Improving animal diets

Changing animal diets can also lead to a reduction in N input, leading to lower rates of denitrification. Zebarth et al (1999) constructed a large-scale N budget for an area of approximately 70,000ha heavily used for animal husbandry including the production of feed. They found that through improved manure storage and fertilizer management practices, in combination with an improved animal diet by removing surplus dietary crude protein and balancing protein, carbohydrates and amino acids in the diet leading to a reduction in N in the excreta of between 20 and 25 per cent, the total N input across the region could be reduced by 17 per cent and the N surplus by 24 per cent. Moreover, it was estimated that the improved animal diet would reduce denitrification by 22 per cent compared to the reference scenario. If we apply improved animal diets by assuming a 20 per cent reduction of the N in animal excreta, manure N application to arable land falls from 33.3 to 26.2Tg yr-1 (Table 5.3). This causes a reduction of the global N2O emission from arable land of 4 per cent.

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