Contents
- President’s Ramble
- Little Helpers
- Milking St. Croix
- I Want it Right Now!
- Just a Bend in the Road
- Treasurer’s Report
Spring/Summer Newsletter, 2017
A coefficient of inbreeding is a measure of how much homozygosity we expect as a consequence of inbreeding. Genes are said to be heterozygous when an individual has two dissimilar genes for a trait; when the two genes are the same, the individual is homozygous for that trait (or that gene pair). We don’t have the technology to measure the actual gene combinations, but we can calculate the probability the genes will be the same by looking at the pedigree.
Each parent contributes 50% of their genes to their offspring. Thus, half-siblings like Ram B and Ewe C in the example below have 50% of their genes in common with Ram D, since they are both fathered by Ram D. But Ram B and Ewe C may have from 0 to 50% of their genes in common with each other – that is, of the 50% of the Ram D genes that Ram B received, somewhere between all or none of those genes may have also been sent on the his half-sibling Ewe C. On average, they will have received the same genes from Ram D half the time – so they should share 25% of their genes with each other.
Now, if the half-siblings are bred together, they each contribute half of their Ram D genes (25%) to their offspring. On average, their offspring are expected to get the same Ram D genes from Ram B and Ewe C half the time – so Sheep A is expected to be homozygous for 12.5% of its genes.
Ram D | ||
Ram B | ||
Ewe E | ||
Sheep A | ||
Ram D | ||
Ewe C | ||
Ewe F |
Relationship between the parents | Coefficient of inbreeding for the offspring |
Father-daughter, mother-son | 25% |
Half-siblings | 12.5% |
Grandparent-grandchild | 6.25% |
First cousins | 6.25% |
When multiple ancestors are found on both the sire and the dam’s pedigree, then the calculations for coefficient of inbreeding become more complicated. A thorough discussion of 2 different ways of calculating a COI, and the errors involved in using only 5 generations of data to do so (using Thoroughbred horse pedigrees), is Coefficients of Inbreeding: An Investigation into Wright’s Equation and Hardiman’s Method.
It is much easier to use a software program to calculate coefficients of inbreeding than to calculate them by hand. There are various software programs available for this purpose, from free-ware to relatively expensive pedigree programs. A few are listed below.FSpeed Rapid Computation of Inbreeding Coefficients. FSpeed is a Windows program for calculating Wright’s coefficient of inbreeding very, very quickly. A free version is available. Breedmate /Pedigree-X The Breed Mate family of Pedigree Software Packages covers dogs, cats, horses and other animals. The software must be purchased. WinCanis FREE! pedigree software. Originally designed for use with Dalmation dogs, can be easily modified to keep track of sheep pedigrees. The Visible COI add-on software is very useful in calculating the relative contribution of each ancestor towards the overall breeding coefficient.
Interested in showing your St. Croix sheep but don’t know how or where to do it? Take some tips from Dr. Ed and Linda Barnes of Portland, OR. Several years ago, this couple wanted to promote the St. Croix breed in their area. They went to the Oregon State Fair officials and requested to have their sheep as an “exhibit” breed at the fair. They continued exhibiting St. Croix for three years and were joined by other breeders as well. When enough St. Croix folks were exhibiting their sheep, the fair added official classes for the breed. To make sure they had enough entries to continue that option, the Barneses recruited breeders from as far away as CA to attend and show at the Oregon State Fair. Ed and Linda also donated lambs to children who were interested in raising sheep. They subsidized the children so they would also show their St. Croix, and that added the family dimension to the Oregon State Fair venue. Their efforts and enthusiasm have paid off in a big way: the OSF is currently the largest venue for showing St. Croix in the nation, and in 2010 they were the Featured Breed.
If there are fairs or shows in your area, contact the officials and find out what you need to do to have your St. Croix there. It may begin with small numbers and no judged classes, but when the public is exposed to these sheep, interest is generated and opportunities open up.
