Prolactin (PRL), secreted from the anterior pituitary, plays extensive roles in osmoregulation, corpus luteum formation, mammogenesis, lactogenesis, lactopoiesis, and production of crop milk. In birds, prolactin (PRL) is generally accepted as crucial to the onset and maintenance of broodiness. All the actions of prolactin (PRL) hormone are mediated by its receptor (PRLR), which plays an important role in the PRL signal transduction cascade. It has been well established that the PRL gene is closely associated to the onset and maintenance of broody behavior, and could be a genetic marker in breeding against broodiness in chickens. Meanwhile, the prolactin receptor (PRLR) gene is regarded as a candidate genetic marker for reproductive traits. PRLR is also an important regulator gene for cell growth and differentiation. The identified polymorphism of this gene is mainly viewed in terms of egg production traits. Due to different biological activities attributed to PRL and PRLR, they can be used as major candidate genes in molecular animal breeding programs. Characterization of PRL and PRLR genes helps to elucidate their roles in birds and provides insights into the regulatory mechanisms of PRL and PRLR expression conserved in birds and mammals.

MAZUROWSKI A., FRIESKE A., KOKOSZYÑSKI D., MROCZKOWSKI S., BERNACKI Z., WILKANOWSKA A. 2015. Examination of growth hormone (GH) gene polymorphism and its association with body weight and selected body dimensions in ducks. Folia Biologica (Kraków) 63: 43-50.The main objective of the study was to assess the polymorphism in intron 2 of the GH gene and its association with some morphological traits (body weight-BW, length of trunk with neck-LTN, length of trunk-LT, chest girth-CG, length of breast bone-LBB, length of shank-LS). Polymorphism in intron 2 of the GH gene was evaluated for four duck populations (Pekin ducks AF51, Muscovy ducks from a CK and CRAMMLCFF mother and Mulard ducks). Genetic polymorphism was determined with the PCR-RFLP method using the BsmFI restriction enzyme. In the studied duck sample two alleles (GH + and GH 6 ) and three genotypes (GH/TT, GH/CT, GH/CC) were found at locus GH/BsmFI. In both groups of Muscovies and in Mulards the dominant allele was GH 6 . On the contrary in Pekin ducks AF51, the frequency of both alleles was found to be similar. The most frequent genotype in the examined ducks was GH/TT. In Pekin ducks AF51 three genotypes were observed, while in Mulard ducks and in male Muscovy ducks from a mother marked as CK, two genotypes (GH/TT and GH/CT) were identified. Muscovy duck females from a CK mother and all males and females of Muscovy duck from a CRAMMLCFF mother were monomorphic with only the GH/TT genotype detected. The results showed that males of Pekin duck AF51 with the GH/TT genotype were characterized by higher (P<0.01) BW value than those with the GH/CC and GH/CT genotype. In females of Pekin ducks AF51, this same trend was observed; individuals with GH/TT genotype were superior (P<0.05 and P<0.01) to birds with two other detected genotypes in respect to BW, CG, LBB and LS. In the case of Mulards, ducks with the GH/TT genotype were distinguished by higher values of all evaluated traits compared to ducks with GH/CT and GH/CC genotypes, however most of the recorded differences were not significant. The only trait markedly impacted (P<0.05) by the polymorphism of the GH gene intron 2 was the LS value in males.

The main aim of the study was to estimate the polymorphism of prolactin (PRL) gene and its relation with some morphological traits (body weight-BW, length of trunk with neck-LTN, length of trunk-LT, chest girth-CG, length of breast bone-LBB, length of shank-LS) of Muscovy, Pekin and Mulard ducks. A secondary objective of this study was to evaluate the effect of age, origin on ducks' growth performances. Three genotypes at locus PRL/XbaI and one genotype at locus PRL/PstI were found. The results showed that Pekin ducks with the PRL/TT genotype in selected terms of evaluation characterised by higher (p < 0.05) LS and LBB values than those with the PRL/TG genotype. In Mulard ducks, PRL/XbaI polymorphism had an effect (p < 0.05) on BW and LS in birds aged 10 and 12 weeks (wk). The effect of age, origin on the growth traits of ducks was evaluated as well. All growth traits examined significantly increased with age. There was a significant (p < 0.01) effect of the ducks' origin. Until the 7 wk of age, the Muscovies were lighter and had lower (p < 0.01) values of LTN, LT, CG, LBB, LS than Pekin and Mulard ducks. The results confirm that there were significant associations between interaction of considered factors and estimated traits.