Reproductive traits are genetically called threshold traits (controlled by multiple genes, showing discontinuous traits). That is, there is no difference between 0. 1 ...). It is determined by heredity and influenced by environment.
Breeding is to change heredity. Because threshold traits are controlled by multiple genes, it is difficult to concentrate and homozygous these genes that control litter size, so it is often difficult to improve litter size through selection. For example, after about 20 years of breeding in western Europe, the litter size only increased by 1~2, which was significantly improved after the introduction of Taihu pig in China. The environment will affect the number of babies. Nutrition, management and climate are all called environment. If you are overnourished, you will grow too fat; Malnutrition; Excessive temperature, etc. It can lead to estrus in sows, decreased ovulation or death of fertilized eggs, and decreased semen quality in boars. Improper management can lead to miscarriage.
Technical measures to improve reproductive efficiency of sows
The reproductive performance of sows is an important index of pig production. Giving full play to the reproductive performance of sows is an important means to improve the yield and economic benefits of pigs. How to quickly change the traditional misunderstanding of breeding, scientifically manage sows, improve the birth weight and weaning weight of newborn piglets, scientifically breed, and maximize the production potential of sows is an important problem and difficult problem that the majority of scientific and technological workers urgently need to solve.
First a variety, choose the best and wash the worst.
Selecting high-yield varieties is an effective way to improve the reproductive rate of sows. Studies have shown that the effective nipple number of sows is directly proportional to the birth rate. Choose a good sow, choose a sow that conforms to the characteristics of this breed, is strong, well-proportioned, gentle, with neat nipples, big ears, straight back and waist, big belly and no need to mop the floor as a breeding pig.
Third, make full use of heterosis. The first generation produced by hybridization between different varieties or strains has higher vitality and growth intensity than their parents, which is heterosis. Landrace pigs with high lean meat rate and fast growth rate can be selected to cross with Yorkshire sows to produce "grown-up" binary hybrid sows, which have good maternity, strong reproductive ability, litter size of about 12, good lactation performance, rough feeding tolerance, strong adaptability and lean meat rate of over 65%, and are excellent female parents for producing commercial pigs. Duroc boars in Taiwan Province Province can be selected to produce pure foreign ternary (Du Changda). Such ternary pigs gain weight quickly, not less than 800g/ day, and the feed reward is high, reaching 2.8 ~ 3.0: 1, thus greatly shortening the fattening period, reaching the goal of listing 90kg in five months, reducing the cost of raising pigs and obviously improving the benefits.
2. Reasonable nutrition, obesity control, short-term optimal feeding and ovulation increase.
It is very important to strengthen the management of sow feeding. Sows are fed roughage during empty pregnancy, middle pregnancy and late lactation, and green feed is appropriately fed; During pregnancy, protein, concentrate rich in minerals and vitamins, green and juicy feed should be adequately supplied, but not too much energy, otherwise it will affect the intake during lactation and reduce lactation capacity. At the same time, it is necessary to provide a relatively stable living environment for sows and minimize external stimuli such as herding, driving and fighting.
Sows are overweight: litter, little survival, small and uneven weight, severe diarrhea and poor milk production. Sows are too thin: the fetus is stunted, and the weight of sows will drop soon after delivery, and in severe cases, postpartum paralysis will occur. How to control this situation? Staged feeding can be adopted to create conditions for high yield of sows. The gestation period of sows (1 14) includes: early pregnancy (from mating to the first month), middle pregnancy (2-3 months) and late pregnancy (the last month). Feeding sows full-price high-quality feed10–15 five days before breeding can increase ovulation (short-term excellent feeding can increase ovulation). In the early pregnancy, that is, the first month after pregnancy, feed with low nutritional level was given at a daily dose of 1.8kg ~ 2.2kg, but the protein content was not lower than 13%/ day/head ~ 14%/ day/head. In the second trimester of pregnancy (from the second month of pregnancy to 80 days before delivery), sows have increased appetite, vigorous metabolic function and improved feed utilization rate. It can be given a feed with a moderate nutritional level of protein 14%~ 15% and 2.5 kg/day/head. After entering the third trimester of pregnancy (80 days after pregnancy ~ 107 days), the fetal weight and length increase very rapidly, accounting for about 2/3 of the birth weight. At this time, sows should be given a slightly higher nutritional level of 3 kg/day/head. Crude protein 16%~ 18%. Using this method has a great effect on controlling sow fat, increasing litter size, promoting fetal protection and improving the weight of newborn piglets.
At the beginning of estrus, injecting 500–1000 iu of chorionic gonadotropin into the muscle or skin of sows can improve the ovulation rate, pregnancy rate and litter size of sows.
Third, timely breeding to improve the conception rate.
The first mating age of gilts should be 7-8 months old and the weight is about 1 100 kg. How to grasp the timing of timely mating has become a key issue. First of all, it is necessary to identify sow estrus in management. Sows show anxiety during estrus, climbing or being climbed by other sows, frequent urination, and redness and swelling of vulva. This is not the best time to breed. When the swelling of sow's vulva subsides, mucus is extracted, the back-pressing reflex is obvious, or there is ear motor reflex or tail root vibration, and the limbs are stretched out to mate, this is the best time for breeding. The ovulation time of adult sows is from 24 hours to 36 hours after the start of estrus, the peak is about 3 1 hour, and the ovulation duration is from 8 hours to1hour. The time to maintain the fertilization ability of eggs in vivo is 8 hours to 12 hours, and the fertilization ability of sperm entering sows can generally be maintained from 10 hours to 15 hours. After insemination, the forward speed of sperm reaches the fertilization site of fallopian tube in about 2 to 3 hours. Therefore, we began to mate for the first time 24 hours after estrus, and the interval was 10 hour to 12 hour.
Fourth, strengthen fetal protection measures. Sows are prone to miscarriage 9 days after mating-13 days, and 2 1 day before delivery. We should strengthen measures to protect the fetus, try to supply protein, minerals, vitamins and other rich concentrate and green juicy feed, and avoid feeding frozen, moldy and deteriorated feed. Pregnant sows try to avoid mechanical stimulation, such as squeezing, biting, slipping, whipping and scaring. The breeding of pig farms should be recorded in detail to avoid inbreeding. Pig farms should do a good job in the prevention and control of epidemic diseases, especially Japanese encephalitis, epidemic fever, brucellosis and other diseases, and treat diseases in time when they are found. Those with threatened abortion should be injected with progesterone 15 mg -25 mg immediately, and the fetus should be induced by oral sedative.
5. Early weaning to increase the number of babies per year.
Weaning in an average of 28-30 days can ensure that a sow can produce 2 or 2.5 litters a year. Most sows after early weaning can estrus for 5-7 days, and the pregnancy rate is between 90% and 95%. Generally speaking, sows are fed aphrodisiac 3 -5 days after weaning. After the sow is in estrus, it can be bred during lactation, and it can also increase the annual fetal yield.
6. Eliminate the update and optimize the pig structure.
The old, weak, sick, disabled and low-yield sows should be eliminated and updated in time, and the general annual elimination rate is 25%~30% of the sow herd, and the reserve sows should be replenished in time to ensure the reasonable proportion of old sows, middle sows and young sows in the pig herd.