Effects of protozoa on bacterial nitrogen recycling in the rumen.

Abstract

The effects of protozoa on ruminal NH3-N kinetics and bacterial N recycling were measured in five sheep (57.6+/-7.1 kg BW, x +/- SD) with ruminal and duodenal cannulas in naturally faunated, defaunated, and refaunated periods. The sheep were fed a diet of 239 g of alfalfa haylage and 814 g of barley concentrate per day (DM basis) divided into 12 equal portions and allocated at 2-h intervals. A pulse dose of 300 mg of 15N as [15N]NH4Cl was administered into the rumen (on d 1 and 15) and 300 mg of 15N as [15N]urea was administered intravenously to the blood (d 8). Enrichment of 15N was measured in ruminal NH3-N, bacterial N, and plasma urea N over a period of 35 h. Total collection of urine was made for 5 d and analyzed for purine derivatives to calculate the flow of microbial N. Ruminal parameters and nutrient digestibilities were also measured. Sheep were defaunated using a rumen washing procedure 50 d prior to measurements in the defaunated period. Sheep were refaunated with ruminal contents from a faunated sheep receiving the same diet. Measurements began 26 d following refaunation, at which time protozoal numbers had returned to those in the originally faunated sheep. Data reported in parentheses are for faunated, defaunated, and refaunated sheep, respectively. Total culturable and cellulolytic bacterial numbers were unaffected by defaunation, but there was an increase in flow of microbial N from the rumen (10.8, 17.3, and 11.1 g N/d; P < .05) in the defaunated period. Flux, irreversible loss, and intraruminal recycling of NH3-N and recycling of NH3-N from plasma urea N were not affected by defaunation. Defaunation had no effect on reducing the absolute amount (13.8, 10.0, and 11.3 g N/d; P > .20) of bacterial N recycling and the percentage of N flux through the bacterial N pool. Total-tract digestion was reduced in defaunated compared with faunated sheep by 8, 17, 15, and 32% for OM, N, NDF, and ADF, respectively. In conclusion, defaunation improved ruminal N metabolism through the enhancement of bacterial protein synthesis, and improvement in the flow of microbial protein to the host animal.

Mitigation strategies to reduce enteric methane emissions from dairy cows: Update review

“…The reduced ruminal methanogenesis observed with defaunation can be attributed to factors such as a shift of digestion from the rumen to the hind gut or the loss of methanogens associated with protozoa during defaunation (Hegarty 1999 (Itabashi 2001). On the other hand, protozoa have been reported to negatively affect ruminal protein metabolism through predation of bacteria, which reduces the flow of microbial protein leaving the rumen (Ivan et al 2000;Koenig al. 2000).…”

Comparison of effects of Isotricha monofauna and total mixed fauna on dietary copper metabolism in lambs

“…Also, in comparison with FF sheep, ruminal Cu solubility was decreased by a much smaller percentage (41) in the present experiment than would be expected from the magnitude of a possible increase (300%; Ivan et al 2000b) in feed protein utilization and released S due to TF. This difference could be due to higher bacterial turnover and microbial protein recycling in the rumen of sheep with TF as compared with FF sheep (Demeyer and Van Nevel 1979;Koenig et al 2000). The higher bacterial turnover would result in increased microbial utilization of available S for microbial synthesis of protein.…”

Change in body condition of Gobra zebu cattle under different level of feeding. Relationship with body lipids and energy

“…As shown in Figure 4, the changes in plasma allantoin levels for the three lambs during 30 h after inoculation was low at one hour reaching peak levels at 6 h after inoculation and gradually decreasing thereafter. The above findings show that an effect of protozoa on plasma allantoin level is not clear, however, it should be that plasma allantoin level is closely related to metabolism of nucleic acid in the rumen and/or lower gut caused by the changes of microbial population in the rumen as protozoa feed by engulfing bacteria (Koenig et al, 2000). Figure 5 shows the changes in urinary PD excretion throughout the experimental period.…”

“…Several methods are used to estimate the microbial protein synthesized in the rumen. They include, microbial markers (2,4 diaminopimelic acid: DAPA and purine bases) (Hutton et al, 1971;Zinn and Owens, 1986), the tracer method using isotopic substance such as 15 N (Koenig et al, 2000), 32 P and 35 S (Stern and Hoover, 1979) and more recently, the indicator method based the use of urinary purine derivatives (PD) (Fujihara et al, 1987;Chen et al, 1990). Nucleic acids from ingested feed are generally completely degraded in the rumen.…”