Time In Sheep Research Articles

Relationships between organic-matter digestibility, dry-matter intake and solute mean retention times in sheep given a ground and pelleted diet

SUMMARYThe relationships between organic-matter digestibility (OMD), dry-matter intake (DMI) and the mean retention time (MRT) of unabsorbed solutes in the gastrointestinal tract were examined using six fistulated, cross-bred, castrate male sheep. Measurements were made on each sheep at two different DMIs within the range 28–81 g D.m./(day. kg0·75). There were negative, curvilinear relationships between MRTs (both rumen and total) and DMI and positive, curvilinear relationships between OMD and MRTs. As a consequence, there was a negative, rectilinear relationship between OMD and DMI. OMD declined by 0·022 when DMI increased from calculated maintenance to twice maintenance. The proportion of the total MRT accounted for by rumen MRT did not change significantly; the mean value was 0·364 ( ± S.e. 0·010).

Stability of prothrombin times in sheep dosed with natural and synthetic anticoagulants

Sheep were dosed with natural and synthetic anticoagulants to prolong prothrombin time (PT) in the one stage PT test. The stability of subsequent values of PT of up to 40 seconds was measured at various times over a 24 hour period in plasma and whole blood stored at 0, 20 and 30 degrees C, representing ideal to unsuitable conditions of sample preparation and storage. In contrast to cautions in the literature, the various treatments had little influence on PT. These findings should encourage the use of PT in field diagnosis and research in sheep by surmounting the tenet of the difficulty in effectively preserving blood samples for PT determinations.

Pharmacokinetics of pentobarbital and thiamylal as combined anesthetics in sheep.

This study was performed to investigate the possible mechanisms underlying prolongation of anesthesia times in sheep caused by the sequential administration of thiamylal and pentobarbital. Sodium thiamylal was injected as an intravenous bolus dose (13.2 mg/kg) followed in 7 min by sodium pentobarbital (14.3 mg/kg) by the same route to seven sheep. Separate studies were conducted for each of the two drugs administered separately to the same animals at the same doses. Mean anesthesia times (to the return of the palpebral reflex) were 7.89 min (thiamylal), 5.39 min (pentobarbital) and 34.1 min (the sequential combination). The kinetic parameters Vd(area), Vd(ss), t 1/2 beta, and ClB for either drug were not affected by the other when given in combination. The t 1/2 alpha was shorter, and the Vc was smaller, for pentobarbital when administered with thiamylal, while there were no changes in thiamylal disposition for the combination regimen. Computer-generated curves, associated with the two-compartment open model showing the fraction of dose in each compartment as a function of time, illustrated that pentobarbital rapidly achieved higher concentrations in the peripheral compartment after prior thiamylal administration. Protein-binding studies showed that this could not be attributed to displacement of pentobarbital from plasma albumin by thiamylal. Calculation of total and free drug concentrations at the time of awakening showed that, when the drugs were combined, the concentration of each drug was less than half of that observed at awakening when they were studied separately. It can be concluded that the prolonged sleeping times associated with the sequential combination of the two agents were not due to an alteration in kinetic parameters of either drug caused by the other, but rather to an additive effect of the subanesthetic concentrations of the two drugs when combined. The fact that sleeping times were supra-additive is attributed to a shift of awakening time from the distribution (alpha) phase, when given independently, to the elimination (beta) phase when administered in combination.

The relation between food intake and abomasal emptying and small intestinal transit time in sheep.

