Agriculture Reference
In-Depth Information
3
Modelling Reproduction in Broiler
Breeder and Laying Hens
R.M. Gous*
University of KwaZulu-Natal, Pietermaritzburg, South Africa
Abstract
The aim of this chapter is to describe the potential reproductive performance of individuals, such that
the potential reproductive performance of a population of hens may be simulated. This requires an
understanding of systems such as the attainment of sexual maturity in a flock of pullets and the physio-
logical control of egg production in hens. The potential performance, that is, the number of eggs pro-
duced over the production cycle of a single laying hen is dependent on the age at which it becomes
sexually mature, on its internal ovulatory cycle length and egg weight, and the rates at which these
change over time, all of which are genetically determined and may be satisfactorily modelled. Using
stochasticity, the potential laying performance of a flock may then be simulated from individual re-
sponses. While laying hens are usually given
ad libitum
access to feed, the daily food intake of broiler
breeders is restricted. In both cases it is useful to be able to predict the amount of energy and of each
nutrient that is required to meet the maintenance and potential laying performance of each hen so that
the voluntary intake of a feed of any given composition can be predicted, and the consequences on per-
formance of food intake being constrained can be determined. It may not be economically justifiable to
meet the requirements of the most demanding hens in a population: the economic optimum intake of
nutrients would depend on the relative cost of feeding these birds and the revenue derived from the sale
of the eggs they produce. The optimum daily nutrient intake must then be converted to a dietary con-
centration for feed formulation purposes, and to do this successfully voluntary food intake must be
accurately predicted. If this can be done, such a model may then be used to optimize the way in which
these different strains of laying hen should be fed so as to maximize profit for the enterprise.
Introduction
This would improve the possibility of opti-
mizing the composition (and daily allocation,
in the case of broiler breeders) of the feed
offered to the flock. In order to achieve these
goals, a comprehensive understanding is re-
quired of the factors influencing the attain-
ment of sexual maturity in these birds, of the
ovulatory cycle and how this changes during
the laying cycle, of the changes that occur in
Emphasis in this chapter is on being able to
describe the potential performance of a flock
of commercial laying hens, from which it would
be possible to calculate the daily nutrient in-
takes required to meet the potential perform-
ance of each individual in terms of numbers
of eggs produced over the production cycle.
