Sequestration of Holotrich Protozoa in the Reticulo-Rumen of Cattle

Abstract

Studies were carried out to determine the means by which holotrich protozoa can maintain their numbers within the rumen against the washout effect associated with the flow of ingesta. When a diet composed of 2 kg of concentrate and 1.5 kg of rice straw was fed to Holstein cows, about a fourfold increase in holotrich numbers per ml of rumen fluid was observed within 1 h after the commencement of feeding, and an abrupt decrease followed. This fluctuation in numbers was not related to the time of feeding. A sole feeding of 2 kg of concentrate had almost the same effect on the holotrichs as a sole feeding of 1.5 kg of rice straw. Administration of either 2 kg of concentrate or 1.5 kg of rice straw through the rumen fistula caused similar changes, though the extent of response to the former was greater than that to the latter. The administration of either 0.7 kg of starch or 0.2 kg of glucose through the fistula had a relatively minor effect on the holotrich population. Addition of rice straw to 0.5 kg of concentrate increased the change in numbers, but its addition had little, if any, effect when 1 kg of concentrate was fed. These results suggested that the fluctuation in holotrich numbers was related not only to the nature or component of feed but also to other factors such as the quantity or volume of a diet and the act of ingesting feed. Increasing the number of feedings up to eight times per day at 3-h intervals caused a decrease in the peak heights of holotrich numbers per milliliter of rumen fluid. A thick protozoal mass which primarily consisted of holotrichs was found on the wall of the reticulum of Holstein steers slaughtered after overnight starvation. These findings suggest that holotrichs would usually sequester on the reticulum wall and migrate into the rumen only for a few hours after feeding, and that this mode of behavior would be essential for holotrichs to maintain their population within the rumen of cattle. Possible mechanisms of the migration are also discussed.

Assessment of Ruminal Bacterial Populations and Protozoal Generation Time in Cows Fed Different Methionine Sources

“…The counts of both entodiniomorphids and isotrichids increased considerably in ruminal fluid of both dorsal and ventral sites after feeding a mixed forage and grain diet (Martin et al, 1999). Therefore, both the high feed intakes and bihourly feeding regimens (Abe et al, 1981;Dehority, 2003) probably enhance protozoal passage (Sniffen and Robinson, 1987) and reduce this potential sampling bias in the current study. Because of their low abundance and subsequently greater likelihood for discrete data (few counts per counting chamber), though, further experiments need to be repeated using animals with greater numbers of isotrichids than in our study to use this procedure to more fully evaluate their outflow.…”

“…Leng et al (1981) suggested that ruminal sampling might not represent the isotrichid populations because of their diurnal migration pattern and sequestration, so ruminal counts might not represent the protozoal populations leaving the rumen. In contrast, continuous feeding (12 times a day) of the diets probably triggered chemotactic migration of isotrichid protozoa from the reticulum toward the soluble sugars in the diet, thus increasing their chances of passing out of the rumen (Sniffen and Robinson, 1987) and probably promoting multiple, attenuated isotrichid counts vs. time curves between each feedings (Abe et al, 1981;Dehority, 2003), greatly reducing the potential error in ruminal counting of isotrichids in the current study.…”

Diurnal variation in ciliate protozoa in the rumen of black buck (Antilope cervicapra) fed green forage

“…However, in black buck, which is also a grazer, both the genera of holotrich protozoa were present. On feeding oat or berseem, the abrupt increase in the population of holotrichs, especially Dasytricha, within the first 2 h might be due to migration, in response to chemical stimuli originating from the diet, of holotrichs from the wall of the reticulum where these protozoa sequester (Clarke 1965;Abe et al 1981;Dehority & Tirabasso 1989;Ankrah et al 1990). Berseem may have stimulated migration more than oa,t, because of the higher cell contents of soluble carbohydrate and protein.…”

Digestive strategies of small hindgut fermenters

“…The rumen has a differential retaining mechanism with high selectivity for large particles (Sutherland 1988). Besides, there may be an advantageous mechanism for protozoa to survive in the reticulo-rumen (Abe et al . 1981).…”