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1 Amino acid digestibility of pregnant sows and growing and finishing pigs
Stein (1999, 2001) compared the amino acid digestibility of different feed ingredients in pregnant sows and growing-finishing pigs. It was found that the apparent amino acid digestibility of pregnant sows on corn, soybean meal, barley, wheat, rapeseed meal and meat and bone meal was higher than growth. Finishing pigs, so the traditional amino acid metabolism data of growing and finishing pigs will not be suitable for sow nutritional needs.
2 Test methods for sow amino acid nutrition needs
2.1 N balance
N balance is the most common method for studying the nutritional needs of pregnant sows (Rippel et al., 1965; Allee and
Baker, 1970), Dourmad et al. (2002) used a nitrogen balance method to measure sows in large white pigs. The test collected feces from the 30th to 40th day of pregnancy, and N deposits (NR) in sows when fed daily at 2.75kg. The relationship between the standard and digestible lysine intake is:
N retained (g/d) =ï€ âˆ’2.76 ï€«ï€ +1.664 standardized digestible lysine intake (g/d)
When the dietary standard digestible lysine intake is 10.5g/d, that is, the sow diet standard digestible lysine content is 0.38%, the sow nitrogen deposition reaches a maximum of 14.7g/d, and the best standard is digestible. The ratio of threonine lysine is 0.71.
2.2 Effects of protein intake of pregnant sows on the development of tissues such as breast
Kusina et al. (1999) studied the intake of three different protein intakes (corresponding lysine intake of 4, 8, 16 g/d) for 25-105 days of primiparous white pregnancy without affecting mammary gland development.
2.3 maternal nutrition and fetal development
2.3.1 Maternal maternal protein nutrition and fetal organ development
Pond et al. (1968) reported that young sows were fed a protein-deficient diet during pregnancy, and sows were still able to produce live piglets. Mahan et al. (1979) fed gestation sows with diets supplemented with vitamins and minerals, and were fed at high nutrient levels during lactation until the third reproductive cycle, when the sow's gestational amino acid deficiency had an effect on reproduction. come out. Therefore, due to the ability of pregnant sows to buffer proteins, it is difficult to determine their requirements.
Desai et al (1996) used rats to test that limiting protein intake not only reduces fetal organ growth, but also causes irreversible damage to fetal organ structure and function. Pond et al. (1991) suggested that the fetus was most sensitive to maternal protein deficiency during the embryonic attachment period of 13-20 d of the sow and the placenta development of 2-60 d of pregnancy. The protein-deficient pregnant rat placenta becomes smaller, the concentration of IGF-I, placental lactogen in the maternal and fetal serum, and the concentration of most amino acids in the fetal and urine membrane fluids decrease, but has no effect on the concentration of amino acids in the maternal plasma (Wu Etc., 1998).
Protein restriction feeding has different effects on the offspring produced by sows and females. This may be due to the use of maternal protein by the sow to provide nutrition for the fetus, and the insufficient storage of body protein in the mother has met the needs of growth and development of the pups. However, whether the sow's use of body protein to supply fetal growth and development has an impact on the long-term reproductive performance of sows needs further study.
Pond et al. (1991) fed a diet containing 0.7% protein to pregnant sows and found that the brains of newborn piglets decreased significantly, showing that the brain's ability to obtain nutrients preferentially is also relative.
2.3.2 Pregnancy maternal nutrition and fetal organ development
The nutrition of the sow's pregnancy is important for the development of the pig's organs. Atinmo et al. (1974) reduced the energy intake of pregnant sows (50% normal intake) and found that the nutritional levels of sows during pregnancy, especially energy levels, had no significant effect on brain weight of newborn piglets, and had significant effects on liver and kidney weight. This indicates that different organs of the fetus have different sensitivity to changes in maternal nutritional levels, and the brain and heart have stronger anti-nutrition ability, while the liver, kidney and spleen are weaker. The reasons may include two aspects: First, the growth rate of the fetus in different stages of pregnancy is different, and the organ with relatively faster growth rate in the late pregnancy seems to have a greater impact. At least 80 days before pregnancy, fetal and organ growth does not depend on maternal nutrients. The amount of food consumed; second, the ability of cells to divide and divide and synthesize nutrients in different organs.
2.3.3 The nutritional effects of amino acids on the fetus
Amino acids, as essential precursors for tissue proteins, hormones, peptidases, and some specific biosignal molecules, play an important role in the sow's pregnancy (Reedsand et al., 1994). Studies in sheep have shown that amino acids are an important source of energy for embryonic development (Bell et al., 1989). In addition, glutamine is indispensable for embryonic carbon and nitrogen metabolism (Vaughn et al., 1995). Suburo et al (1995) used rats to test that arginine regulates uterine arterial blood flow by producing nitric oxide to increase embryonic nutrient supply.
2.3.4 Effects of arginine on the fetus
2.3.4.1 Early pregnancy to improve embryo implantation
Zeng et al (2008) found that the addition of 1.3% L-arginine hydrochloride to SD rats in early pregnancy significantly increased serum NO, arginine, proline, ornithine, glutamine and progesterone. Concentration, providing sufficient nutrients for embryonic development; significantly increasing the expression of induced nitric oxide synthase (INOS) and cyclooxygenase (COX-2) in pregnant mice, improving the uterine environment , thereby promoting embryo implantation.
