FEEDING BEHAVIOR AS THE NEW BREEDING TRAITS IN PIGS
Pig breeding for improvements of growth and carcass traits, reproductive qualities as the main breeding criteria has been implemented in breeding practice for a long time. However, the used productivity traits do not involve a number of important economic indicators, in particular feed efficiency and behavioral characteristics of animals. The selection response for such traits is expected to give an additional increase in the accuracy of the breeding value of young animals when used at large nucleus farms. Undoubtedly, the transition to mass testing of animals at automatic feeding stations is currently the most accurate method for evaluating feed conversion rate and related traits of feeding behavior. This work aimed to study the genetic features of feeding behavior and growth traits of Duroc boars in relation to the residual feed intake (RFI) for use in the breeding process. The studies were carried out at Nucleus Farm TopGene for a population of 800 animals. Individual records for feed intake were collected using automatic feeding stations. Additionally, parameters of feeding behavior, average daily gain (ADG), and feed conversion rate (FCR) were recorded. To eliminate the influence of growing factors on the studied traits, a regression analysis was performed to correct feed conversion rate, as well as the calculation of genetic and paratypical variances. The RFI values were obtained based on the difference between the actual and predicted average daily feed intake, considering the average metabolic weight, and the body weight gain of animals according to the multiple linear regression equation. The average values and heritability of the main breeding traits were: feed conversion rate 2.20 kg/kg (h<sup>2 </sup>= 0.214, for the adjusted value), average daily feed intake 2.51 kg (h<sup>2 </sup>= 0.221), number of visits per day 7.9 units (h<sup>2 </sup>= 0.494), feed intake per visit 0.37 kg (h<sup>2 </sup>= 0.284), time spent in feeding per visit 11.3 min (h<sup>2 </sup>= 0.168), feeding rate 35.4 g/min (h<sup>2 </sup>= 0.269). For RFI, the ratio of genetic variation was h<sup>2 </sup>= 0.215. According to the ratio of RFI and ADG, the groups of Duroc boars were selected for desirable negative or low RFI values of -254.9 and -276.2 g vs. +266.8 and +353.9 g for positive RFI. Individuals that showed high gains (1057 g per day) with reduced feed intake (2.34 kg/day) can serve as the basis for developing a specialized line of pigs (group I) capable of efficient using feed energy for body growth. Boars with positive RFI values significantly differed for FCR<sub>corr </sub>(-0.15 and 0.24 kg/kg), back fat (-1.90 and -2.49 mm), muscle eye area (+4.57 and +6.10 cm<sup>2</sup>); for feeding behavior, the differences were -2.8 and -8.0 minutes for time spent in feeding per day, +1.7 and +2.0 visits per day, and -2.7 and -4.2 minutes for time spent in feeding per visit. That is, the more frequent visits to feeding stations at less time spent in feeding per visit, the more efficient the use of feed. The estimation of breeding value showed the similar RFI pattern for the desired group of animals. The higher estimates for feed intake compensated the existing differences between the phenotype and genotype for the number of visits per day and feeding rate due to the identified genetic correlations with RFI, r <sub>g </sub>= 0.702 and r <sub>g </sub>= 0.033, respectively. Thus, the feeding behavior traits of pigs along with the residual feed intake (RFI) are genetically determined and can be used to improve pig populations for economically important and productive characteristics.