Research On Some Factors Affecting Reproductive Performance Of Sows

In modern pig industry,the production efficiency was depended on the reproductive performance and the lifetime productivity of sows.But the reproductive performance of sows was affected by many factors,such as breeds,parities,seasons,lactation periods and hybrid modes.In order to enhance the level of pig industry in China,we analyzed the relative correlation between reproductive performances of sows and many factors(breeds,parities,back fat and hormone(PG600)treatment).The main results were as follows:1.The results of analyzing the production data of sows(n=850)showed that the litter size(9.14±2.73)and the qualified litter size(7.73 ± 2.54)of Duroc sows were significantly lower than that of Yorkshire sows(10.76±3.07 and 9.24±2.62)and Landrace sows(10.67±3.13 and 8.99±2.86)(P<0.01).Average piglet weight of the Landrace sows was significantly higher than that of the Yorkshire sows(13.84±4.24 kg)(P<0.05),and was extremely significantly higher than that of the Duroc sows(11.54±4.01 kg)(P<0.01).2.By analyzing the production data of sows(n=640)with litter sizes,we found that the litter performance of Yorkshire,Landrace and Duroc sows was similar with the parity.The litter size(11.20±2.29,10.97±2.58,9.53±2.62,respectively)of 3-6 parity sows both of them was significantly higher than that of 1-2 parity sows(10.20±3.01,10.11±2.45,8.79±2.98,respectively)and more than 7 parity sows(10.14±2.66,10.14±3.08,8.62±2.50,respectively)(P<0.05).The qualified litter size(9.93±2.39,9.56±2.47,8.24±2.19,respectively)in 3-6 parity sows both of them was extremely significantly higher than that of more than 7 parity sows(8.31±2.58,8.46±2.64,6.96±2.48,respectively)(P<0.01),but no difference from the 1-2 parity sows between both of them(P>0.05).3.Using the PG600 treatment of the over weaning sows without estrus,we found that the oestrus rate of sows in the PG600 treatment group was significantly higher than that in the natural oestrus group after 7 days of weaning(92.31%,61.82%,respectively)(P<0.01).No difference of the conception rate with them(P>0.05).4.Based on the analysis of the relationship between backfat thickness and puberty of gilts,we discovered that earliest oestrus of gilts appeared at 170.45 d when their 100 kg corrected backfat was between 12.00 to 12.90 mm,and the latest oestrus appeared at177.87 d when their 100 kg corrected backfat was under 8.9 mm.5.By analyzing the effects of backfat when mating on reproductive performance of gilts,we found that the litter size in normal backfat group(16.00～20.00 mm)gilts was significantly higher than that in the thick backfat group(≥21.00 mm)and thin backfat group(≤15.00 mm).The litter sizes of the two groups were 10.63±1.66 and 10.60±1.76,respectively(P<0.05).The qualified litter size(9.62±1.78)was significantly higher than that of thin backfat group(8.73±2.26)(P<0.01),but no difference from that of thick backfat group(9.25±1.56).But there was no difference on the number of weak piglets,the number of abnormal piglets,the number of stillborn piglets and the number of mu mmified piglets in different thickness backfat group gilts(P>0.05).After analyzing to relationship between backfat before delivery and reproduction performance,we found that the litter size(12.15±2.10)and qualified litter size(10.01±2.70)in normal backfat group(16.00～20.00mm)gilts was extremely significantly higher than that in the thin backfat group(≤15.00mm)(P<0.01).And the litter size(10.45±2.56)and qualified litter size(7.87±2.50)in thin backfat group(≤15.00 mm)gilts was significantly higher than that in the thick backfat group(≥21.00 mm).The number of stillborn piglets(1.32±1.56)in thick backfat group(16.00～20.00 mm)gilts was significantly higher than that in the thin backfat group,but there was no difference on the number of weak piglets,the number of abnormal piglets and the number of mu mmified piglets.At last,after studying on backfat of weaning gilts,we found that the oestrus rate(90.4%)within 7 days in the normal backfat group(13～15 mm)was 3.3% higher than that in the thick backfat group(≥16 mm).Also 12.14% higher than that in the thin backfat group(≤12 mm).The result showed that the interval between weaning and estrus(3.50±1.35)in normal backfat group gilts was significantly shorter than that of the thick backfat group and the thin backfat group(P<0.05).6.In addition,through measuring to reproductive hormone levels of sows with different weaning backfat at different times after weaning,we have found that FSH level in the high weaning backfat group was significantly higher than that in the low weaning backfat group on 0 days after weaning,and PRL level was significantly lower than that in the low weaning backfat group on D0 after weaning(P<0.05).There was no significant difference in FSH,LH and PRL levels between the two groups at other times(P>0.05),except that the LH levels of the 4-day high weaning backfat group were significantly higher than those of the low-weaning backfat group.