Professor Shi Baoming: Application of soybean oil, flaxseed oil, and fish oil in pig production

Application of soybean oil in the production of growing pigs at cold temperatures：

Under low temperature conditions, the basal metabolism of pigs increases, and the challenges faced by the immune system increase, which leads to pigs needing more energy to maintain body temperature and life activities. Due to the lack of a brown fat storage reservoir, pigs have a lower ability to maintain body temperature through non shivering heat production, and low temperatures have a greater impact on pig health. This results in pigs mainly relying on energy intake from their feed to maintain a constant body temperature, thereby resisting the negative effects of cold. Therefore, researchers from Northeast Agricultural University attempted to add soybean oil to the feed to increase the energy level of the feed, alleviate the negative effects of cold temperatures on pigs, and evaluate its practical application effects. Compared with raising pigs under suitable temperature conditions of 22 ℃, the daily weight gain of growing pigs under low temperature conditions of 14 ℃ decreased by 20.0%, and the daily feed intake increased by 11.1%. By adding 4.17% soybean oil to the feed, the net energy level was increased from 2490 kcal/kg to 2680 kcal/kg. It was found that compared with feeding the basic feed, adding soybean oil increased the daily weight gain of growing pigs by 18.2% and reduced their daily feed intake by 9.7%; Compared with the moderate temperature group, there was no significant difference in daily weight gain and feed intake. In addition, low temperature induced metabolic disorders in growing pigs, resulting in severe shifts in their blood metabolite composition and upregulation of multiple metabolites. These metabolites involve multiple pathways related to lipid metabolism, mainly including linolenic acid metabolism, primary bile acid biosynthesis, steroid hormone biosynthesis, sphingolipid metabolism, unsaturated fatty acid biosynthesis, sphingolipid signaling pathway, and phospholipase D signaling pathway. After feeding high-energy feed, various metabolites were down regulated and restored to the same metabolic state as the growth pigs in the appropriate temperature group. Low temperature also induces changes in the structure of intestinal microbiota, increases the abundance of various pathogenic bacteria related to intestinal inflammation and host inflammatory mucosal diseases, reduces the abundance of various bacterial genera involved in energy metabolism and short chain fatty acid production, and leads to intestinal villus damage. Supplementing soybean oil in the feed alleviated the negative effects of low temperature on intestinal microbiota, making the composition of pig intestinal microbiota similar to that of the growth pigs in the appropriate temperature group, and increasing the levels of short chain fatty acids and protein expression of short chain fatty acid receptors in the intestine. In addition, low temperature leads to an increase in hydrogen peroxide levels in the liver of growing pigs, induces liver apoptosis and ferroptosis, and ultrastructural analysis shows mitochondrial changes. Functional and structural damage, increased mitochondrial fission. After supplementing with soybean oil, ultrastructural analysis showed that the morphology and structure of liver mitochondria returned to normal, metabolism became more vigorous, mitochondrial fusion increased, and oxidative stress was alleviated.

Application of flaxseed oil in fattening pig production

N-3 PUFA can reduce the incidence of cardiovascular disease and regulate the body's immune function. In recent years, most of the meat consumed by people has a low content of PUFA, and the content of n-6 PUFA is usually higher than that of n-3 PUFA. With the development of science and technology, people's consumption habits of pork products have gradually shifted from fatty meat pork to lean meat and high-quality flavored pork, and ultimately developed into a consumption habit of pursuing health oriented pork. Studies have shown that the content of n-3 PUFA and n-6 PUFA in different tissues of pigs can vary with the composition of the feed. Flaxseed has a fat content of 35% -45% and is rich in ALA in n-3 PUFA, making it an important economic oil crop in China. However, flaxseed also contains anti nutritional factors such as cyanogenic glycosides and anti pyridoxine factors, which limits its application in pig farming. Given the high content of n-3 PUFA in flaxseed, researchers at Northeast Agricultural University have attempted to use flaxseed to produce healthy pork that meets people's consumption needs and is rich in n-3 PUFA. The research results showed that although flaxseed contains anti nutritional factors, feeding 10% flaxseed did not have a significant negative effect on the production performance, slaughter performance, and meat quality of 60kg growing and fattening pigs, and could significantly reduce the thickness of pig backfat and regulate the composition of pig carcass fat. In addition, adding 10% flaxseed to the feed can significantly reduce the ratio of n-6/n-3 PUFA in the longest back muscle, back fat, abdominal fat, liver, and kidneys of pigs, and increase the ratio of n-3 PUFA and PUFA. Among them, the increase in linolenic acid in the longest back muscle is the largest, with a 2.6-fold increase of 10-12. This indicates that feeding flaxseed can increase the content of n-3 PUFA in different tissues of pigs, improve the composition of fatty acids in tissues, and thus produce pork and lard rich in n-3 PUFA. Adding flaxseed to the feed can also increase the concentration of immunoglobulin M (IgM) in pig serum, enhance the activity of glutathione (CSH) and catalase (CAT) in pig serum, and strengthen the body's immune and antioxidant functions. Compared with the control group, feeding 10% flaxseed increased the content of vitamin E in pig abdominal fat by nearly 4 times, promoting the deposition of vitamin E in pig abdominal fat.

