The reproductive performance of sows directly affects the production performance of modern intensive pigs. There are many factors that affect sow reproductive performance, such as breed, management, environment and nutrition. This article reviews the regulation of sows' reproductive performance by nutrition and feeding management.
1 Effect of nutritional factors on reproductive performance of sows
1.1 Energy and Amino Acids
Energy and amino acid intake are important for lactation and subsequent reproductive performance. Glucose is the most important nutrient for lactation and it accounts for 60% of the total nutrients absorbed by the mammary gland. 70% of body glucose is used by the mammary gland (Boyd and Kensinger? 1998). The energy dependence of lactation sow's milk synthesis, and found that the ability to use lysine to produce milk depends on the amount of feed intake. As energy intake increases, the effect of increasing lysine intake increases.
Protein and amino acid intake during lactation is important throughout the lactation period. Studies have shown that high levels of dietary protein and lysine are given during pregnancy and lactation to increase the level of estrogen in milk, and that estrogen in milk can increase the survival rate of piglets (Bate and Hacker 1982). Pettigrew? 1997? pointed out that the lysine requirement during the lactation period is the daily weight gain of the litter and maintenance needs (49mg/kgBW0.75?2.55g/d). At the same time, the composition of amino acids, especially the branched chain amino acids leucine, isoleucine and valine, is balanced during lactation. Li Xiuxia and Xu Li (2002) pointed out that branched-chain amino acids can regulate the lactation of female animals. The use of branched-chain amino acids by female animals is lower than the utilization of other amino acids, especially proline, which may be due to oxidation of CO2 in the mammary gland. Studies have shown that sows are fed 2 g of the leucine metabolite, $-hydroxy-l-methyl-nitric acid, daily for 3-4 days before delivery, which increases milk production by 41% on the third day of lactation; Eating 4 g of proline and increasing the intake of isoleucine up to 7 g/d can increase the weight of weaning litter linearly; at 0.5% isoleucine, the valine is increased from 0.72% Increased to 1.42%, milk fat content increased significantly, lactose content decreased significantly (Zhang Jing et al., 2004).
1.2 Vitamins and Minerals
1.2.1 Vitamin E and Selenium
Vitamin E, also known as Tocopherol, is a generic group of all tocopherols with the same chemical structure as tocopherols and all phenolic compounds such as tocotrienols. It mainly acts on the anterior pituitary and promotes it. Secretory hormones, which are beneficial to sows’ estrus, ovulation, conception and implantation of embryos, prevent miscarriage, and increase the reproductive function of sows.Vitamin E deficiency can reduce sow’s reproductive ability, estrus can cause abnormal ovulation, embryos can easily die. For example, juvenile sows need to have vitamin E 11 IU/kg for diets, and 44IU/kg for pregnant and lactating sows.
Selenium (Se) is a trace element necessary to maintain the health of pigs. Selenium in plants is in the form of amino acid selenium, so the selenium in plants is easily digested, absorbed, and metabolized. However, due to the low selenium content of selenium produced in selenium-deficient areas, inorganic selenium sources or organic selenium should be used. The lack of selenium has a great influence on the reproductive performance of sows and can lead to estrus disorders after delivery, infertility or weakness of newborn piglets. Selenium can promote the increase of the number of breast cells, the development of mammary glands, and the increase of milk production after delivery, thereby improving milk quality. With vitamin E has a good synergy.
