Study on the inductive factors of hypobiosis of Ostertagia ostertagi in cattle

Two experiments were carried out to determine the causes producing the Ostertagia ostertagi hypobiosis phenomenon in cattle. In the first experiment, the effect of time on third-stage larvae in the environment was studied during a 2-year period. Three experimental paddocks contaminated with O. ostertagi eggs at different times of the year were used, and the levels of hypobiosis were recorded by using 'indicator' and 'tracer' calves. The results suggest that time as such is not a hypobiosis-inductive factor. The second experiment was conducted under laboratory conditions, where the effects of temperature and light on infective larvae were studied. Infective larvae were subjected to different conditions of temperature and light during 6 weeks, and then inoculated to parasite-naive calves, which were slaughtered after 4 weeks. Percentages of hypobiotic larvae in these calves varied from 3.5 to 94.8%, depending on the different storage conditions the larvae underwent before inoculation. Results suggest that increasing temperature and increasing time of light exposure simulating spring conditions would be the factors which act upon third-stage larvae inducing them to a later hypobiotic stage in the host.     

Influence of the number of days spent training in an abattoir with access to live cows on the efficiency of do-it-yourself artificial insemination

Data relating to 35,389 inseminations carried out in the first three years after inseminators were trained were collected by postal questionnaire from 94 do-it-yourself (DIY) artificial inseminators in the UK. The mean calving rate from 14,528 inseminations they carried out on 92 farms in the first year after they were trained was 59.4 per cent (range 5 to 92 per cent). In the second year the mean calving rate from 11,515 inseminations by 64 inseminators was 62.3 per cent (range 33 to 88 per cent), and in the third year the mean calving rate from 9346 inseminations by 49 inseminators was 64.6 per cent (range 41 to 92 per cent). There was an increase of 5.2 per cent in the mean calving rate over the three years with an overall mean calving rate of 61.5 per cent. Each trainee carried out an average of 376 inseminations (range 20 to 800) during the three years. Thirteen instructors were responsible for the tuition and the average time the trainees spent in an abattoir with access to live cows was 2.88 days, with a range from none to five days. For the trainees who spent up to three days training in an abattoir there was an increase of 5.9 per cent in the calving rate they achieved in their first year for every day they spent training with access to live cows (P < 0.005), but there were no significant effects on the outcome of their inseminations in their second or third years.     

Metabolic changes concerning the effect of castration on some blood constituents in male rabbits

This experiment was conducted to determine the effects of castration on some metabolic alterations concerning proteins, lipids and minerals metabolism in both immature and mature rabbits. Twenty male New Zealand White rabbits (10 immature and 10 mature) were used. Blood samples were collected from the immature and mature intact animals (control non castrated). Moreover, the castrated animal groups (immature and mature) were sampled at 2, 4, 6 and 8 weeks after castration. The obtained results revealed that, castration caused a significant decrease in serum total protein, albumin, alpha 1-globulins and alpha 2-globulins concentrations. Meanwhile, gamma-globulins level was decreased temporarily at 2 weeks after castration in mature rabbits. beta-globulins level revealed non significant decrease at 2 weeks after castration in immature rabbits followed by a non significant increase. In mature rabbits beta-globulins level non significantly increased. A significant decrease in serum total nucleic acid concentrations was observed after castration throughout the experimental periods, whereas the value of serum uric acid level markedly increased after castration. Serum lipids concentrations (total lipids, total cholesterol, phospholipids and non esterified fatty acids) were increased after castration. The value of serum trace elements including copper, iron, zinc and manganese concentrations showed a significant decrease after castration. The decrease in serum copper and zinc levels were markedly observed in mature castrated rabbits. Also, serum sodium and potassium concentrations were decreased after castration. Testosterone propionate administration in mature castrated rabbits restored most of the investigated serum blood parameters to the levels of intact non castrated mature rabbit. It could be concluded that castration (deficiency of testosterone) induced marked decrease in protein synthesis and increased protein degradation, but serum lipids markedly elevated after castration in both immature and mature animals. Also, castration caused a marked decrease in some serum minerals and trace elements.     

