Environment Management II

S OF PAPERS 213 M72 Relationship of Hatch Time to Broiler Chick Percentage Yolk Sac and Subsequent Live Performance John Brake*1, Serdar Ozlu2, Okan Elibol2 1North Carolina State University, Raleigh, NC; 2University of Ankara, Ankara, Turkey Broiler hatching eggs from broiler breeder flocks (Ross 344 X 308SF) at 59 and 55 wk of age were used in Experiments 1 and 2, respectively. Eggs were stored in a cooler for 1-3 d prior to setting in Petersime incubators under standard single-stage conditions. Early hatch time was 472-480 h or 471-477 h, Middle hatch time was 488-492 h or 480-486 h, and Late hatch time was 496-510 h or 494-510 h, respectively, in Experiments 1 or 2. Chicks were deemed to be hatched when they exhibited healed navels and dryness about the head and neck. At 510 h of incubation, hatched chicks were removed from the trays, feather sexed, counted, identified with neck tags, weighed, and placed in floor pens on new wood litter shavings. Chicks were necropsied and yolk sac weight determined at placement in pens and 24 h later (1 d) in Experiment 1 and immediately at each hatch time (477 h, 486 h, and 510 h) and also at placement in Experiment 2. For each hatch time, chicks were assigned to 8 pens of 10 male and 10 female chicks each or 9 pens of 9 male and 9 female chicks each for a total of 480 or 486 chicks in Experiments 1 and 2, respectively. BW and feed consumption were determined at 1, 7, 28, and 35 d of age or 7, 14, 21, and 35 d of age in Experiments 1 and 2, respectively. Mortality was noted daily. Data from the 3 (hatch time) x 2 (sex) completely randomized design were subjected to analysis of variance. Percentage yolk was greater in Late hatch compared to Early and Middle hatch chicks at placement and at 1 d in Experiment 1. Percentage yolk was similar in all groups in Experiment 2 at hatch time but Early hatch chicks exhibited less percentage yolk at placement. Chick BW was greater at placement in Late hatch chicks compared to Early hatch chicks in both experiments but this was no longer apparent by 7 d. BW was greater in the Middle hatch compared to Late hatch chicks with Early hatch chicks intermediate at 7 and 35 d in Experiment 1. Although Early and Middle hatch chicks exhibited greater BW loss between hatch and placement and lower BW at placement compared to Late hatch chicks, Early hatch chicks had significantly larger BW than Late hatch chicks with Middle hatch chicks intermediate at 35 d in Experiment 2. Late hatch chicks consumed less feed and exhibited lower relative growth rate to 7 d and exhibited greater cumulative mortality in both experiments. Late hatch chicks had greater percentage yolk sac and BW at 510 h of incubation, which was followed by reduced feed consumption to 7 d. Mortality and BW gain was also poorer in Late chicks relative to Early and Middle hatch chicks.