Ruminal flora studies in the sheep. IX. The effect of pH on the ciliate population of the rumen in vivo

Abstract

Daily infusion of 7, 35, and 70 g of glucose m solution (1, 5, and 10 per cent. of the ration) into the rumen of Merino sheep maintained on an adequate diet resulted in the ruminal pH falling 2–4 hr after feeding, from a mean of 5.66 without added glucose to 5.40 at the higher glucose levels. The concentration of ammonia also decreased, whereas that of volatile fatty acids increased. At the 10 per cent. glucose level, food intake was depressed and the ruminal pH in this treatment did not fall below that at the 5 per cent. glucose level. A significant daily fall in the ruminal pH minima was found during the 3-day sampling period. No consistently significant differences in the concentration of ciliate Protozoa were found at four different sites in the rumen, either before or 1 hr after feeding, although there were significant differences between sheep. Samples taken from the bottom of the rumen immediately inferior to the ruminal cannula, before feeding and 1, 2, 4, 6, 8, 12, and 16 hr after feeding, showed: (a) Only oligotrichs in the ciliate population; (b) Marked diurnal fluctuation in the ciliate population, the concentration after feeding falling to as low as one-third of the prefeeding levels; (c) A diurnal cycle for dividing Protozoa which indicated that their capacity to multiply was strongly inhibited by the low pH experienced 2–4 hr after feeding. A depression of the average ciliate concentration daily during the 3-day sampling period was also demonstrated. This was related to a consistent but inexplicable fall in the daily ruminal pH minima over this period. It was concluded that the minimum pH within the rumen is an important factor controlling rumen protozoal concentrations in the sheep, and the need for cognizance of this phenomenon in studies of rumen Protozoa is stressed.

Digestion of a dehydrated lucerne/barley diet (70:30) in defaunated, Isotricha-monoinoculated and mixed-fauna-inoculated rumen in sheep

“…It is generally accepted that highly acidic pH values in the rumen can inhibit the growth of ciliates (Purser and Moir, 1959) and may even cause their complete elimination (Eadie et al, 1970;Whitelaw et al, 1972;Rung et al, 1986). The decline in the number of entodiniomorphid ciliates noted here during the 3 h following the meal in the rumen juice was always observed in the numerous experiments we carried out.…”

Influência do hospedeiro no perfil populacional e nas populações de ciliados do rúmen de bovinos

“…A distribuição dos gêneros e respectivas concentrações observadas, possivelmente relacionam-se aos valores do pH, tendo sido os mais baixos registrados em A3, que foi o hospedei ro que apresentou as menores concentrações e a menor diversidade de ciliados. Estas considerações concordam com o observado por PURSER & MOIR (1959) quanto à inibição da reprodução de ciliados do rúmen nos períodos diurnos de pH mais baixo. Tanto a instalação quanto a manutenção das populações de ciliados do rúmen parecem estar relacionadas ao pH, conforme já relatado por PURSER & MOI R (1966), EADIE (J 962a), NOGUEIRA FILHO et aI.…”

The Macropodid Oesophagus IV. Observations on the Protozoan Fauna of the Macropodid Stomach and Oesophagus

“…5 X 10 4 -15 X 10 4 per gram of macropodine stomach content with the highest counts always recorded from the proximal stomach compartment with numbers decreasing progressively along the middle stomach compartment. It is known from ruminant studies that holotrich ciliates are sensitive to acidity (Purser and Moir 1959;Hungate 1966), proliferating in neutral to slightly alkaline environments (pH 7· 5-8· 5) suitably enriched by the presence of freshly ingested food containing soluble carbohydrates (Hungate 1966).…”