Effects Of Weight Loss Of Lactating Sows On Reproductive Performance And Its Mechanism

This thesis mainly studied the effects of weight loss of Yorkshire lactating sows on reproductive performance, also studied the changes of serum hormone levels in lactating sows, and explored the related mechanisms of the effects of weight loss of lactating sows on reproductive performance. These can provide the theoretical foundation for improving the level swine production management and reproductive performance.(1) According to the degree of weight loss of lactating sows, the 40 sows were divided into four groups respectively:group D of weight gain (weight gain from 0 to 5%, n=8), group L of slightly weight loss (weight loss from 0 to 5%, n=12), group M of moderate weight loss (weight loss from 5% to 10%, n=11), group H of high degree of weight loss (weight loss more than 10%, n=9). Results of the statistical analysis of the effects of weight loss of lactating sows on reproductive performance were as follows:As for the parity, there was a partly positive correlation between weight loss and backfat loss. The weaning survival rate of litter and the weaning survival litter showed the downward trend as the weight loss rate increased, Among forth groups, the weaning survival rate of litter of group D was significantly higher than that of group M (P<0.05); There were no significant difference of the weaning survival litter between each group (P>0.05), but there was a tendency to reduce as the weight loss rate increased. When the weight loss was less than 10% range, daily weight gain of piglets、weight of litter at weaning and weight of weaning piglets would increase as the weight loss rate increased, but reduced when weight loss was more than 10%. There were no significant difference of daily weight gain of piglets between each group (P>0.05).The weight of litter at weaning of Group D and L were significantly lower than that of group M (P<0.05).The weight of weaning piglets of group L and M were significantly lower than that of group D and H (P<0.05).As for the next parity, the weaning-to-estrus interval (WEI) would lengthen, estrus rate of the week and conception rate would decline as the weight loss rate increased. The rate of newborn alive, number of newborn and litter weight at birth showed the downward trend as the weight loss rate increased. There were no significant difference of the number of newborn and litter weight at birth between each group (P>0.05), but the rate of newborn alive of group D and L were significantly higher than that of group M and H (P<0.05).The above results show that, the reproductive performance of lactating sows is better when weight loss is less than 5%, and it will decline when weight lose from 5% to 10%, and it is poor when weight loss is more than 10%.(2) All sows were fasting blood at the time of parturition, a week after parturition and weaning. Then determine the level changes of serum biochemical indicators, metabolic hormones and reproductive hormone. The results showed that:the serum concentration of every hormone was close before parturition for each group of weight loss of lactating sows, and there were no significant difference between each group (P>0.05), but the hormone showed different changes of rising or falling from parturition to weaning were as follow:As for the serum biochemical index:the level of serum Glu and FFA first down then up. The greater the degree of weight loss of lactating sows had a low Glu concentration at the time of weaning. Group D significantly higher than that of group H (P<0.05); The greater the degree of weight loss of lactating sows had a high FFA concentration at the time of weaning, and there were no significant difference between each groups (P>0.05).As for the serum metabolic hormones:the level of serum Insulin was first up then down, serum Leptin was down first and then up, serum GH and IGF-I were getting lower all the time. The greater the degree of weight loss of lactating sows had a low Insulin and IGF-I concentration at the time of weaning, and the falling range was large; The greater the degree of weight loss of lactating sows also had a low Leptin concentration, but the rising range was small; GH concentration in was high, the falling range was small. The Leptin and IGF-I of Group D and L were significantly higher than that of group H (P<0.05); The Insulin of Group D was significantly higher than that of group H (P<0.05); but there were no significant difference of GH between each group (P>0.05).As for the serum reproductive hormone:the level of serum FSH、E2 and P4 all were down first, and then up,but LH were up all the time. The greater the degree of weight loss of lactating sows had low FSH、LH and E2 concentration at the time of weaning, and the rising range were small. They had a high P4 concentration,and the rising range was large. There was no significant difference of P4 between each group(P>0.05), the FSH、LH and E2 of Group D and L were significantly higher than that of group H (P<0.05).The above results show that:as the weight loss rate of lactating sows increase, the secretion and release of reproductive hormone (FFA、LH、E2 and P4) is affected at the time of weaning, which will influence the follicle growth and development, and then influence the reproductive performance. And as the weight loss rate increased, the concentration of Glu、Insulin、Leptin and IGF-I will decrease at the time of weaning and the concentration of FFA and GH increase gradually. It remains to be further research whether the change rule of the above hormone have indirect or direct influence on the secretion and release of reproductive hormone.