Forage kochia (Bassia prostrata L.) has been used extensively by grazing animals in Central Asia. Forage kochia was introduced into the U.S.A. in 1966 from a Stavropol Botanical Gardens (USSR) planting, and released as a cultivar (Immigrant) in 1984. It has been included in fire and rangeland rehabilitation seed mixes and planted on at least 200,000-400,000 ha in the USA. However, in central Nevada (USA), it has been linked to cattle mortality by frothy bloat (primary ruminal tympany) under specific ecological site conditions. In order to assess its potential to cause frothy bloat in free roaming cattle, we investigated the nutritive value of forage kochia across a grazing season (September-January), and compared in vitro gas production, and foam production and strength with fresh alfalfa. Crude protein values were highest in October-November (23.3 and 21.5%, respectively), while NDF was lowest during the same period (38.8 and 39.3%, respectively). Gas and foam production were higher for alfalfa than kochia over a 12 h incubation period. In general, alfalfa produced twice as much gas and foam as forage kochia (P<0.001). However, forage kochia foam strength (g/DM) was double that of alfalfa (P<0.002), and by 6 h incubation time, foam height of forage kochia was twice that of alfalfa (P<0.001). Forage kochia when used as the sole forage in the diet has the potential to cause frothy bloat in cattle. Fresh alfalfa produces more gas in the rumen; however, foam from forage kochia digestion is likely to be more persistent, potentially leading to frothy bloat development.
