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Developmental changes of the gastrointestinal tract were probably responsible for the changes in faecal composition during the first week of the foals' life, which resembled small intestinal ingesta of adult horses, suggesting a minimal colonic modification. Faecal composition at the time of foal heat diarrhoea was suggestive of a secretory-type diarrhoea, in that the electrolyte concentration accounted for most of faecal osmolality and the faecal pH was alkaline. After foal heat diarrhoea faecal composition slowly approached that of adult horses. These data suggest that foal heat diarrhoea is most likely caused by hypersecretion in the small intestinal mucosa, which may overwhelm an immature colon that is unable to compensate by increased fluid and electrolyte absorption.

Neonatal piglets were anesthetized, and two jejunal loops, 20 cm in length, were prepared. Then, either water or 0.12, 0.25, 0.5 or 1.0 mg/kg of lidamidine-HCl was injected intraduodenally on a randomized basis, one treatment per pig. Following this, a crude heat-stable enterotoxin (ST) preparation produced from E. coli no. 1261 was injected into the proximal jejunal loop, and trypticase soy broth (TSB) (with osmolality adjusted to equal the enterotoxin preparation) was injected into the distal jejunal loop. Piglets remained anesthetized for 3 h and were then killed. Fluid was collected from the loops for measurement of volume and Na, K and Cl concentration. Empty loop lengths were measured. There was a significant dose-related reduction of volume and Cl content, and a dose-related, but not significant, reduction in Na content in St-treated loops. A comparison of the mean differences in responses between toxin- and TSB-treated loops indicated that the major 'counter-toxic' effect of the lidamidine was a dose-related increase in water and electrolyte absorption.

The phloroglucinol microassay technique for measuring plasma concentrations of xylose was compared with the more tedious orcinolferric chloride technique. Sequential blood samples were collected from 5 dogs and 6 horses every 30 minutes after oral administration of 0.5 g of D-xylose/kg of body weight. Comparison of the results by regression analysis shows a highly significant (P less than 0.01) positive linear correlation for both dogs (r = 0.95) and horses (r = 0.77). These results indicate that xylose in canine and equine plasma can be accurately measured by the phloroglucinol technique.

Five 5 to 6 month old horses were surgically prepared with silver electrodes sutured to the serosa of gastric antrum, duodenum and proximal portions of the jejunum. Normal migrating motility complex (MMC) periodicity was determined during daytime hours in horses that were fed and horses from which food was withheld for 24 hours. Periodicity was defined as time span from the end of one period of regular spike activity (RSA) to the end of the next RSA in the MMC. The periodicity was 120.5 +/- 9.5 (SEM) minutes in horses from which food was withheld, and was 125.7 +/- 20.3 minutes in horses fed hay free choice. Coincident with each duodenal RSA, antral spike activity ceased. Xylazine (0.25 and 0.5 mg/kg), given IV during the period of intermittent spike activity of the MMC to either fed or unfed horses induced, within 2 minutes, a RSA complex in the duodenum that migrated to the proximal portion of the jejunum. This was followed by a period of no spike activity of normal duration, which proceeded on to a period of intermittent spike activity of varying duration to complete the MMC cycle. Pretreatment IV administration of an alpha 2-adrenergic antagonist, tolazoline (1 mg/kg) also provoked a RSA complex, but blocked the xylazine effect. The results indicated that xylazine resets the duodenal MMC in the horse, but does not seriously disrupt proximal gastrointestinal tract motility, and that control of MMC periodicity in this region probably involves more than alpha 2-adrenergic receptors.

