An evaluation of effective energy in the formulation of diets for laying hens.
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Date
1998
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Abstract
Emmans (1994) introduced a concept of energy utilisation applied across species, in
which a heat increment in feeding is considered to be linearly related to five measurable
quantities. Subtracting the heat increment of feeding from the metabolisable energy
supplied defines the energy supply scale called effective energy.
Two trial protocols were developed and run in controlled environment chambers at hot
and cold temperatures using laying hens in individual cages. The first trial tested the
response of hens at temperatures of 18°C and 32°C to the dilution of a basal diet with
ingredients selected to promote a heat increment in different manners, according to the
effective energy system. Diluents were soy protein isolate, fishmeal, sunflower oil, husks
and sugar and starch mix. Six diets were offered to Amberlink and Hyline Brown hens
for two successive periods of six weeks at the two temperatures. Responses in
performance and calculated heat production indicated that heat increments could be
induced by particular diluents. These affected the response in laying performance of the
birds, particularly at high environmental temperatures.
A second protocol tested the absolute value of the effective energy system by using
Amber link hens for three consecutive seven week periods at 30°C, 20°C and 30°C,
respectively. High and low effective energy diets were formulated, and blended, and
compared against commercial high and low density diets. The effective energy diets and
the commercial diets were also offered as a choice to the hens. The data illustrate a
marked linear response to the effective energy in the diet. High effective energy
produced the same response as a high nutrient density at high temperatures. Highest
performances in lay were achieved on the choice diets. The hens demonstrated the ability
to change the proportion of the choice of the effective energy diets at the different
temperatures.
Dynamic heat exchanges with the environment become significant, especially at higher
temperatures in the thermally active hen. Effective energy considers this heat response,
and can assist in ameliorating the response of the laying hen to high environmental
temperatures when incorporated into principles of feed formulation.
Description
Thesis (M.Sc.Agric.)-Unversity of Natal, Pietermaritzburg, 1998.
Keywords
Poultry--Feeding and feeds., Poultry--Nutrition., Poultry--Effect of temperature on., Feeds--Composition., Eggs--Production., Theses--Animal and poultry science.