Evaluation of the white-coat effect in cats

The diagnosis and management of systemic hypertension in cats requires a reliable method for measurement of systemic arterial blood pressure (BP) in clinical patients. Unfortunately, the setting of a clinical practice and the act of measuring BP might raise BP and heart rate (HR), an effect referred to as the white-coat effect in human patients. The purpose of the present study was to determine if a white-coat effect was experienced by cats. Radiotelemetric implants were used to measure BP and HR in 13 conscious cats in a research colony while undisturbed in their cages and while subjected to simulated visits to a veterinarian's office. The white-coat effect was taken to be the difference between the overall 24-hour average value for parameters of BP and HR and the corresponding value during the simulated office visit. A white-coat effect was observed in cats. In healthy cats, the systolic BP measured during the examination period of the simulated office visit exceeded the 24-hour average systolic BP by 17.6+/-1.5 mm Hg. However, marked heterogeneity occurred in the pattern and magnitude of the increase in systolic BP above the 24-hour baseline and the increase varied between 75.3 and -27.2 mm Hg for the healthy cats. Variation in response to the simulated office visit was observed among cats and among visits by the same cat. During an office visit, the magnitude of the white-coat effect tended to decrease, but not disappear, over time. The magnitude of the white-coat effect varied when cats were subjected to 5 repeat office visits, but did not diminish in the group as a whole. The mean increase in systolic BP during the examination (22.3+/-0.9 mm Hg) was greater (P < .05) in cats with renal insufficiency. Although the heterogeneity of response expected from companion animals might be greater than that observed in these colony cats, these results indicate that veterinarians should carefully consider the white-coat effect in evaluation of BP in cats. A quiet, undisturbed environment and adequate time for acclimation should be included in the standard protocol for measurements of BP. Because of day-to-day variation in the white-coat effect in individual cats, multiple serial measurements following a standard protocol should provide the best estimate of BP in cats.     

Characterisation of equine T helper cells: demonstration of Th1- and Th2-like cells in long-term equine T-cell cultures

The aim of this study was to characterise CD4+T-cells in equines, as these cells are pivotal in establishing immune responses or regulating established ones. Peripheral blood mononuclear cells from a pony immunised with ovalbumin were cultured in vitro in the presence of the specific antigen and autologous antigen presenting cells. During the antigen starvation phase, cells were maintained on recombinant equine IL-2. After 35 days of culture, most of the cells were CD4+, CD8-and sIg-. Cells proliferated specifically in the presence of antigen, as tested on day 42 of culture. These cells were analysed by in-situ hybridisation to detect m RNA for IL-2 and IL-4, the presence of which suggested the existence of of Th1- and Th2-like cells.     

Pulsed Doppler assessment of left ventricular diastolic function in normal and cardiomyopathic cats.

Left ventricular (LV) diastolic function was evaluated in 16 cats with primary hypertrophic cardiomyopathy (HCM) using pulsed Doppler (PD) assessment of transmitral flow and isovolumic relaxation time. Data obtained was compared to data from 12 healthy, adult, research cats. Compared to normal cats, the HCM group showed significantly (p value less than 0.05) reduced early LV inflow velocities (mean +/- standard error [SE], peak velocity of 0.70+/-0.04 m/s versus 0.54+/-0.04 m/s and integrated velocity of 0.48+/-0.08 m/s versus 0.37+/-0.03 m/s); a reduced rate of deceleration of early inflow (mean+/-SE, -12.0+/-1.0 m/s2 versus -5.1+/-1.1 m/s2); prolonged isovolumic relaxation time (mean +/- SE, 45.7+/-3.3 ms versus 76.0+/-3.1 ms); and increased atrial systolic flow velocities (mean +/- SE, peak velocity of 0.29+/-0.04 m/s versus 0.48+/-0.04 m/s and integrated velocity of 0.21+/-0.03 m/s versus 0.34+/-0.03 m/s). The results suggest that PD provides a noninvasive method of identifying and quantifying functional diastolic impairment in cats with HCM.     

An In Vitro Comparison of Hollow Ground and Trocar Points on Threaded Positive-Profile External Skeletal Fixation Pins in Canine Cadaveric Bone

OBJECTIVE: To compare the microstructural damage created in bone by pins with lathe-cut and rolled-on threads, and to determine the peak tip temperature and damage created by positive-profile external fixator pins with either hollow ground (HG) or trocar (T) tips during insertion. STUDY DESIGN: An acute, in vitro biomechanical evaluation. SAMPLE POPULATION: Twenty-seven canine tibiae. METHODS: Lathe-cut thread design with T point (LT-T), rolled-on thread design with T point (RT-T), and rolled-on thread design with HG point (RT-HG) pins were evaluated. Twenty pins of each type were inserted under constant drilling pressure into 12 canine tibiae (12 diaphyseal and 8 metaphyseal sites per pin type). Peak pin tip temperature, drilling energy, end-insertional pin torque, and pullout force were measured for each pin. For the histologic study, five pins of each type were inserted into cortical and cancellous sites in 15 additional tibiae. Entry and exit damage, and thread quality were assessed from 100 micron histologic sections by using computer-interfaced videomicroscopy. RESULTS: T-tipped pins reached higher tip temperature in both diaphyseal and metaphyseal bone compared with HG-tipped pins. RT-T pins had higher pullout strength (diaphyseal) and end-insertional torque compared with other combinations. No differences in drilling energy or insertional bone damage was found between the three pin types (P < .05). CONCLUSIONS: T-tipped pins mechanically outperformed HG-tipped pins. Pin tip and thread design did not significantly influence the degree of insertional bone damage. CLINICAL RELEVANCE: T-tipped pins may provide the best compromise between thermal damage and interface friction for maximizing performance of threaded external fixator pins.     

