| Increased nutritional requirements as well as poor appetite of modern genotype sows during lactation make the current recommended nutrition can not meet the needs of production,then a large scale body mobilization of sows appearing so as to satisfy the demands of lactation.As a consequence,however,weaning-to-estrus interval of sows extension and sow elimination rate increase and shorten the reproductive life-span of sows,thus reducing the breeding enterprise economic benefits.Furthermore,the lower level antioxidants within the plasma of lactation sows may closely refer to oxidative stress while elevated oxidative stress is reported to be associated with sow reproductive performance.It is important to note that the high oxidative stress status in lactation sows would extend the sow weaning-to-estrus interval and reduce the sow performance,and at the same time,too much free radicals accumulated in the body will disorder body immune function and lead to endocrine disorder.Methionine,as a essential amino acid and one of the sulphur amino acids,play an important role in body protein synthesis and antioxidant function as methionine can form cysteine or glutathion via sulfur metabolism.Therefore,improving sow lactation performance and piglet growth performance and sow reproductive performance as increasing the amount of methionine in lactation diet.The research was conducted to study the effects of different dietary Met-to Lys ratio in lactation diet on sow feed intake,lactation performance,reproductive performance,piglet growth performance,composition changes within milk,changes in blood free amino acids,and changes in oxidative stress in sows during lactation by adding different doses of crystalline methionine in high-yield sow lactation diet,then measuring the appropriate methionine to lysine ratio for hyperprolific lactating sows.A total of 130 parity 3 to 6 multiparous sows(Large White)were used in this trial and randomly allocated based on body weight to 4 dietary treatments(n=33,32,32,33)with 4 dietary ratios of SID Met to Lys of 0.27:1,0.37:1,0.47:1,0.57:1,and each sow a repeat.Among them,0.27 group fed basal diet,and 0.37 group fed the diet by adding 0.09% methionine into the basal diet,and 0.47 group fed the diet by adding 0.18% methionine into the basal diet,and 0.57 group fed the diet by adding 0.27% methionine into the basal diet,a trial period for the entire lactation period.During the period,the performance data of sows and piglets were measured and recorded,blood samples and milk samples from sows each group in different time-point were collected and analyzed.The experiment results are show as follows:1.Effects of different dietary Met-to Lys ratio in lactation diets on sow feed intake,lactation performance and body weight and backfat changes in sows during lactation: Different dietary Met-to Lys ratio had no significant effect on the feed intake of sow during lactation,on the lactation performance,on sow lactation weight loss,backfat change,weaning estrus interval and weaning estrus rate(P>0.05),but the average weaning estrus interval within 7 days in group 0.47 was the shortest,besides,the weaning estrus rate after a week in group 0.47 was the highest.Hence,the group 0.47 could improve the sow reproductive performance by shortening sow reproductive cycle.2.Effects of different dietary Met-to Lys ratio in lactation diets on the growth performance of piglets: Different Met-to Lys ratio in lactation diets had no significant effect on the number of litter size each week and weaned piglets(P>0.05).In group 0.47,the weaning weight of piglets were significantly improved when compared with the control group(P<0.01),while others such as litter weight and litter weight gain were no significant difference(P>0.05).3.Effects of different dietary Met-to Lys ratio in lactation diets on the composition of colostrum and milk as well as concentration of FAA(Free amino acid): Increasing dietary Met-to Lys ratio had no significant effect on the concentration of conventional ingredients such as milk protein in colostrum and milk(P>0.05).While compared with the control group,However,the content of crude protein in the milk at day 7 from sows in group 0.57 was significantly higher than that in the control group(P<0.01).Increasing dietary Met-to Lys ratio also barely affects the FAA concentration in milk either.The above results showed that different Met-to Lys ratio did not affect the content of conventional components and concentration of FAA within colostrum and milk.4.Effects of different dietary Met-to Lys ratio in lactation diets on concentration of PUN(Plasma urea nitrogen)and blood FAA: At day 7 of lactation,the concentration of PUN in 0.37 group was significantly lower than those in control