If you want to increase your frustration level, try searching for research on the impact of atmospheric ammonia on dairy calves.
Much of the published work refers back to standards set for occupational exposure limits for humans. That is, 25 parts per million (ppm) for an eight-hour exposure and 35 ppm for a short-term exposure over 15 minutes. Several articles mentioned threshold values for livestock of 15 ppm but without any supporting references.
Of some promise is a recent article "Impact of atmospheric ammonia on livestock animals - a minireveiw" that, unfortunately for me, was published only in German in March, 2013. I can only hope for a translation in the near future. Maybe this work by J. Seedorf of the Institute of Animal Hygiene and Animal Welfare, School of Veterinary Medicine in Hanover, Germany will propose health-related thresholds.
But we can draw from the guidelines of our European colleagues. Documented atmospheric ammonia levels found in calf facilities is available for selected European countries:
Calves on straw bedding: ppm
Country Mean Maximum
England 0.4 3.2
Denmark 1.9 5.7
Germany 1.9 8.3
Calves on slatted floor, group housing: ppm
Country Mean Maximum
Netherlands 7.7 13.7
Germany 5.1 8.5
Using a toxic-gas detector tool (Matheson-Kitagawa Model 8014-400B), I have been trying to measure ammonia gas levels in calf facilities for the past six years. I have been using a baby pig standard of 5 ppm as a desirable threshold.
When I find levels much above 10 ppm at calf-nose level in pens and barns I seem to pretty consistently find persistently high pneumonia treatment levels. At 20 and 25 ppm nearly all the calves are being treated for respiratory symptoms.
For right now it seems like the advice "ventilate, ventilate, ventilate" is the workable alternative for maintaining a low ammonia exposure level. Of course, there are other factors involved in respiratory health issues.
I have noticed in a few barns that converted from individual pens with calves fed six quarts of milk a day, to group pens fed either ad libitum acidified milk or automatic feeder at 10+ quarts daily, that a good deal more bedding has been needed to keep down ammonia levels. I guess it is to be expected that if more liquid goes into the calves more urine is going to come out as well.
To read more of Dr. Sam Leadley’s calf-focused blog, visit www.dairycalfcare.blogspot.com.