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.

I . Effects of feeding liquid milk-substitute to young calves either by nipple-pail or open-bucket o n the rumen by-pass and on the rate of passage were studied.z. Sixteen Holstein calves, aged I week initially, were used in three experiments in which calves were slaughtered after they were given liquids (milk-substituteand water) containingchromic oxide and SrCI, .6H,O as a tracer either by the nipple-or bucket-feeding method, and the distribution of tracers to the rumen, abomasum and the lower alimentary tracts was examined.3. When the liquid milk-substitute containing tracers was given by the nipple-or bucket-feeding method to calves having been trained to the corresponding procedures for the preceding I week, most of the tracers was directed into the omasum and abomasum. There seemed no difference in the functioning of oesophageal groove closure between the two feeding procedures. Even when the liquid milk-substitute containing tracers was given by the nipple-or bucket-feeding method to calves which had been accustomed to different procedures for the preceding week, the majority of tracers were found in the abomasum immediately after administration, though a slightly greater proportion of the tracers entered the reticulo-rumen.4. Continuing bucket feeding of liquid milk-substitute effected an efficient closure of the oesophageal groove at least up to 16 weeks of age. After calves were accustomed t o consume liquid milk-substitute from the bucket from I to 4 weeks of age, drinking warm water from the bucket also caused efficient closure at least up to 16 weeks of age.5. When tracers were administered with warm water, Cr,O, and strontium, especially the latter, transferred much more rapidly to the lower gut than when they were administered with liquid milk-substitute, probably reflecting the curd formation of the milk-substitute in the abomasum. When liquid milk-substitute with tracers was fed by the bucket-feeding method, Sr transferred more rapidly to the lower gut than when the milk-substitute was fed by the nipple-feeding method, indicating that the feeding procedure of liquid milk-substitute has a n apparent effect on the rate of passage.Milk-substitutes have been used in many intensive farms as the means of reducing cost of rearing calves. Feeding procedures of the liquid milk-substitute are divided into two main classes : the nipple-feeding method and the bucket-feeding method. The nipple-feeding method has been considered to be more adequate for young calves from the physiological aspect than the bucket-feeding method, in view of earlier work which showed that the reflex closure of the oesophageal groove depended on the stimuli associated with sucking milk from a teat (Wise & Anderson, 1939) or on the posture of calves while sucking (Wise et al. 1942). However, the bucket-feeding method has been adopted by large numbers of Japanese farmers because of its simplicity.Subsequently, Hegland et al. (1957) observed a complete closure of the oesophageal groove of calves during 6 weeks after birth, independe...

I . Four feeding trials were made to investigate relations between diet and protozoal population in the rumen.2. When a ration containing no concentrate was used, the number of entodiniomorphs decreased rapidly. The number of entodinioniorphs increased with the amount of concentrate.Rice straw, which was used as a sole source of roughage, was not always necessary for protozoa to survive in the rumen.3. The type of diet affected the holotrich population to a much smaller extent than the entodiniomorph population.During the past two decades there has been a gradual accumulation of information about the factors that influence the number of protozoa in the rumen (Warner, 196;; Hungatc, 1966;Eadie & Mann, 1970). For example, the physical form of ration and the frequency of feeding have generally been accepted to influence protozoal concentrations in the rumen. However, much more detailed work will be needed.The present work describes four experiments designed to investigate the influence of the type and amount of diet on protozoal concentrations in the rumen. E X P ER I IVI ENT A L Feeding trialsThree Holstein cows with permanent rumen fistulas, and weighing approximately 500 kg each, were used in four experiments. Before each experiment, they were given a basal ration (B) and then other rations (1-6) as shown in Table I . They were fed twice daily at 08.00 and 16.00 hours and allowed free access to water.Expt I. Effects of three rations on protozoal population in the rumen were examined. Three cows were used in a 3 x 3 Latin square design as shown in Table I. The three treatment periods were 5 d each. As ration z contained no roughage and was generally poor, each treatment period was followed by 10 d intervals on ration B to restore the condition and appetite of the animals. On the last days of three treatment periods, samples of rumen fluid were collected at 15.30 hours through the fistula by the use of a vacuum pump and a rubber tube.