2.3.4.2 Improve embryo survival rate in the middle and late pregnancy
Ronald et al. (2007) did not change the total litter size of sow litter when 1.0% L-arginine hydrochloride was added to the primiparous sows during the 30-110 d gestation period, but the total number of live litters was Add two ends. Arginine can increase the survival rate of embryos in the later stages of pregnancy.
3 sows during pregnancy growth and stage breeding
3.1 Growth and development characteristics and tissue composition changes of sows during pregnancy
3.1.1 Characteristics of growth and development of sows during pregnancy
Ji et al (2005) performed slaughter tests on the soft tissues, bones, gastrointestinal tract, spleen, pancreas, kidney, liver, uterus, fetus, mammary gland, 0, 45, 60, 75, 90, 102, 112 d of pregnancy. The remaining organs were separated and weighed and analyzed for chemical composition. It was found that the weight of the sputum increased in a quadratic curve; the weight of the soft tissue of the corpus callosum and the uterus and the placenta increased linearly; the single embryo, the total embryo, the single mammary gland, and the total mammary gland increased in three degrees; the crude protein of the corpus callosum increased three times, while the corpus callosum dry matter, The rice extract increased linearly. In addition, the fetal and mammary gland protein deposition rates were different before 70 days of gestation and 70 days after pregnancy. At different stages of pregnancy, the growth rate of sows' body tissues is different, and the demand for nutrients such as energy and protein is different. Therefore, it is important to accurately determine the protein nutrient requirements at different stages of pregnancy.
3.1.2 Changes in amino acids in reproductive tissues at different stages of pregnancy
Wu et al. (1995) found that the concentration of amino acids in maternal blood during sows did not change significantly during the chemical analysis of sow reproductive tissues at different stages of pregnancy. Glycine is the most abundant free amino acid, about 30% of the total free amino acids. In the embryo, glutamine is the most important free amino acid, accounting for 25%, 20%, 17% and 19% in 45, 60, 90 and 110 days of pregnancy, respectively; most amino acid concentrations in amniotic fluid are 45 in pregnancy. It will decrease from d to 90 d; arginine and ornithine are the most abundant in allantoic fluid. Therefore, it is necessary to study the functions of these special amino acids in different periods.
Kwon et al. (2003) studied sheep and found that the concentration of some amino acids in amniotic fluid and allantoic fluid also changed greatly during pregnancy. In the early stage of pregnancy, glutamine accounts for a particularly large proportion of amniotic fluid and allantoic fluid; in the middle and late pregnancy, arginine and citrulline (precursor of arginine) are relatively high in the allantoic fluid of sheep.
3.2 Effects of different gestational nutrition on the fetus
3.2.1 Early pregnancy
Early pregnancy nutrition is important for embryo survival. Jindal et al. (1997) fed 52 primiparous sows with a common diet (1.5 times maintenance requirement) and a high nutrient level diet (2 times maintenance requirement) during the first three days of pregnancy, and found that the first 24 weeks after sow breeding. Feeding levels within 48 h are critical, and high levels of feeding can reduce plasma progesterone concentrations and increase embryo mortality. Baidoo et al. (1992) found that sows fed a low feed intake (3 kg/d) during lactation, and increased feed intake (3.6 kg/d) in the early second trimester would increase embryo survival. rate. Kirkwood et al. (1988) found that continuous intake of high-energy diets was detrimental to embryo survival when dietary crude protein levels were constant.
3.2.2 Mid-pregnancy
Nutrition in the second trimester affects the formation of embryonic muscle fibers. Dwyer et al (1994) increased the feeding amount of the white sows (twice the normal feed intake) at 25-50 d, 50-80 d, and 25-80 d of gestation, and found that the mother was raised during the 25-50 d gestation period. Pig feed intake can increase the number of secondary muscle fibers in piglets.
On the other hand, feeding sows during pregnancy should fully satisfy the growth and development of the breast to ensure that the sows in the lactating period can secrete enough milk to meet the growth needs of the piglets. The apparent growth of the mammary gland is mainly after 75 days of gestation, when the total amount of DNA and RNA in the mammary gland increases rapidly (Weldon et al., 1991). The energy intake of young sows during pregnancy is too high (5.76 Mcal ME/d vs. 10.5 Mcal ME/d), which reduces the DNA, RNA and protein content in the parenchymal tissue.
3.2.3 Late pregnancy
In the second trimester of pregnancy, the growth of the fetus is rapid, and the nutrients required are also increased sharply. If only feeding is needed for maintenance, the sow will show a negative energy balance, mainly due to maternal fat loss. Noblet et al. (1990) suggest that digestive energy can be digested daily during the second trimester of pregnancy. At least 7.3 Mcal is required for intake. Cromwell et al (1989) reported that during the last 23 days of pregnancy, the daily feed intake increased by 1.36 kg, the birth weight of piglets increased by 40 g, and the weight gain of 170 g was increased by 21 g.