1.2.2 Folate and Biotin
Folate (Flates or Folic acids) consists of a pteridine ring, p-aminobenzoic acid and glutamic acid. The main coenzyme form of folic acid in the body is tetra-ammonium folic acid (FH4) and the storage form is 5-methyl tetrahydrofolate. Ensminger et al. (1951) added 210-6 mg/kg folic acid to semi-synthetic diets, and the number of sows litter size and survival rate of piglets increased to some extent. The results were consistent with other reports (Lindemann et al., 1989; Thaler et al., 1989; Cafetanis et al., 1995). Zou Yong and Jiang Dilai (2000) found that the addition of 1 mg/kg folic acid in diets increased the number of litters from 10.23 to 11.17 in the control group, and the number of live births was 9.86. The head increased to 10.79 heads. Tremblay (1989) reported that feeding a sow supplemented with 5 mg/kg folic acid to a sow gives a 7% increase in embryonic survival rate on day 35 of gestation; the effect of folic acid supplementation on embryonic survival when ovulation number increases It is more obvious that it can reach 10%. Folic acid supplementation is very effective in raising litter size at delivery (Lindemann 1989). The reason for this is that the survival rate of the embryo is increased, not the number of ovulation. In terms of the folic acid addition phase, supplementation of folic acid into the diet during the second trimester can increase the litter size, especially in the sows (Lindemann et al., 1989; Thaler et al., 1989). The most critical period should be the first 60 days of pregnancy (Mahan, 1997). Post-pregnancy folic acid supplementation does not improve sow reproductive performance (Pharazy et al., 1987). The folic acid requirement recommended by Matte and Girard (1995) is 10 mg/kg feed, which is higher than the recommended value of NRC (1998) 1.3 mg/kg feed.
Biotin functions as a cofactor for the participation of carbon dioxide in the immobilization of several enzymes in metabolism. Adding biotin to sows' diets can significantly improve the hardness and density of the hoofs, compressive strength, and improve the quality of the skin and coat, and reduce foot cracking and footpad damage (Grandhi and Sstrain 1980). Young sows need to provide biotin 0.05mg/kg per kg of diet and adult sows need 0.02mg/kg.
1.2.3 Iron
Early piglet production is very fast, requiring 7-16 mg of iron per day, which is prone to iron deficiency anemia. Huang Guoqing et al. (1999) showed that the fertility rate of the first-time sow was increased by an average of 7.21% for the first time, compared with the control group with 205 mg/kg ferrous sulphate. The average number of litters increased by 0.37, the average stillbirth rate decreased by 2.91%, the survival rate of weaned piglets increased on average, and the average time between weaning and postpartum estrus breeding was shortened by 1.35 days; from the second to the eighth The maternal mortality rate of sows was reduced by 7.12% to 29.63%, and the survival rate of weaned piglets was reduced by 3.12% to 6.21%. The body condition of sows fed with iron methionine changed steadily. Until the 8th child's piglets still have a high rate of bred. Pan Yu (1998) showed that the addition of 180 mg/kg organic iron to pregnant sows diets can significantly increase the birth weight of piglets and reduce the mortality of the litter size compared with the same dose of inorganic iron (P<0.05). A large number of studies have shown that adding 200 mg/kg of organic iron to pregnant sows can improve sow reproductive performance.
1.2.4 Chromium
Chromium is an essential trace element for animals. Because it can affect the sow's reproductive performance, it is called "Send Aberdeen Guanyin." Lindemann et al. (1995) conducted two trials respectively. In the first trial, supplementation of 200 ug/kg chromium (Cr) began 6-7 months before mating. The results showed that the number of litter size and number of weaned piglets increased by 2 The 21-day-old litter weight increased by 8kg. In the second trial, chromium supplementation began at the time of mating, and 0.4, 0.8, and 2.0 piglets were produced in the first, second, and third litters, respectively. Moreover, Lindemann (1998) further tested and found that 200 ug/kg of chromium-picolide was added to the diets during the 6th month of gestation, lactation, and breeding of sows, which increased the litter size by 2.09%. <0.05, the litter size was increased by 3.75% (P<0.05), and the weaned pigs increased by 3.77% (P<0.05). The mating was obtained within 7 days after weaning. The number of sows increased by 2.71%?P<0.05?.
1.2.6 Potassium
The main dietary electrolytes that affect acid-base balance in pigs are monovalent electrolytes such as sodium, potassium, and chloride ions. Diets with imbalanced electrolytes can inhibit animal growth and development. Moreover, there is a functional interaction between potassium and amino acids. In the metabolic process, amino acids can replace the potassium ions in the intracellular fluid. Potassium ions can change the catabolism of lysine and arginine, and can also promote cells. Intake of amino acids and protein synthesis. NRC (1998) recommends a 0.2% recommendation for pregnant and lactating sows. The traditional view is that there is no need for additional potassium supplements in pig diets. However, with the improvement of swine breeds, the existing recommendations simply cannot meet their high-yield needs. Studies have shown that from calving to lactation for 21 days, whether or not the climate is hot or cool, adding mineral potassium can improve the weaned weight of piglets (Dove et al., 1994), and at the same time can increase the plasma potassium ion concentration of piglets (Coey 1987).
