Bovine lymphocytes: erythrocyte rosettes in normal, lymphomatous and corticosteroid-treated cattle.

Spontaneous erythrocyte rosettes, antibody-complement rosettes and nonrosetting cells were enumerated for peripheral blood lymphocytes of normal adult, lymphomatous adult and immature cattle as well as for peripheral blood lymphocytes of adult cows both before and after injection of corticosteroids. Calf thymic lymphocytes were also examined for rosette formation. Results indicate significant reduction in peripheral blood lymphocyte-erythrocyte rosettes and nonrosetting cells in tumour-bearing cows with a simultaneous elevation in percent antibody-complement rosettes. Calf thymus had a significantly greater percent erythrocyte rosettes than did peripheral blood lymphocytes from the same individuals. Corticosteroid injection reduced peripheral blood lymphocytes without altering proportion of cells as erythrocyte rosettes, antibody-complement rosettes or nonrosetting cells.     

Pathophysiology of ovine trypanosomiasis: ferrokinetics and erythrocyte survival studies.

The haematological changes, erythrokinetics and ferrokinetics of sheep were investigated after infection with Trypanosoma congolense. Following the detection of parasites in blood, the infected sheep developed macrocytic hypochromic anaemia. Studies with 51Cr-red cells, 125I-albumin and 59Fe as ferric citrate 11 weeks after infection revealed that infected sheep had significantly lower mean circulating red cell volumes but higher plasma and blood volumes than control sheep. The infected sheep also had enhanced erythropoietic activity as judged by significantly higher plasma iron turnover rates, faster disappearance of radio-labelled iron and higher iron incorporation rates than control sheep. The rate of disappearance of 51Cr-labelled red cells was greater in infected than in control sheep. It was concluded that the anaemia observed at this stage of infection was due to an increased rate of removal of red cells from the circulation coupled with haemodilution, with no evidence of dyshaemopoiesis.     

B-lymphocyte differentiation, using pokeweed mitogen stimulation: in vitro studies in leukemic and normal cattle.

B-lymphocytes from 7 normal cattle and from 3 persistent lymphocytotic, 6 lymphosarcomatosus, and 3 bovine leukemia virus-infected animals with diverse defects in humoral immunity were examined for their capacity to undergo terminal differentiation in vitro. Pokeweek mitogen-stimulated cells from normal and leukemic cattle were stimulated to synthesize and secrete immunoglobulins, and these were detected by radial immunodiffusion. Lymphocytes from normal cattle synthesized more IgM than those from persistent lymphocytotic-, lymphosarcomatous-, and bovine leukemia virus-infected cattle. Leukemic cattle have a higher percentage of cells containing intracytoplasmic immunoglobulins; most cells are believed to contain IgG. The serum IgM in normal cattle is significantly (P less than 0.05) higher than that in leukemic cattle. The results indicate that there is an abnormality either in synthesis or secretion of IgM or in abnormal catabolism of Ig from leukemic B-lymphocytes.     

Echo-guided studies on portal and hepatic blood in cattle

The objectives of the present study were (1) to establish and maintain catheters non-surgically in the portal and hepatic veins of cattle for long-term monitoring of postprandially absorbed metabolites, and (2) to assess the safety of the technique used. Aspiration and catheterization were not performed if there was risk of bleeding, as determined by hemostatic data and enlargement of portal and hepatic veins. In five Holstein cattle, before and 60-min after feeding, percutaneous ultrasound-guided aspiration of portal and hepatic blood, together with jugular blood, was performed utilizing 17G x 17.5 cm needles. Concentration of ammonia nitrogen tended to be higher after feeding, but that of urea nitrogen and glucose were not significantly changed. In five other Holstein cows liver veins were catheterized with 14 x 16.5 cm guide-needles attached with 50 cm polyethylene tubes and blood samples were collected from portal, hepatic and jugular veins at 30-min intervals for 4.5 hr. The concentration of plasma acetate and 3-hydroxybutyrate (3-HB) were significantly increased after feeding, while that of lactate was not changed. Catheters in the portal and hepatic veins enabled the collection of blood samples up to 15 days (mean, 7 days). After a 7-day observation period, five cows were euthanised and necropsied. Changes in the intercostal musculature, peritoneum and liver were negligible. During the observation period, clinical profiles, aspartate aminotransferase, alanine aminotransferase and total and differential WBC counts were within normal ranges.     