Whenever you know of an event where you can show or display your St. Croix sheep, please contact our secretary using the Contact Us page with details. Take pictures so we can include them in the newsletter and on the website. If you can give advance notice about these events, we’ll put them on the website immediately so other breeders can become involved or attend.
While there is no single, simple recipe that can be applied to all breeds or circumstances, the ALBC has designed a breeding plan to illustrate key requirements and to allow a breeder to more easily manage a flock within a conservation breeding program. This plan allows a breeder to keep three lines, but to use only one ram per year on his or her flock, by managing the three as one unit and using rams from different lines in different years. Each ram is used for only 1 year in the flock, so that his genetic influence is not excessive, and the genetic diversity within the line can be retained.
First, three groups of sheep must be identified to form the lines. Each group should be of approximately equal size, and consist of a number of ewes and 1 or more rams. Ideally, the sheep within a group should be more related to each other than to the flock as a whole, but the method of grouping is not critical. For instance, groups could be made by pedigree, with all descendents of a particular sire or dam in the same group. Or, if the flock has been built from several other flocks, the groups can be formed according to these foundation flocks. These groups will then be considered lines within the flock, and will be designated in this discussion as lines A, B and C.
In the first cycle, the ram from Line A will be used on the entire flock. Ewe lambs that are sound representatives of the breed are retained in their mother’s lines, but may produce progeny for more than one line. For instance, lambs sired by the A-line ram and out of A-line ewes will be A/A (linebred, more than ½ A), but lambs sired by the A-line ram and out of B-line ewes will be A/B (linecross, with no line more than ½) and can produce lambs for the B line when bred to a future B-line ram, or for the A-line when bred to a future A-line ram. Ram lambs are kept only out of A-line ewes, and when mature, the best A-line ram is used for breeding (see cycle 4).
In the second cycle, the ram from the B-line is mated to all the ewes in the flock. Again, both linebred (B/B) and linecross (B/A, B/C) lambs are produced. Ewe lambs are retained in their mothers lines, but ram lambs are retained only out of B-line ewes.
Cycle | Ram used | Ewes bred | Offspring Produced | |
Linebred —save males and females | Linecross —save only females | |||
1 | A | A, B, C | A | A/B, A/C |
2 | B | A, B, C A/B, A/C | B (includes B/AB) | B/A, B/C, B/AC |
3 | C | A, B, C, A/B, A/C, B/C, B/AB, B/AC | C (includes C/AC, C/BC, C/BAC) | C/A, C/B, C/AB, C/BAB |
4 | A | A, B, C, A/B, A/C B/C, B/AB, B/AC C/A, C/B, C/AB, C/BC, C/AC, C/BAB, C/BAC | A (includes A/AB, A/AC, A/BA, A/CA, A/ABC) | A/B, A/C, A/BC, A/CB, A/CBC |
*Table modified for the short generation time of sheep. From Sonenberg & Christman. 1995. A Conservation Breeding Handbook. Page 81.
The key to this breeding program is that the genetic makeup of each line is alternating between inbred (linebred) and outbred (linecross). The distinct genetic identity of the line is retained, while the linecross individuals provide input of new genes, reducing the amount of inbreeding that the line accumulates. These linecross animals may also show hybrid vigor. Inbreeding is occurring in as many directions are there are bloodlines, so the genetic distance between the lines is maintained through time.
In contrast, most breeding programs attempt to reduce inbreeding across the entire flock at the same time. The consequence is that inbreeding slowly accumulates in the same direction throughout the flock. Thus, there is no outcross available within the flock and the breeder must seek outside the flock to bring in new vigor or to address other inbreeding problems. If other breeders have used similar strategies in managing their flocks, there may not be any flocks with enough genetic distance remaining to provide a true linecross, and the vigor sought may not be obtainable within the breed.
For a conservation breeding program to succeed, there must be enough individuals within each line to produce a good replacement male and several replacement females at every breeding cycle. Additional animals are required if the breeder wishes to select for better conformation, size, or production. The ALBC suggests a minimum of 10 females per line (including both linebred and linecross females). However, if your flock management results in a large percentage of twins and triplets, this number can be reduced somewhat.
