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System of Mating in Sheep and Goats: Natural Mating, Artificial Insemination and Breeding Management
The system of mating in sheep and goats plays an important role in achieving efficient reproduction, improving flock productivity, and enhancing genetic progress. Mating practices can be broadly classified into natural mating and artificial mating systems. Each system has its own advantages, management requirements, and applications depending on the breeding objectives and production conditions.
The two major systems of mating in sheep and goats are natural mating and artificial mating. Each system and its subtypes are discussed below.
Natural Mating
- Hand mating
- Pen mating
- Flock mating or pasture mating
1. Hand Mating
In the hand mating system, a teaser ram or buck detects ewes or does in heat. These females are then separated and bred with the desired ram or buck. The females are allowed to mate one by one.
In this system, a ram or buck is generally not allowed to mate more than three ewes or does per day. This method of hand mating ensures the expected time of lambing. It also allows the farmer to confirm that the animal has actually been bred.
Hand mating reduces the risk of injuries to animals and is beneficial when mating an older male with a younger female. It also improves the breeding efficiency of the male, resulting in an increased number of females that can be bred within a shorter period.
2. Pen Mating
In the pen mating system, ewes or does are divided into batches of 20–25 animals. Males are introduced into the flock only during the night and are separated during the daytime, which provides adequate rest for the males and allows proper feeding.
This system of mating also prevents disturbance of the ewes by the male during grazing hours.
3. Flock Mating
Flock mating is commonly practiced by farmers. In this system, males are allowed to remain with the females throughout the day and night. However, this system has several disadvantages.
The ram may lose a significant amount of body reserves while chasing ewes and may experience a decline in body condition. Sometimes, a ram or buck may develop a preference for a particular ewe or doe in heat and mate with her repeatedly, while other females remain unattended, resulting in open ewes or does and reduced fertility.
Moreover, the ram or buck may sometimes exhaust itself overnight by mating more than a dozen times. Consequently, the females served later may not receive an optimum number of spermatozoa and may remain unconceived.
Artificial Mating
- Artificial insemination
- Embryo transfer technology
1. Artificial Insemination
Artificial insemination offers the best means of distributing germplasm from nucleus breeding flocks to many small flocks within an ecosystem. Both fresh and frozen semen can be used.
The speculum method of insemination is used in ewes and does. Generally, artificial insemination results in lower reproductive rates than natural service, and frozen semen produces even lower pregnancy rates, approximately 40 percent. Cervical insemination is generally preferred for achieving better conception rates.
2. Embryo Transfer Technology
Embryo transfer requires surgery in sheep; therefore, it may not be practical under production conditions. However, it offers significant potential for enhancing genetic progress.
Management Methods to Optimize Breeding
Oestrous Stimulation
A useful practice for stimulating and, to some extent, synchronizing breeding is to place vasectomized males with females approximately 10 days to 2 weeks before the start of the breeding season.
A similar effect can be achieved through fence-line contact by placing a ram or buck in an adjacent pen. As a result, a large proportion of the ewes will ovulate and conceive during the early part of the breeding season.
Oestrous Synchronization
The oestrous cycle of ewes can be synchronized so that large numbers of animals come into heat at the same time. This helps reduce the cost of artificial insemination or natural breeding and subsequent lambing management.
It results in a more uniform flock of lambs, facilitating marketing and often improving returns. It can also be effectively employed for breeding sheep during the spring season.
Ram Effect
The sudden introduction of a ram into a flock of ewes after a prolonged period of separation induces a greater number of ewes to come into oestrus. This phenomenon is known as the ram effect.
Telescoping
Telescoping is practiced by introducing a ram into the flock after keeping it separated for 2–3 months. The sudden introduction of the ram causes approximately 70–80 percent of the ewes to come into heat during the first oestrous cycle.
Hormonal Method
Synchronization of oestrus is initiated by administering progesterone hormones or their analogues simultaneously to ewes through feed, implants, or progesterone-impregnated vaginal sponges. After 14 days of administration, the hormone treatment is withdrawn.
The animals come into heat within three days. Since the reproductive females are still under the influence of progesterone, the conception rate ranges from 30–40 percent during the first synchronized cycle. However, conception rates of 70–90 percent may be achieved during the subsequent cycle.
Prostaglandin F2α or its synthetic analogues, which cause lysis of the corpus luteum, are also used for this purpose. Two intramuscular injections of 10 mg each at an interval of 10 days can bring all animals into heat within 72–96 hours.