The influence of sulphur, molybdenum and cadmium exposure on the growth of goat, cattle and pig

In growing billy goats, bulls and heifers, the supplementation of 10 g elementary S/kg ration dry matter reduced the daily weight gain by about 15%. The offer of 10 g S and 10 mg Mo/kg ration did not intensify growth depression. It occurred, however, when 10 g S were applied together with 3 mg Cd. Under these conditions, fattening bulls gained 19% less weight. The monogastric pig reacted less sensitively to the same exposure. The growth depression only reached about 10% and remained insignificantly. On the other hand, pigs with 10 g S and 3 mg Cd gained 17% less weight (p less than 0.05). The supplementation of 20 g elementary S/kg reduced their growth dramatically. These pigs only gained 89 g weight per day. The effect of S (and Mo or Cd) supplementation was mainly due to decreased feed consumption.     

Application of a constant blood withdrawal method in equine exercise physiology studies.

The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBWM was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pump was used to control blood aspiration from an i.v. catheter via an extension line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. Blood withdrawal using CBWM was made during a treadmill standardised exercise test (SET). A blood flow of 12 m/min was used and samples collected every 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1+/-0.2 ml, with a delay time of mean +/- s.d. 25.3+/-0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of exercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate concentration was observed between 2.5 and 5.5 min after the end of SET. CBWM permits the kinetics of lactate and other blood-borne variables to be studied over time. This method could be a valuable aid for use in studying equine exercise physiology.     

Melatonin and prolactin concentrations in blood of cattle exposed to 8, 16 or 24 hours of daily light

In two experiments, 17-wk-old Holstein bulls exposed to 16 (Exp. 1) or 24 h (Exp. 2) of light daily were compared with bulls given 8 h of light. Blood was sampled at 30-min or 120-min intervals for 48 h at the beginning and again after 4 wk of light treatment. Melatonin concentrations varied episodically in serum, and means were 1.6-fold to 5.1-fold greater during darkness than during light periods. Continuous lighting abolished the nocturnal increase in concentrations of melatonin in three of four calves. Prolactin (PRL) was greater (P less than .05) in calves receiving 16 h (30.9 ng/ml of serum) than in calves receiving 8 h (7.0 ng/ml) of light daily. Prolactin was not different between calves receiving 24 or 8 h of light daily. In a third experiment, one pinealectomized (PX) and two sham PX (SPX) calves were exposed to continuous lighting and infused with melatonin for 16 h/d for 5 wk, and one PX and two SPX calves were infused for 8 h daily. Melatonin infusion increased average concentrations of melatonin in serum 7.2-fold to 18-fold above baseline concentrations. Duration of melatonin infusion did not affect PRL (21.0 vs 20.8 ng/ml of serum). Also, surgical treatment did not affect PRL concentrations. Similarly, in a fourth experiment, PRL in postpubertal heifers fed melatonin to mimic and 8L:16D photoperiod averaged 27.1 ng/ml of serum, which was not different from PRL in heifers receiving 16L:8D and fed vehicle (32.6 ng/ml). We conclude that PRL and melatonin are each affected by photoperiod but are not casually related in cattle.     

Effect of monensin withdrawal on rumen fermentation,methanogenesis and microbial populations in cattle

This study was designed to obtain information on the residual influence of dietary monensin on ruminant fermentation, methanogenesis and bacterial population. Three ruminally cannulated crossbreed heifers (14 months old, 363 ± 11 kg) were fed Italian ryegrass straw and concentrate supplemented with monensin for 21 days before sampling. Rumen fluid samples were collected for analysis of short chain fatty acid (SCFA) profiles, monensin concentration, methanogens and rumen bacterial density. Post‐feeding rumen fluid was also collected to determine in vitro gas production. Monensin was eliminated from the rumen fluid within 3 days. The composition of SCFA varied after elimination of monensin, while total production of SCFA was 1.78 times higher than on the first day. Methane production increased 7 days after monensin administration ceased, whereas hydrogen production decreased. The methanogens and rumen bacterial copy numbers were unaffected by the withdrawal of monensin.