Effect of Growth Hormone Locus Polymorphism on Weight Gain of Gosling

Introduction: Compared to other poultry, geese are more resistant to adverse environmental factors, so they are less likely to get sick. Geese are fast-growing poultry, and they are easy to raise. Due to the importance of goose meat due to its high calorie content compared to the meat of other poultry species and its high palatability, as well as its resistance to many diseases, it is necessary to raise this bird on an economic scale. In industrial goose breeding, there arises a need to develop strains tailored for specific purposes such as meat, egg, and dual-purpose. This allows breeders to align breeding objectives with associated costs and optimize productivity for the industry's requirements. Consequently, the economic coefficients of breeding, coupled with the relative selection of products, necessitate consideration in four primary aspects: achieving high weight gain, reducing the food conversion ratio, increasing the egg count, and enhancing egg fertility. It is crucial to acknowledge the negative correlation coefficient with the egg production trait within the realms of management and breeding sciences. This is because an improvement in one trait may inversely impact the values of another trait. Among the effective strategies in breeding, the selection is based on genetic markers that lead to the reduction of the generation gap and increase in production. Due to the ever-increasing growth of the population, a lot of effort is needed to overcome unfavorable environmental conditions, including biological and non-biological factors, and to increase the quantity and quality of the product. In recent years, many advances have been made in the field of molecular biology and biotechnology, which has provided a powerful tool for the genetic study of animals. Considering that the growth hormone gene (GH indicator) is one of the candidate genes for various traits, especially weight gain, but it has not been used in goose breeding programs so far. Therefore, in order to determine the contribution of this gene in goose breeding, its relationship with the weight gain trait of chickens should be determined, which is actually the purpose of designing and implementing this study.Materials and Methods: In order to implement this research, 300 gosling hatched from eggs of Malekan research station geese and reared for 5 months. The hatched goose chicks were kept and fed according to breeding standards Gosling weighted monthly and blood samples was collected from them in vacuum tubes containing EDTA at end of raising period. Genomic DNA was extracted by Pronase procedure. A spectrophotometer was used to determine the quality of the extracted DNA, and for this purpose, a wavelength of 260 nm was used to determine the amount and concentration of DNA, and a wavelength ratio of 260/280 was used to determine the purity and quality of the extracted DNA. Amplification of the desired region from exon 2 of the growth hormone gene was done by thermocycler using the designed primers GH-G F and GH-G R to amplify 162 base pairs. 2% agarose gel with ethidium bromide staining was used to identify PCR products. The SSCP technique was used to determine the genotypes of the growth hormone gene. Denatured SSCP products was electrophoresed on 10% polyacrylamide gel and stained by silver nitrate. Effects of GH gene on growth performance were analyzed by SPSS software version 23 in CRD design.Results and Discussion: Genotypes pattern of 1, 2 and 3 were recognized. Frequencies of 1, 2 and 3 patterns resulted 48.15, 44.44 and 7.15 percent, respectively. Results indicated that GH genotypes affected live weight of gosling in 1 and 2 month of age, the 3th pattern had heavier live weight in these periods. Despite of heavier live weight in pattern 3, for months of 3, 4 and 5 no significant differences observed among them. Low frequency of pattern 3, that affected live weight in gosling, can be increased in study population in favor of this pattern. The results of this research showed that the growth hormone gene and especially exon 2 of this gene can be considered as a genetic marker in the selection of geese for the weight gain trait.Conclusion: Given the considerable importance of the economic coefficient of egg production in geese, which outweighs the emphasis on increasing the weight of breeding geese, and considering that the economic activities of the station align more closely with augmenting the number of chicks produced per breeding goose, the observed negative correlation between egg production and weight gain in geese suggests a lower prevalence of the effective genotype influencing the weight gain of geese in this station. The selection focus at Malekan station has predominantly aimed at enhancing the egg laying rate, in stark contrast to the growth rate of geese. Consequently, this deliberate selection has led to an increase in the frequency of the effective genotype impacting egg laying and concurrently a reduction in the frequency of genotypes influencing the weight gain of goose chicks.