1. Copper deficiency was induced in five Friesian cattle offered a semi-synthetic diet containing < 1 mg Cu/kg. Changes in blood and liver Cu contents and in the Cu-containing enzymes, ferroxidase I (caeruloplasmin;EC1.16.3.1) and monoamine oxidase (EC1.4.3.4) of plasma and cytochrome oxidase (EC1.9.3.1) of liver and skeletal muscle were monitored during Cu depletion.2. Rapid decreases in blood and liver Cu and plasma ferroxidase I activity were found at least 80 d before the first appearance of overt clinical signs of deficiency. Plasma monoamine oxidase and liver cytochrome oxidase activities decreased less rapidly and thus may provide useful indices of chronic Cu depletion.3. Although results of these assays indicated that Cu depletion was occurring and metabolic defects supervening, none facilitated the early recognition of individuals that subsequently showed marked overt clinical signs of Cu deficiency compared with those less severely affected.4. Irrespective of their clinical appearance at slaughter, Cu-depleted cattle showed gross or microscopic lesions of the skeleton and cardiovascular system and, in some instances, lesions of the ligamentum nuchae and small intestine. The aetiology of these lesions is considered with particular respect to changes in the activities of the Cu-dependent enzymes studied and to the interpretation of field surveys based solely upon determination of blood or liver Cu content.5. A second group of five cattle was offered the same diet supplemented with Cu to provide 8 mg Cu/kg and, later, 15 mg Cu/kg. Although no pathological lesions attributable to Cu deficiency were detected at slaughter a marked reduction in liver Cu content, a decrease in plasma ferroxidase I activity and, in four animals, the development of a diarrhoea controlled by oral administration of Cu, suggested that 8 mg Cu/kg diet did not meet their requirement for Cu.

A technique is described for feeding young sheep for long periods entirely by the infusion of volatile fatty acids into the rumen and protein and other essential nutrients into the abomasum. When the energy infused was twice the estimated requirement for maintenance, growth rate and nitrogen retention were essentially the same as in normally-fed sheep.There are several principles of the nutrition of ruminants which are difficult to study because their diets are fermented to yield volatile fatty acids (VFA). The VFA can vary both in the amounts produced and in composition, and both can vary during a feeding cycle. The rumen micro-organisms produce microbial protein in varying amounts and the dietary protein is degraded by rumen microbes to varying extents (Orskov, 1977). Infusion of VFA at higher levels was attempted by Armstrong & Blaxter (rg57b) and Orskov & Allen (1965) fed increments of salts of VFA with concentrate diets. These latter studies suffer from the disadvantage of possible interference of the VFA, or their salts, with the digestion and metabolism of the basal diet since it was only achieved when the animals were given a basal diet of solid food, and even with that regimen only small additions of VFA or VFA salts were possible. Attempts to sustain long-term infusion of VFA alone have generally been abandoned owing to problems of electrolyte imbalance and acidity of rumen contents. Tao & Asplund (1979, however, have recently sustained lambs at maintenance energy levels for periods of some weeks by infusion of partially-neutralized VFA and buffer solutions into the rumen, and amino acids into the abomasum, but they also reported several problems and deaths due to electrolyte imbalance.The method reported here was developed to sustain ruminants at high feeding levels and maintain normal growth by complete intragastric infusion. EXPERIMENTALThe following is a description of the infusion technique as it was developed after several attempts which failed. Since, however, the blood composition and rumen pH were measured routinely it was possible when an animal showed signs of severe stress or died to make an appropriate change in the procedure. The first attempts failed because VFA alone was infused as a result of which the animal developed, after some days, a severe acidosis. Other attempts failed as a result of partially neutralizing the VFA with sodium hydroxide. Toxic levels of sodium in the blood in excess of 200 mmol/l were observed. It was finally realized that the rumen pH and blood electrolytes could be kept in the normal range provided a 0007-1 145 179 13185-2710 f 01'00

SUMMARY1. The pattern of small intestinal digesta transit was studied in six young pigs (20-30 kg) by simultaneous electromyography and radiology. Pigs showed migrating myoelectric complexes (m.m.c.s) in the small intestine both when fasted and after feeding. The m.m.c.s were modified by feeding; quiescence was much reduced in duration and irregular spiking activity (i.s.a.) was prolonged; m.m.c.s were not disrupted and phases of regular spiking activity (r.s.a.) were still seen after feeding.2. The r.s.a. phase could be recognized on the screen and in spot films from both fasting and fed pigs as a band of intense rhythmic contractions pinching off the intestine and propelling all intestinal contents ahead of it. The r.s.a. moved caudad clearing the small intestine of digesta and leaving an empty quiescent intestine behind it. It was particularly characteristic in the fasted pig where it was usually associated with the progression of a gas bubble. 6. Two patterns of transport into the large intestine were seen. Usually digesta was transported by peristaltic rushes starting 100-200 cm from the ileo-caecal junction. The rush then continued through 1-11 turns of the spiral colon; occasionally the terminal ileum emptied by slow peristalsis. In this case there was no colonic rush and digesta went into the caecum.

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SUMMARYRadiological examinations were carried out on ten sheep to see what changes in intestinal motility and flow of digesta were caused by intestinal cannulation. Barium sulphate was injected or infused into the abomasum via an implanted catheter; its passage through the intestine and associated muscular contractions were observed using X-ray image intensification. Once the normal pattern had been established for each individual, single or re-entrant cannulae were inserted into one of four positions in the small intestine.All the cannulations caused some disruption of the normal flow of digesta, causing retention of digesta and distension of the intestine around and proximal to the intraluminal flanges of the cannulae. The duodenum was affected the most, particularly by one type of re-entrant cannula which reduced the degree of jejunal filling; peristaltic contractions often failed to propagate beyond these cannulae and also caused some retrograde movement of digesta between the cannulation site and the duodenal bulb during the irregular contraction phase (ICP) of the migrating myoelectric complex (MMC). These re-entrant cannulae also impaired the clearing effect of regular contraction phase (RCP).