Nitrogen and phosphorus are key environmental pollutants in agriculture, leading to environmental damage and pollution of water systems. Farming systems above a certain size are required to meet the regulations of the Integrated Pollution Prevention and Control (IPPC) system, which regulate how housing in designed and how odour, noise and waste is managed. For poultry, this is required for systems which place +40,000 birds and thus most game bird rearers do not fall in this category. However, recurrent use of land for the rearing of game birds and poor feed management practices can still contribute to environmental pollution. Therefore, it is important that there is a degree of self-regulation within the industry to show that these issues are taken seriously and that the game industry is reputable and responsible.

Along with Best Available Techniques (BATs) set out by the IPPC, there are strategies which game bird rearers can implement by working with their FAR feed advisor to better define their nutritional strategies.

One such strategy is the use of digestibility enhancers such as enzymes. Enzymes help to break down components of the feed into more digestible fractions, meaning that the bird can utilise more of the nutrients for growth, whilst reducing the amount excreted into the environment. Phytases are enzymes which are key to reducing phosphorus entering the environment through the excreta. In plant materials, phosphorus is bound to a molecule called phytate, which prevents its release and absorption as it passes through the digestive tract. Therefore phosphorus, bound to phytate, is released into the environment, where it can have severe consequences following leaching into water systems, causing eutrophication and the loss of aquatic life. The use of phytase enzymes in feed breaks these bonds between the phytate and phosphorus, making the phosphorus available to be used by the bird (for bone mineralisation for example) and reduces the amount of mineral phosphate added to the diet and the amount of undigested phosphate passing into the environment.

Excess protein is an important contributor to nitrogen pollution. The nitrogen content of a feed (from protein) can be crudely calculated by dividing the protein level by 6.75. Therefore, every 1g of protein which is not digested and is excreted has the potential to contribute 0.15g nitrogen into the environment. Poor protein digestion can occur for several reasons – poor quality dietary protein in the feed with low digestibility, gut health challenges and dysbacteriosis and poorly designed and managed feeding programmes. Protein digestibility can be enhanced by a number of reasons such as: selecting highly digestible raw materials; carefully balanced nutrients avoiding oversupply; and practicing good biosecurity and water hygiene to help reduce gut challenges and dysbacteriosis, thereby allowing the gut to work more effectively for nutrient digestion and absorption.

By considering what is fed and when (by following a recommended feeding programme and with support from their feed provider) game rearers can help reduce their nitrogen and phosphorus impact with minimal effort.

Dr Laura Beeson
Laura Beeson - Poultry Nutritionist for ABN & Sportsman