Effects of egg position during late incubation on hatching parameters and chick quality

Chicken eggs are commonly incubated for 17 to 18 d in setters, after which they are transferred to the hatchery for the last 3 to 4 d of incubation. Whereas eggs are positioned vertically with the air cell up during the first incubation phase, they are placed horizontally for the hatching phase. It is unknown whether egg position in the last phase of incubation is of importance to the hatching process and chick quality. An experiment was conducted to investigate effects of egg position in the last 4 d of incubation on the hatching process and chick quality. The experiment consisted of 2 identical trials, where 300 fertile eggs per trial were transferred to a hatching cabinet at embryo day 17. Eggs were placed in 1 of 3 positions: with the air cell up (ACU), with the air cell down, or horizontally (HOR). Starting at embryo day 18, the following data were collected for each egg at 3-h intervals: time of internal pipping (IP), external pipping (EP), hatching, and position of EP. Approximately 6 h after hatch, BW, chick length, and chick quality based on the Pasgar score, were determined for each chick. In addition, residual yolk weight and yolk-free body mass were determined in every fourth chick that hatched. Time of IP was not affected by egg position, but EP occurred 5 h later in ACU eggs, and thus, the IP-EP interval was increased by 3 to 4 h in this group compared with the other egg positions. Hatching occurred 1 to 2 h earlier in HOR eggs than in the other 2 positions. Body weight, yolk weight, and yolk-free body mass were not affected by egg position. Chick length was 1 to 2 mm shorter and the Pasgar score was slightly lower in air cell-down eggs compared with ACU and HOR eggs, mainly caused by a high incidence of poor navel quality, red hocks, and red beaks. Hatchability was not affected by egg position. We concluded that egg position in the last phase of incubation affects the duration of the hatching process, and has small effects on chick quality.