Heritability and correlation of litter traits in pigs determined by REML method

Abstract

The aim of this study was to determine the heritability coefficients and the correlation between the number of live born piglets (NBA), the number of stillborn piglets (NSB), the number of total born piglets (NTB) and the number of weaned piglets (NW) in the part of population in Swedish Landrace sows in R. Serbia. The results obtained should enable the selection of litter size traits that would be proposed to be included in the selection - breeding program for this breed. The analysis of parameters was carried out on the basis of data on fertility of 4.061 Swedish Landrace sows and their 15.209 litters realized on two pig farms in R. Serbia. There was a genetic relationship between animals among the farms. Components of variance and covariance of observed traits, the share of additive genetic variance component in the phenotypic and correlation of traits at phenotypic and genetic levels, were evaluated using the method of Restricted Maximum Likelihood (REML) using the Multitrait Model (MM). Heritability estimates for the NBA, NSB, NTB and NW amounted to 6.4, 1.6, 6.7 and 1.1%, respectively. Correlation between the NBA and NTB at the phenotypic and genetic level was complete (rP = 0986, rG = 0938). Correlation between the NBA and NW at the phenotypic level has not been established, while at the genetic level it was weak. We believe that this is the result of the procedure of equalizing of litters after farrowing. In order to obtain objective genetic parameters for NW this procedure should not be applied in pure breed sows.

Cilj istraživanja bio je da se utvrde koeficijenti naslednosti i povezanosti između broja živorođene prasadi (NBA), broja mrtvorođene prasadi (NSB), broja ukupno rođene prasadi (NTB) i broja odgajene prasadi (NW) u delu populacije krmača rase švedski landras u R. Srbiji. Dobijeni rezultati treba da omoguće izbor osobina veličine legla koje bi bile predložene za uključivanje u selekcijsko - odgajivački program za ovu rasu. Ocena analiziranih parametara sprovedena je na osnovu podataka o plodnosti 4061 krmača rase švedski landras i njihovih 15209 legala ostvarenih na dve farme svinja u R. Srbiji između kojih postoji genetska povezanost među životinjama. Komponente varijanse i kovarijanse posmatranih osobina, udeo aditivne genetske komponente varijanse u fenotipskoj i povezanost osobina na fenotipskom i genetskom nivou ocenjene su metodom ograničene najveće verovatnoće (REML - Restricted Maximum Likelihood) primenom višeosobinskog modela (MM - Multitrait Model). Heritabiliteti za NBA, NSB, NTB i NW su iznosili 6.4, 1.6, 6.7 i 1.1 %, respectively. Povezanost NBA i NTB na fenotipskom i na genetskom nivou je bila potpuna (rP = 0.986, rG = 0.938). Povezanost NBA i NW na fenotipskom nivou nije utvrđena, dok je na genetskom bila slaba. Smatramo da je to posledica postupka ujednačavanja legala posle prašenja. Radi dobijanja objektivnih genetskih parametara za NW ovaj postupak ne treba primenjivati kod čistorasnih krmača.