Impact of single nucleotide polymorphisms of the B3 gene on growth performance and carcass characteristics in broiler chickens

Abstract

The experiment was carried out at the poultry field of the Research station, college of Agriculture and Marshes, University of Thi-Qar, during the period from 9/15/2024 to 3/16/2025.The study consisted of two phases: field and laboratory work. The fieldwork phase included raising 300 ROSS 308 broiler chickens starting from the first day post-hatching until 35 days of age.  The broilers were tagged with plastic numbers, each having a unique number. To evaluate weight gain and feed conversion efficiency, body weight measurement were conducted at the onset and conclusion of each week during the experimental period. Additionally, other weekly body measurements were taken, including bird length, chest circumference, and chest width. At the end of the production period, blood was drawn from the wing vein of broiler chickens. Thereafter, the birds were slaughtered and weighed in order to assess the primary and secondary carcass yield percentages. The main and secondary cuts, as well as edible viscera (heart, liver, and gizzard), were also weighed. The analytical procedures were carried out at the Marshes Research Center Laboratory affiliated with Thi-Qar University, aiming to extract DNA and determine the phenotypic structures of the TGF-B3 gene. Electrophoretic analysis was conducted on the obtained samples, after which the amplified PCR products were submitted to Macrogen Corporation (South Korea) for sequencing. This was done to determine the nucleotide sequence of the targeted gene fragment and to identify the genotypic variants of the TGF-B3 gene. The relationship between these genotypes and some productive traits of broiler chickens was also studied. The studied fragment was registered in the genetic bank. The results showed that both mutations, 321 C>T and 290 A>G, occurred in intron 2, a non-coding region that does not affect the peptide chain of the TGFB3 protein. The C>T 321 mutation showed a significant effect (p≤0.05) on the relative weights of the heart and liver, with the CT genotype demonstrating superior performance over the CC genotype.  However, No statistically significant differences were detected among the genotypes of the investigated gene at the A>G 290 mutation site with respect to the relative liver weight, heart, and gizzard. Additionally, no significant differences were found in carcass weight, dressing percentages, or carcass cuts in both mutations A>G 290 and C>T 321.