Kinetics of large ciliate protozoa in the rumen of cattle given sugar cane diets.

1. Experiments were undertaken to examine the kinetics of large ciliate protozoa in the rumen of cattle on sugar-cane diets. 2. Three Zebu bulls were fed once daily on a diet of sugar cane and wheat bran. The diurnal patterns of volatile fatty acids and ammonia concentrations, and the numbers of protozoa in rumen fluid were determined. The numbers of protozoa reached values of 5 X 10(4)/ml for holotrichs (large ciliates) mainly Isotricha and Dasytricha spp and 4 X 10(5) for smaller protozoa, mainly Entodinia (small ciliates). 3. A method was developed which allowed large ciliate protozoa in rumen fluid to be separated from plant material and bacteria and concentrated in a relatively uncontaminated form. Analysis of these protozoa indicated that 1.8 X 10(5) large ciliates contained 1 mg nitrogen and approximately 32 mg dry matter. 4. A labelled preparation consisting mainly of large ciliates (principally Isotricha spp.) was obtained by incubating isolated protozoa in rumen fluid (free of plant materials) containing [14C-methyl]choline and then isolating them by sedimentation and differential centrifugation. 5. A portion of the preparation containing labelled protozoa was incubated in vitro with rumen fluid to determine the turnover of 14C-labelled metabolites. There was no apparent dilution of the label in the protozoa over a 22 h period. 6. A major portion of the preparation containing labelled protozoa was returned to the rumen of each of the donor cattle as a single injection. The specific radioactivity in the large protozoa (microCi/mg N) was monitored frequently for over 30 h, and thereafter daily for a further 12 d. The kinetics of tracer dilution were analyzed to give estimates of the size of the pool of these large ciliates in the rumen (24-46 g N), and of their apparent rate of turnover. 7. In contrast to the slow turnover of the large ciliates, the rate of turnover of the rumen fluid pool (approximately 54 1), estimated from the rate of dilution of polyethylene glycol, was considerably faster. Large ciliates were therefore selectively retained within the rumen.

Protein nutrition of growing lambs. 2. Effect on nitrogen digestion of supplementing a low-protein-cellulosic diet with either urea, casein or formaldehyde-treated casein.

1. Lambs with cannulas in the duodenum and ileum were allowed free access to one of four diets: a basal diet of oat hulls and solka floc, or the basel diet supplemented with either urea, urea plus casein or urea plus formaldehyde-treated (HCHO)-casein. Mean nitrogen intake was 1.9 g N/d for the basal diet and 15.0. 32.4 and 36.9 g N/d respectively for the other diets. 2. The rate of irreversible loss of ammonia from the rumen pool estimated using 15NH4+ was highest on the casein diet (33 g NH3-N/d) by comparison with 18 g NH3-N/d for the urea and HCHO-casein diets and 7 g NH3-N/d for the basal diet. 3. The proportions of bacterial and protozoal N in the rumen derived from rumen ammonia did not differ significantly between the supplemented diets and were 0.66 and 0.52 respectively. 4. Estimation of 15N flowing to the duodenum during continuous infusions of 15NH4+ into the rumen indicated considerable ammonia absorption from the rumen on all the diets. Greatest absorption of ammonia (21 gN/d) apparently occurred in animals on the diet supplemented with urea and casein. 5. The estimated microbial non-ammonia-N (NAN) flowing out of the rumen per unit organic matter fermented in the rumen (FOM) was similar on all diets, i.e. 21.3 (+/- 1.09) g N/kg Fom. the requirement for dietary fermentable N for microbial N production on these diets was 1.2 (+/- 0.07) g N/MJ ME. 6. The flow of NAN into the duodenum and through the ileum, and total N in the faeces was significantly influenced by the form of N supplementation. The flow of NAN into the duodenum for the HCHO-casein diet (27 g N/d) was more than twice that for the other diets (11 g N/d). The flow of NAN through the ileum and excretion of total N in the faeces was also greater with the HCHO-casein diet than with all other diets. The apparent digestibility of NAN in the small intestine ranged between 0.62--0.66 for all diets. 7. Urea and casein supplements were apparently completely degraded in the rumen. In contrast, the HCHO-casein was almost completely resistant to degradation in the rumen and only 65% of the HCHO-casein was digested in the small intestine. 8. Protein absorbed : energy absorbed (expressed as NAN digested in the small intestine/MJ ME) was calculated to be 5.5 (+/- 0.70) for the basal, urea and urea-plus-casein diets, and 11.6 (+/- 1.71) for the urea-plus-HCHO-casein diet.

Methane production and digestibility measurements in the grey kangaroo and sheep.

Three grey knagaroos and three sheep were given a diet of lucerne chaff and measurements were made of feed intake, digestibility coefficients, methane production rate and volatile fatty acid content of the "stomach" and caecum for each animal. The kangaroos had lower intakes of digestible dry matter and organic matter than the sheep; this was related to lower intakes of dry matter and lower apparent digestibility coefficients particularly of the crude fibre fraction. Methane production in the sheep (collected in respired air through a mask) was 0-81 litre/h; no methane was collected in the respired air from kangaroos. Anal release of methane in sheep and kangaroos indicated that some methane was produced in the hind gut of kangaroos and that all of this methane was lost via the anus. This finding was different to the sheep which apparently excreted 80-90% of the hind gut methane via the lungs. Thus in both sites of apparent high microbial growth in the gut of kangaroos methane production is negligible or lower than in the same sites in sheep. Possible explanations for the absence of measurable methane production in the kangaroo fore-stomachs are discussed.