Digestive Physiological Characteristics and Nutritional Regulation of Piglets

1 Digestive Physiological Characteristics of Piglets

1.1 The digestive tract of lactating is immature, and the morphological structure of the digestive system changes significantly after weaning.

Suckling piglets gastric fundus gland is underdeveloped, gastric juice secretion is small and unstable, the secretion of hydrochloric acid ability is poor, the lack of free hydrochloric acid in the stomach,PHValue too high, stomachPH≥4Pepsin activity is affected, which is not conducive to protein digestion. Piglets reach8~10The acidity in the stomach of adult pigs can only be reached at the age of 4 weeks.PH=2~3 5The level. However, the volume and weight of the digestive tract of piglets develop faster, and it has been reported that the weight and volume of the piglets in the stomach25The intestinal villi were long and thin fingers, the height of the villi decreased with increasing age, and the duodenal intestinal villi were higher than the jejunum and ileum. Birth No.1The intestinal glands can be seen in the day, and then the glandular cells continue to increase, the volume increases, and the glandular fossa gradually increases with age.

After weaning, the morphological structure of the small intestinal cells of the digestive system of piglets changes significantly, because weaned piglets have to change from eating easily digestible liquid food to solid feed containing a large amount of grain raw materials, under the high mechanical wear of the dry matter of the diet, the small intestinal villi become rapidly shorter, the small intestinal villi change from high density finger-like to flat tongue-like, villous atrophy and crypts deepen. As a result, the digestion and absorption area becomes smaller, and nutrients cannot be effectively absorbed, and the rich nutrients, suitable temperature and mild pH in the intestine provide breeding conditions for harmful bacteria, and the growth fork of harmful bacteria produces a lot of toxins(Ammonia and amines, etc.)It has toxic and pharmacological effects on animals and aggravates diarrhea.

1.2 The digestive enzyme system of suckling piglets is imperfect, and early weaning affects the secretion and activity of digestive enzymes.

The digestive enzyme system of suckling piglets is imperfect and changes rapidly within a few weeks of birth, showing the activity of lactase and enzymes related to the digestion of sugars in breast milk after birth.2~3It peaked at the week and then fell very decidually. The activity of amylase and enzymes involved in digesting starch and carbohydrates is low at birth and then gradually increases. Chymosin is more active at birth,1~2It reached the peak at the age of weeks, and then decreased with the increase of age, and the activity of other proteases was very low. Although pepsinogen can be detected at birth, and the concentration3~6weeks, but because the piglets gastric fundus gland is not developed, hydrochloric acid secretion ability is poor, pepsinogen can not be activated, so its role in20It can only be shown after age.

The intestinal glands and pancreas of suckling piglets are fully developed and can secrete a variety of digestive enzymes that digest breast milk. Among them, trypsin, pancreatic lipase and lactase content in intestinal juice are very high, which can better digest the fat and protein in breast milk, but it is difficult to adapt to the plant protein in feed. Post-weaning changes in intestinal morphology cause villous brush border enzyme(such as lactase, sucrase, isomaltase and alpha-glucosidase)Decreased activity, reduced absorption capacity of the digestive tract, these changes can lead to intestinal nutrient digestion and malabsorption. Piglets inO~4During the weeks of age, pepsin, pancreatic lipase, pancreatic amylase, trypsin activity doubled,4The activities of various digestive enzymes decreased to pre-weaning 1/3 within one week after weaning at the age of two weeks. After weaning piglets digestive enzyme activity decreased, resulting in piglets often can not adapt to plant-based feed, which is also after weaning piglets1~2An important cause of indigestion and growth inhibition during the week.

1.3 Weaned piglets have weak immunity and poor disease resistance

Due to the placental barrier, fetal piglets can not absorb immunoglobulin and other macromolecular substances from the mother through the blood, so they do not have innate immunity. Immunoglobulins are obtained mainly through breast milk, and these immunoglobulins ensure the healthy growth of piglets. Colostrum contains immunoglobulin7%, while regular milk only contains0.5%. So colostrum is irreplaceable food for piglets. Piglet10After the age of the self-produced immune antibodies, the formation of active immunity, with the growth of the age from the mother obtained the amount of antibodies gradually decreased,.6After the age of weeks, mainly by their own synthesis of antibodies.2~6Weeks of age is the transition period from passive immunity to active immunity, during which weaning can reduce the level of circulating antibodies in piglets, inhibit cellular immunity and reduce resistance. Plus affected by weaning stress. Decreased resistance to disease, prone to diarrhea, dysentery and other diseases.

1.4 Post-weaning piglet micro-ecosystem imbalance

Piglets at birth, the digestive tract is sterile, after birth2Microorganisms such as E. coli and streptococcus can be detected in the stool within hours. In the process from birth to natural weaning, various parts of the digestive tract are gradually occupied by various bacteria, but the balance is not reached. Under normal circumstances, the microflora will change within a certain physiological range with the change of the external environment and diet, but if the fluctuation exceeds the normal physiological range, it will cause ecological imbalance. Studies have shown that Escherichia coli, Clostridium wechi, Streptococcus, Lactobacillus, Bacteroides, etc. are the main flora of the gastrointestinal tract of suckling pigs, and after weaning, due to the lack of gastric acid, digestive enzyme secretion and intestinal mucosal injury of piglets, intestinal Escherichia coli, Streptococcus, Enterobacteriaceae and other harmful bacteria multiply in large numbers, and even become dominant bacteria, causing intestinal microecosystem imbalance, this leads to diarrhea.

2 Nutritional regulation of piglets

2.1 Energy

The digestive enzyme system in the digestive tract of suckling piglets is not perfect, but there is rich lactase, so compared with other energy substances, lactose can be better digested and absorbed by piglets to provide energy for the body. The main component of whey powder is lactose, and the lactose content of whey powder with good quality is about60％～85%, crude protein content12More than%, adding a certain proportion of whey powder to the teaching trough material can significantly improve the production performance of piglets. The lactic acid produced by the decomposition of lactose can maintain the health of piglets, and has good palatability, easy digestion and absorption, help digestion and prevent diarrhea in piglets. Lactose can provide fermentation matrix for various beneficial microorganisms in piglets intestine, and help piglets form a favorable micro-ecological environment in the intestine.

Diarrhea of weaned piglets is directly related to excessive feed intake, while feed intake of pigs increases with dietary energy. Therefore, by improving the dietary energy to regulate the feed intake of pigs, the diarrhea rate of piglets can be effectively reduced. Increasing dietary energy can be achieved by adding fat, and the type of fat added should be8~14Carbon atoms in the long chain fatty acids and unsaturated fatty acids. high nutrient concentrations in the diet of weaned piglets containing8％～10Supplemental fat at% provides fat levels similar to sow milk.