Simply defined, reproduction is giving birth to offspring. The survival of a species largely depends on its ability to reproduce its own kind. Reproduction is a series of events (gamete production, fertilization, gestation, reproductive behavior, lambing/kidding, etc.) that terminates when a young is born. Hence, reproduction is a vital function of all living organisms. Reproduction is a complex process. Sheep and goats are considered to be the most prolific of all domestic ruminants. Reproduction determines several aspects of sheep and goat production and an understanding of reproduction is crucial in reproductive management. A high rate of reproductive efficiency is important for:
- Perpetuation of the species,
- Production of meat, milk, skin and fiber, and
- Replacement of breeding stock.
Males and females play different reproductive roles, and in most animal species, the role of females is not completed until a viable offspring is produced. Even after birth, females play a significant role in the provision of post-natal care and, in mammals, must lactate to provide nourishment for their young. Understanding basic anatomy and reproductive physiology of sheep and goats is important in implementing appropriate reproductive management.
The Estrus Cycle
Once puberty is reached, large domestic animals such as sheep and goats display a polyestrous (repeated reproductive cycles) pattern of reproductive activity. The estrus cycle, defined as the number of days between two consecutive periods of estrus (heat), is on average 17 days in ewes and 21 days in does. The estrus cycle may be divided into two phases, namely the follicular phase (growth and expulsion of the ova or egg), and the luteal phase, which starts after ovulation and formation of the corpus luteum (yellow body).
- Bleating continuously
- Swollen – red colored vulva
- Flagging of the tail
- Frequent urination
- Cervical mucus discharge, which causes hairs to stick together
- Mounting other goats and seeking the buck
The signs of estrus in the ewe are not obvious unless a ram is present. As in the doe, the vulva is swollen and redder than usual, and there is a discharge of mucus but is difficult to see in a ewe with a tail or fleece. All of the symptoms mentioned may not be exhibited by a doe or ewe in estrus. The best confirmation of estrus is when the doe or ewe stands when being mounted. This is commonly called ‘standing heat. ‘The duration of estrus is variable in that it is shorter in younger ewes and does but longer in older animals. Normal duration will be 24 to 36 hours.
Estrus detection techniques
Estrus in sheep and goats is relatively easy to detect compared to that in cattle as heat signs are well pronounced, particularly in goats. Still, where controlled mating or artificial insemination (AI) is used, regular detection of estrus is necessary through using a teaser ram or buck. Teasers are males that have been either vasectomized or epididymized. Tying an apron made of leather or canvas around the body of a ram/or buck to prevent the penis from entering the vagina of female using a teaser with a marking harness. When a ram/buck with a marking harness mounts a female in estrus, some of the marking pigment will be transferred to the rump of the female.
Artificial Insemination (AI)
Artificial insemination is a technique in which semen is collected from a ram or buck and put into the reproductive tract of a ewe/doe. The standard procedure of inseminating does involves lifting up of their rear quarters with their front legs remaining on the ground. With the aid of speculum and pen light the cervical opening or ‘os’ is located and, under visual control, an insemination pipette is passed into or through the cervix for semen deposition. If difficulty is encountered in passing through the cervix, semen has to be deposited intra-cervically or caudal to the cervical os.