What are the key points of technical measures for sheep flock breeding management
Spring, summer and autumn are the peak seasons for estrus and breeding in sheep flocks. Generally, estrus in sheep lasts from several hours to 3-4 days. Therefore, during feeding and management, special attention should be paid to the estrus status of ewes to ensure timely mating. When a ewe is found to be restless, eating less, bleating continuously, actively approaching rams and wagging her tail, with hind legs spread apart, vulva congested and swollen, and standing still when the rump is pressed by hand, she has reached the peak of estrus and can be mated. Ewes generally begin mating at around 9 months of age, and rams generally begin mating at around 1.5 years of age. The best breeding method is artificial insemination as the main method, with natural mating as a supplement. Regardless of the breeding method, repeat mating should be used (that is, mating again at an interval of about 12 hours after the first mating). In natural mating flocks, the ratio of rams to ewes is best at around 1:25.
During the breeding process of sheep, special attention should be paid to increasing the proportion of ewes of suitable age in the flock (generally, ewes of suitable age are required to account for more than 60% of the flock), promptly culling old sheep over 7 years of age, and ewes that are infertile, have habitual abortion, poor mothering ability, poor lactation, give birth to single lambs or stillborn lambs, or have defects in reproductive organs and udders, and supplement the flock each year with young ewes of large build and good growth and development.
Fertility indicates the strength of the reproductive function of livestock and their ability to produce offspring. In sheep production, improving the fertility of ewes is a key link in increasing economic benefits. There are many factors restricting ewe fertility; breed, age, environment and so on all affect ewe fertility. In the rural areas of our province, many sheep farmers are still mainly engaged in grazing and free-range raising up to now, and long-term indiscriminate crossbreeding and inbreeding greatly affect the fertility of sheep flocks. In addition, improper feeding and management and hygiene-related factors are also reasons for the low fertility of sheep flocks among rural sheep farmers. Facing the increasingly prosperous sheep market, the author believes that in order to improve the fertility of sheep flocks and obtain more economic benefits, the following technical links should be emphasized in production.
1 Select high-quality breeding sheep. There is a great difference in fertility among ewes of different breeds. For example, the twinning rate of China's Hu sheep, Small-tailed Han sheep and Finland's Landrace sheep is much higher than that of other breeds, and the lambing rate can reach 200%-300%. Another report states that the Qingshan sheep in the Jining area of Shandong has very strong multiple-birth ability, sometimes producing 3-5 lambs per litter. Ewe fertility is hereditary; generally, ewes that give birth to twins will also have offspring with this high fertility. Research shows that for ewes giving birth to a single lamb at first parity, the average lambing numbers in the following 3 parities are 1.33, 1.31 and 1.04; while for ewes giving birth to twins at first parity, the lambing numbers in the following three parities are 1.73, 1.71 and 1.88 respectively. Therefore, introducing high-yielding breeds for crossbreeding improvement and carrying out selection and breeding of one's existing flock will, over the long term, improve the fertility of the entire flock. High-quality breeding rams can be selected through their mother's reproductive performance and progeny testing, and must be offspring of high-yielding ewes.
2 Improve the feeding level of breeding rams and breeding ewes. Nutritional conditions have a great impact on the reproductive ability of rams and ewes. Sufficient and complete nutrition can increase the libido of breeding rams, improve semen quality, and at the same time promote estrus and increase ovulation number in ewes. Below, take the feeding of Small-tailed Han sheep as an example.
Feeding of breeding rams. Breeding rams should be kept robust during feeding, with body condition at medium or above. The forage fed at ordinary times should be nutritionally complete, and it is recommended to use high-quality forage such as alfalfa. For grazing-based breeding rams during the non-breeding season, supplement each breeding ram daily with 0.5 kg of concentrate, 2 kg of dry hay, 0.5 kg of green feed, 5-10 g of salt and 5-10 g of bone meal. Starting 40 days before mating, supplement daily with 0.7-0.8 kg of concentrate, then gradually increase. During the mating period, supplement daily with about 1.2 kg of concentrate, 2.5 kg of green dry hay, 0.5-1 kg of carrots, 2-3 eggs, 5-10 g of salt and 5-10 g of bone meal, with appropriate grazing. Maintain about 2 hours of exercise per day, and massage the testicles every day. For breeding rams raised in confinement, during the non-breeding period, feed daily 2.5 kg of high-quality dry hay, 1.0-1.5 kg of succulent feed and 0.8 kg of mixed concentrate; during the mating period, feed daily 1.0-1.5 kg of green feed, 1.0-2.0 kg of mixed concentrate, 2-3 eggs, 5-10 g of salt and 5-10 g of bone meal.
