One of the environmental challenges that the poultry industry has faced is manure utilisation and/or disposal. Poultry manure and its nitrogenous compounds can be a potential pollutant causing eutrophication, nitrate or nitrite contamination of water, ammonia volatilisation, and acid deposition in the air. Therefore, reducing nitrogen excretion and emissions in poultry manure is important to maintain a clean environment. Proper nutrition is an important first step to optimise performance and growth in animals as well as to reduce the negative impacts on the environment. Amino acids are components of protein nutrition that greatly influence animal growth. However, excess or insufficient amino acid supplementation in diets increases nitrogen excretion and emissions. One way to reduce this is to prevent uricase activity in the microflora in poultry manure. Egg yolk antibodies are economic alternatives for administering in feed to poultry. Supplementation of feed grade antibodies into poultry diets can be a potential approach to minimise bacterial uricase activity and reduce ammonia emissions from poultry manure. In order to use this dietary strategy effectively, a well-balanced feed formulation and a more practical way of delivering the antibodies in feeds remains to be developed.

This paper describes, under laboratory and/or field conditions, an approach that could be used to predict nitrogen (N) mineralization of poultry litter. Proper composting of poultry litter results in N mineralization, reducing or eliminating the environmentally harmful effects of ammonia (NH3) odours and nitrate leaching. Addition of straw to poultry manure provides sufficient available carbon and increases NH3 binding capacity, overruling any greater influence of diet composition on methane (CH3) formation. C:N ratio ranges (6–25) vary in the amount of low N loss depending on substrates. Aerobic decomposition of manure results in formation of humified organic compounds and decreased nutrient availability, while anaerobic decomposition forms low molecular weight compounds (volatile fatty acids and NH3+- N). The differences in the size of the composted particles results in physical separation and decomposability of high and low C:N ratio substrates. Temperatures ranging from 14 to 35°C did not affect the rate of N mineralization, but affected N loss from poultry manure pellets by decay nitrification at 14 and 35°C compared with 25°C. Uric acid and undigested proteins in poultry litter have optimal degradation rates at pH of 5.5 or higher, with the optimum pH for uricase being about 9. Variations in manure composition are seen between different species such as cattle, swine and poultry. The chemical composition of the manure and not the substrate N status influences the rate of decomposition or microbial availability. The N mineralization potential of some vegetable residues correlated better with the total and water soluble N contents than with their C:N ratios. Poultry manures are applied to agricultural soils at rates determined by the amount of available N that they are assumed to contribute to the crops. Many equations have been developed to calculate these application rates.

The endogenous urinary excretion of the purine derivatives allantoin, uric acid and xanthine plus hypoxanthine were measured in twenty-nine lambs, ten cattle (six steers, one cow and three preruminant calves) and four pigs. The sheep and mature cattle were nourished by intragastric infusion and the calves were given a milk-substitute. The pigs were fed on a purine-free diet. The excretion of total purine derivatives was substantially greater by the cattle, being 514 (se 20.6) μmol/kg live weight (W)0·75 per d compared with 168 (se 5·0) μmol/kg W0·75 per d by the sheep and 166 (se 2·6) μmol/kg W0·75 per d by the pigs. Plasma from normally fed sheep, cows and pigs was incubated with either xanthine or uric acid. Sheep and pig plasma had no xanthine oxidase (ec 1. 2. 3. 2) activity whereas plasma from cattle did. Uricase (ec 1. 7. 3. 3) was not present in plasma of cattle and pigs and appeared to be present in trace amounts only in sheep plasma. It is suggested that the species differences in endogenous purine derivative excretion were probably due to the different profiles of xanthine oxidase activity in tissues and particularly in the blood. This is because a high xanthine oxidase activity in tissues and particularly in the blood. This is because a high xanthine oxidase activity would reduce the chance to recycle purines, by increasing the probability of degradation to compounds which could not be salvaged.