Impact of Crossbreeding Between Local and Foreign Strains on the Growth Traits and the Expression of Insulin-Like Growth Factor Genes on Their Chicks

Abstract: The aim of this work was to evaluate the impact of crossing pure Gimmizah or Bandara (local breeds) with pure Ross (a foreign breed) on growth rate, and the expression of IGF genes. Two local breeds, Gimmizah (G) and Bandara (B), plus one exotic strain of meat-type Ross 308 (R) parents, were used. Combinations of these genotypes were tested on a total of 120 birds from three pure parents. The 180 hatched chicks were divided into three purebreds G×G, B×B, and R×R and three crossbreds R×G, R×B, and G×R and reared for 7 weeks. Body weight and weight gain were recorded for each genetic group. The feed intake and feed conversion ratio were calculated. At the 7th week of age, tissue samples from breast muscle and pituitary gland were collected for IGF gene mRNA expression analysis. The results revealed that the R×R chicks displayed significantly higher final body weight, average daily weight gain, and average daily feed intake when compared to the G×G, B×B, and other crossbred chick lines. While both R×B and G×R crossbred chicks had significantly higher final body weights and average daily weight gains than R×G crossbred chicks and local chicks (G×G and B×B). A better feed conversion ratio was observed in G×R, B×B, R×R and R×B chicks. Crossbred lines (R×B and G×R) had higher dressing percentages than R×G and local breeds. The highest muscular expression of the IGF-II gene was recorded in R×G chicks, while the other crossbred lines, R×B and G×R expressed higher levels of the IGF-II gene than purebred lines. In relation to IGF-I*, R×B chicks had higher relative expression of this gene than other crossbred and purebred lines. When compared to other crossbred lines (R×B and G×R), the expression of IGF-I in brain tissues was significantly higher in the R×G crossbred line. IGF-II and IGF-I* expression levels in brain tissue were higher in the R×G chicks compared to the G×R, G×G, B×B, and R×R chicks. It was concluded that crossing pure Gimmizah or Bandara, as local breeds, with pure Ross 308, as a foreign breed, improved growth traits in the obtained crossbred chicks.