Phenotypic and genetic characterization of the Italian bantam chicken breed Mericanel della Brianza

The development of the large-scale intensive poultry production system caused, in recent past, an almost complete disappearance of native breeds. The Mericanel della Brianza (MB) is an Italian bantam chicken breed characterized by optimal rusticity and a very good attitude to broodiness. The aim of this study was to assess peculiar phenotypic characteristics, breeding performance and genetic makeup of a small MB chicken nucleus under an in situ conservation program at the Poultry Conservation Centre of Local Genetic Resources of the University of Milan since 2010. The number of selected breeders in the nucleus progressively increased over the 5 years time from 22 (8M+14F) in 2010 to 58 (10M+48F) in 2014. FAO guidelines for phenotypic characterization of animal genetic resources were used to describe the productive, the reproductive traits and the performance of the MB chickens. The mean number of eggs per hen per week increased progressively from 1.86 in 2010 to 2.33 in 2014. Overall mean egg weight was 33.8 g (SD 3.71 g and CV 11%) and proportion of fertile eggs was 84%. Genetic screening of breeders was performed in 2010, 2012 and 2014 using the panel of 30 microsatellite loci recommended by ISAG and FAO for biodiversity studies. A total of 120 blood samples from twenty-four families (eight in 2010, six in 2012 and ten in 2014) were included in the study. The Mean Number of Alleles (MNA), the allelic frequencies, the observed (HO) and expected (HE) heterozygosity, the Polymorphism Information Content (PIC) and the inbreeding coefficient (FIS) value were estimated. All markers were polymorphic with the exception of the MCW0034 and MCW0248 loci. These two markers and other 4, not properly amplifying, were excluded from analyses. A total number of 77 alleles (MNA = 3.08) in 25 microsatellites have been detected in the overall population. The genetic diversity within and among families was determined with the Wright's F-statistics fixation index (FST). FSTshowed similarities among breeders within the nucleus in 2012 and 2014, but disclosed a variation respect to the nucleus of individuals of 2010. The genetic distance observed across years was confirmed by the PCA analysis. Despite the selection applied to decrease the presence of undesired traits (i.e. both morphological and reproductive traits), the genetic variability was conserved in the nucleus population across years.