Part 1: Conservation Breeding
Part 2: What is Conservation Breeding?
Part 4: Three Disadvantages of Conservation Breeding
So now that we have a common set of definitions, we can come back to the original question: What is Conservation Breeding?
Conservation breeding can be described as a breeding program that protects genetic diversity within a breed. Genetic diversity within a breed “is necessary for the breed’s long-term well-being and commercial utility.” The breed benefits from the presence of many lines, as these distinctive genetic groups provide the material for linecrossing. If the distinct lines within the breed are lost, then there are no longer any groups within the breed to mate with to increase vigor, reproductive measures, and disease resistance, or to avoid a widespread negative trait; it also becomes more difficult to create an outstanding individual with bloom and presence. In extreme cases, breeders may be forced to bring individuals in from outside of the breed to address genetic problems caused by loss of genetic diversity.
Conservation breeding is designed to help a breeder maintain one or more lines, while also reducing inbreeding to manageable levels. In a conservation plan, each line of more closely related individuals is managed as a unit. This unit is alternately bred to a ram from within the line (linebred) and to rams from outside the line (linecross). All daughters are retained in the line, but linecross sons are not retained for breeding. The line as a whole retains its genetic distinctiveness, but inbreeding is reduced as the line consists of individuals with both more and less inbreeding.
Part 1: Conservation Breeding
Part 3: An Example of a Conservation Breeding Plan
Part 4: Three Disadvantages of Conservation Breeding
A summary by Karen Gerhart, drawing heavily from A Conservation Breeding Handbook, 1995, D.P. Sponenberg and C.J. Christman.
Breeders of purebred animals commonly employ one or more of the following breeding systems: inbreeding, linebreeding, and linecrossing. Each has advantages and disadvantages, and a breeder may wish to use only one system, or all three at different points to reach different goals.
Inbreeding: Defined as “mating together animals which are related so that the resulting offspring have one or more ancestors that occur on both the sire’s side and the dam’s side of the pedigree.” Close inbreeding would include the mating of full siblings, or father to daughter; more distant inbreeding might involve second cousins.
While inbreeding can be an emotionally charged subject, in itself it is neither good nor bad. Inbreeding tends to bring recessive traits (in St. Croix, these would include horns and colors other than white) to the surface; because of this, it should always be coupled with selection for excellent breed characteristics and the strict culling of individuals with undesirable traits. Used in this way, inbreeding tends to increase uniformity and consistency within a flock, and it has been used in the formation of most breeds. The St Croix breed started with only 22 bred ewes and 3 rams, and therefore all mating within the breed today involves some degree of inbreeding. However, for practical purposes, recent relatives have the most genetic impact and usually only the first 5 generations of the pedigree are considered when inbreeding calculations are made.
Inbreeding can lead to “inbreeding depression”, a reduction in vigor, fertility and disease resistance. Studies of wool sheep suggest that each 1% increase in inbreeding corresponds to a reduction of 1.4 lambs born per 100 ewes bred, a reduction of 2.78 lambs weaned per ewe lambing, and a loss of 2.44 pounds per lamb weaned (Lamberson et al. 1984, as presented in the Sheep Production Handbook, 1995). However, breeds and populations differ in their tolerance to inbreeding depression; a general guideline used by the American Livestock Breeds Conservancy (ALBC) is to keep inbreeding below 5% per generation, and 30% in any individual.
Learn more about a Coefficient of Inbreeding and software for calculating COI’s
Linebreeding: A form of inbreeding, linebreeding involves concentration of a particular ancestor within a pedigree (rather than several ancestors, as in other forms of inbreeding). Usually, this individual is a particularly excellent representative of the breed. The goal is to create a flock as much like this individual as possible, so matings often involve breeding half-brother to half-sister.
Like inbreeding, linebreeding reduces the variation within the flock, making the individuals more uniform and therefore more predictable. Again, the possible risk is inbreeding depression, including reduced vigor and reproductive performance. Strong selection and strict culling are necessary in a successful linebreeding program.