Six healthy six to eight-month-old horses were surgically prepared with Ag bipolar electrodes sutured to the gastric antrum and duodenum. Leads from the electrodes were exteriorised through a stab incision in the flank. During experimental sessions the horses were lightly restrained in stocks and electrode leads were connected to a physiograph to record antroduodenal myoelectrical activity. Intravenous (i.v.) injection of 0.05 mg/kg bodyweight (bwt) of the opioid agonist/antagonist, butorphanol was followed within 2 to 3 mins by a normal appearing period of repetitive spike activity, or phase III, of the migrating motor complex (MMC) on the duodenum. This was followed by a period of no spike activity, or phase I, of the MMC and then resumption of intermittent spike activity, or phase II, of normal duration. Pre-treatment with 15 micrograms/kg bwt of the non-selective opioid antagonist, naloxone, or with 1 mg/kg bwt of the alpha 2-adrenergic antagonist, tolazoline, did not block the myoelectrical response to butorphanol. It was concluded that a dose of butorphanol that has effective analgesic effects in a colicky horse resets the antroduodenal MMC without causing undesirable effects on antroduodenal motility. This particular effect of butorphanol might not be mediated by either a2-adrenergic or opioid receptors, although the latter question needs further investigation.

Serum concentrations and the pharmacokinetics of chloramphenicol were determined in 6 healthy mares after a single IV administration (50 mg/kg of body weight) or after the 1st and 5th sequential intragastric (IG) administration (50 mg/kg/6 hours) of chloramphenicol. Synovial fluid, peritoneal fluid, CSF, and urinary concentrations of chloramphenicol after the IG administrations also were determined. Mean (+/- SEM) overall elimination rate constant (K) values for the IV, 1st IG, and 5th IG dosages were 0.42 +/- 0.064/hr, 0.42 +/- 0.049/hr, and 0.29 +/- 0.074/hr, respectively, and were not significantly different from one another (P greater than 0.05). Bioavailability was 40 +/- 8.6% after the 1st IG administration and was 21 +/- 5.2% after the 5th IG administration. Values for the area under the curve (AUC) for the 1st and 5th IG dosages were significantly different from the AUC value for the IV dosage, and the AUC value for the 5th IG dosage was significantly different from that for the 1st IG dosage. Chloramphenicol was administered to 2 mares in 6 consecutive doses; the first and last doses were given IV and the others were given IG. Mean K values after the 2 IV doses were 0.38 +/- 0.112/hr and 0.56 +/- 0.078/hr, which were not significantly different from each other or from the mean value for the IV dosage given to all 6 mares. Absorption of chloramphenicol decreased with repeated IG administrations, resulting in lower concentrations of chloramphenicol with subsequent administrations. Five consecutive IG doses of chloramphenicol were administered to 4 of the mares in a separate experiment and did not alter intestinal xylose absorption.

This study examines effects of variations in fiber content on nutrient assimilation, fecal output, and gastrointestinal transit time in the dog. Four normal Beagles were fed four diets in a randomized block design. The basal diet was a canned, balanced, meat-based dog food (Alpo Trio) to which added 3, 6, and 9% by weight of alpha cellulose (Solka Flok). Food intake and fecal outputs were recorded for 5-day periods. Samples of diets and fecal collections were analyzed for dry matter, nitrogen, fat, carbohydrate and ash; digestibilities were calculated. Transit times were measured by a radiographic marker technique. Fecal weight and water increased linearly; digestibility of dry matter decreased from 90 to 70% and ash from 43 to 32% with added fiber. Responses of protein, carbohydrate and fat were less pronounced but were regular; regressions of their digestibilities on added fiber were significant. Regression estimate of true digestibility for alpha-cellulose was 6%. Intestinal transit time decreased from a mean of 37.4 to 28.7 hours with added fiber. Decreased intestinal time would contribute to depression of fry matter digestibility. Increased fecal water output probably also reflected retention by fiber.

Fat balance studies and quantitative analysis of fecal trypsin were done on 2 groups of Beagles fed either a meat-base (8.8% fat) or a cereal-base (10.5% fat) diet. In the amount fed, the meat-base diet provided 2.5 to 3 times more fat than the cereal-base diet, yet the mean daily fecal fat output of the 2 groups was not significantly different. Thus the percentage assimilation of fat in cereal-base diet (90.0%) was significantly (P less than 0.01) lower than that in the meat-base diet (96.9%). Dietary composition made no significant difference in fecal trypsin output, although the mean output from dogs fed the meat-base diet 4 times higher than that from dogs fed the cereal-base diet.

