1. Sows breast structure characteristics
Pigs are multi-fetal animals, and sows generally have more than six pairs of nipples, arranged longitudinally along both sides of the ventral line. The mammary gland leads to the nipple in the form of a secretory canal. The vast majority of the mid-anterior nipples have two to three secretory canals, while the vast majority of the posterior nipples have only one secretory canal, and some pigs have the breast ducts of the last pair of nipples incompletely developed. There is no breast tube. Since the number of mammary ducts in each papilla is different, the milk yield of each papilla is not exactly the same. The mammary glands of pigs are completely independent in function and have no connection with the adjacent parts.
The structure of the sow's udder is different from other domestic animals such as cattle and sheep. Cows and sheep's udders have milk storage pools, while pig breast milk storage pools are extremely underdeveloped and cannot accumulate milk. Therefore, piglets cannot suck milk at any time. Only when the sow “feeds milk†can the milk be eaten. The start of the process requires sufficient stimulation of the piglets and increases the pressure of the breasts. However, the stress caused by the noisy and unfamiliar environment to the sows may cause the body to antagonize the release of oxytocin, which may lead to the failure of milk discharge.
The basic structure of the porcine mammary gland is mature before the age of two. The re-development mainly occurs in the lactation period, and only the nipples that are fed by piglets can fully develop their mammary glands. For first-time sows, the full use of their nipples is crucial. If the number of litters born in sows is too small and some nipples are not used, the mammary glands of this part of the nipple are not fully developed and even stop moving. Therefore, trying to make all the nipples often fed by the piglets (such as taking a nest and feeding, or training the piglets of some of the pens and feeding two nipples at the same time) can increase and maintain the lifetime of the sow. .
2. The law of lactation
Due to the structural characteristics of the sow's breasts, the sow's lactation has a clear regular “circulating milk†law.
[Lactation behavior]: When the piglets are hungry and demand breast milk, they will constantly rub the sow's breasts with their noses. After 2 to 5 minutes, the sows start to emit rhythmically "pounding and squeaking" sounds. It indicates that the nipple began to secrete milk, which is commonly referred to as milking. At this point, the piglet immediately stops rubbing the breasts and begins to suck. The duration of each sow's sow is very short (up to about 1 minute, usually about 20 seconds). The number of breast-feedings during the day and night gradually decreased with the number of days after delivery. In the first few days after delivery, the interval between breastfeeding is about 50 minutes, and the number of days and nights for breast milk is 24 to 25; about 3 weeks after childbirth, the interval between milking is about 1 hour or more, and the number of days and nights is 10 to 12 times. However, the duration of each time of breast feeding was kept constant from 20 seconds to more than 10 seconds after 3 weeks.
[Lactation]: The sow's lactation varies according to breed, litter size, sow gestational age, lactation stage, feed nutrition and other factors. The amount of lactation per fetus is also different, usually the highest in the third child, and gradually decreases afterwards. Take the example of Landrace pigs reared at higher levels of nutrition: milk yield during a 60-day lactation period is approximately 600 kg. During this period, the average daily milk production is 8.5 kg for 1 to 10 days after delivery, and 12.5 kg for 11 to 20 days. 30 days were 14.5 kg (peak lactation), 12.5 kg for 31-40 days, 8 kg for 41-50 days, and 5 kg for 51-60 days.
According to the different chemical composition, the milk is divided into colostrum and regular milk. The milk within the first 3 days after delivery is called colostrum, and the subsequent milk is regular milk. In colostrum, dry matter and protein are higher than regular milk, while milk fat, lactose, etc. are lower than normal milk. Colostrum contains many maternal antibodies that are beneficial to increase piglet resistance. In addition, colostrum contains magnesium that promotes excretion of feces and stimulates digestive tract activity in piglets. Therefore, piglets must have colostrum after birth, and piglets that do not eat colostrum are difficult to feed.
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