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Nutritional and Environmental Effects on Ammonia Emissions from Dairy Cattle Housing: A Meta‐Analysis
Author(s) -
Bougouin Adeline,
Leytem April,
Dijkstra Jan,
Dungan Robert S.,
Kebreab Ermias
Publication year - 2016
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2015.07.0389
Subject(s) - dry matter , manure , livestock , zoology , environmental science , dairy cattle , chemistry , agronomy , biology , ecology
Nitrogen excreted in dairy manure can be potentially transformed and emitted as NH 3 , which can create livestock and human respiratory problems and be an indirect source of N 2 O. The objectives of this study were to: (i) investigate environmental factors influencing NH 3 emissions from dairy housing; and (ii) identify key explanatory variables in the NH 3 emissions prediction from dairy housing using a meta‐analytical approach. Data from 25 studies were used for the preliminary analysis, and data from 10 studies reporting 87 treatment means were used for the meta‐analysis. Season and flooring type significantly affected NH 3 emissions. For nutritional effect analysis, the between‐study variability (heterogeneity) of mean NH 3 emission was estimated using random‐effect models and had a significant effect ( P < 0.01). Therefore, random‐effect models were extended to mixed‐effect models to explain heterogeneity regarding the available dietary and animal variables. The final mixed‐effect model included milk yield, dietary crude protein, and dry matter intake separately, explaining 45.5% of NH 3 emissions heterogeneity. A unit increase in milk yield (kg d −1 ) resulted in a 4.9 g cow −1 d −1 reduction in NH 3 emissions, and a unit increase in dietary crude protein content (%) and dry matter intake (kg d −1 ) resulted in 10.2 and 16.3 g cow −1 d −1 increases in NH 3 emissions, respectively, in the scope of this study. These results can be further used to help identify mitigation strategies to reduce NH 3 emissions from dairy housing by developing predictive models that could determine variables with strong association with NH 3 emissions. Core Ideas Season and flooring type significantly affected NH 3 emission rates. Open lots had the highest emissions in this study but the lowest by USEPA. Crude protein and dry matter intake had positive impacts on NH 3 emissions. Milk yield had negative impacts on NH 3 emissions.