Linecrossing: A line (or strain) is a group of animals that are more closely related to each other than to the population as a whole. They might be the product of an inbreeding or linebreeding program. Linecrossing is the mating of individuals from one such line to those of another line. Generally, linecross individuals will show greater vigor, better growth, and more ‘bloom’, or ‘presence’ than individuals from either of the parent lines for at least the first generation. Thus, linecross individuals are more likely to succeed in the showring. Linecrossing can also be used to bring new vigor into an inbred or linecross flock.
Each of these three breeding systems have advantages and disadvantages. If the goal is a flock with high predictability and low variability between individuals, then some degree of inbreeding or linebreeding will help the breeder achieve this goal. Individuals from such flocks will produce lambs much like themselves.
If, however, the breeder’s goal is to produce excellent individuals, then linecrossing may be the better approach. These outstanding individual sheep may not be consistent in the types of lambs that they produce, however, and may not be able to produce lambs as good as themselves.
One advantage of a Conservation Breeding plan is that it can allow a breeder to include advantages of both linecrossing and linebreeding within a relatively simple program.
Part 2: What is Conservation Breeding?
Part 3: An Example of a Conservation Breeding Plan
Part 4: Three Disadvantages of Conservation Breeding
Maybe you have a few acres that are overgrown or that you are tired of mowing. Maybe you want to raise a few sheep as a novelty or to maintain a minor breed. Maybe you like to eat lamb and are tired of paying more than $5.00 per pound for a leg of lamb. Maybe you want livestock but do not have the room, equipment or the finances for cattle. Maybe you want to use sheep to teach your child responsibility. Maybe you just like sheep. Regardless of your reason, there are several things to consider before getting sheep. This paper highlights limitations, requirements and uses of sheep. Sources of information are also identified for those who want to raise sheep regardless of the reason.
Sheep are ruminants, which means they have a multiple-compartment stomach containing microbes that are able to digest forages (grasses, legumes, or shrubs). Sheep can survive solely on forage without grain supplementation, provided there is forage of sufficient quality and quantity. Sheep, like cattle, can also utilize hay, silage and many by-product feeds. Sheep are gregarious, which means they like to be around other sheep and move as a group rather that an individuals. This means that having only one sheep may be a disadvantage and you may need to have four or five at a minimum. There are a multitude of breeds of sheep available in the United States. These include sheep that are grown primarily for wool, that are grown primarily for meat production and even sheep without wool. Mature size of sheep ranges from 50 lbs to 500 lbs depending on breed.
Sheep are known as seasonal breeders. This means the female only cycles and accepts the male during times of shortening day length. Cycling usually initiates by the end of August to early in September. If not bred, the ewe will cycle and ovulate every 17 days. Once bred, the gestation length (the time from breeding to lambing) is five months. Ewes that are bred in late August to early September lamb in January and February. There are many breeds capable of breeding year round. To have lambs at other times during the year than just the spring, or to have ewes produce more than one time per year, you may want to consider one of these breeds.
On average, approximately half of the ewes will have twins therefore the average lamb crop will be 1.5 lambs/ewe (150% lamb crop). Breeds differ in their prolificacy. Lambs suckle the ewe for 2–3 months naturally, but can be weaned at one (1) month of age. Lambs are marketed at 90–130 lbs at 4 to 8 months of age (depending on breed).
There are two natural enemies of sheep: internal parasites and predators. Both can be partially controlled by the intervention of the sheep owner. Severe infestation by internal parasites can cause death in young lambs and even adults and is, therefore, one of the major problems in sheep production worldwide. The sheep owner has several management practices that aid in controlling internal parasite infestation, drugs called anthelmintics can be given to sheep to kill the parasites and practices such as pasture rotation can be utilized. These will be further discussed later.