1. The incidence of diarrhoea, digestibilities of nutrients and the faecal bacterial flora were compared among three groups of Holstein male calves up to 3 weeks of age. Two groups of four calves were given a milk-substitute containing tallow by nipple-pail ( g o u p TN) and by open-bucket (group TB). The third group of four calves was nipple-fed a milk-substitute containing soya-bean oil (group SN). Each of the milk-substitutes contained approximately 300 g milk-protein and 100 g fat/kg dry matter (DM).2. Mean faecal DM contents (g/kg) were 217, 185 and 112 for groups TN, TB and SN respectively and the corresponding pH values were 7.21, 7.00 and 6.50. The difference between groups TN and SN was statistically significant (P < 0.05).3. No difference was observed between groups TN and SN in the apparent digestibilities of DM, crude protein (CP; nitrogen x 6.25). diethyl ether extract (EE) and total reducing sugars. But in the group TB, the digestibility of EE was significantly lower (P < 0.05), and that of CP tended to be, though not significantly, lower than in the other two groups.4. Bacterial flora in faeces showed considerably wide quantitative variations among individual calves, but there was a tendency for increased viable counts of Lacrobacilli in faeces of group SN.5. The present results suggested that an appreciable difference in the mechanism would exist between diarrhoea occurring when milk-substitute was offered by bucket and when highly-unsaturated vegetable oils were contained in it. Possible mechanisms were also discussed.In general the incidence of diarrhoea is higher in calves given a milk-substitute than in those receiving whole milk. The etiology of diarrhoea resulted from feeding a milk-substitute is quite manifold, since many nutritional factors are responsible for it.In Japan milk-substitutes are usually fed by bucket rather than by nipple-pail, because of simplicity. Compared with nipple-feeding, bucket-feeding resulted in faster rates of drinking a liquid milk-subs titute, resulting in a more rapid passage through the abomasum and the lower gut probably due to less efficient coagulation in the abomasum (Abe et al.

1. Nutritional effects of a diet consisted of corn , soybean meal and other common feedstuffs by-passing the rumen of calves were compared with those of the same diet undergoing the rumen fermentation . 2. An equal amount of the diet given daily to two groups of seven Holstein calves each from 7 to 12 weeks of age , eigher in a pelleted form to suffer the rumen fermentation ('dry-fed' group; DFG) or in liquid suspension from a bucket to avoid the rumen fermentation ('liquid-fed' group; LFG) .At 87 days of age, two calves each in one group were sacrificed , and jugular blood samples were taken from the remaining calves. 3. The quantity of ammonia in the rumen was similar in both groups, but that in the large intestine tended to be greater in DFG than in LFG. The quantity of volatile fatty acids (VFA) in the rumen was greater in DFG than in LFG, but their quantity in the large intestine tended to be greater in LFG than in DFG. 4. In DFG, the molar proportion in the VFA of acetic acid was higher, and that propionic and butyric acids was lower in large intestine than in the rumen .In LFG, the molar proportion of acetic acid was higher, and that of butyric and isobutyric acids was lower in the rumen than in large intestine. 5. The plasma glucose was at the same level in both groups. Plasma levels of ketone bodies (P<0.01) and glycogen content in liver (P<0.05) were significantly lower in LFG than in DFG. 6. Plasma levels of triglycerides and phospholipids were significantly higher in LFG (P <0.05).The content of total lipids in liver was significantly higher in LFG than in DFG (P< 0.05). Total lipids in liver of LFG calves had significantly increased lipid fractions of triglycerides, total cholesterol and free fatty acids (P<0.05), and contained larger amounts of highly unsaturated C18 fatty acids. 7. Riboflavin levels in blood and liver were similar in both groups.The rumen plays a very important role in the nutrition and the metabolism of ruminant animals. In our previous report1) , it was described that body-weight gains were much depressed when calves were given a diet consisted of corn, soybean meal and other common feedstuffs in liquid suspension to avoid the rumen fermentation. Apparent digestibilities of crude protein and nitrogen-free extracts were lower when the same diet was introduced into the rumen and suffered the fermentation in it. However, the digestibility of crude fibre was not lowered in calves receiving liquid feed, and these calves had more developed caecum and large intestine as well as less developed rumen and omasum than calves receiving dry feed, predicting some shifts in the