Breeding Season Preparations for Sheep Flocks
There are a few key management aspects that are critical during breeding season preparations. These include evaluating body condition, flushing the ewes, conducting a ram breeding soundness exam, and considering aspects that promote embryonic survival.
Evaluating Body Condition
Body condition scoring allows producers to evaluate both nutrition and genetics within a flock. Proper body condition will help to ensure a successful breeding season, followed by a successful lambing season. Sheep are scored on a 5-point body condition scale, with 1 being very thin and 5 being very fat. Evaluations should take place throughout the year as body condition scores change. Good times to evaluate body condition are before the start of the breeding season, about four to six weeks before lambing, and after weaning.
Body condition is evaluated by handling sheep in the loin area. In particular, the amount of fat is checked across the spinal column along the back of the sheep and at the transverse process, which is a vertical bone located below the loin muscle. Producers can also assess the fullness of the muscling in the loin and leg muscles, as well as consider how prominent the hip bones and ribs are by sight and feel. The ideal body condition score during most times of the year would be a 3. At this score, the spine should not be visible down the top of the sheep, the transverse processes should be well covered with muscle, and the loin and leg muscles should be full and not appear atrophied. In addition, the hip bones should be well covered with muscle and fat, and the ribs should not be seen but can be felt with some pressure.
Sheep with a body condition score of 1 will have a visible spine and ribs. The transverse processes will also be visible and easily felt. These emaciated sheep will show atrophy of the loin and leg muscles. A good goal for increasing the body condition of thin ewes would be to increase body weight by 10% over a 100-day period through supplemental energy and protein.
Sheep with a body condition score of 3 will not have a visible spine or ribs, but the spine and ribs can be felt with slight pressure. The transverse processes should also not be seen, but can be felt with slight pressure. The loin and leg muscles of a sheep with a body condition score of 3 will be well filled out. These sheep would be considered in ideal body condition for the breeding season.
Sheep with a body condition score of 5 will have a spine and ribs completely covered with fat, which can only be felt with pressure. The transverse processes are also completely covered with muscle and fat and can only be felt with pressure. The loin and leg muscles on sheep with a body condition score of 5 will be full and covered with fat. These sheep often exhibit fat patches over the dock. These overly fat sheep should be avoided. Rams with a body condition score of 5 may have issues with libido during the breeding season, while ewes will have an increased likelihood of problems during late pregnancy and when lambing.
Body condition scoring before the breeding season allows producers to make culling decisions and assess the flock's nutritional program. Monitoring body condition throughout the year and before the breeding season allows producers to make any needed adjustments to nutrition. Maintaining sheep in ideal body condition can improve flock performance during the breeding season and at lambing time.
Flushing
Once a producer completes body condition scoring, they can make decisions about nutritional adjustments to flush the flock. Flushing is the practice of increasing the plane of nutrition before the breeding season to encourage ewes to produce twins. This is generally done by increasing the energy content of the ewe ration and should begin 2 to 3 weeks before introducing the ram to the ewes.
With increased dietary energy intake, the ewe will begin to improve body condition. This will then signal the ewe's body that she can support more than one lamb. In turn, this will increase her ovulation rate, which should result in a higher lambing percentage, or more lambs born per ewe.
Energy can be increased in the ration by adding grain at a rate of one-half to one pound per ewe per day or by moving the entire flock to a lush pasture. Many producers feed corn as the grain source, while others prefer a mixed-grain formulation. The total amount of grain fed should be adjusted based on the ewe flock's body condition.
The additional energy in the ration should be fed throughout the breeding season and continue until a few weeks after the ram is removed. This will allow the embryos to be implanted in the uterus. For these reasons, flushing has the greatest impact early in the breeding season. Ewes with body condition scores of 2 to 3 often respond best to flushing.
While emphasis is placed on ewes for flushing, rams will also benefit from the additional energy in the ration because it helps them lose less weight during the breeding season. Plus, the added energy helps the rams maintain their vigor for breeding.
Ram Breeding Soundness Exams
Before breeding, evaluate the breeding soundness of all rams to prepare for the breeding season. A good-quality ram should have adequate size and muscling, be vigorous and active, and have a strong, masculine appearance. He should be structurally correct, should stand with all four feet squarely underneath him, be up on his pasterns, and be able to move freely. Sheep that produce wool should also have a high-quality and uniform fleece.
New rams should be purchased at least 1 month before the breeding season. This will allow the ram time to adjust to the new location and give a producer ample time to quarantine the ram from the rest of the flock to ensure he is not carrying any contagious diseases.
Before the start of the breeding season, a physical examination of the ram should be conducted for breeding soundness. Allow enough time for the ram to heal from any injuries, or replace him if he is found unsound. The examination should include palpation of the testicles and epididymis, and visual appraisal of feet, legs, eyes, and teeth. In addition, be sure to check the ram's body condition. Rams that are in poor body condition will often have poor semen quality, and rams that are too fat often lack the libido to breed ewes.
