1. Variety reason
Some breeds have low reproductive capacity and cause fewer litters. Such as: Pietrain, Duroc, etc., because of the variety of reasons, the increase in the number of litters is very difficult, in the maternal breeding process of commercial pig production, can not only pay attention to the pig's body size and lean, and neglected the reproductive ability.
2. Age reasons
The age and parity of the pigs affect the number of litters and at the same time the number of live pigs. The reproductive performance of sows with 12-pregnant children was low, the number of ovulation was small, and the number of litters was small. The reproductive performance of 35 fetuses was the best, the number of litters and the number of live-born pigs were the highest; the reproductive performance of sows after 6 months of birth was reduced, and the litter size was decreased. The number of births and the number of live births decreased. And due to the influence of physical strength, the litter process is prone to fatigue, and the time is too long, resulting in a large proportion of stillbirths. In the production, midwifery of low- and high-incidence pigs should be strengthened, and the interval between births should be reduced.
3. Causes of feed
There is no nutritious, full-priced compound feed for sows. Some producers believe that sows do not use or use additives to avoid causing sows to become obese, which is not correct and must be corrected. Some feed companies also believe that the sow's feed is not important, and the formula is not serious, not full price, cutting corners, and causing erroneous ideas that the effect of adding pigs without additives is not obvious.
4. Management issues
(1) Month is too young when mating. The gilts were too low in body weight and their monthly age was too small. Due to the fact that pig breeds are growing too fast and they are mated prematurely, they do not reach body maturity, resulting in fewer litter size and the mating gilt should have a mating age of 7 months. the above.
(2) There is no control of the lyrics before mating. The gilts did not limit feeding, resulting in overweight and overweight at the time of mating, and the number of litters decreased. Excessive lean, aborted, and return sows in weaned sows after sow weaning all affected sows’ ovulation numbers and thus affected litter size.
(3) There is no short-term excellent feeding before mating. In order to increase the number of ovulation, gilts and weaned sows should be fed for a short period of time in the first 45 days before breeding, feeding high quality full-priced feed and increasing the amount of ovulation to increase the number of ovulation.
(4) The amount of feeding during pregnancy is irrational. In the first trimester of pregnancy, the amount of dietary feeding per day was 1.52 kg, the appropriate amount in the medium term was 22.5 kg per day, and the daily feeding amount was 33.5 kg per day. At the same time, the amount of feed was adjusted depending on the individual body condition of the sow.
5. Other reasons
Vaccination time is unreasonable, and epidemics and other factors also affect the sow's litter size.
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