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.

Thermal Manipulation: Embryonic Development, Hatchability, and Hatching Quality of Broiler Chicks

“…The effect of TM on hatchability in the present review is contradictive, with 65% of 20 studies that reported hatchability found no significant effect, 30% being reduced, and a comparative study by Dalab and Ali [46] reported increased and decreased hatchability with intermittent TM at different embryonic age. Also, earlier studies regarding TM and hatchability have shown contradicting results, for instance, Yahav et al [11] and Piestun et al [22] reported significantly increased hatchability with TM at 39.5°C for 3 h/d from E8 to E10 and 38.1°C for 24 h/d from E0 to E5, respectively.…”

“…Studies by Zaboli et al [41], Al-Zghoul et al [45], and Dalab and Ali [46] reported depressed embryo, hatch, or chick weight due to intermittent high-temperature TM, which partially agrees with Piestun et al [14]. However, Piestun et al [14] reported that only continuous (24 h) elevation in incubation temperature (39.5°C) from E7 to E16 negatively affected embryo growth and development and hatch weight.…”

“…Also, Al-Rukibat et al [40] showed no effect on hatchability after TM at 38.5 or 40°C for 6 h at E16, 9 h at E17 and 12 h at E18. However, TM at 39°C for 18 h/d at early embryonic age (E7-E11) significantly enhanced hatchability but in late (E11-E18) and long-term (E7-E18) negatively affected hatchability and chick quality compared with control (37.8°C) [46]. Janisch et al [32] reported significant increase in hatch weight with low-temperature TM between (E7-E10) and (E10-E13) and Krischek et al [33] found a significant decrease in embryo weights at low-temperature TM at E7-E10 and E10-E13 compared with high-temperature and control treatments (37.8°C).…”

“…and a combination of both intermittent and continuous in only one study [17], in which no depressing effect of intermittent (12 h/d) TM between E7 and E16 on embryogenesis was reported, however, continuous (24 h/d) reduced embryo weight from E16 to E21. Among the 24 intermittent TM studies, 20 articles reported the TM effect on hatchability, of which 65% found no significant effect, 30% being reduced, and a comparative study by Dalab and Ali [46] reported increased and decreased hatchability at different embryonic age. Meanwhile, embryo and/or hatch weight and chick quality were reported in 18 articles, of which 12 (67%) found no significant effect, three studies reported increased [2,38,50], and three reported reduced effect of TM on embryo and/or hatch weight and chick quality [42,45,46].…”

HSF3 and Hsp70 Expression during Post-Hatch Cold Stress in Broiler Chickens Subjected to Embryonic Thermal Manipulation

“…In the current study, TM was achieved by raising the incubation conditions to 39 • C and 65% RH for 18 h/day from ED 10 to 18. Previous studies used similar TM treatment parameters, including incubation at 39 • C for 18 h/day from ED 7-11, at 38.5 • C from ED 16 to 18 and at 39 • C for 18 h/day from ED 12 to 18, and these parameters were shown to significantly enhance BW as well as upregulate expression of muscle marker genes [27,[31][32][33]. The duration of TM was reported to affect thermotolerance acquisition in broilers, and different TM treatments led to differences in physiological parameters as well as varied mRNA expression profiles of heat shock genes [34][35][36][37].…”