3.3 Branched chain amino acid metabolism and its nutritional effects
Branched-chain amino acids are more studied in lactating sows and less in pregnant sows. Self et al (2004) found that the concentrations of branched-chain amino acids such as leucine, isoleucine and valine in embryonic tissues did not change during the 20-30 d period of pregnancy. At 35 days of pregnancy, the concentration decreased significantly and decreased for 35 days. Mainly used for the synthesis of glutamine. At 35-110 d, the concentration was basically maintained at the same level. On the 40th day of pregnancy, Self et al. (2004) took placental tissue and incubated with 2 mM branched-chain amino acids. The results showed that the transamination efficiency of branched-chain amino acids was 4.45 nmol/mg tissue, while glutamine and alanine synthesis. The efficiency is 4.23 nmol/mg tissue, and it is speculated that the branched-chain amino acids in the embryonic period are important sources of synthetic glutamine. Embryos require different amounts of branched-chain amino acids at different stages of pregnancy, which may be due to the different effects of branched-chain amino acids on embryos during different periods of pregnancy.
3.4 gestational sow lysine nutritional needs
NRC (1998) considers the genetic potential of modern sow lean meat, and recommends that the total lysine requirement of pregnant sows is 0.52-0.58%, which is much higher than the corresponding 0.43% of NRC (1988), while Pettigrew and Yang (Pettigrew and Yang ( 1997) It is considered that the total lysine level of the diet needs to reach 0.59-0.66% to meet the pregnancy needs of the sow. However, Dourmad and Étienne (2002) found that pregnant sows weighing 247 kg had a total lysine and true digestible lysine content of 0.48% and 0.38% when the dietary protein reached 14.3%, respectively. You can reach the maximum. Using the test data of Dourmad and Étienne (2002) and the formula recommended by NRC (1998), it is not difficult to find that the true digestible lysine requirement of pregnant broil weighing 245 kg is 0.40%, which indicates that it is based on nitrogen. The conclusions of the remaining lysine requirement are close to those recommended by NRC (1998).
The effects of weight, age and parity on sow nutrition make lysine research more complicated. Studies have shown that the need for lysine decreases with sow weight and age (Pettigrew and Yang, 1997), while dietary lysine levels in the same parity case increase body weight and back in pregnant sows. It is difficult to determine the effect of sorghum, the weight gain of primiparous sows fed a high lysine diet is not as good as that of a low lysine diet, but the sows of the second and above are not affected (Cooper et al. 2001).
When actually estimating the amino acid requirement, lysine is usually a reference amino acid for calculating various amino acid requirements. For example, the NSC (1998) requirement for sow amino acid is calculated on the basis of lysine. The actual demand for lysine is a problem debated by nutritionists. To determine the lysine requirement of breeding sows, not only the sow parity, body weight, expected weight gain and fetal development, but also the pregnancy needs to be considered. The effect of amino acid intake on breast development.
Pettigrew et al. (1997) modeled the relationship between body protein deposition (Y) and lysine (X) beyond the maintenance requirement during pregnancy, and gave regression equations for different pregnancy periods: The previous period is Y=5.5X, the medium term is Y=7.6X, and the later stage is Y=8.7X.
4 ideal amino acid pattern in different stages of sow
Kim et al. (2009) determined that the amino acid requirements of pregnant sows vary with different stages of pregnancy by studying embryo growth, breast growth, and maternal tissue growth. The true digestible lysine is 5.57 g on the 0-60 d day of pregnancy. At this time, the ratio of lysine, threonine, proline and leucine is 100:79:65:88; and the pregnancy is 60-114. d, the daily digestible lysine requirement is 8.78 g, and the corresponding ratio of lysine, threonine, proline and leucine is 100:71:66:95. This sow stage nutrition needs to provide a new level.
5 Summary and research outlook
Embryo growth and development are closely related to maternal nutrition, and the nutrients required for different stages of embryo development are also different. In the early pregnancy, it mainly meets the implantation and differentiation of embryos, and the nutritional level is not high, but some special amino acids, such as arginine and tryptophan, can regulate embryo implantation. In the second trimester, it is mainly the differentiation of embryonic organs. At this time, protein deficiency will affect the development of organs and cause great damage to the growth of late embryos. In the late pregnancy, the embryo grows rapidly, so the nutritional level is relatively high.
Prospects for amino acid research in pregnant sows:
1 Pregnant sows have strong metabolic compensation ability. In the pregnancy stage, the nutritional deficiency of the diet can be compensated by maternal tissue to compensate for embryonic development. In addition to meeting the needs of maintenance, reproduction, and growth, excess nutrients will be used for body tissue storage. The nutrients stored in body tissues are metabolized and supplied to the fetus when the embryos require rapid development and rapid nutrition. However, this storage-decomposition process reduces the efficiency of nutrient utilization. It is important to accurately determine the nutritional requirements of sows at different times.
2 Pregnant sows have different growth rates at different stages, and the demand for protein is different. In addition, the proportion of amino acid demand is different.
3 Some special amino acids such as arginine may have an effect on the reproductive performance of sows at different stages of pregnancy.
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