Actually, if a ewe is on some type of accelerated lambing schedule, she may be mated three times in two years, or an average of one and one-half times per year. On a limited sex life such as this, the halves are significant.

What is ideal reproduction in sheep? The ideal ewe is fertile year round, conceives on the first service, gives birth to twins unassisted, is a good mother, milks well, weans off over a hundred pounds of lamb at 60 days, shears 10-12 pounds of wool and does this every year for 10 years. The ideal ram is fertile year round, sound and healthy, has high libida and fertility, settles ewes on the first service and can breed 100+ ewes in a breeding season.

These are not unattainable goals for the sheep flock, although, there are not a high number of sheep capable of performance such as this. However, most flocks have a few ewes that fit this description.

The Birds and The Bees

Sheep do not need an uncomfortable talk from their parents or to watch a film in school about the birds and the bees. Good sheep instinctively know what to do and when to do it.

Sheep are technically described as seasonally polyestrous in their breeding patterns. In other words, they will cycle (come into heat, have an estrus cycle) many times during a set season.

Most sheep breed only in the fall and winter months. Sheep are known as short day breeders. The ratio of light to dark in a 24-hour period is an important control in physiological responses in reproduction.

Many breeds were developed in northern climates, with distinct seasonal weather patterns and daylight-to-dark ratios. Thus, it was a survival advantage for the specie to give birth to their young during periods of favorable weather and feed supplies. Therefore, through natural selection, sheep were propagated that bred in the fall and gave birth in the spring. Most breeds of sheep are seasonal in breeding activity, because of this selection.

Reproduction in sheep is a complex mix of environmental factors and hormonal responses in ewes and rams. However, the ewe is affected to a greater degree than the ram.

It is beyond the scope of this article to give an in depth coverage of reproduction in sheep. For those wishing to become extremely knowledgeable on the subject, there are volumes of books available. Briefly, reproduction in sheep is controlled by the hypothalamus area of the brain, the pituitary gland and the ovaries. As the amount of daylight decreases over time, this is sensed by the hypothalamus, which in turn signals the pituitary gland via gonadotrophin releasing hormone. The pituitary then stimulates the ovaries by releasing follicle stimulating hormone and luteinizing hormone. Then, the ovary secretes estrogen and a heat cycle results.

Once sheep cycle, they will continue to come into estrus every 15 to 17 days until successfully bred or until they reach the anestrous period. Gestation in ewes lasts for 144 to 152 days, depending on breed and season of lambing.

Management to Optimize Reproduction

Pounds of lamb marketed per ewe exposed is the barometer to judge the success of most sheep operations. This is influenced by fertility, prolificacy (lambing rate), lamb survivability, mothering ability, milk production, etc. The key to optimizing reproductive performance is to correctly manage genetics, nutrition, and health into a management system that is practical.

Most sheep operations do not want a lambing rate over 200%. Too many management challenges result. If every ewe gave birth to twins unassisted, had ample milk, and raised them to weaning age, chances of a profit would be good. Optimal reproduction certainly varies by environment and management system.

Genetic make-up of the flock is a major factor in reproductive performance. Some breeds and lines of sheep are known for out-of-season lambing (more extended breeding season), high prolificacy, good mothering, high milk, etc. Conversely, some sheep are genetically incapable of responding to management practices to optimize reproduction. One of the big keys to successful sheep production is to match up genetics with environment and management systems. This is especially true of reproduction.

Dorsets, Rambouillets and hair sheep breeds are known to be fertile (exhibit estrus) year round. Interestingly, all but Dorsets were developed close to the equator, where the light to dark ratio has less variation. There is some danger in making general statements about breeds, in that there is certainly variation within breeds. Especially, Dorset sheep have had infusions of other white-faced breeds to increase their size, so short sighted breeders can win ribbons at shows. There are some genuine, pure Dorsets left in the United States, but, they are getting more difficult to find.

Breeds known for high prolificacy are Finnsheep, Booroola Merino and Romanous. These breeds actually have from two to five lambs in a litter. Breeds known for their prolificacy are best used in a "watered down" fashion. In other words, a commercial flock may contain 1/8 to 1/4 Finn blood to increase fertility or prolificacy. Most sheep producers are unable or unwilling to deal with ewes giving birth to three or more lambs.

Healthy sheep are more reproductively useful than diseased sheep. Footrot, internal parasites, abortive diseases, lack of thrift, nutritional diseases, etc., can all affect reproduction in sheep. Certainly, a ram or ewe free of disease will more closely approach an ideal individual.

Three stages of the production cycle can be managed nutritionally to optimize reproduction. These periods are; pre-breeding, late gestation and lactation. The pre-breeding period can positively influence production by flushing both the rams and ewes with increased energy. Increasing energy to ewes should increase body weight and number of eggs ovulated, thus, increasing lambing rate. Usually, flushing is accomplished by feeding 1/2 to 1 pound of grains high in energy. Nutrition during late gestation affects lamb size at birth, lamb vigor and survival, ewe mammary system development and ewe body fat reserves. All of these factors are crucial in increasing productivity. Certainly, proper nutrition during lactation affects the milking ability of ewes and subsequent production.

Don't Forget the Ram

Without the ram, there would be no lamb crop. Many times rams go unnoticed and neglected until just prior to their use. Do not expect miracles from a thin, unsound, unhealthy ram. Usually, infertility or reduced fertility and libido results from ram neglect.

On a body weight basis, rams have the largest testicular tissue of any other farm specie. Ram semen is the most highly concentrated semen of any other livestock specie. A mature, healthy ram can breed from 50 to 100 ewes in a season. Well grown ram lambs can breed from 15 to 30 ewes, with extra care and management. Ram lambs will reach puberty from 5 to 7 months of age.

Rams can be given a breeding soundness exam prior to breeding to screen for potential problems. General health is examined, along with scrotal circumference, concentration of semen, motility of semen and semen morphology. A breeding exam for rams is money well spent to avoid any potential disasters such as no lamb crop.

Sheep reproduction can be adversely affected by high body temperatures prior to breeding. In fact, rams can exhibit temporary sterility for a 6 to 8 week period if subjected to high body temperatures. This can be exercised induced, health related (fever) or genetically controlled.

Handle With Care

Embryonic implantation in ewes does not occur until 21 to 25 days after fertilization. Thus, anything to reduce stress should decrease embryonic mortality. Overworking ewes with dogs during the breeding season is probably not beneficial to reproductive efficiency. However, once the embryo is implanted, ewes can handle normal amounts of environmental challenges.

Summary

The key to optimal reproduction is to match the genetics, health and nutrition program to the output desired. Not all operations need a 200% lamb crop. However, many need to increase production to increase profits. Keep rams and ewes healthy and happy and their sex life will improve.

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