The testicles of the ram should be firm, adequate in size, and free of any lumps or abscesses, which could indicate an injury or disease. The tail of the epididymis is located at the bottom end of the testicle. It should be slightly rounded and free from any hard knots. This is important because the tail of the epididymis is where most of the sperm are stored.
Ram lambs that are 8 to 14 months old should have a scrotal circumference of 30 to 36 cm, while mature rams should have a scrotal circumference of 32 to 40 cm. The size of the testicles relates to the ability of the ram to produce sperm. This, in turn, will allow the ram to breed a large number of ewes. Larger scrotal circumference directly correlates with greater semen volume and sperm viability. Larger scrotal circumference also correlates with siring ewe lambs that reach puberty earlier than ewe lambs produced by rams with a smaller scrotal circumference.
Trim feet and conduct a visual appraisal of the feet and legs to look for lameness and evidence of foot rot or foot scald. Signs that a ram has these issues include red inflammation or a white, moist appearance between the toes. Foot rot will appear as though the foot is rotting. Foot rot will have a foul odor.
Check the ram's eyes to ensure that they appear normal. The membranes around the eye should be bright pink to red. If they are gray or white, the ram is likely anemic and needs deworming. FAMACHA scoring should be used to assess the need to deworm.
Shear rams before the breeding season, then check body condition. The ram should have some extra condition or fat reserves, but not be overly fat. Rams should have a body condition score of 3 to 3.5. Thin rams may have less stamina throughout the breeding season, while fat rams may have less libido. As the breeding season progresses, a ram can lose as much as 10% of its body weight. Overly fat rams may be lazy and not want to breed. In addition, rams that are too hot from having long wool may not want to breed. These rams are also more susceptible to heat stress, which can decrease semen quality. On the other hand, thin rams are expected to have less energy for breeding and may have lower semen quality.
Elevated body temperature that results from illness or from heat stress affects semen quality very quickly. Sperm production takes approximately six weeks to complete, and so rams affected by elevated body temperatures may have reduced ability to breed ewes for that length of time successfully.
If there are questions regarding the breeding soundness of a ram, his ability to breed ewes can be checked either through a semen evaluation or by using a method that allows the ram to mark the ewes as he breeds them. A veterinarian or a breeding service should be able to conduct a semen evaluation test. Evaluations will involve collecting semen and then viewing under a microscope to look for numbers of live and motile sperm cells, plus numbers of abnormal sperm cells.
Even though a ram succeeds in getting ewes pregnant, it is important to follow good management practices to ensure that the ewes remain pregnant until the lambs are ready to be born.
Aspects to Promote Embryonic Survival
In addition to body condition scores, body weight management of young ewes is important. Yearlings should weigh at least 80% of their mature weight by the start of the breeding season, and ewe lambs should weigh 65 to 70% of their mature weight. For ewe lambs to reach this desired weight, most will require a grain supplement. In general, sheep gain approximately a quarter to a third of a pound per day on pasture. This rate of gain results in ewe lambs weighing less than the recommended breeding weight. Therefore, producers should calculate the weight gain required and adjust rations to accommodate a faster rate of gain if they plan to breed ewe lambs.
Maintaining body condition scores or improving body condition in thin ewes during the first 90 days of pregnancy helps promote embryo survival. The embryo implants in the uterus about 3 weeks after fertilization, and placental development occurs shortly thereafter. The placenta connects the developing fetus (lamb) to its dam, providing nourishment for the fetus to grow and eliminating waste products. Good nutrition allows the placenta to develop to full size during this period, thereby providing optimal nutrients to the fetus. Poor placental development can impact lamb birth weights and can ultimately impact the future reproductive potential of a lamb. Lamb birthweight is one of the greatest predictors of lamb survival: smaller lambs are less likely to survive birth as compared to lambs with average birth weights. Approximately 70% of lamb mortalities that occur before weaning occur during the first 48 hours after birth.
Rations should provide adequate energy, protein, vitamins, and minerals. Typically, good-quality pasture and a good-quality mineral mix provide sufficient nutrients to support the pregnancy. However, pay close attention to pasture mixtures during the first 45 days of gestation. Legumes, and red clover in particular, produce phytoestrogens. These estrogenic compounds can impact reproduction by reducing ovulation and conception rates. Fertility generally returns to normal within four to six weeks after removing the sheep from pastures containing high levels of phytoestrogens.
As the breeding season continues, be sure to assess ewes' and rams' body condition scores. Make sure they receive adequate nutrition to support a body condition score of 3 or provide additional nutrients in the ration to improve body condition scores. The ultimate goal is for ewes to consume a diet that promotes ovulation rates to conceive twins, supports embryo survival, and results in a healthy set of twins. All of these steps taken before the breeding season can lead to a more successful lambing season.
