Symposium: Managing the embryo for performance managing incubation: Where are we and why?

An improvement in the rate of gain of broilers during the past 20 yr has made the incubation period a larger percentage of the overall growth period for commercial poultry and has played a larger role in improving growth efficiency. Recently, hatchery managers have observed concomitant decreases in hatchability and chick performance, whereas temperature profiles in the setters and hatchers have not changed appreciably. Therefore, these decreases in hatchability, first week livability, hatch time, and overall chick quality have precipitated the need for a change in the way we manage our hatcheries. Historically, the broiler industry within the United States and United Kingdom have successfully utilized multistage incubation. Currently, the use of singlestage incubation in Europe has increased, because research has shown this system more precisely meets the developmental demands of the embryos. Therefore, re-search has focused on multi- and single-stage hatcheries to determine the proper hatch conditions necessary to optimize embryonic development, chick quality, and their effects on posthatch performance. Studies have shown how increases in shell temperature, independent of machine temperature, can result in increases in embryonic mortality, decreased heart weight as a percentage of chick weight, decreased yolk-free BW, and increased yolk weight. Factors that have contributed to the increase in heat stress on developing embryos include egg size, air flow, age of the embryo, and breeder flock fertility. Other studies have shown that the variation in chick performance can be explained by heat stress in the hatchery. Therefore, symposium presentations will show how improvements in our knowledge of the requirements of the developing avian embryo can help improve not only hatchability and first week livability but posthatch performance.