A Comparison between Performance, Tibia Bone Characteristics and Intestinal Morphology in Ross 308 and Arian Broilers

The continuous effort of breeders towards producing high-quality broiler strains demands continuous evaluation of broiler strains in terms of traits beyond performance. Increase in leg disorders in commercial broiler chickens resulted in considerable attention being given to the characteristics of leg bones. Furthermore, digestive tract characteristics have been considered to have a critical role in the poultry growth. Therefore, in this study, feedlot performance, intestinal morphology and tibial bone characteristics were compared and investigated in two strains of broiler chickens (Ross 308 and Arian) in Iran.

One-day-old chicks from Ross308 and Arian strains were separately allocated to two treatment groups. The initial number of each strain was 48, divided into 12 replicate cages, each with four chicks. The body weight and feed intake were recorded in weekly intervals for six consecutive weeks. The randomly selected broilers were slaughtered at 32 days of age, to make measurements of the morphometric characteristics in the different segments of small intestine, and also tibial morphology, breaking strength and composition. Feet relative weight and carcass percentage were determined at the end of the rearing period.

The whole feed intake of the Arian broilers was significantly higher throughout the experimental period, but overall body weight and feed conversion ratio (FCR) were not statistically different between the two strains. In accordance with the present results, in most of the studies conducted in Iran, Ross and Arian strains were not superior to each other in terms of body weight gain and feed conversion ratio during the breeding period of 1 to 42 days. Carcass yield in both slaughter ages was lower in Arian than in Ross. This may be due to the lower relative weight of the feet, visceral fat, or internal organs in the Ross308 broiler chickens in comparison with the Arian broilers. The villus thickness and the jejunal and the ileal surface area were significantly greater in the Arian broilers than in the Ross308. However, ileal goblet cell densities were lower in the Arian broilers than in Ross308. A decrease in the acidic goblet cells may be considered relevant to increased susceptibility of the small intestine to bacterial translocation, which theoretically may lead to inflammatory responses in the broiler body. Among the tibial characteristics, only the diameter of the diaphysis and the medullary canal were significantly wider in the Arian broilers than in the Ross308.

Ross308 strain had lower feed intake (in the entire period of trial), the better feed conversion ratio (up to 28 days of age), and higher carcass yield in comparison with those in Arian. It is possible that the gut microbial flora of the Arian strain has a role in higher feed consumption and lower density of acidic goblet cells in the intestinal villi of this strain. However, the Arian chickens had a tibial bones with higher diameters and intestinal villi with greater absorptive surfaces than those in Ross308; the features which may lead to the reduction of leg disorders (especially in the cage breeding system) and better absorption of nutrients in the broiler chickens, respectively. In general, according to the experimental conditiond and economic considerations, Ross308 strain is recommended for broiler farms.