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 StateUniversity 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.) All heifers were fed for the same rate of gain per day. 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 PennState 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 from the manure of the high-concentrate heifers were no different than emissions from the manure of heifers fed the low-concentrate diet. Again, this is largely the result of reduced dry matter intake by the high-concentrate/yeast-culture-fed heifers, notes Jud Heinrichs, dairy scientist at PennState and one of the study authors.

Dietary manipulation can impact the amount and nutrient composition of manure and its resulting ammonia emissions. To learn more about how to formulate diets for less manure, click here.