Implications of excreta uric acid concentrations in broilers offered reduced crude protein diets and dietary glycine requirements for uric acid synthesis |
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Authors: | Peter H Selle David I Cantor Leon R McQuade Bernard V McInerney Juliano Cesar de Paula Dorigam Shemil P Macelline Peter V Chrystal Sonia Y Liu |
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Institution: | Poultry Research Foundation within The University of Sydney,Camden,NSW 2570,Australia;Sydney School of Veterinary Science,The University of Sydney,Sydney,NSW 2006,Australia;Australian Proteome Analysis Facility,Macquarie University,Sydney,NSW 2109,Australia;Evonik Nutrition and Care GmbH,Hanau-Wolfgang 63547,Germany;Poultry Research Foundation within The University of Sydney,Camden,NSW 2570,Australia;School of Life and Environmental Sciences,Faculty of Science,The University of Sydney,Sydney,NSW 2006,Australia;Poultry Research Foundation within The University of Sydney,Camden,NSW 2570,Australia;Baiada Poultry Pry Limited,Pendle Hill,NSW 2145,Australia |
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Abstract: | In a previous experiment, male Ross 308 broiler chickens were offered dietary treatments with 3 levels of crude protein (222, 193, 165 g/kg) and 3 feed grains (ground maize, ground wheat, whole wheat) from 7 to 35 d post–hatch. Maize-based diets supported superior growth performance in comparison to wheat-based diets. Uric acid concentrations in excreta were retrospectively determined and related to total nitrogen (N) excreta concentrations. Uric acid concentrations ranged from 28.5 to 69.4 mg/g and proportions of uric acid-N to total excreta-N ranged from 27.4% to 42.6% in broiler chickens offered the 3 × 3 factorial array of dietary treatments. Proportions of uric acid-N to total N in excreta in birds offered the 165 g/kg CP, maize-based diet were significantly lower by 10.6 percentage units (27.4% versus 38.0%; P = 0.00057) than their wheat-based counterparts. Total excreta analysed had been collected from 35 to 37 d post–hatch when feed intakes and excreta outputs were monitored. There were linear relationships between proportions of uric acid-N to total N in excreta in birds offered the three 165 g/kg CP diets with weight gain (r = ?0.587; P = 0.010), feed intake (r = ?0.526; P = 0.025) and feed conversion ratios (r = 0.635; P = 0.005). The possibility that increasing uric acid-N proportions in excreta is indicative of excessive ammonia accumulations compromising growth performance is discussed. The mean proportion of dietary glycine involved in uric acid excretion was 49.2% across all dietary treatments but ranged from 25.0% to 80.9%. Thus, the appropriate amount of dietary glycine is variable and largely dependent on the volume of uric acid synthesised and excreted. |
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Keywords: | Ammonia Broiler chicken Glycine Reduced crude protein diet Uric acid |
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