Researchers from Northeast Agricultural University used abdominal fat from pigs fed with flaxseed to refine lard rich in n-3 PUFA. They found that the concentration of low-density lipoprotein cholesterol in the serum of rats fed with lard rich in n-3 PUFA (with 10% flaxseed added) was significantly lower than that of rats fed with ordinary (10% control group) lard, and there was no significant difference compared to rats without added fat (see Table 3). Rich n-3 PUFA lard can also increase the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH Px) in rat heart and liver, reduce the concentration of malondialdehyde (MDA), and enhance the antioxidant function of rat heart and liver.

Application of flaxseed oil in sow production：

The health status and productivity of sows directly affect the economic benefits of pig farms. Researchers from Northeast Agricultural University found that adding 3.5% flaxseed oil to the feed of sows during late pregnancy and lactation significantly increased weaning weight and average daily weight gain of piglets compared to adding 3.5% soybean oil, promoting their growth and development. Feeding flaxseed oil did not significantly change sow litter size, live litter size, and piglet birth weight, and had no significant effect on sow physical condition. Feeding 3.5% flaxseed oil can also increase the content of milk fat in sow colostrum and regular milk, increase the proportion of n-3 PUFA in sow milk, plasma, and piglet plasma, and reduce the ratio of n-6 PUFA to n-6/-3 PUFA. Among them, the content of linolenic acid in colostrum increased by 1.2 times, the content of linoleic acid in regular milk increased by 3.4 times, and the content of linolenic acid in piglet plasma increased by 1.8 times.

In addition, researchers from Northeast Agricultural University found that feeding sows with flaxseed oil can also change the content of fatty acids in the tissues of offspring piglets, significantly increase the proportion of n-3 PUFA in the liver, brain, sebum, and longest back muscle of piglets, reduce the ratio of n-6/-3 PUFA, and increase the content of DHA and EPA in the brains of piglets, promoting their brain development. This indicates that feeding flaxseed oil to sows can increase PUFA in piglet tissues through breast milk and promote PUFA deposition in piglet bodies. Adding flaxseed oil to sow feed can also reduce the levels of total cholesterol and triglycerides in sow plasma, promote fat synthesis and metabolism in sow body, and increase the levels of immunoglobulin G (IgG) and immunoglobulin A (IgA) in breast milk and IgG, IgA, and lysozyme in piglet plasma, enhancing piglet's disease resistance. Feeding sows with flaxseed oil can regulate the mRNA expression of alpha tocopherol transfer protein (α - TP), Δ 5 desaturase (D5D), and Δ 6 desaturase (D6D) in piglet liver, and reduce the mRNA expression of fatty acid synthase (FAS) in piglet liver. In addition, there is an increasing trend in the mRNA expression of peroxidase proliferator activated receptor - α (PPAR - α). Studies have shown that n-3PUFA and n-6PUFA can induce the expression of PPAR - α, thereby inhibiting the activity of FAS.

Application of fish oil in sow production：

Fish oil is a yellow to reddish brown oily liquid with a strong fishy odor, extracted from fish and its processing by-products. Fish oil is rich in n-3 PUFA, which are mainly composed of EPA and DHA. EPA and DHA are essential for fetal formation, growth, and development in the mother's womb, and can be absorbed by piglets through the sow placenta. Studies have shown that adding 8% fish oil to pig feed can significantly increase the n-3 PUFA content in pig fat and muscle tissue. N-3 PUFA is essential for fetal development and postpartum self-development in sows. Adding fish oil to the feed of pregnant sows can increase the n-3 PUFA2 in milk, thereby improving the growth performance of piglets.

A study by Northeast Agricultural University has shown that adding fish oil to the feed of sows from 7 days before pregnancy to the end of lactation has a trend of increasing weaning weight and average daily weight gain of offspring piglets, as well as increasing IgG content in the plasma of sows on the day of delivery and 14 days after delivery. Similar results were also obtained by measuring the plasma of offspring piglets. The addition of fish oil to the feed significantly increased the levels of IgG and IgA in the colostrum of sows, and showed a trend of increasing the glucose content in the plasma of sows on the day of delivery and 21 days after delivery. Fish oil improved the composition of fatty acids in sow colostrum, increasing the content of EPA and DHA by 6.7 times and 4.9 times, respectively. In addition, fish oil affects the fatty acid composition in the cortex, liver, and longissimus dorsi muscle of piglets, increases the content of DHA in piglet sebum, liver, and longissimus dorsi muscle, and reduces the mRNA expression of sterol regulatory element binding protein-1 (SREBP-1), stearoyl CoA desaturase (SCD), and FAS genes in piglet liver tissue. After adding fish oil to the feed, a large amount of EPA and DHA in piglet tissues can promote the expression of peroxisome proliferator activated receptor x (PPAR-x) gene, and improve the body's fatty acid metabolism by inhibiting the SREBP-1 pathway and downregulating the expression of FAS gene.

The role and application of different fat sources in pig production

Authors: Shi Baoming, Sun Guodong, Zhaoyang

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