Matching the nutritional requirements to performance in broiler breeder hens.
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Date
1997
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Abstract
Quantitative food restriction during the rearing and laying period has become the
standard management procedure in commercial broiler breeder operations to control
the rapid growth rate of broiler breeders. This raises problems with the amount of
each nutrient to be supplied each day. Food allowances are manipulated according
to the pattern of egg production. Birds are fed a generous allowance early in lay
followed by a period of mild regulation over peak production and a subsequent
reduction in allowance as egg production declines in the later part of lay. In the past
little work has been done on developing the theory of determining the nutrient
requirements of broiler breeders. Consequently, this generally accepted method of
feeding these breeders is without a sound theoretical basis.
The objective of this study was to address two aspects concerned with meeting the
requirements of broiler breeder hens during the laying period, specifically in the later
stages of lay. The first is the obesity in broiler breeders that results from an
excessive intake of energy and leads to a decrease in egg production. The second
is the rapid decline in egg production in ageing hens.
Individual data were collected from broiler breeder hens in two experiments. The
first to determine the extent to which broiler breeder hens could be made to utilize
excess body lipid reserves whilst maintaining laying performance. The second to
measure the responses to lysine at different ages and to determine if the efficiency
of utilization of lysine changes at different ages.
Results from the first experiment indicated that broiler breeders can utilize their body
fat reserves as an energy source providing that their protein intake is sufficiently
high and that they could maintain egg production for at least a limited period of time.
Birds fed an energy intake of 1490 kJ ME/bird d and a protein intake of 25.8 g/bird d
showed no decline in egg production compared to birds fed much higher energy
intakes (1900 to 2000 kJ ME/bird d). It was concluded from this experiment that if
birds become overfat at any stage in their productive lives this situation can possibly
be rectified by feeding them diets with low energy contents. In the later stages of
lay and on cold days birds can probably be fed energy intakes below their
requirements with no detrimental effect on egg production.
Results from the second experiment indicated that the efficiency of utilization of
protein declines as broiler breeders age. The efficiency of utilization of lysine was
significantly lower for birds of 53 and 65 weeks of age compared to birds of 31 and
42 weeks of age. This decline in efficiency with age was attributed to the fact that
efficiency decreases when the rate of lay decreases to below 50%. There was
therefore no indication that the protein requirements decrease as the laying year
progresses although egg production declines. It was suggested that new methods
of feeding broiler breeder hens later in lay be investigated because the present
method of decreasing the food allowance at this time is probably not the most ideal
way to achieve maximum performance.
Description
Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 1997.
Keywords
Broilers (Chickens)--Nutrition., Broilers (Chickens)--Feeding and feeds., Poultry--Feeding and feeds., Poultry--Nutrition., Poultry--Nutrition--Requirements., Theses--Animal and poultry science.