Breeding in sheep *Schedule
Age at mating : Sheep normally attain good growth at about 24 months (range 18-36) of age. Breeding too young ewes results in more weaklings and higher lamb losses. It is desirable to use rams for mating from the age of 2 years till the age of 7 years.
Mating season and estrus cycle : Sheep are seasonally polyestrus. In India, there are three main breeding seasons viz. summer (Mar-Apr), autumn (Jun-Jul) and post-monsoon (Sep-Oct). In general, higher fertility is observed in autumn season in the plains and in summer season in the hilly areas. The ewes usually come in heat about 2 months after lambing. The duration of the estrus cycle is 17 days (range 14-19) and heat period lasts for 27 hours (2-60). Ovulation occurs about 12 hours before the end of heat period.
Preparations for breeding :-
1. Flushing : Feeding extra grain or lush pasture 2-3 weeks prior to the breeding season for the purpose of increasing the number of ova shed from the ovary and increase the incidence of twinning. Feeding about 250 gms grains daily to each ewe results in an increase in the lamb crop by about 10-20 per cent.
2. Tagging : This refers to the shearing the locks of wool and dirt from the dock of the ewes, thus facilitating mating by the ram.
3. Eyeing : This refers to the clipping of excess wool around the eyes to prevent wool blindness in some breeds.
4. Ringing : This refers to shearing of wool from the body of the ram, especially in the neck, belly and sheath region prior to the breeding season.
Detection of estrus : As sheep in heat show few external indications of estrus other than standing to be mounted, heat is generally detected with the help of a teaser. Wet paint (dye mixed in grease or linseed oil) can be smeared on the brisket of the teaser ram to spot the ewes in estrus. The colour of the dye should be changed every 16-18 days so that the repeaters can be discovered. Other indications of estrus are vulvar swelling, frequent urination, restlessness and reduced appetite.
Mating : As far as possible, rams should be kept away from the ewes and the two should be brought together only for breeding. Natural breeding is done either by flock mating, pen mating or hand mating.
§ In flock mating, breeding rams are usually turned out in the flock during the mating season at the rate of 2-3 per cent of the ewes all through day and night.
§ In semi-flock breeding or pen mating, rams are turned out for service with the flock in the pen during night, and confined and stall-fed or grazed separately during the day time in order to conserve their energy and give them rest.
§ Hand mating is practiced when exotic purebred sires are used, or when it is considered desirable to extend the services of the ram over much larger flocks.
Identifying pregnant ewes : Identification of pregnant ewes is essential for the re-breeding of empty ewes and efficient management of pregnant ewes. Pregnancy can be diagnosed by observing for cessation of estrus cycle, abdominal ballotment (from third month onwards) and by means of a chemical test.
Procedure : Mix 5 ml of urine sample and 5 ml of 1% Barium chloride solution. Turbidity indicates pregnancy whereas clear solution indicates non-pregnant condition.
Care of pregnant ewes : Careful management of pregnant ewes will have a marked influence on the percentage of lambs dropped.
§ Do not handle the pregnant animals too frequently.
§ House the pregnant ewes in separate enclosures and protect from inclement weather and extremes of temperature.
§ Crutching is done 7-10 days prior to lambing to avoid lambs suckling dung.
§ Separate the advanced pregnant animals form the main flock and take effective care in their feeding and management.
§ Extra feed during the later part of pregnancy (3-4 weeks before parturition) will be beneficial for the condition of pre-parturient ewes, thus improving milk production of ewes, and birth weight and growth of lambs. Inadequate and poor nutrition may result in pregnancy toxaemia, abortions and premature births of weak lambs.
§ Bring lambing ewes into lambing corrals 4-6 days before parturition and provide soft, clean bedding, individual lambing pens and maximum comfort.
§ Watch gestation length which ranges from 142-150 (avg. 147) days.
Care at lambing : An ewe about to lamb prefers to leave the flock. She is restless, the udder is often distended and external genitals are in a flushed and flaccid condition. Normally there is no necessity of assisting the ewes at the time of lambing except in the case of dystokia. The following precautions may be taken at lambing:-
§ Maiden ewes in poor condition or small-framed ewes mated to big rams will generally have difficulty in parturition and will have to be assisted.
§ Ensure that the nose and mouth are free of membranes and mucoid fluid immediately after birth.
§ Ligate, sever and antiseptically dress the navel cord of the lamb.
§ Do not handle lambs too frequently immediately after birth and let the dams lick and recognize them properly.
§ Newborn lambs, after being licked by their mother, generally stand on their legs and start seeking for teats and suckle milk. In case they are not able to do so, assist them in suckling colostrum.
§ Take up artificial milk feeding or arrange foster mother for disowned or orphan lambs. These lambs can either be reared on goat milk or by foster mothers. To aid the adoption of the orphan lambs by the foster mother, rub its milk on the rump of the orphan and the nose of the foster mother, keep both animals in close proximity to each other. Orphan lambs can also be reared by hand using a clean bottle and nipples, feeding about 30 gm milk at two hourly intervals for the first two days, and increasing the quantity and decreasing the frequency subsequently.
§ Give a teaspoonful of castor oil or liquid paraffin to the lamb to facilitate defecation and easy passing out of meconium.
§ Allow newborn lambs to be with their dams all day long during the first week.
§ Protect newborn lambs from adverse climatic conditions.
§ Feed sufficient quantity of good quality hay and concentrates to the lactating ewes for meeting the nutritional requirements of early lactation.
§ Provide plenty of clean, fresh drinking water as the lactating ewes drink higher amounts of water.