Analysis Of Selection Effects Of Residual Feed Intake In Broilers

The cost of feed in the broilers production occupies the largest proportion of the total farming expense,about 70%of the total production costs.Improving the feed utilization efficiency and reducing the input-output ratio through breeding are vital to the improvement of economic benefits.However,it is difficult to achieve the direct genetic selection of feed utilization efficiency in actual breeding because of the difficulty of determination and time-consuming.Previous studies have shown that the residual feed intake（RFI）as an effective selection index to improve feed utilization efficiency has been used in the breeding of livestock and poultry breeds such as beef cattle and pigs,but it has not been reported in broiler breeding.In this study,the fast broiler（B line,terminal sire）of a breeding company in Guangdong was acted as the experimental material.We used the method,combined individual selection and family selection,to select the important economic indicators of residual feed intake（RFI）and body weight for four generations.Phenotype and pedigree data of 17 traits of 5668 chickens were recorded.Based on the BLUP method,the genetic parameters of residual feed intake（RFI）,feed conversion rate（FCR）,average daily feed intake（ADFI）and other traits were estimated by ASReml3.0 software.The selection progress of RFI,body weight and related carcass trait changes were analyzed,which would provide a reference for the breeding of breed of fast type broiler.The research mainly obtained the following results:（1）The heritability of 9 characters such as RFI was estimated.Among them,the heritability of RFI and FCR were 0.189 and 0.128,respectively,RFI and FCR were middle low heritability traits.The heritability of breast muscle percentage was the highest,reached to 0.356,followed by abdominal fat percentage and body weight on28d(BW₂₈),which were 0.355 and 0.335,respectively.The heritability of ADFI,average daily weight gain（ADG）,body weight on 42d(BW₄₂)and leg weight percentage were 0.220,0.136,0.265 and 0.172,respectively.（2）RFI had a weak genetic correlation with BW₂₈ and BW₄₂（r_g=-0.016,0.103）,a highly positive genetic correlation with FCR,ADFI and abdominal fat percentage（r_g=0.763,0.629,0.409）,a genetic correlation with ADG of 0.214,a moderately negative genetic correlation with breast muscle percentage（r_g=-0.219）,a moderately negative genetic correlation between FCR and ADG（r_g=-0.208）,a negative genetic correlation with breast muscle percentage and leg weight percentage.It shows that RFI can be used as an index of feed efficiency.（3）After G5 to G8 generations of breeding,feed efficiency,growth traits and carcass traits had all made progress to varying degrees.Among them,FCR phenotypic value significantly decreased by 6.91%,breeding value decreased by 0.0049,growth traits ADG,BW₂₈ and BW₄₂ increased by 27.82%,13.47%and 13.00%,respectively,and the differences were significant.Carcass traits:breast muscle weight,breast muscle percentage,leg weight and leg weight percentage increased by 28.57%,8.19%,23.73%,and 3.96%,respectively,and the difference was significant,abdominal fat increased by 1.78%,but the difference level is not significant.The results showed that RFI could improve feed efficiency and meat percentage.（4）From 5668 individuals,50 individuals with low residual feed intake（L＿RFI）and 50 individuals with high residual feed intake（H＿RFI）were compared,the RFI difference was 42.34 g,average daily intake difference was 47.02 g,feed conversion ratio difference was 0.68,average daily gain and body weight on 42d were no significant difference,50 individuals with low feed conversion ratio（L＿FCR）and 50individuals with high feed conversion ratio（H＿FCR）were compared,the average daily gain difference was 30.72 g,average daily intake was no significant difference.Compared with high feed efficiency groups,the RFI and average daily intake of L＿RFI group were lower,the L＿FCR group had lower feed conversion ratio and higher average daily gain.It shows that RFI is more closely related to food intake,while FCR is related to body weight gain.In summary,the results of the actual breeding showed that under the premise of individual determination of feed intake and RFI.Using a combination of individual selection and family selection,RFI and body weight achieved significant genetic progress.Using RFI as an index for selecting feed efficiency can reduce feed intake without affecting body weight gain.