| dc.description.abstract | Incubation temperature is one of the most important factors determining embryonic development and hatchability. Duration and timing of thermal manipulation (TM) alters egg moisture loss, hatchability, chick body weight (BW), growth performance, and carcass characteristics. The objective of the study was to evaluate the effect of TM during late-stage incubation (LSI) on embryonic mortality, hatchability, broiler growth performance, carcass characteristics, and the incidence and severity of the breast meat quality defects, Wooden Breast (WB) and White Striping (WS) in fast-growing broilers. Yield Plus × Ross 708 broiler breeder eggs (n = 2,160) ranging from (60 to 65 g) were incubated at 37.5°C from embryonic day (ED) 0 to 10. From ED 11 to 18, eggs were incubated at 1 of 3 air temperature set points: 37.5°C (CTL), 36.4°C (COLD), or 38.6°C (HOT; n = 2 incubators per treatment). On ED 18, all eggs were individually weighed to determine moisture loss and transferred to baskets in hatchers set to 36.7°C with 60% RH. Chicks were pulled from hatchers simultaneously, vent sexed, placed in floor pens blocked by incubation treatment and sex (n = 6 replicate pens per treatment of 30 birds), fed a common diet in 3 phases (starter d 0 to 9, grower d 10 to 23, and finisher d 23 to 32), and processed at d 33 (n = 15 per pen). Data were analyzed as a 1-way (TM) or 2-way (TM × sex) ANOVA with the GLIMMIX procedure of SAS (v9.4). Means were separated with the PDIFF option at P ≤ 0.05. Tendencies were declared when 0.0501 ≤ P ≤ 0.10. No differences were observed in hatchability, proportion of chick sexes, or embryonic mortality. Moisture loss tended to be greater in eggs from HOT incubators (8.4%) compared with those from COLD incubators (7.6%) but were similar to those incubated at CTL temperatures (8.3%; P = 0.0793). No differences among hatch of fertile, early, middle, and total dead, pipped, or malpositioned chicks as well as proportions of male and female chicks were observed among treatments (P > 0.1463). A relatively small temperature gradient during LSI (from ED 11 to 18) tended to increase late-dead embryonic mortality in both COLD and HOT incubators compared with those at CTL temperatures (P = 0.0932). Broilers hatched from CTL incubators had the greatest overall BWG, while those from COLD incubators had the poorest overall FCR (P = 0.0086) but had similar BWG as those from HOT incubators (P = 0.0056). Broilers from the COLD incubators had higher incidence of WB score 3 breast fillets than those from the HOT treatment but were similar to those from the CTL incubators (P = 0.0259). No differences in WS were observed (P ≥ 0.1650). Sub-optimal incubation temperatures during LSI resulted in differences in post-hatch performance and carcass characteristics. These results underscore the importance of careful management during incubation to optimize growth performance and ultimately carcass yields. | en_US |
