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United Suffolk Sheep Association |
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August/September 2004 Question Question: How do I manage my sheep at breeding time? Answer: Pipestone Veterinary Clinic and Supply Preparing Ewes for Breeding Season Breeding season is either upon us or a few weeks away. If you haven’t yet, now is the time to give some thought to your ewes. Make sure that the ewes are in the proper condition for breeding season. You will want to begin flushing ewes 2-3 weeks before ram turnout. This can be accomplished by moving the ewes to a fresh green pasture or feeding ewes one-half to three-fourths of a pound of grain a day. By moving the ewe to a higher plane of nutrition before breeding we can increase the number of ova that she ovulates and thereby increase the number of multiple births. Late summer is also a good time to deworm the ewes prior to breeding. Summer pastures become heavily populated with worm larvae by late summer and it is best to move ewes to a clean pasture at the time of deworming. Valbazen is an excellent choice of dewormers as long as the ram has not been turned out. Ivomec or Levasole are good options but they will not be effective against tapeworms. Now is also a good time to vaccinate the ewes for Chlamydia and Vibrio. Any ewes that are lame or unthrifty should be sorted from the pasture and treated or culled. As you are handling the ewes be on the lookout for moist wool. This is often the only indicator of fly strike. Treat ewes affected by clipping the wool around the wool and spraying the wound with screw worm spray. Don’t forget about the ram. Make sure he is in good body condition, sound on his feet and legs and passes a breeding soundness exam. The hot weather that we experience in late July appears to make some rams temporarily infertile. Remember the success of your sheep flock starts with breeding.
Breeding Time Management It is once again time to start planning for the next year’s lambing season. The first step should be in determining when you want the ewes to begin lambing and counting back the 147 days which is an average gestation. The success of the next year’s lamb crop actually begins prior to the breeding season. The rams need to be in adequate body condition because they will lose weight during the breeding season. Having a ram breeding soundness exam is a good suggestion. The ram breeding soundness exam should include an overall physical exam of the ram as well as a semen collection and semen evaluation. In smaller flocks that only have one or two rams this is more critical, because if one ram is infertile or has an inability to breed a ewe it will impact an entire lamb crop. In larger operations often a ram’s poor performance is masked by other rams. Purebred producers who wish to make specific matings with a group of ewes to a particular ram, should follow the next heat cycle with a proven stud to prevent a large number of ewes from being left open. The use of a marketing harness is an excellent tool to help identify problem rams or recycling ewes. Purebred breeders or small flock owners who wish to keep track of matings should place a marking harness on their rams starting out with a light color such as yellow. Then every 17 days switch to a slightly darker color such as orange, then red, then blue followed lastly by a dark green or black. If you wish to switch rams then you can also record if a ewe remarks and to which date a particular ram mounted her. If you keep a written daily record of the activity you can also use this information at lambing time to help identify which ewes are near lambing. Rams also need to be wormed and have their feet trimmed prior to breeding season. It is also a good idea to begin flushing the rams with some grain prior to the breeding season if you do not already have the rams on a diet containing some grain. They should not be in full fleece, if you shear prior to turning out with the ewes in the summer make sure to use a fly control product such as Delice. Avoid turning out ram lambs into large pastures or mixing them in with a set of older rams. Ram lambs have a tendency to be well fed and used to getting a high quality diet. If they suddenly get placed out on a pasture with only a “water hole” and salt feeder they can look quite different in 2 to 3 weeks. Combine their diet change with some older dominant rams competing for the same ewes and the ram lambs quickly become statistics. Handling the ewe prior to the breeding season is essential to your program’s success. There is a lot of literature written on this particular topic and well worth your time to read and understand. Unfortunately we are going into this breeding season with a limited choice of abortion vaccines. Colorado Serum Company has a license on their Campylobacter Fetus (Vibrio) Bacterin which is a 5cc product given 2 weeks prior to breeding and boostered in 60 to 90 days for first time vaccinates. Previously vaccinated sheep need only the annual booster prior to breeding. High risk flocks that have a history of vibrio abortion or flocks that make new additions should always revaccinate at mid-gestation. The Colorado Serum product is an aqueous suspension of inactivated (killed) cultures of Campylobacter fetus sub sq. jejuni and intestinalis with aluminum hydroxide as an adjuvant. Colorado Serum has also been working on getting a Chlamydia vaccine released, but it is not available at the present time and we do not really expect to have it prior to the breeding season, however, we continue to be optimistic that it will eventually be released. Prior to breeding is a great time to worm the ewes with a product that will also get tapeworms such as Valbazen, Panacur or Synanthic. The products that are effective on tapeworms also have a risk to pregnant ewes and we prefer not to use them during gestation. Many producers also take this as an opportunity to do a final culling on any ewes that are excessively thin, lame or have lumps in their udders. Make sure there is plenty of salt available, we recommend using additional selenium and Vitamin E during this period and again prior to the lambing season.
