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Many egg markets have switched to cage-free egg production. In this type of facility, the behavior of the layers in the nests has an important economic characteristic.
Manual collection of eggs from the floor in an aviary is very expensive and a major hassle for egg producers. Eggs laid on the floor can cause increased cloacal cannibalism in the flock which is a problem for animal welfare. It is common in a flock of young layers for the birds to lay a few eggs on the floor while establishing their nest-use behavior.
Generally, the number of eggs laid on the floor will reach a low level in 2–3 weeks. Eggs on the floor are generally in the 1-4% range throughout the life of a layer flock.
BEHAVIOR OF BIRDS IN THE NESTS
It is very important to understand the behavior of the bird in the use of the nests to develop the appropriate programs to minimize the eggs laid on the floor.
Behavior before laying
As part of the pre-laying ritual, an hour or two before laying an egg, the hen is restless and begins to explore potential nesting sites. The bird frequently visits sites before choosing the place to nest, on average the bird visits the nest approximately 21.3 times for each egg laid. During these visits, the bird can eat, drink and clean itself as well as express other behaviors. (Photo 1).
After selecting the site, the bird returns several times, exhibiting nest-building behavior. If there is loose material like sawdust, the bird spends more time making the nest. Just before laying the egg, the hen spreads its neck and body feathers.
The onset of pre-laying behavior is caused by the last ovulation of the hen (release of the ovarian follicle in the oviduct) and not by the presence of an egg ready to be laid. Previous ovulation releases hormones, estrogen, and progesterone, responsible for the bird’s behavior before laying.
Hens prefer comfortable nests in dark, secluded, warm areas.
Birds prefer nests with solid floors over wire floors. Birds prefer nests located in corners or at the end of lines. They also generally prefer nests in elevated locations compared to nests at ground level. Young inexperienced birds may prefer nests occupied by other hens (gregarious nesting; this behavior tends to decrease with the age of the bird (Photo 2).
Photo 2. The gregarious behavior of layers is more common in young inexperienced birds.
In aviary systems, birds will select the most isolated nests located along the wall before using nests located in other parts of the aviary.
Nesting is a learned behavior, but once established, it is difficult to change. Birds tend to return to the same nesting sites every day.
Layers that consistently lay eggs in nests or layers that lay eggs on the floor can be identified in a flock.
For egg producers, the management challenge is to make designated nests attractive to birds and to eliminate alternative nesting sites where birds can lay eggs outside the nest.
Factors Affecting the Incidence of Eggs on the Floor
Behavior of the bird
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