The relation between the level of food intake and gastrointestinal motility and digesta flow in the abomasum and small intestine was studied in sheep fitted with nichrome-wire electrodes in the gut wall, an abomasal and a duodenal catheter and a terminal ileal cannula. Abomasal volume and outflow were calculated from CrEDTA dilution in six sheep and small intestinal transit time by the passage of Phenol Red in ten sheep. The frequency of the migrating myoelectric complex of the small intestine was not altered by the level of food intake but the duration of the periods of irregular spiking activity, the amplitude of abomasal activity and the frequency of duodenal rushes were decreased as the level of food intake was decreased. There was a linear relation between the level of food intake (FI) and abomasal outflow (mean with SEM: 327 (69) ml/h for each kg FI/d; P less than 0.01), and abomasal volume (mean with SEM: 344 (50) ml/kg FI per d; P less than 0.001), without any significant change in the half-time of marker dilution in the abomasum. Small intestinal transit time decreased with an increase in food intake (mean with SEM: -54.9 (5.6) min/kg FI per d; P less than 0.001). It is concluded that abomasal volume and the rate of digesta flow from the abomasum and along the small intestine are linearly related to the level of food intake.

Glucosephosphate isomerase polymorphism in sheep.

Two types of glucosephosphate isomerase (GPI) are described for the first time in sheep. Type T produced a 3-band pattern on polyacrylamide gel electrophoresis of serum samples, whereas type M produced a pattern of 5-7 bands. When 23 Scottish Halfbred ewes showing type T were mated to 3 Suffolk rams showing type M, their 32 offspring had frequencies of 0.72 and 0.28 for T and M respectively. There was no conclusive evidence that the types were controlled by codominant alleles or by simple Mendelian inheritance and neither was sex-linked. The frequency of the rarer type (M) was sufficiently high to provide conclusive evidence of true enzyme polymorphism.

Regulation of excretion of copper in bile of sheep: Effect of anaesthesia and surgery

1. 1. Copper excretion in bile increased up to 20 times in sheep operated on under halothane or thiopentone anaesthesia. 2. 2. The enterohepatic circulation of bile salts had no significant effect on the output of copper in bile. 3. 3. The concentration of copper in the liver did not influence either the copper concentration in bile or the post-operative increment in copper output in bile. 4. 4. Intravenous injection of hydrocortisone did not affect bile flow, but increased biliary copper excretion in conscious sheep. 5. 5. It was concluded that corticosteroids released in response to anaesthesia and surgery may have promoted excretion of copper in bile.

Influence of forage quality on rumination time in sheep.

Influence of forage quality on rumination time in sheep.

Bluetongue in the Desert Bighorn Sheep

A young desert bighorn ram (Ovis canadensis) approximately 8 months old was found ill in its natural habitat. Inoculation of a suspension of its lung tissue into domestic sheep resulted in lesions typical of bluetongue disease. Serological studies confirmed the diagnosis. The possibility is presented that this disease may have been partially responsible for the disappearance of the desert bighorn from the Trans-Pecos area of Texas. Bluetongue is a viral disease of sheep primarily, although cattle and goats may be affected (Howell 1963). It has been hypothesized that wild ruminants are reservoirs of infection. Experimental transmission to the blesbuck (Damaliscus albifrons) (Neitz 1933), an African antelope, has been achieved. No clinical signs were reported. This disease is widely distributed in Africa and the Middle East but was not reported in North America until fairly recently. An entity, first called soremuzzle and later identified as bluetongue, was reported in Texas by Hardy and Price (1952), and it is believed that the disease was present in Texas several years earlier than this report (Hardy 1966, Personal communication). Dr. D. H. Bennett described the lesions and epidemiology of soremuzzle in Texas as early as 1923 in a communication with Dr. H. Schmidt. Transmission of the virus isolated in Texas was accomplished experimentally in sheep by the use of insects of the genus Culicoides (Price and Hardy 1954). The incubation time in sheep varied from 1 to 2 weeks and the severity of the disease was variable and unpredictable. The clinical signs observed in domestic sheep usually include an increase in temperature, hyperemia of the mucous membranes, and swelling of the face and lips (Howell 1963). Buccal erosions may occur and coronitis is often observed in animals with light colored hooves. A clear mucopurulent nasal exudate usually is present, and terminal pneumonia commonly occurs in fatal cases. The disease must be reproduced in susceptible sheep to establish a positive diagnosis. The occurrence of this disease in wild ruminants such as deer, bighorn, and pronghorn antelope has not been reported, although it has been reported in domestic sheep (Howell 1963) throughout the southwestern United States.