Effects of housing system, floor type and temperature on ammonia and methane emissions from dairy farming: A meta-analysis

This study provides an overview of ammonia (NH3) and methane (CH4) emissions from measurements conducted on a practical scale in different dairy housing systems. In addition, the influence of housing system, floor type and air temperature on NH3 and CH4 emissions is statistically analysed using the wide range of data provided by various studies. A number of overviews of NH3 and CH4 emission data differentiated according to dairy housing system and season exhibit wide ranges of emission data both between and within individual studies. Although differences in both farm conditions (e.g. herd size, breed, animal productivity, area ratios, ventilation, feeding strategy, management) and measurement concept (e.g. analytics, methods, measurement duration, single farm vs. several farms) make data comparison difficult, clear effects on NH3 and CH4 emissions can be demonstrated. The NH3 emissions of tied housing are lower than those of loose housing systems with cubicles (p = 0.001). Furthermore, within the 'loose housing system with cubicles' category, air temperature influences both NH3 (p < 0.001) and CH4 (p < 0.001) emissions. As the air temperature rises, so do the emissions. This also leads to a close positive correlation between NH3 and CH4 emissions (r = 0.80). There are no differences for either NH3 or CH4 emissions (p = 0.76 and p = 0.49, respectively) between the 'perforated' and 'solid' floor types in loose housing systems with cubicles. (C) 2019 The Authors. Published by Elsevier Ltd on behalf of IAgrE.