308 Effect of Thermal Variation During Late-Stage Incubation and Sex on Broiler Chicken Body Weight and Carcass Parts Uniformity

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Abstract Low uniformity of broiler live body weight, carcass, and parts weights can reduce overall processing yields and profitability. The objective of this study was to evaluate the effects of thermal manipulation (TM) during late-stage incubation (LSI) and sex on the uniformity and coefficient of variation (CV) in high yielding broilers. Yield Plus ′ Ross 708 broiler breeder eggs (n = 2,160) 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 transferred to baskets in hatchers set to 36.7 °C. Chicks were vent sexed, placed in floor pens blocked by incubation treatment and sex (n = 6 replicate pens of 30 birds per treatment), and fed a common diet. Broilers were individually weighed at d 9, 23, and 32, then, the 15 birds from each pen closest to the pen median BW were processed on d 33. The distance of each bird BW from the pen mean and median, TM treatment, sex, and whole flock BW over time, uniformity of BW (within 10% of the mean), and intra-pen CV were calculated. Data were analyzed as a 2-way ANOVA using the GLIMMIX procedure of SAS ver. 9.4 with TM treatment and broiler sex serving as the main effects. Means were separated at P ≤ 0.05 with the PDIFF option. On d 9, a TM by sex interaction was observed, and the BW of female CTL chicks was less variable from the pen mean compared with broilers hatched from COLD and females from HOT incubators (P ≤ 0.026). On d 9, sub-optimal incubation temperatures (HOT and COLD) during LSI resulted in higher individual female bird BW variation from the pen mean and median (P = 0.013). Incubating chicks in COLD incubators during LSI increased d-9 individual bird BW distance from the treatment, sex, and flock mean and median BW compared with CTL and HOT (P ≤ 0.037). In addition, BW uniformity within a pen was less in broilers hatched from COLD incubators than both CTL and HOT on d 9 (P = 0.033) and tended to be less on d 32 (P = 0.099). The inverse was observed for CV (P ≤ 0.040). Broilers hatched from COLD and HOT incubators had greater CV for carcass (P = 0.049) and wing (P = 0.028) as well as drumstick (P = 0.079) weights. These results indicate that sub-optimal LSI conditions can negatively influence uniformity of broiler live BW, carcass and parts weights and highlights the importance of achieving optimal incubation conditions.