Metabolic Modifiers Effects on the Nutrient Requirements of Food-Producing Animals (1994) / Chapter Skim
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6. Effect of Metabolic Modifiers on Nutrient Requirements of Poultry
6. Effect of Metabolic Modifiers on Nutrient Requirements of Poultry
Pages 52-58
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From page 52... ...
For example, the proportion of broiler production costs expendect in deposition of the abdominal fat pad, a by-product of no consumervalue, accounts for fiscal cost of $94 million annually for the 20 leading poultry integrators in the United States. Effect of Metabolic Modifiers on Nutrient Requirements of Poultry Exogenous administration of ST from mammalian sources is ineffective as a growth promotant in aves (Libby et al., 1955; Glick, 1960; SelIand Balloun, 1960)
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From page 53... ...
; however, plasma cST concentrations decreased by 33 percent. Bolus administration of human GRF at doses of 80 and 320,ug/kg body weight/day increased the rate of body weight gain slightly in 1- to 3-week-old broiler chicks (Baile et al., 19861.
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From page 54... ...
The effects of prolonged treatment and the consequences on growth and nutrient partitioning have not been reported. Compensatory Growth Restriction offeedintake to maintenance energy6 to 12 days posthatch followed by release to ad libitum intake results in true compensatory growth (fractional growth rate accelerated compared to ad libitum fed controls; Plavnik et al., 19861.
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From page 55... ...
are adequate to provide a diet reasonably close to those actually used commercially, yet meeting or exceeding all of the bir(l's nutrient requirements. Assuming that the objective of experiments concerning metabolic modifiers is to accelerate the rate of lean tissue growth, amino acid requirements will generallybe increased comparecTto current NRC requirements.
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From page 56... ...
Input-output models also predict that increasing the rate of growth by 10 percent increases amino acid requirements 10-fold more than decreasing the carcass fat by 10 percent at a slaughter weight of 2.5 kg. Another way to model changes in nutrient requirements caused by metabolic modifiers is to use empirically obtained nutrient requirements over a range of growth rates to predict requirements at new rates.
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From page 57... ...
Although this assumption is valid for birds with normal growth rates, it is not known whether the relationship holds at augmented rates. Third, it is assumed that metabolic modifiers inducing augmented fractional growth rates do not change the proportion of amino acids required for maintenance relative to protein accretion.
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From page 58... ...
In either case it is important that diets be usecI that permit the expression of increased growth and/or improved lean tissue accretion. Current knowledge of nutrient requirements versus growth rate of broilers indicate that cliets that meet current NRC nutrient levels are not aclequate for research on metabolic modifiers.
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