Assessment of early-stage thermal variation on embryonic mortality, hatchability, growth performance, and carcass characteristics of broiler chickens
Type of DegreeMaster's Thesis
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Timing and duration of thermal variation (TV) alters egg moisture loss, hatchability, chick BW, and performance. The objective was to evaluate the effect of TV during early-stage incubation on embryonic mortality, hatchability, post-hatch body weight, performance, carcass characteristics, and incidence and severity of 2 meat quality defects. Ross 708 Yield Plus breeder eggs (54 to 59 g) were allotted by weight into incubator egg trays. From ED 4 to 11, TV was applied, and eggs were incubated at 1 of 3 temperatures (n = 2 incubators per treatment); 97.5F (COLD), 99.5 F (CON), or 101.5 F (HOT). Incubators returned to the control temperature of 37.5 C from ED 11 to 21. Chicks were vent sexed, allotted to floor pens by TV treatment and sex (n = 6 replicates per treatment), fed a common diet in 3 phases, and processed at d 34. Wooden Breast (WB) and White Striping (WS) scores were determined 24 h post-processing by manual palpation. Incubation data were analyzed as a 1-way (TV) and performance and processing data were analyzed as a 2-way (TV sex) ANOVA using the GLIMMIX procedure of SAS. Means were separated at P ≤ 0.05 with the PDIFF option. No differences were observed in embryonic mortality, hatchability, or proportion of chick sexes. HOT eggs were lighter than COLD eggs (P < 0.0001) at ED 18. COLD chicks were heavier at hatch than HOT and CON chicks (P = 0.001), likely due to hatch patterns among TV treatments. HOT chicks were heavier than COLD chicks (P < 0.0001) on d 9, 23, and 32 post-hatch. Greater overall BWG was observed in HOT and CON compared with the COLD (P = 0.0285). Birds from CON incubators had greatest overall feed intake (FI; P = 0.0084). COLD birds tended to have a 25-g reduction in breast weight (412 vs. 438 and 443 g; P = 0.0656) which resulted in a 6% decrease in breast meat yield compared with CON and HOT birds (P = 0.004). Altering incubation temperature did not impact WB or WS incidence or severity (P > 0.3762). These results underscore the importance of careful incubation temperature management to optimize broiler growth performance and carcass yields.