Ammonia emissions from the manure of heifers fed a high-concentrate diet were no different than those released from the manure of heifers fed a low-concentrate diet. Researchers at Penn State University arrived at this conclusion after examining the effect of different forage-to-concentrate ratios on ammonia emissions from heifers fed corn silage as the only forage source. Study results were reported in the November 2008 Journal of Dairy Science.

 In the first of three experiments, the researchers fed heifers either a low-concentrate diet (77 percent corn silage, 23 percent concentrate) or a high-concentrate diet (33 percent corn silage, 67 percent concentrate.) Both diets resulted in a similar amount of ammonia volatilization from manure that accumulated on the barn floor.

In the second experiment, there also was no difference in ammonia emissions from the manure of heifers fed a high-concentrate diet and those fed a low-concentrate diet.

However, in both experiments, there was a tendency for the high-concentrate diets to yield less ammonia volatilization. One possible explanation for this is the lower dry matter intake of the heifers fed the high-concentrate diet and subsequent reduction in manure output, explain the Penn State authors.

During a third digestibility study, the researchers added yeast culture to a high-concentrate or low-concentrate heifer diet. Ammonia emissions were greater per unit of manure for the high-concentrate heifers fed yeast culture. However, total daily ammonia emissions were no different between the two diets.