Increasing Turkey Egg
Production and Reproductive Efficiency
As a result of selective breeding strategies
to increase turkey production in recent decades,
turkeys' growth rates and body size have
been maximized at the expense of their reproductive
efficiency. Turkeys currently have the shortest
reproductive cycle and produce the fewest
eggs of any poultry species.
Commercial turkey breeders rely on management
procedures to extend turkey hens' egg-laying
period and discourage nesting and incubation.
The breeders have found it increasingly difficult,
however, to identify and manage nesting hens
in commercial operations that typically consist
of 20,000 to 30,000 hens per flock. Current
management procedures are time-consuming,
labor-intensive, and only moderately effective
in forestalling the onset of nesting behavior
and subsequent drops in egg production.
With funding from the National Research
Initiative (NRI) Competitive Grants Program,
researchers at the University of Minnesota
are investigating physiological factors that
control nesting behavior in turkeys. The
scientists have discovered that elevated
circulating concentrations of the hormone
prolactin inhibit hens' ovarian function,
stimulate nesting behavior, and decrease
With the long-term goal of increasing egg
production by controlling amounts of circulating
prolactin, the investigators have undertaken
additional studies to learn more about the
physiological factors regulating prolactin
synthesis and release. The regulatory mechanisms
governing secretion of prolactin have been
shown to involve the hypothalamus (a region
of the brain) and the pituitary gland.
The scientists have developed sophisticated
surgical techniques to collect blood from
tiny vessels connecting the hypothalamus
and the pituitary gland. These blood vessels
transport a crucial hormone vasoactive intestinal
peptide (VIP)from the hypothalamus
to the pituitary gland.
Although the neuromechanisms regulating
reproductive behavior are not yet clearly
understood, VIP is a known physiological
stimulator of prolactin secretion in turkeys.
Studies have demonstrated, for example, that
turkeys displaying nesting behavior have
elevated brain levels of the hormone.
The University of Minnesota scientists have
designed a strategy to "immunize" turkeys
against the effects of VIP by injecting them
with additional VIP. This causes the turkeys'
immune systems to generate antibodies against
The antibodies neutralize the effects of
VIP on the reproductive system, thereby decreasing
circulating concentrations of prolactin,
decreasing nesting behavior, and increasing
egg production. In two recent studies, immunization
of turkey hens against VIP resulted in a
production increase of more than 30 eggs
per hen during a 21-week period.
The potential of VIP immunization to increase
turkey egg production is clear. Researchers
currently are seeking ways to generate large
quantities of pure VIP through genetic engineering
and recombinant DNA technology.
The scientists recently isolated the gene
encoding VIP in turkeys and have initiated
studies to determine whether recombinant
turkey VIP will prevent nesting behavior
in turkey hens and increase egg production
as effectively as the natural VIP. The results
of this research are expected to help benefit
the turkey indus try and, ultimately, the
consumer by helping growers increase avian
reproductive efficiency and egg production.
Back to Animal Reproduction Home Page