Explore And Analyze The Factors Affecting Weaning Weight And Weaning Number Of Piglets

The weaning weight and weaning number of piglets are crucial indicators to measure the economic benefits and technical level of the large-scale pig farm.The weaning weight of piglets not only affects the feed conversion rate,survival rate,and market time of piglets before weaning,but also has a positive correlation with the growth,development,and disease of post-weaning pigs.Also,the number of weaned piglets directly influences the number of weaned piglets in the sow’s nest,which then affects the number of weaned piglets per year（PSY）.Therefore,both will have an impact on the economic benefits of the pig farm.To explore the relationship between different factors and weaning weight and weaning number of piglets,and provide theoretical guidance for piglet production,comprehensive management,and genetic improvement in large-scale pig farms,this study investigated eight indicators at the sow level（feed intake,hybrid combination,parity,delivery season）,piglet level（birth weight,uniformity）,and environmental level（environmental parameters,geographical location）.We investigated the impact on the weaning weight and weaning number of piglets,obtained the differences between various levels,and obtained the linear regression models and hierarchical linear regression models to predict the weaning weight and weaning number of piglets using analysis of variance analysis（ANOVA）,multiple comparison,correlation analysis,and regression analysis in the R software（R Core Team,2021）.The main results of the study are as follows:（1）The sow feed intake during late gestation and lactation significantly affected the litter weaning weight,mean weaning weight,corrected 28-day weaning weight,and number of weaned piglets（P<0.05）.The piglet litter weaning weight,mean weaning weight,and corrected 28-day weaning weight reached the maximum value when the sow feed intake was the highest,and vice versa（P<0.001）.In addition,the number of weaned piglets was highest when the sow ingested a medium feed intake,and it was lowest when the feed intake was lowest（P<0.05）.This study also found that the average daily feed intake in the late gestation was extremely significantly negatively correlated with the average daily feed intake during lactation（r=-0.179,P<0.01）,the sow feed intake 7 days before delivery was significantly and moderately negatively correlated with that 7 days after delivery（r=-0.444,P<0.01）,and the sow feed intake 7 days after delivery was significantly and moderately positively correlated with the feed intake 8-28days after delivery（r=0.392,P<0.01）.In addition,the sow average daily feed intake in late gestation,lactation,and the whole experimental stage had a significantly positive relationship with the weaning weight and weaning number of piglets（r>0,P<0.05）.And the strongest correlation with weaning weight and number of piglets was the sow average daily feed intake in the whole experimental stage,followed by that during lactation,and finally that in late gestation.（2）By analyzing the influence of the region of the farm on the weaning weight and weaning number of sows,it was found that the Large White sows’piglet litter weaning weight,mean weaning weight,corrected 28-day weaning weight,and number of weaned piglets were as follows:South China>Northwest>Northeast,and the piglet litter weaning weight,mean weaning weight,and number of weaned piglets of Landrace and Large White×Landrace sows（LY）were as follows:Northeast>South China>Northwest.Exploring the influence of environmental indices in the pig house,it was proved that the values of temperature,relative humidity,light,ventilation,carbon dioxide（CO₂）,ammonia（NH₃）,and hydrogen sulfide（H₂S）in the nursing house at different times were significantly different（P<0.05）,and the different heights（except temperature,relative humidity,and CO₂）and positions（except temperature and relative humidity）showed similar changes（P<0.05）.Additionally,there was no significant difference between the weaning weight and number of piglets and the humidity,light,NH₃,and H₂S in the pig house（P>0.05）,but there was a relationship between the ventilation,CO₂,and temperature.（3）By investigating the effects of sow parity and hybrid combination on the weaning weight and weaning number of piglets,we proved that the piglet litter weaning weight bred by three-parity sows was the highest,while that of one-parity sows was the lowest,and the piglet mean weaning weight and corrected 28-day weaning weight of four-parity sows was the highest.And the number of weaned piglets from 3 and 8 parity sows was the largest and lowest,respectively（P<0.05）.In addition,the litter weaning weight of purebred Large White sows（YY）was the highest,the corrected 28-day weaning weight of Large White×Landrace sows（LY）was the highest,the number of weaned piglets of Landrace×Large White sows（YL）was the highest,and the number of weaned piglets of Duroc sows（DD）was the lowest（P<0.05）.（4）The piglet birth weight and uniformity are important factors affecting the weaning weight,and weaning number of piglets（P<0.05）.When the piglet birth weight was in the range of 1.81-2.00kg,the litter weaning weight,mean weaning weight,and corrected 28-day weaning weight were the highest,and the range of 0.80-1.00kg was the lowest;when the birth weight was within the range of 1.21-1.40kg,the number of weaned piglets was at its highest,and when it was within the range of 0.80-1.00kg,it was at its lowest（P<0.05）.Furthermore,with the improvement of piglet uniformity in birth weight,the litter weaning weight,mean weaning weight,and corrected 28-day weaning weight also increased（P<0.05）.And when the coefficient of variation at birth weight of piglets was the lowest（3.00%-10.00%）,the number of weaned piglets was the highest（P<0.05）.（5）The sow delivery season had a significant impact on the weaning weight and number of piglets bred by different breeds of sows（Large White,Landrace,and Large White×Landrace）（P<0.05）.The piglet litter weaning weight and corrected 28-day weaning weight of Large White:Autumn>Winter>Spring>Summer,and the number of weaned piglets:Spring>Winter>Summer>Autumn.And the litter weaning weight and corrected 28-day weaning weight of Landrace:Autumn>Winter>Spring>Summer,the number of weaned piglets:Winter>Spring>Autumn>Summer.Moreover,the litter weaning weight and the corrected 28-day weaning weight of Large White×Landrace sows:Autumn>Spring>Winter>Summer,and the number of weaned piglets:Spring>Winter>Autumn>Summer.In addition,there were significant differences in the litter weaning weight,mean weaning weight,corrected 28-day weaning weight,and number of weaned piglets between 2020 and 2021（P<0.05）.（6）To predict the piglet weaning weight by the sow feed intake,mean birth weight,average daily gain of piglets,and other factors,simple and multiple linear regression models with reasonable accuracy（R²close to 1）were developed.Moreover,the models for predicting the weaning number of piglets were also obtained through the sow feed intake,the number born alive,the number born healthy,and the mean weight of piglets at birth,but the fitting effect of the model was general.The tests of the regression models obtained in this study are significant（P<0.05）,indicating that these regression models can achieve good prediction.（7）Through the hierarchical linear regression model,the variables at the high level（pig farm level）and the low level（sow level）were included in turn.The results showed that the explanatory power of model 2 was 1.2%and 12.2%higher than that of model 1when comparing the independent variables that only include the pig farm level variables and also include the sow level variables.In addition,the comparison between the linear regression model and the hierarchical linear regression model showed that the fitting ability of the latter was better than the former.In summary,the factors explored above at the sow level,piglet level,and environmental level are all related to the weaning weight and number of piglets.In addition,regression models that can predict weaning weight and weaning number of piglets can be established through indicators such as sow average daily feed intake,number born alive,number born healthy,and mean birth weight of piglets.