group(P<0.05),but group 0.37 was significantly higher than those in the control group at weaning(P<0.05),indicating that the 0.37 group would significantly reduced the amino acid utilization efficiency of lactating sows in late lactation.At day 7 of lactation,the plasma free methionine concentration increased gradually with the increase of Met-to Lys ratio gradient,and the 0.57 group was significantly higher than the other three groups(P<0.01),and the 0.37 group as well as 0.47 group were significantly higher than those in the control group(P<0.01).The concentration of plasma free serine decreased gradually with the increase of Met-to Lys ratio gradient,and the group 0.57 was significantly lower than the other three groups(P<0.01).Except for the concentration of free Ser,the free Met concentration in plasma at weaning was consistent with the change in blood at day 7.5.Effects of different dietary Met-to Lys ratio on methionine metabolites in blood and milk of sows:(1)In blood: it could significantly improve the sow lactation blood Hcy content and the levels of GSH and Tau at weaning while the dietary Met-to Lys ratio was 0.57(P<0.01),indicating that the methionine in lactation diet was added in excess while the dietary Met-to Lys ratio was 0.57 as well as the sulfur metabolism of methionine was promoted when increasing dietary Met-to Lys ratio.In addition,the concentration of Hcy in sows blood at parturition were at a high level and decreased gradually with the lactation process.(2)In milk: the levels of Hcy in the milk from treatment group sows were significantly higher than those in the control group(P<0.01),indicating that increasing the dietary Met-to Lys ratio significantly increased the concentration of Hcy within milk in late-lactation period.Moreover,the levels of Hcy within milk in early-lactation period of each group were also at a high level.6.Effects of different dietary Met-to Lys ratio on oxidative stress status in sows during lactation: In the whole lactation period,the level of ROS(Reactive oxygen species)in the blood of sows were no significant difference among groups as well as time points(P>0.05).While at day 7 of lactation,the content of malondialdehyde in the plasma of sows belong to group 0.57 was significantly higher than that of the control group(P<0.05),and the content of malondialdehyde in the blood of 0.57 group shows a trend of significantly higher than that of the control group at weaning day(P=0.06),Indicating that it would increase the sow body lipid peroxidation damage while the dietary Met-to Lys ratio was 0.57.Furthermore,the content of 8-hydroxy-2′-deoxyguanosine in plasma of 0.37 group was obviously lower than that of control group at day 7 of lactation as well as significantly lower than that of control group at weaning(P<0.05),indicating that while the dietary Met-to Lys ratio was 0.37,to a certain extent,it could alleviate the DNA oxidative nuclear damage of sow body cells.Compared with the control group,the group 0.37 and 0.47 could significantly increase the activity of GSH-PX in the blood of sow during lactation(P<0.01),but group 0.37 has the best effect.Besides,the total antioxidant capacity of sows in lactation were significantly increased when dietary Met-to Lys ratio was 0.47(P<0.01).In summary,the research can draw the following conclusions:When the dietary Met-to Lys ratio is in the range of 0.27 to 0.57,increasing dietary Met-to Lys ratio of lactating sows would not significantly affect sow performance,piglet performance,the content of conventional components such as milk protein within milk,but significantly increased the content of Hcy within milk in late-lactation.In addition,while the dietary Met-to Lys ratio is 0.37,it could increase the activity of glutathione peroxidase and alleviate the DNA damage of the body cells to a certain extent,but the amino acid utilization efficiency of the sows are reduced.It could significantly improve the total antioxidant capacity of lactating sows while the dietary Met-to Lys ratio is 0.47,and also could improve sow reproductive performance by shortening the sow reproductive cycle to a certain degree.When the dietary Met-to Lys ratio is 0.57,it can significantly improve the level of glutathione and taurine in plasma of lactating sows,but also could increase the sow body lipid peroxidation damage and lead to sow body cell Hcy excessive accumulation at the same time.Therefore,although it shows a good potential for application while the dietary Met-to Lys ratio is 0.47,there is still room for further improvement as it would increase the level of Hcy in late-lactation period and the high level of Hcy in the blood and milk of perinatal sows themselves. |
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