Examination of the Measurement Condition of Rumen Osmolality of Cattle

Abstract

We examined the effect of the measurement conditions of rumen osmolality in cattle using freezing point methods. Rumen fluid was collected from ruminally cannulated healthy Holstein cattle. When the crystallization temperature of the osmometer was set as －5.6 ℃, the standard for blood plasma, osmolality was not able to be measured in the samples at all. When rumen fluid samples were subjected to supercooling, the samples were coagulated in the range of －3.9 to －5.5 ℃. Therefore, when the crystallization temperature of the osmometer was set as －3.7 ℃, osmolality was able to be measured in all samples. The osmolality of rumen fluid filtered using a double cheesecloth had a high level compared with samples carried out by centrifugation, or filtration with the membrane filter (0.45 or 0.20 μm pore-sized). After it was frozen and then thawed, rumen fluid showed a lower osmolality than samples that had not been frozen.