Feeding of breeding ewes. Under grazing conditions, ewes in the non-pregnant period do not need supplementary feeding if they can eat their fill every day; in winter, some dry hay can be supplemented appropriately. For breeding ewes in poor body condition, short-term flushing can be carried out about 40 days before mating to promote estrus and ovulation. Pay attention to keeping ewes at a body condition score of 7-8. In the first 3 months of gestation, fetal development is slow, and except during the dry forage period, no supplementary feeding is needed. In the last 2 months of gestation, the fetus grows rapidly, and the ewe's energy metabolism and material metabolism increase by 30%-40% compared with the non-pregnant period. At this time, each ewe can be supplemented daily with 0.45 kg of mixed concentrate, 1-1.5 kg of green dry hay, 0.5 kg of green feed and 5-10 g of bone meal. During gestation, attention should be paid to protecting the fetus and minimizing stress on the ewe. In the lactation period, for ewes giving birth to a single lamb, give daily 0.3-0.5 kg of concentrate, 0.5 kg of green dry hay and 1.5 kg of succulent feed. For ewes giving birth to twins, supplement daily with 0.4-0.6 kg of mixed feed, 1 kg of green dry hay and 1.5 kg of succulent feed. In the late lactation period, because lambs no longer rely entirely on milk as their main source of nutrition, the feeding amount for ewes should be appropriately reduced.
3 Maintain an appropriate proportion of breeding ewes in the flock. Whether the flock structure is reasonable has a great impact on the fertility of the flock. The twinning rate of ewes increases with age, reaches the highest level after 1-3 years, and begins to decline after the 6th-7th parity. The main reasons for the decline in fertility of aged ewes are degeneration of sexual function, poor egg quality, and weakened uterine function, resulting in lower conception rates and increased embryonic death. Therefore, increasing the proportion of ewes of suitable age (2-5 years old) in the flock is an important measure to improve sheep fertility. On breeding sheep farms, the proportion of suitable-age breeding ewes can be increased to 60%-70%; in vast agricultural areas, it should generally be controlled at above 40%-50%.
4 Carry out breeding scientifically
Selection of breeding season. The timing of mating is mainly determined by what time of lambing is most conducive to lamb survival and the health and strength of both mother and offspring. In summer, the weather is hot, ram libido weakens, and semen quality declines; in winter, ewes are in poor body condition, are not prone to estrus, or have a low conception rate after estrus. In our province, most areas choose to mate only once a year, in autumn, that is, mating in October-November each year and lambing in March-April of the following year. The advantages of this breeding arrangement are: when the ewe is pregnant, because nutritional conditions are relatively good, the birth weight of the lamb is relatively large, and after weaning the lamb can eat green grass, so it grows and develops relatively quickly, and its ability to overwinter and pass through spring in the first year is relatively strong. In addition to autumn mating, mating can also be carried out in spring, that is, in April-May each year; mating at this time requires storing sufficient forage and feed in winter and preparing a sheep shed with good insulation.
Scientific breeding methods. There are two breeding methods for sheep, namely natural mating and artificial insemination. Natural mating is the most primitive method in sheep raising, that is, mixing rams and ewes together for grazing during the breeding season; it saves labor and does not require equipment. However, applying this method has many adverse effects on the fertility of the entire flock. Because of inbreeding and lack of knowledge of the sheep's blood relationships, it brings difficulties to later selection and mating, and it also produces many deformed fetuses, directly reducing the fertility of the flock. Carrying out artificial insemination can effectively improve the above shortcomings; it can expand the utilization rate of excellent rams, improve the conception rate of ewes, and greatly help improve the fertility of the flock. If artificial insemination is not carried out, artificial assisted mating can be used, that is, grazing rams and ewes separately, testing ewes for estrus every day during the breeding season, and then mating estrus ewes with designated rams; this is conducive to selection and mating of sheep.
Strengthen management before and after parturition. Before lambing, various instruments should be disinfected, and the ewe's tail base, vulva, anus and udder should be disinfected with 1% Lysol or 1‰ potassium permanganate solution. After the lamb is born, cut the umbilical cord 5-8 cm from the lamb's umbilical recess and disinfect with iodine tincture. If there is a seemingly dead lamb, promptly lift its hind legs, pat its back, or let it lie flat and use both hands to press its chest rhythmically to revive it. If dystocia occurs, after checking the fetal position, manual assistance can be carried out; otherwise, find a veterinarian to perform a cesarean section. After the fetus is born, let it suckle colostrum in time, start feeding early, train it to eat grass, expel meconium and enhance gastrointestinal peristalsis. Newborn lambs have relatively poor resistance and need strengthened care. If the ewe's milk supply is insufficient, artificial nursing or foster care should be adopted in time.