The use of humic acids in ruminants makes sense in that it promotes rumen microbial growth as it does in the soil. Thus, increasing rumen microbial population which is conducive for nutrient digestion.
Liquid humate extracts, primarily humic acid, have been assessed in several USA beef cattle and dairy trials. Through these well-conducted trials, varying levels of humic acid were fed, observing enhanced weight gain and decrease in feed dry matter conversion (i.e. lbs dry feed/weight lbs gain).
In one recent United Kingdom trial, lactating dairy cows fed humic acid were observed to have significant improvement in milk production and percenateg milk protein.
In another United Kingdom trial with piglets fed humic acid at 3 different levels, significant improvement in growth and decrease in scours through the feeding period were observed. Pigs are monogastrics and not dependent on rumen microbial activity. The interesting item is the humic acid molecule may have acted to promote beneficial intestinal microbes, thereby reducing scours and piglet morbidity and mortality.