Morphological Investigations of the Effect of Thermal Manipulation During Embryogenesis on Body Performance and Structure of Pectoral and Thigh Muscle of Ross Broiler Chicken
ABSTRACT The aim of this study was to determine the optimum timing of thermal manipulation during early, mid, late and long lasting embryogenesis that may result in improvement of body performance and myofiber development (fiber diameter and thickness of perimysium) of pectoral and thigh muscles by a comparative morphometrical investigation on post-hatch day 35. 1440 fertile Ross broiler eggs were divided randomly and equally into 5 treatment groups: control (no TM), TM1, TM2 TM3 and TM4 were thermally subjected to 39ºC for 18h with 65% relative humidity daily during embryonic days ED 7-11, ED 11-15, ED 15-18 and ED 7-18 respectively. Out of TM conditions that were investigated, TM1 resulted in a significant improvement of hatchability rate (95.14%)and body performance when compared to the control. On post-hatch day 35, there were significant differences in BW, skinned carcass, breast, thigh and gut weight for all groups when compared to each other with a higher significant in TM1 and TM2 when compared to those of the control. FCR in this study was lower in TM groups when compared to the control group. In TM3 and TM4 the chicks show a significantly lower value of body performance when compared with those of the control group, TM1 and TM2.The histological evaluation of Pectoral muscle revealed myofibers of different diameter (38.39-40.27 µm) and perimysial thickening (17-30.5 µm), while myofibers diameter of thigh muscle ranged between (29-32.9 µm) and the perimysial thickening ranged between (14.36-22.15 µm). Thus, these results indicate that TM duringED7-11 improved muscle growth and body performance and this finding may be applied by commercial breeders to produce more enhanced broiler chickens.