Predators are the other major enemy of sheep. Predators include coyotes, wolves, mountain lions but most commonly dogs. Unfortunately, (for the sheep owner) often times it is the neighbor’s dog that causes the problem. Usually, the dog will maim or kill the sheep for sport and not consume the kill. There are two methods to control predators. One is by excluding the predators with proper fencing and the other is by protecting the sheep with guard animals. Recently, the availability of high voltage or high power fence chargers for electric fencing has improved our ability to keep sheep in, and more importantly, to keep predators out. In addition, several breeds of dogs can be used as guard animals and in fact donkeys [and llamas] are often used as guard animals to protect the sheep.
If the sheep owner can control the parasites and control the predators, sheep will survive.
Feed/land— To utilize the sheep’s natural characteristics of being able to consume pasture, shrubs and browse, perhaps the first thing to evaluate is the area available for grazing. The feed from pasture is the most economical and should be the base of the operation. How much land is available and what the productivity of that land is should be determined. Improved pasture may yield four to five tons per acre per year if properly managed, whereas hilly or tree covered land may average considerably less.
A general rule of thumb to consider in determining the number of sheep that you can have on a given land area is to consider that five or six ewes and their lambs are equivalent to one cow and her calf. Therefore, if land is known to carry one cow per acre then you can safely assume that you can carry five to six ewes and their lambs on the same area. In some parts of the U.S., 10 – 20 acres are required per cow/calf, so considerably fewer sheep can be kept on that area.
While pasture should be the base of the feed resource, other feeds can be utilized to supplement the pasture. Hay can be grown on the farm (but this requires a large investment in equipment) or can be purchased from other producers. If you can plan ahead, hay can be purchased at the time of harvesting directly from the field at a reduced cost. However, if purchased during harvest, a place will be needed to store the hay and you must have the finances to purchase the hay all at one time rather than throughout the year as you need it.
Sheep can also utilize by-product feeds including materials coming from garden, by-products of peanuts, corn, cotton, soybeans and even day-old bread. Feed can also be purchased from feed mills or feed stores. Sheep are capable of eating and readily like most cereal grains including corn, oats, barley and rye. These grains can be fed directly to sheep without processing.
Some feed stores will have available special mixtures made for sheep and goats. Care should be taken not to use feed that is advertised for dairy, beef, swine or poultry use. The reason for this is that these feeds will contain high amounts of copper and are toxic to sheep. Again, care should be taken not to use feeds that are made for other species of animals!
Sheep are generally offered required minerals in the form of a mineral block or as a free choice mix. A mineral mix should be purchased that is formulated for sheep to meet their requirements and prevent copper toxicity.
Buildings and equipment— The building requirements for housing sheep are minimal. Sheep survive outside without a barn as long as there is some shelter from wind and/or inclement weather. Shelter can be in the form of a converted machinery shed, and old garage, an old tobacco barn or a farm building. If sheep are given access to a shelter, they can decide whether to be inside or outside. Putting sheep into a tight, close fitting barn can be very stressful on the animals because of high temperatures and high humidity in the barn. The best shelters are dry, open-sided, and well ventilated. Sheep generally will not utilize the shelter except to get out of very inclement weather or to seek shade. Another time when a shelter may be necessary is during the lambing season, especially if ewes are lambing during cold, wet or snowy weather. In this case, sheep are often kept inside or are sheared prior to lambing to make the ewe seek shelter so that the lamb will be in a protected area.
Unless you are planning to make hay, the machinery necessary for sheep is minimal. A mower may be used to cut pastures that are overgrown, but with proper pasture management, no mower will be needed. It is advantageous to have an area or pens in a barn or in the open that can be used as a corral to sort and manage animals. Tasks such as weighing lambs, trimming feet, docking tails and treating for internal parasites are facilitated with a corral. These facilities are quite easy to make out of normal building materials or panels. Plans are available from several sources, as noted below.
A set of clippers for shearing [of wool sheep], foot trimmers and equipment for administering anthelmintics will be needed.
Fencing— The fencing may be one of the most important components of a successful sheep operation. A properly designed and constructed fence will keep the sheep in and predators out. Traditionally, woven wire has been used as sheep fence. However, the expense of woven wire is quite high and it is difficult to justify fencing large areas in woven wire fence. The perimeter fence around the entire area where the sheep are going to be contained must be of high quality material. If woven wire is used, posts must be put close enough together so that animals (the sheep and predators) cannot get through.