Quantitative fat and trypsin analysis was done on the feces of dogs with chronic diarrhea. The results of clinical examination, quantitative fecal analysis, and other laboratory tests permitted assignment of the dogs into one of 4 groups: (1)pancreatic exocrine insufficiency,(2)small intestinal malabsorption,(3)colitis, and(4)other nonspecific or incompletely diagnosed diarrhea. The mean 24-hour fat output was significantly higher (p less than 0.01) in dogs with malabsorption or pancreatic insufficiency than in clinically normal dogs, dogs with colitis, or dogs with nonsteatorrheic diarrheas. The mean 24-hour trypsin output with pancreatic insufficiency was significantly (P less than 0.01) lower, and in dogs with malabsorption, significantly (P less than 0.05) higher than in clinically normal dogs. Normalization of the output data for body weight enhanced the value of fat and trypsin analyses in the differentiation of pancreatic insufficiency and intestinal malabsorption from other causes of chronic canine diarrhea.

Three adult sheep were prepared with a denervated pouch of fundus of the abomasum and a reentrant fistula system that connected the remaining proximal and distal portions of the abomasum. The proximal cannula of the reentrant system was close to the omasoabomasal orifice, allowing for easy collection of fluid leaving the omasum. Intravenous injection of 0.5, 1.0, or 2.0 microgram/kg/hr of synthetic human gastrin I caused a marked decrease in flow rate of fluid from the omasum. The concentration of particulate matter in the digesta was inversely related to rate of omasal outflow. An increase in acid output from the denervated abomasal pouch during gastrin injection indicated that the hormone was given at pharmacologically effective doses. Results indicate that gastrin has a modulating effect on the flow of ingesta through the ruminant forestomachs. Actual sites of action were not identified.

A base-line study of bacteria isolated from horses admitted to the Veterinary Medical Teaching Hospital during a 6-month period was performed to determine the extent of multiresistant nosocomial infections caused by gram-negative aerobic bacteria other than Salmonella spp. Results of this study indicated that 21.9% of the 105 horses from which cultures and sensitivities were available had developed nosocomial gram-negative aerobic infections, with high rates of resistance to gentamicin, kanamycin, and trimethoprim sulfadiazine, three of the most often prescribed antibiotics in this hospital. In addition, a prospective study of antibiotic-resistant bacteria of fecal origin was performed to determine whether there was a change in the degree of antibiotic resistance of a horse's intestinal flora while the horse was hospitalized. Bacterial culturing for gram-negative lactose fermenting bacteria was done on fecal specimens collected directly from the rectum on day 1 and day 7 of a horse's hospitalization. Susceptibility testing was done on each isolant. Of the 24 paired fecal specimens obtained, Escherichia coli and Klebsiella sp isolated on day 7 were resistant to a significantly higher number of antibiotics than day 1 isolants (P = 0.003, P = 0.043, respectively).

Five weanling ponies were subjected to an intensive 6-week deworming program after which 4 Ag-AgCl bipolar electrodes were implanted surgically on the distal ileum. For 3 hours each day for 5 consecutive days, ileal myoelectrical activity was recorded from fed ponies under 3 sequential conditions: preinoculation, after oral administration of 1,000 killed Strongylus vulgaris infective larvae (3 ponies), and after oral administration of 1,000 live S vulgaris infective larvae. Recordings were analyzed for slow wave frequency, percentage duration of phases I, II, and III of the migrating myoelectrical complex (MMC), and the frequency of distinct, rapidly migrating action-potential complexes within phase 2 of the MMC. After administration of live and killed infected 3rd-stage larvae, there was a marked increase in the number of disrupted phase III complexes, and a significant (P less than 0.001) increase in the number of migrating action-potential complexes. In addition, after inoculation of live 3rd-stage larvae, there was a significant increase (P less than 0.001) in the percentage of time that the MMC was occupied by prolonged periods devoid of spike activity (phase I). The results indicate that S vulgaris larval mucosal penetration and submucosal migration can cause changes in ileal myoelectrical activity that could cause colic, and that larval antigen alone within the lumen may disrupt ileal motility.