1.3 Crude fiber
Sows replenishing a certain amount of crude fiber during pregnancy can increase the production of volatile fatty acids, provide a ketogenic matrix for the developing fetus, and increase the energy reserves of the fetus. Wu Huadong et al. (1998) pointed out that because sows are in a state of “pregnancy anabolism†during early pregnancy, the rate of digestion and absorption of nutrients is increased. At this time, dietary nutrient concentrations should be controlled so that the crude fiber content is About 10%, digestive energy is 11.50MJ/kg, enter the late pregnancy, sows are in a "pregnant fever" state, this time, the crude fiber content should be about 8%, digestive energy should be 11.90MJ/kg, This will ensure the nutritional needs of pregnant sows under the preconditions, not only to satisfy their satiety, but also reduce the cost of feeding and improve the economic benefits of pigs.
2 Effect of feeding and management on the reproductive performance of sows
The nutritional status of the gilts during their growth and puberty stages influences the reproductive performance and longevity of the sows in the future. Etienne et al. (1983) pointed out that feeding before the weight of 61 kg is limited, even if it is changed to free intake, it will be delayed. Love period.
Johnston et al. (1999) pointed out that pregnant sows can be divided into pre-pregnancy (1-30 days), mid-pregnancy (31-75 days) and late pregnancy (76- delivery). During pregnancy, it is necessary to ensure that the sow has a good nutritional reserve to reduce the weight loss during lactation, to maintain a good body condition during reproduction, and to promote the development of breast tissue, to ensure adequate lactation during lactation; on the other hand The sow should consume enough nutrients to promote the survival, growth and development of the embryo. The principle of "low pregnancy and high lactation" should be adhered to throughout the entire period. Restricted feeding during the first and second trimesters of pregnancy can make it moderately palliative and avoid overfeeding at the time of delivery, which reduces feed intake during lactation while saving feed costs. In the later stages of pregnancy, the amount of feeding should be increased. In particular, protein nutrition should be enhanced while ensuring the quantity and quality of protein, but the energy intake level should not be too high, otherwise it will have an adverse effect on lactation intake and increase sow lactation mastitis, metritis and anovitis. The incidence rate (Wang Chudang et al., 2002).
Cole (1990) pointed out that the loss of excessive body weight or body condition during lactation of lactating sows prolongs the time interval between weaning and estrus, reduces the number of sows that are weaned within 10 days of weaning, and reduces the pregnancy rate and embryo survival rate. The report was unanimous (Everts 1994, Foxcroft 1996, Liu Yannian, 1999). Therefore, the key step in this phase is to increase lactation mid and late lactation intake, minimize sow weight loss during lactation, maximize sow lactation and milk quality to maximize litter weight gain, and minimize sow weight loss during lactation. , shorten the weaning-estrus interval as much as possible and increase the number of ovulations in the next breeding cycle (Dourmad et al., 1994). However, the intake of lactating sows should be limited within 5 days after birth (Zhang Jing et al., 2004).
After weaning, improving the reproductive performance of sows after weaning through nutrition and feeding management is not ideal, and more effective measures are appropriate feeding during pregnancy and lactation. However, for the sows with poor body condition, raising the feeding level after weaning can shorten the time interval between weaning and estrus of the newly born sows and increase the proportion of estrus within 10 days after weaning.
3 Conclusion
With the continuous improvement of animal species, reproductive performance of sows has been greatly improved. In the production practice, according to the reproductive performance of the sow, it is necessary to comprehensively consider the physiological characteristics of the nutrients at each breeding stage and the intended production targets, formulate reasonable nutrition parameters, scientifically formulate the diet, and adopt appropriate breeding management to achieve the best production. Achievements.
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