Differences in growth and fat deposition between White Plymouth Rock and Nagoya breeds as a tool for QTL analysis

Two breeds of chickens were used in this study White Plymouth Rock (WPR ( and Nagoya (NAG) in addition to tracking of their crossbred (♀ WPR Χ ♂ NAG) of two generations (F1and F2) for evaluating the differences in growth characteristics and fat deposition. Body weights were measured weekly from the first day (hatch day) till 4 weeks of age and different weight gains were also calculated. In addition to feed intake (for the period of 3-4 weeks of age) and feed conversion ratio were estimated. At four weeks of age, birds were dissected and the major internal organs including liver and gizzard were weighed, moreover the parts of breast muscle were also recorded. The results showed that, WPR was significantly higher in body weights, body weight gains and feed intake than NAG chicken. Also, WPR showed significantly larger sizes for liver, gizzard, pectoral muscles, abdominal fat (AF), ventriculus fat (VF), subcutaneous fat (SF) and total fat weight than NAG chicken. The correlation analysis showed that body weight at one week of age and body weight gain of the first week of age were found to have positive correlation with liver triglycerides and serum triglycerides levels in WPR while it was associated with decreasing of level of total cholesterol in serum in NAG. These results served as evidence for elucidating the major differences observed between the two breeds concerning growth and fat deposition. In addition to the relationship between increasing body weight and fat deposition was established. Thus, future QTL analysis can be performed for identification of chromosomal regions controlling growth and fatness traits and subsequently candidate gene influencing these traits could be revealed in further investigations.