Environmental factors affecting the embryo and the chick during brooding have a significant impact on the final performance of the adult broiler, according to Cobb Europe technical and sales director, Pelayo Casanovas.

“Too many producers think that the life of a broiler starts the day it is hatched,” he says. “But the reality is that the bird is already 21 days old by that stage. When a bird is culled at 41 days, it is actually 62 days since conception.”

Getting the conditions right for the developing embryo and during the first five days after hatching is crucial. “Up to this stage, the chick is effectively cold blooded and can’t thermoregulate itself. Excellent control of the surrounding temperatures must be the focus.”

Emryo stage

Achieving an embryo temperature of close to 38C (100F) will ensure good hatch and good chick quality, says Mr Cassanovas. Deviations from this target usually produce poorer hatchability and chick quality, while temperatures slightly higher than target can increase hatchability but negatively affect chick quality.

“It is hard to measure embryo temperature, but by measuring shell temperature we get a good correlation.”

Research has shown that overheating the egg will give rise to a smaller chick, a bigger unabsorbed yolk sac and a smaller heart, as the metabolism increases and the carbohydrate runs out quicker, forcing the chick to use protein as a source of energy.

There is also evidence that overheated embryos are more prone to E coli problems. “It’s not entirely clear why this should be, though it may be stress-related or it may be because the chicks hatch earlier and therefore spend longer in the hatchers.”

There is also a strong correlation between larger yolk sacs – a function of overheating – and the percentage of chicks with E coli.

The situation is further complicated by egg size and shell quality. Large eggs – which are mainly a function of breed, but also the age of the parent flock – can result in slower air flows in the incubator, leading to higher temperatures. “Larger embryos also produce more heat,” says Mr Cassanovas.

Optimum embryo temperature

“But egg shell quality can also be a problem, as the heat transferred from an egg with a better shell is slower. There also seems to be a link between embryo heat output and birds bred for higher meat yield.”

Overheated chicks tend to have poorly absorbed yolk sacs and are whiter. In more serious cases of poorly absorbed yolk sacs, the chicks can have unhealed navels. The aim should be for as maximum yolk weight of 10% of the final chick weight.

Overheated chicks also tend to be smaller, with shorter shank lengths. And they may have excess feathering, indicating that they have spent too long in the hatcher baskets.

Effectof embryo temperature on broilers

What to measure for optimum performance

Hatchery managers need to pay close attention to a number of factors to ensure their chicks are top notch, including:

• Monitor the rate of hatch once the trays have been moved to the hatcher. The aim should be a maximum 25% hatch 24 hours before pull, and 75% hatch 12 hours before pull.
• Check uniformity of egg shell/embryo temperatures. Look for hot and cold spots in the setter and ensure all are within the range 99.5F to 101F
• Egg shell cleanliness. Excess Meconium on the shells post-hatch suggests the chicks have hatched too early and been in the baskets too long
• Sample chicks for yolk retention at hatch. Yolk weight should be less than 10% of total chick weight.

* The above article is based on a paper first presented by Pelayo Casanovas at last September’s Poultry Meat Conference at Stoneleigh