that you sell weanling lambs for $1.50/ lb at auction (this is actually quite conservative for our Eastern ethnic markets).
You have an additional 200 lb. * $1.50/lb = $330 additional income for minimal input.
If you use this ram for 2 years (typical for many flocks), that ram could produce an additional $660 income from 50 ewes in 2 years.
In many circumstances, this additional income alone will account for most if not all of the ram's purchase price.
But there are other things to factor: if you retain replacement ewe lambs from this ram, they will also have that additional growth that they will transmit to their offspring.
There are also maternal traits to consider: MWWT (maternal weaning weight) is an indication of the ewe's milking ability- if the purchased ram has as a strong MWWT EBV, his daughters will milk heavier, resulting in heavier lambs.
An increase in NLW (number of lambs weaned) results in a greater number of lambs weaned from the purchased ram's daughters.
It is difficult to put hard economic values on the reproductive traits, but we all know that they are very crucial to impacting the profitability of the farm.
While the EBV ram may have seen more expensive at the forefront (especially when tempted to buy another (non-EBV) ram at half the price with few solid records behind him), in the end he was a bargain!
We have heard this comment more than once (from both show and non-show folks).
In short, it is not true.
Show flocks can (and some do) certainly select for production, while flocks that use EBVs should only be using EBVs as ONE TOOL in their 'selection tool box', not as their sole selection tool.
Other tools used in selection decisions in the K Bar K flock include: ease of lambing, mothering ability, out of season lambing ability, structural conformation, breed type, disposition, and ability to thrive in a forage-based diet.
We have culled animals with outstanding EBVs that have had structural or production problems.
Even if that particular ram can grow fast (or large loin eyed) lambs, if they can't move properly to move and graze, or have some other physical issue, they aren't worth keeping.
Selection based on EBVs is only one tool that should be used when selecting your next flock sire.
There are other factors that are just as important, such as flock management.
It is important that you purchase a ram that is either from a flock that is managed similarly to yours, or from a 'rougher' (more extensive) environment.
That way the ram (and his offspring) are ready to work in your environment.
If a ram is genetically selected based upon a confined diet of alfalfa and corn, he may or may not excel in a pasture-based system.
Also consider conformation and phenotype.
If you do not like to look at the animal, or if he isn't structurally sound, he is not likely to stick around long on your farm or produce lambs that you like.
And finally, do not forget about flock health issues.
With the purchase of any animal, the diseases come for 'free'.
Ask lots of questions regarding health status of the flock, ask to see sheep on the farm other than the group that is for sale, and ask if the producer tests or is willing to test for diseases (which may be at the buyer's expense) that are of concern to you.
Ask questions about the flock management, such as how many ewes require assistance at lambing, how many bottle lambs are raised, what is the lamb mortality (and causes of mortality), etc.
You can gain or lose a lot more genetic ground in your ram selection than your ewes.
Keep in mind that if you use one sire, all lambs from that mating contain genes from that ram, but only a small percentage of lambs (usually 1-2 lambs per lambing season) will carry the genes of any particular ewe.
If you are buying a ram to create your own replacements:
Concentrate on maternal traits first (MWWT, NLW)
Recognize that these traits won't be expressed until the daughters from this ram have lambed
Maternal traits have lower heritability compared to growth and carcass traits, so genetic progress is slower
Maternal traits can have a big economic impact so small changes are economically worth it
Obviously phenotype is also important- is the ram structurally correct, express good breed character, and produce daughters that have the body capacity to carry multiple lambs while consuming a high- (or all-) forage diet.
Some characteristics, such as out of season lambing or acceleration, are not currently captured with EBVs. This is where requesting other information, such as the lambing record of the dam, can be important.
Scrapie resistance (Codon 171) may be important to you in a maternal sire who is producing the replacement ewes for your flock.
Let's assume you want to increase number of lambs weaned in your flock.
Your retain 40 ewe lambs sire by a new ram that has a NLW EBV of +0.3.
We assume that your flock has a current NLW EBV of 0.0, then you could expect 6 additional lambs weaned per the following calculations:
If these lambs are worth $150 each, there is a potential $900 of additional gross revenue every time those daughters lamb.
If you are buying a ram to produce terminal lambs:
Growth and carcass traits are most important. The specific traits will depend on the type of lamb you want to produce. These traits also have the highest heritability and express themselves quicker. They can also be evaluated in the ram's offspring a lot sooner than maternal traits, where one must wait until the ram's daughters lamb.
Scrapie resistance (Codon 171) may not be as important a factor, since all lambs are headed to a terminal market.
Let's assume you want to increase weaning weight.
If you direct market 60 lambs, and your new ram has a WWT EBV of +4.0 for weaning weight (and your flock has a current average WWT of 0), you can potentially have the following additional revenue:
The long answer is that we only retain a very select few rams to offer for sale (usually 15-20% of the top of the crop at most).
Why do we do this?
First, the expense of carrying too many rams over a year can quickly become cost-prohibitive.
Secondly, in order to make genetic improvement in our flock or yours, we should and can only retain the 'cream of the crop'. I won't retain average or inferior animals simply to make additional sales.
We have often found that the 'best of the best' rams don't often sell first. Sometimes rams sell based on price (lower priced rams sell first), sometimes they sell on other attributes that may not be of interest to the next buyer, so an ideal ram may still be waiting to improve your flock genetics.
So, just because there are only a few rams for sale, be assured that they are the 'top of the crop' and that you are selecting from the best of our flock, sometimes rams that we've used ourselves in our flock and are selling to allow us to use the next generation.
