Influence of Egg Shell Embryonic Incubation Temperature and Broiler Breeder Flock Age on Posthatch Growth Performance and Carcass Characteristics

Influence of temperature stimulation during the last 4 days of incubation on secondary sex ratio and later performance in male and female broiler chicks

1. In 6 incubation trials a total of 9883 eggs (Ross 308) were incubated from d 1 to 17 under normal incubation conditions (37.2-37.4 degrees C) and then sorted into three hatch incubators (control: 37.2-37.4 degrees C; chronic warm incubation: 38.2-38.4 degrees C, 24 h daily; short-term warm stimulation: 38.2-38.4 degrees C, 2 h daily) in incubation trials 1 and 2 or two hatch incubators (control and short-term warm stimulation) in trials 3-6. 2. The one-day-old chicks were selected by sex and chick quality was analysed in random samples using the Pasgar score. A total of 120 male and 120 female one-day-old chickens from each incubator were used for a 35-d fattening period. 3. Neither chronic nor short-term increase in incubation temperature had a negative effect on hatchability and chick quality. Short-term warm stimulation improved hatchability by more than 1.5% and was associated with a significantly higher proportion of hatched male chicks. 4. In the subsequent broiler growth trial, the mean daily weight gain of the short-term warm stimulated male broiler chicks was significant higher than for the control group, which results in a body weight increase of 2.9%. 5. Feed conversion (feed:gain ratio) of the short-term warm stimulated male and female broilers was significantly lower than in the males and females of the control and chronic warm incubated groups. 6. In conclusion, an incubation temperature profile which includes short-term temperature variation can be important in improving poultry performance (European patent pending since March 2008).

Acclimation to heat during incubation. 1. Embryonic morphological traits, blood biochemistry, and hatching performance

Eggs obtained from broiler breeders at 32 (young), 42 (middle aged), and 65 wk (old) were used to measure the effects of heat acclimation during incubation on morphological, physiological, and metabolic traits at internal pipping (IP) and at hatch. All eggs were from the same stock, and hatching performance was also evaluated. Eggs from each breeder age were incubated at control (CONT) or 38.5 degrees C for 6 h daily from d 10 to 18 of incubation (HA). On d 10 after heat exposure and on d 14, absolute and proportional weights were significantly lower for HA than CONT embryos. By the time of hatching, HA chicks were heavier than CONT chicks, which suggested accelerated growth. This effect was consistent across ages. Liver and heart weights were lower for HA than CONT chicks. At IP, pH was similar for HA and CONT embryos, whereas pO(2) and Na(+) were significantly higher and pCO(2), HCO(3)-, and K(+) significantly lower for HA than CONT embryos. Blood pH was higher in embryos from older than for younger and mid-aged parents at IP. At hatch there was no effect of heat acclimation for blood HCO(3)-, Na(+), and K(+) levels, whereas plasma triglyceride and T(3) levels were higher and plasma uric acid, glucose, and lipid peroxidation levels were lower for HA than CONT chicks. Embryonic mortality was similar among parental ages for CONT. In contrast for HA, embryonic mortality from older parents was higher than for younger and middle-aged parents. A delay in external pipping and hatching time with high incubation temperature was consistent across the breeder ages. It was concluded that lower blood pCO(2), HCO(3)-, K(+), and higher pO(2) at IP stage, plus increased plasma triglyceride concentrations at hatch, indicate adaptive responses of embryos.

Relationships Among Egg Characteristics, Chick Measurements, and Early Growth Traits in Ten Broiler Breeder Strains

This study evaluated egg traits, yolk utilization, chick conformation, and early growth rate in 10 broiler breeder strains. The strains included pure-, specialized- and commercial-line products. The 210 eggs/strain were weighed and randomly designated to 1 of 3 experimental determinations: 8 eggs for measurement of eggshell conductance, 52 eggs for determination of egg characteristics, and 150 eggs for incubation and chick traits. Egg characteristics included egg weight, specific gravity, yolk weight, albumen weight, albumen height, eggshell weight, and eggshell thickness. Chick traits included navel condition, hock color, chick length, shank length, and abdomen score by manual palpation. At hatch, half the birds per strain were dissected to assess the weight of the yolk sac, heart, liver, and breast muscle. The remaining chicks were randomly distributed into 4 rearing pens for a 14-d assessment of growth rate. There was a 3-g range in egg weight among the strains. Eggs from a pure line had the greatest amount of yolk (22.6 g), with yolk weight ranging to a low of 20.9 g in 2 other strains. The male line strain and 2 female line strains had the highest hatching weights (46.3, 46.5, and 45.4 g, respectively), whereas a commercial strain had the lowest hatching weight (43.1 g). Egg size affected chick weight more than did yolk size. The residual yolk mass at hatch ranged from 5.50 g (in the male line) to 3.70 g in the commercial strains. Residual yolk mass accounted for approximately 10 to 14% of chick BW at hatch. The abdominal palpation score correlated with actual hatch residual yolk weight (r = 0.50; P < 0.0001). At hatch, differences in breast muscle and internal organ weight were present. Shank length at hatch correlated more strongly with 14-d BW (r = 0.39; P < 0.0001) than did hatch weight and 14-d BW (r = 0.35; P < 0.0001). The results of this trial demonstrated significant strain variation in internal organ weight, residual yolk sac mass, and chick carcass reserves, which, when added together, resulted in observable differences in chick weights across strains.