Effect of ascorbic acid and cooling during egg incubation on hatchability, culling, mortality, and the body weights of broiler chickens.

Five experiments involving 3,100 settable eggs with living embryos of commercial broiler parent stock were conducted to determine the effect of ascorbic acid (AA) and cooling during egg incubation on embryonic weight, hatchability, percentage of cull chicks, embryonic mortality, and body weights of the hatched chicks. The treatments were carried out at 15, 15, 17, 11 and 19 d of incubation for Experiments 1, 2, 3, 4, and 5, respectively. The treatments for the experiments were as follows: 1) eggs injected with 0.1 mL of sterile saline solution; 2) eggs injected with saline containing 0.5, 1, 3, and 12 mg of AA per egg; and 3) control for Experiment 1; 1) eggs injected with 3 mg of AA per egg; 2) eggs cooled at 22 C for 24 h; and 3) control for Experiments 2 and 3; 1) eggs injected with 3 mg AA per egg; and 2) control for Experiments 4 and 5. Ascorbic acid at a dose of 3 mg during egg incubation improved hatchability and body weight, and decreased number of cull chicks, whereas a dose of 12 mg decreased embryo weight and hatchability and increased the number of cull chicks and embryonic mortality. Injection of AA hatchability improved when injected on Days 11 and 15 of incubation; effects diminished if AA was injected on Day 19 of incubation. Cooling eggs at 22 C for 24 h had no significant effect on any of the variables studied when compared with controls. Comparison of AA injection at a dose of 3 mg per egg and egg cooling to 22 C for 24 h at 15 to 17 d of incubation led to the conclusion that AA had two advantages over cooling. These advantages were 1) low embryonic death and 2) greater chick weight at hatch and on Days 15 and 17 of incubation.