Stratifications and Kinetic Changes in the Ingesta of the Bovine Rumen

Abstract

Samples of ingesta from the top and bottom of the rumen of three 2-year-old fistulated steers were taken at hourly intervals over a 12-hour period that included 2 feedings. The samples were analyzed for crude fiber, ash, ether extract, total nitrogen, ammonia, nonprotein nitrogen, water-soluble sugars, alcohol-soluble sugars, volatile fatty acids, and the digestion of cellulose in vitro. In all instances except alcohol-soluble sugars, significant or highly significant differences were observed between the top and bottom samples. Concentrations of all factors measured except ether-extract and the amount of cellulose digestion in vitro were significantly higher in top samples. These data together with the significant time fluctuations indicate that hay and grain particles follow distinctly different physical pathways in traversing the rumen. In a control experiment, duplicate samples were taken from both the top and the bottom of the rumen of a normal (unfistulated) mature Holstein cow by rumenotomy 3 hours after the morning feeding. These data show the same stratification as that seen in the samples from the steers. In additional analyses, pH and titratable alkalinity to pH 5.0 were significantly higher in bottom than in top samples. Observation of stratification in the rumen of the normal mature cow is evidence that the phenomenon is not an artifact resulting from fistulation.