Physiological disposition of C¹⁴-labeled rumen gases in sheep and goats

Transfer of radioactive carbon from rumen gases to blood, milk, and saliva was studied in sheep and goats following intraruminal insufflation of C 14 O 2 and C 14 H 4 . In four sheep allowed to inspire eructated gas, radioactive carbon was detected in blood from the carotid artery 4–5 sec after the first rumen eructation contraction following C 14 O 2 insufflation. In one sheep and one goat, which were not allowed to inhale eructated gas, there was eventual absorption of radioactive carbon from the digestive tract, but at a much lower level and without the marked fluctuations. In three sheep radioactivity gradually increased in the saliva samples until it was more than double that of blood samples collected simultaneously. In one lactating goat (two experiments) dissolved C 14 O 2 appeared in milk within 3 min following the first eructation and reached maximum values within 15 min. Radioactivity was present in milk solids, primarily in the lactose fraction, 20 min after intraruminal insufflation of C 14 O 2 . In one sheep and two goats radioactivity in blood resulting from C 14 H 4 insufflation was much less than after intraruminal insufflation of C 14 O 2 .