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...

Holstein bull calves (n = 51) weaned at 6 wk of age were used in four N balance trials for 4 wk (Trials 1 to 3) or for 2 wk (Trial 4) from 8 wk of age to identify limiting amino acids for a corn and soybean meal diet. The calves were trained to maintain reflex closure of the reticular groove throughout the trials. In Trial 1, administration of .111 g of DL-methionine plus .333 g of L-lysine monohydrochloride/kg BW through the reticular groove increased N retention compared with the control that received isonitrogenous L-glutamine, but administration of .333 g L-lysine monohydrochloride/kg BW alone did not increase N retention in Trial 2. In Trial 3, administration of .111 g of DL-methionine/kg BW improved N balance compared with the control, although the improvement was not detected when DL-methionine was restricted to .022 g/kg BW. In Trial 4, administration of the mixture of .111 g of DL-methionine, .333 g of L-lysine monohydrochloride, and .055 g of L-tryptophan/kg BW increased N retention in calves compared with calves that received an isonitrogenous mixture of .111 g of DL-methionine and .274 g of L-glutamine/kg BW, or .111 g of DL-methionine, .055 g of L-tryptophan, and .234 g of L-glutamine/kg BW. The present results suggest that methionine was the first-limiting and that lysine was probably the second-limiting amino acid for the corn and soybean meal diet in weaned calves less than 11 wk of age, although tryptophan may be either co-limiting with lysine or third-limiting.

Three experiments were conducted to examine the changes of N utilization after early weaning in calves. In Exp. 1, eight male Holstein calves were weaned at 5 wk of age and N balance was determined on the 1st, 6th, 11th, and 19th wk after weaning. In Exp. 2, to examine the effect of weaning age on N utilization, three calves were weaned at 5 wk of age and the other three at 11 wk of age. The N balance of both groups was determined on the same weeks of age (i.e., the 1st, 6th, 8th, and 11th wk after weaning in the earlier-weaned group). In Exp. 3, to examine the effect of a higher content of CP (17.9%) and TDN (75%) in concentrate on N utilization, three calves were weaned at 6 wk of age and the N balance was determined on the 1st, 5th, 10th, and 20th wk after weaning. The intake of concentrate was low in wk 1 but rapidly increased in the next 5 wk (1.74 and 1.72 times in Exp. 1 and 2, respectively). Nevertheless, the TDN intake tended to be lower in calves weaned early just after weaning compared with that in suckling calves in Exp. 2. The apparent N digestibility steadily increased with age and reached a plateau on wk 11 and 6 after weaning in Exp. 1 and 2, respectively. Conversely, the ratio of N retained:N absorbed tended to be high up to wk 6 after weaning and thereafter decreased, leading to a transient high N retained:N intake ratio on wk 6 after weaning.(ABSTRACT TRUNCATED AT 250 WORDS)

Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats.