Role of Diet Manipulation for Environment-Sustainable Swine Agriculture

To reduce the manure nutrient output, diet manipulation can make a difference. From a pig’s perspective, those efforts are categorized into two aspects:

1. by reducing the swine nutrient input to reduce manure nutrient output accordingly;
2. to improve the efficiency of nutrient digestibility and utilization in swine.

Effective methods reported include the dietary incorporation of phytase, a commercially available enzyme, in swine diets. Phytase renders the phosphorous in grain ingredients from its originally bound form available to the pig, so that dietary level of phosphorous could be reduced up to 0.1 percentage, which converts to a reduction of 25-30% of phosphorous output from swine manure. Especially in growing-finishing pigs, the reduction of the dietary protein level with supplementation of some crystalline amino acids, such as lysine, methionine, threonine, and tryptophan showed a positive effect on the reduction of nitrogen output from manure. Many other effective methods have also been demonstrated to reduce the manure output of phosphorous and nitrogen from pig production.

In swine production, there is a lot of ammonia, sulfide and other hazardous gases emitted from manure, which impair the health of the human beings, and is not good for the environment as well by contributing to the greenhouse effect and to acid rain formation. Again, diet manipulation is playing an important role in reducing the gas emission from swine manure, though there is not much change in the amount of manure nutrient output in this way. Increasing the fiber levels (soybean hulls, for example) in swine diets can enhance the fermentation in the pig’s large intestine, which shifts the nitrogen output pattern by increasing the amount of more stable bacterial protein-nitrogen in feces and decreasing the easily ammonia convertible urea-nitrogen in urine. It was also reported that ammonia emission from pig manure could be reduced by 5.4% with each 100-g increase of fiber intake. Binding agents, such as clinoptilolite and clay minerals sometimes can reduce ammonia emission from the intestine by absorbing the hazardous gases. Adipic acid, at the inclusion level of 1% in grower diets, can reduce ammonia emission from swine excretion by 25% through lowering the manure pH value, as reported recently.

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