We have sampled many of the progressive production Dorset flocks from around the country. For the most part, all purchased rams brought something positive to our flock, but my own homegrown rams were consistently out-performing the purchased sires.
By going back to the same flocks (none of which had NSIP or Lambplan EBVs), I would not know whether we were making a positive, stagnant, or negative genetic move until that animal produced EBVs within my flock, which could take a couple of years, especially in the case of reproductive traits.
By that time, the genetics are all through the flock, and if it was a negative genetic move, there is a lot of culling to do that could have been prevented by using a sire with known performance.
Therefore we decided to import genetics from systems with very progressive genetic recording systems. England is the 'motherland' of the Dorset breed, and they had the phenotype and production we were looking for in our flock.
They also heavily emphasize the maternal qualities of the breed, including fall lambing. Combined with outstanding performance records, we decided this was our next genetic move.
Kathy saw the flock during a visit to England, and was impressed with the phenotype and production. After sifting through piles of data, in 2007 we imported semen from the Blackdown flock, a British flock that was at the top of Signet (the UK genetic recording system) and was one of the most genetically linked flocks in the country.
We have used some of this semen, have more semen in storage, and plan on future importations of semen, either from England or from Australia.
We first AI'd with British genetics in fall 2007, again in 2011.
For many of the reasons mentioned above (only retaining a small percentage of the best rams, raising them out for a year) as well as the inputs we have in the genetics of our animals, we can't sell rams for $200 and afford to stay in business for very long.
Each buyer has their own concerns/requirements when purchasing animals (we know we do!), and we often get asked why we don't test for "disease X, Y, or Z".
If we tested the flock for every known disease for sheep, it would financially put us out of business, as there is no way the market could bear what we would need to price these animals.
When you figure in a minimum of $10-15/sample per disease (plus labor, materials and shipping) multiplied by several hundred sheep, repeated annually, the costs can be staggering.
That said, we are more than willing to test for any disease that a buyer requests, at the buyer's expense, unless there would be a positive result, in which case we would absorb the cost and the buyer would be under no obligation.
We necropsy deceased animals of questionable death at the Penn State Animal Diagnostic Lab, and will request a panel of diseases to be tested.
If we observe suspicious symptoms of any disease, we conduct aggressive diagnostics to find and correct the problem, but this has been rare, and has never ended up being anything contagious.
Another factor to consider in disease testing is that many of the diagnostic tools (blood testing, etc.) are not very accurate or specific for sheep, are only valid with animals of a specific age or production stage, or are only specific enough to assess presence in the flock, not individual status of each animal.
This means you can get false readings, which significantly increases the costs with repeated testing, and the confidence in the results is not as high as we would like them to be.
In Fall 2008, 70 of our animals were tested by a buyer for Q-fever, B.ovis, and tuberculosis.
All results were negative.
We have also shipped animals to states that require testing (i.e. B ovis testing for North Dakota and Montana) with no positives.
We do not make health claims on the whole flock based on this sub-sample. We only present the information I have and let buyers decide for themselves.
While we do retain/sell mostly animals of multiple birth, we do retain/sell somesingle-born animals. This is where the power of EBVs (expected breeding values- see the following questions regarding EBVs) can help.
The NLW (number of lambs weaned) EBV must be well above average to retain a single-born animal.
Additionally, some single-born animals are out of a young (12-18 month old) ewe, and we certainly don't hold it against a ewe who shows early prolificacy, especially if their first lambing is in the fall and has good NLW EBVs.
Other reasons that an animal may be single-born is if they are out of a ewe who has accelerated well for us.
For example, we've had ewes have several twin births (sometimes twice in one calendar year), then turn around 7-8 months later and lamb again with a single.
This dam has demonstrated outstanding acceleration, and certainly deserves a 'break' with a single lamb.
That 'single' lamb she raises should carry those acceleration genes, so we don't automatically cull the lamb because it's a single.
That said, any animal that repeatedly has single lambs is culled, as are the offspring.
We have found little advantage to having registration papers.
We do not show, and we are able to track pedigree information through our Ewebyte software and NSIP.
Most of the efforts of the Continental Dorset Club focus on show efforts, which has little impact on our flock.
In 2014, the CDC increased the cost of transfer of sheep by 66% in the name of supporting yet another show.
The EBVs we receive on our sheep through NSIP have much more value to us (and to our buyers) than registration papers.
Currently all of our sheep are eligible for registry.
We do register rams that we use in the flock.
We do not register ewes (i.e. to register offspring that were sold and the buyer wants papers).
However, we are currently weighing whether that additional fees that would be incurred due to the rate increase would be better spent on paying for our NSIP membership fees to support objective genetic evaluation, which has been long-neglected by the sheep industry, including the CDC.
Another productive use of the money we spend annually on registrations/transfers would be to support the commercial aspect of the breed (or breed type)- we may consider offering an equivalent value in ewe lambs in a competitive program to a junior shepherd to start a commercial, production-oriented flock.
We feel a program like this would be more beneficial to young shepherds to promote the commercial aspect of the industry.
We have changed our price structure for our breeding stock as we no longer we feel we can absorb the price of registrations/transfers.
We have priced animals to include registration paper fees, and are now offering a slight discount to those who choose not to have their animals registered that covers the cost of registration/transfer/labor for data entry.
We will let the buyers vote with their dollar.
This may influence the number of animals we register in the coming years depending on the needs and desires of the buyers and the future direction of the CDC.