| Sows are the basis of pig production and their reproductive efficiency is the key to determine the production level and economic efficiency of pig farms.Culling sows with low production performance becomes especially important for large-scale pig farms,but in production,the proportion of passive culling is high due to various reasons.Therefore,clarifying the law of sow culling and the reasons for culling,and reducing the passive culling rate are conducive to improving the production performance and economic efficiency of pig farms.In addition,in evaluating the reproductive efficiency of sows,adopting the index of lifetime productivity can reflect more objectively and comprehensively the influence of reproductive performance on production cost.Lifetime productivity includes the number of litters used over a lifetime and the number of piglets provided for weaning over a lifetime(PSL).At present,there is a lack of research on factors influencing lifetime productivity of sows in China.Therefore,this study aims to clarify the basic situation of sow culling in large-scale pig farms,and reveal the key factors affecting sows’ lifetime litter size and PSL,so as to provide an important basis for production management and decision making.This study collected 341,803 sow culling records from 198 farms and 46,904 lifetime reproductive performance data from 28 farms during the period from January2017 to June 2022 from a large pig breeding company in southwest China,and firstly,descriptive statistics were conducted on the culling data to clarify the culling pattern and factors affecting culling in large-scale pig farms.Subsequently,one-way ANOVAs were conducted on the factors influencing lifetime litter use and PSL,and multiple linear regressions were established for multifactor analysis,and Hierarchical linear models were developed to determine the factors influencing lifetime reproductive performance of sows.The specific results of this study are as follows:1.Basic situation of sow culling: the proportion of active culling sows with high parity was only 4.08%.In the abnormal passive culling sows,non-estrus was the main reason,accounting for 18.27%,followed by other(14.02%)and common diseases(13.09%).The elimination mainly occurred in low parities sows,and the total proportion of gilts(31.25%),first-parities sows(26.58%)and second-parities sows(15.60%)was 73.43%.The main reason for the elimination was non-estrus.In normal weeding sows,the average weeding number was 7.21±1.56.The average number of misculled sows was 1.63±1.86.The average lifetime parity and PSL of 28 pig farms were 1.96±2.00 and 21.02±22.59.Univariate analysis of variance showed that farm class,management level,precise feeding,year,season,breed and cross combination,disease and weeding out parity(PSL only)significantly affected lifetime parity and PSL of sows(P < 0.01).The mean parities and PSL of high management level were2.53±2.13 parities and 27.38±1.90 parities and PSL of medium management level were 1.89±1.90 parities and 20.02±21.06 parities and PSL of low management level were 1.39±1.76 parities and 14.66±19.27.The mean parity and PSL of the untreated regimen were 1.67±2.01 and 17.84±22.69,1.97±1.63 and 20.75±18.48 in the optimized group,and 2.50±2.20 and 27.00± 24.91 in the fiber + optimized group.The average parity and PSL of sows were 1.75±1.89 and 18.80±21.44 in spring,1.89±1.89 and 20.41± 21.58 in summer,and 2.03±1.95 and 21.30±21.74 in autumn.In winter,the parity and PSL were 2.23±2.23 and 24.02±25.27.The lifetime parity and PSL of non-diseased sows were 2.86±1.93 and 30.58±22.31,while those of diseased sows were 2.62±1.76 and 28.04±20.77.The mean lifetime parity and PSL of sows of different breeds and hybrids were different.2.Multiple linear regression analysis of factors influencing lifetime fecundity and PSL showed that management level,precision feeding,season,occurrence of disease,breed and crossbred combination factors significantly influenced lifetime fecundity(P<0.01),and management level and culling fecundity were the most important factors influencing lifetime fecundity and PSL of sows,respectively.However,it appeared that uninfested sows significantly and negatively affected litter size,and the model fit for litter size was low,with autocorrelation between residuals.3.The Hierarchical linear model analysis showed that the intra-group correlation coefficients of lifetime litter size and PSL were 0.092 and 0.089,respectively;type III test results indicated that precision feeding,breed and crossbred combination,season,occurrence of disease and culling litter size(only for PSL)significantly affected lifetime litter size and PSL,and parameter estimation showed that after taking into account farm level variables,the lifetime reproductive performance of large × long binary crosses Reproductive performance was still significantly higher than other breeds and cross combinations(P ≤ 0.01),management level did not significantly affect lifetime reproductive performance of sows(P>0.05),and absence of disease significantly and positively affected litter size and PSL(P≤0.01).Based on the above results,the following conclusions can be drawn:The high proportion of low litter culling was the main reason for low lifetime reproductive performance of sows.PSL increased significantly with longer lifetime use of litters in sows;breed and crossbreed combination,season,and the occurrence of diseases significantly affected lifetime use of litters and PSL;in addition,the use of optimized feeding pattern combined with functional fiber during gestation could significantly extend lifetime use of litters in sows.Compared with the multiple linear regression model,Hierarchical linear models are more suitable for analyzing production data of different pig farms and could dissect the variation caused by the farm level;it is suggested that the company could try to use more large × long sows as crossbred females to improve the lifetime reproductive performance of sows. |
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