The Efficiency Of Nitrogen Utilisation In Growing Chicks

Richardson, Clare Louise (1998). The Efficiency Of Nitrogen Utilisation In Growing Chicks. MPhil thesis The Open University.



High levels of nitrogen excretion result in economic loss in farm animal production. Recent theories have proposed that there is a poor agreement between amino acid oxidation and the rate of protein synthesis. The overall objectives of three separate experiments were to quantify the growth, efficiency of feed and nitrogen utilisation and rate of lysine oxidation in growing chickens. The first experiment compared the growth and efficiency of nitrogen utilisation of birds given eight different dietary crude protein concentrations (130 - 300g/kg). Increasing dietary protein had no effect on weight gains (p>0.05) but an inverse relationship (p<0.001) with the efficiency of nitrogen utilisation. However, the results indicated that diets with increasing protein concentrations had poor protein digestibility. A second experiment compared eight dietary crude protein concentrations (129-305g/kg) each at six lysine concentrations (40-65g/kg of protein). There was a curvilinear increase (p<0.001) in growth rates with increasing dietary protein with maximum growth rates occurring at 280g/kg. There was also a quadratic effect (p<0.01) of lysine concentration on weight gain with the maximum growth occurring at 55g/kg. The optimum crude protein concentration for maximum growth was indicated at 275 g/kg diet and there was no effect of protein concentration (p>0.05) on the efficiency of nitrogen utilisation. The third experiment examined the response of growing chickens to a diet that varied only in lysine concentration (30-100g/kg of protein). The optimum lysine concentration for maximum growth was indicated to be 64g/kg CP and the optimum for maximum efficiency of nitrogen utilisation was also indicated at 64 g/kg CP. Therefore there was no evidence that maximum weight gain and maximum nitrogen retention occurred at different protein and lysine concentrations. Lysine oxidation increased with an increase in dietary lysine and there was evidence of a curvilinear response. A rapid increase in lysine oxidation was indicated at 55g/kg CP. This data therefore gives some support to the theory of increased oxidation of amino acids prior to the point of maximum protein retention in poultry.

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