The Teaser Ram Effect Rams secrete pheromones (a hormonal substance that the ewes can smell) from their wool wax which have a dramatic and immediate effect upon ewes which have been kept apart from rams fro several weeks. In a given flock of ewes that are exposed to a teaser ram (vasectomized ram) roughly one-half will exhibit estrus (standing for the ram) at around 18 days after first exposure, and the remainder will exhibit estrus at around 24 days. Therefore, when teaser rams are introduced into a flock of non-cycling ewes, the fertile rams must replace them no later than 14 days after teaser ram introduction. This should result in the majority of the ewes being served over a 10-day period. The surgical procedure to vasectomizing rams should be completed a month prior to their intended usage. This gives the rams time to heal. Any remaining sperm will be gone from his reproductive tract. You will need to treat the vasectomized ram with antiobiotics and fly spray following surgery. If you were to plan a September 1st breeding date you would need to start the process early. Get the ram vasectomized and healed up so that he can be exposed to the ewe flock in mid-August. The secretion of luteinizing hormone (LH) in the ewe is pulsatile. The main difference between the breeding and the non-breeding season is that the pulses are less frequent during January through June. Within 20 minutes or so of the introduction of a ram to a group of non-cycling ewes, the level and frequency of LH pulses increases dramatically due to the pheromones the rams are carrying. Ewes within a “teased” group will ovulate within 2-3 days of ram introduction. However, this is referred to as a “silent heat”, meaning the ewes are not receptive to the rams. This event, however, starts her natural biological clock and a fertile heat will follow in approximately 17 days in about one half of the ewes. The second half of the flock will short cycle, having another silent heat at 6 or 7 days. These ewes will have a fertile heat at approximately 24 days after the introduction of the teaser rams. This very useful technique is most successful in the transitional period (July-August) when the majority of ewes in the flock have not begun to cycle, but are almost ready to. The use of teaser rams can be used to encourage ewes to breed a few weeks earlier than they would normally. It is used primarily to tighten up the lambing interval and decrease the variation in lambing birth dates. Most producers prefer to lamb as many as possible in the first 17-day cycle to reduce lambing barn hours and to promote a consistent marketing plan. If you have a large flock, be sure to have adequate ram power to successfully mate the ewes in a short period of time. The success of the synchronized heats depends on the proper ewe-to-ram ratios. This generally means 4 to 5 mature rams per 100 ewes. Ram failure will lead to disappointing results.
Breeding Examination of Rams Since the ram is responsible for ½ of the success of the breeding season it is appropriate that time and energy is invested to be certain that the ram is capable of fertilizing as many ova as the ewe flock can produce. Evaluation of the ram should not be left until the day of turnout, but rather should be performed at least one month in advance of breeding season. This will allow time for recovery or replacement if necessary.
History Before you begin you may want to consider the history of the ram to determine if anything in his past may affect his breeding performance. Consider the age of the rams. Ram lambs should be at least 6 months old before they are used for breeding. Rams over four years will often become less athletic and may not be up to chasing ewes over rough pastures. Check your records on the ram’s breeding performance last year. How tight was the lambing period? Determine if the ram was treated for a fever in the past 60 days. If the testicles get too warm the ram may become infertile for up to 60 days.
Physical Examination A physical examination should be performed focusing on areas that are especially important in the next three months. Begin with the teeth. Check the wear on the incisors. Is the bite sound? Palpate the molar tips along the side of the face, are there any that are sharp? Next, check all four feet to ensure that the ram is free of foot rot and trim if necessary. Next, check the condition score of the ram by feeling over its ribs and spine. Lastly, watch the ram as it moves around the pen to be sure that he moves around pain-free and doesn’t limp.
Reproductive Exam The reproductive portion of the exam should include all parts of the reproductive tract that are accessible. Begin with palpating the testicles. They should be uniformly firm and freely movable in the scrotum. Next, measure the scrotal circumference. This is the distance around the largest part of both testicles. The ram should measure greater than 30 cm. This can easily be measured with a scrotal tape, a cloth tape, or even a piece of string an yardstick. Sperm production in rams is directly correlated to testicular width, which is measured by the scrotal circumference. Furthermore, rams with larger testicles will sire more prolific ewes, so if you are keeping replacements you will definitely want to be using large testicle rams. Next, it is important to palpate the epididymis. This is a sperm storage structure that is attached to the testicle on the top and wraps around it to the bottom. It can be visualized and easily felt on the bottom of the testicle. Any injury to the testicle or epididymis will result first in swelling of the testicle, then with time the testicle will shrink and atrophy. In this case the breeding value of the ram is zero and needs to be culled. Finally, a semen examination should be performed on the ram. This involves collecting a semen sample with an electroejaculator and examining the semen with a microscope. The minimum acceptable standards are fair gross motility or 30% individual motility and 70% normal morphology. The semen portion of the examination will require veterinarian assistance. However, all other portions of the exam can be performed at home and poor rams can be culled early.
Lastly, plan your breeding season. If you plan for a short lambing season you will want to have plenty of ram power, such as one ram to 30-40 ewes. Higher than this ration may cause some ewes to get missed and the lambing season will be drawn out. If the ewes are synchronized the number of rams needs to be greater. Ram lambs should only be expected to breed 20 ewes.
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