The most inexpensive and effective fence now utilizes high power electric chargers (~5000 volts). These chargers cost between $75 and $250 and can be run from regular 110 current, from a car battery or from the sun. There are solar chargers available for under $100 that will charge the fence continually during the day, and store a charge in a battery for night use. Spacing of the wire and grounding of the fence is extremely important to provide safety from predators. Most fence manufacturing companies will provide adequate detail on how to construct a sheep fence with their materials. Many have individual instructional video tapes that are available.
Construction of internal cross fences (to divide the pasture within the perimeter) do not need to be as secure or permanent as the perimeter fence. There are several types of portable, temporary fencing material available that are easily moved and can be utilized to cross fence pastures as forage growth changes or as number of animals changes. These types of fences can be easily moved by one person and are very useful in keeping sheep where you want to keep them. Several companies have portable types of fencing appropriate for sheep.
Health care— The major health concern is that of controlling internal parasites. Such control can be effectively carried out by the use of drugs (anthelmintics) to reduce the worm burden on the sheep. These anthelmintics should be given on a routine schedule to make sure that parasites do not weaken the sheep. The cooperative extension service or your veterinarian should be consulted to develop a plan for appropriate parasite control in your area. Generally, for ewes an anthelmintic should be given prior to breeding, before or at lambing and one time during the summer. Lambs should be given an anthelmintic at weaning and at 6 to 8 week intervals depending on level of infestation. Most state veterinary diagnostic laboratories will check the feces for parasite eggs at no charge. If egg counts exceed 1000/gram then an anthelmintic is needed. There are three major anthelmintics approved for use in sheep: levamisole, thiabendazole and ivermectin. Fenbendazole (the only one that kills tapeworms) is not approved for sheep, and before use a veterinarian should be consulted.
Rotating pasture so that sheep do not remain on the same pasture for more than 21 days will help reduce infestation. Biological control can be helped by utilizing cattle of horses to graze after sheep to reduce the larval burden on the pasture. Fertilization with liquid nitrogen also kills the larva on the pasture.
Other management tasks associated with health include hoof trimming at least annually to reduce the chances of footrot.
Fast growing grain-fed lambs should be vaccinated for clostridial diseases and vaccines are also available for tetanus. Consult your state extension service or a qualified veterinarian.
Marketing— If successful you will have a product to sell! Marketing these products is probably where most sheep owners fail in their total operation. In most states there are state pools to market lamb and wool. These offer one route of selling your products. However, the most successful producers develop their own market, whether it be to individuals or specialty stores. Much time and effort is required to develop your own market, but the payoffs can be very high. Consult your state extension service and state sheep associations for more information. In some states the state department of agriculture may have someone hired to assist in marketing your products. You have nothing to lose and the service is free.
Cooperative extension— Every state has a Land Grant University and an Extension Service. There are people in your state and perhaps in your county available to help you when you get started and with problems when they arise. Utilize these services, you pay for them through taxes!
Magazines— There are many magazines that are written with the sheep enthusiast in mind. Two that I have found particularly useful are the Shepard Magazine ( 5696 Johnston Rd.., New Washington, OH 44854) and Sheep! Magazine ( W2997 Market Rd., Helenville, WI 53137). Many of the Breed Associations also have magazines and newsletters.
Organizations— Most states have associations of sheep owners that will be valuable to you to join. There will be people with similar interests and these associations are very helpful to the beginner and experienced person alike. Your extension service should be able to help you make the right contact.
Books— There are many books written about sheep production. Your library should have a few. If you really want a manual for raising sheep, the Sheep Industry development Program (SID) publishes a loose-leaf book called the Sheep Production Handbook. It is the most widely circulated, most informative, and provides updates as produced. To purchase a copy, write to: Sheep Industry Development Program, 6911 South Yosemite St., Englewood, CO 80112-1414 or call 303-771-3500.