Feeding Reduced Crude Protein Diets with Crystalline Amino Acid Supplementation Reduce Air Gas Emissions from Housing

Researchers at Michigan State University have found that it is possible to reduce ammonia emissions from growing-finishing pigs without sacrificing performance by reducing the crude protein level in the diet and using amino acids to ensure the pigs' requirements are met.
calendar icon 24 February 2015
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In the current issue of Journal of Animal Science, W. Powers and colleagues at Michigan State University explain that they designed their study to examine whether reducing dietary crude protein by 1.5 per cent and supplementing crystalline amino acids (CAA) to meet the standardised ileal digestible (SID) amino acid requirements for growing and finishing pigs decreases air emissions of ammonia (NH3), nitrous oxide (N2O) and carbon dioxide (CO2) compared with an industry standard diet, without reducing growth performance.

Seventy-two pigs were allocated to 12 rooms (six pigs per room) and two diets (six rooms per diet) formulated according to a five-phase feeding programme across the grow-finish period (107 days in total).

The diets consisted of a standard diet containing 18.5 to 12.2 per cent crude protein or a reduced crude protein diet containing 17.5 to 11.0 per cent crude protein + CAA over the course of the five-phase feeding programme.

Gases (ammonia, nitrous oxide, hydrogen sulphide, methane, non-methane total hydrocarbon and carbon dioxide) and ventilation rates were measured continuously from the rooms.

Compared with standard diet, average daily gain and feed conversion of pigs fed reduced CP+CAA diets did not differ (2.7kg gain per day and 0.37kg gain per kg feed, respectively).

Compared with standard diet, feeding reduced CP+CAA diets decreased (P<0.01) ammonia emissions by 46 per cent over the 107-day period (5.4 and 2.9g per pig per day, respectively).

Change in ammonia emissions for each percentage unit reduction in dietary crude protein concentration corresponded with 47.9, 53.2, 26.8, 26.5 and 51.6 per cent during phases 1 to 5, respectively.

Emissions of other gases did not differ between diets.

Powers and colleagues concluded that feeding reduced crude protein diets formulated based on SID AA requirements for grower-finisher pigs is effective in reducing ammonia emissions from housing compared with recent industry formulations and does not impact growth performance.


Li Q-F., N. Trottier and W. Powers. 2015. Feeding reduced crude protein diets with crystalline amino acids supplementation reduce air gas emissions from housing. J. Anim. Sci. 93:721-730.

Further Reading

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February 2015

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