Influence of pig substitution on milk yield, litter weights, and milk composition of machine milked sows.

This study was conducted to 1) determine milk yield of sows that were machine milked up to four times daily; 2) determine the effect of pig substitution on milk yield; 3) assess litter weight changes for sows that are milked; and 4) determine milk composition. Eight sows were milked four times daily to d 51 postpartum. Sows either maintained their own litter or had a week-old replacement litter to replace 25-d-old pigs. Individual gland milk yields were obtained on random days throughout lactation, and different diameter and weighted teat cups were rotated so that all glands received all combinations. Composite milk samples were analyzed for fat, protein, and somatic cells. Milk yields peaked at about 19 d postpartum and declined to 45 d postpartum in sows with their own litter, whereas milk yields peaked earlier and had a more dramatic decline after fostering of a younger litter. Litter weights were 17.1 +/- 1.0 kg at farrowing with 13.6 +/- .6 pigs born alive. Final litter weights were 34.4 +/- 11.7 kg for sows with replacement litters and 74.4 +/- 13.5 kg for sows with their own litters, and numbers of pigs weaned were 6.5 +/- 1.3 and 9.7 +/- 1.5, respectively. Milk fat was influenced by route of oxytocin administration (6.53 +/- .12 for i.v. vs 7.21 +/- .19% for i.m. administration; P < .05). Milk fat percentage was highest on d 2 and declined to 13 d postpartum. Milk protein was influenced by time of day of milking (lowest at the fourth milking, 5.57 +/- .11%) and followed a pattern similar to that for milk fat. Milk protein was affected in a linear manner by milk yield, with highest protein associated with lowest milk yields. Somatic cells in milk were influenced by litter replacement (P < .05) and oxytocin administration (P < .01). There was a linear increase in somatic cells from about 8 x 10(6) cells/mL milk at d 2 to more than 12 x 10(6) cells/mL milk at d 51 postpartum. These results show that pig replacement affects the amount of milk obtained. Moreover, milk composition changes throughout lactation. However, milk removal from sows has a severe impact on litter weight gains, and in systems where sow's milk is needed for commercial purposes, pig supplementation is necessary.     

Abnormal regulation of muscle contraction in horses with recurrent exertional rhabdomyolysis.

OBJECTIVE: To determine whether abnormal regulation of muscle contraction similar to that associated with malignant hyperthermia (MH) was evident in intact external intercostal muscle cells from Thoroughbreds with recurrent exertional rhabdomyolysis (RER). ANIMALS: 5 adult Thoroughbred horses with RER and 7 clinically normal adult Thoroughbred or mixed-breed horses. PROCEDURES: Twitch time course variables and contracture responses to various concentrations of potassium, caffeine, and halothane were measured in small bundles of intact external intercostal muscle cells from clinically normal horses and horses with RER. RESULTS: Threshold for significant contracture induced by potassium depolarization was lower for RER-affected muscles, compared with normal muscles, although the relationship between potassium concentration and membrane potential were not different. Thresholds for contracture induced by caffeine and halothane were also lower for RER-affected muscles, compared with normal muscles. Lower thresholds for caffeine- and halothane-induced contractures, as well as depolarization-elicited contractures, in RER-affected muscles suggest a defect in myoplasmic calcium regulation. CONCLUSIONS AND CLINICAL RELEVANCE: Regulation of muscle contraction is abnormal in Thoroughbreds with RER. The specific defect may be attributable to abnormal intracellular calcium regulation. Knowledge of the specific defect involved in RER may lead to improved prevention and treatment of RER-affected horses.     

Effect of furosemide on performance of Thoroughbreds racing in the United States and Canada.

OBJECTIVE: To determine the effect of furosemide on performance of Thoroughbreds racing on dirt surfaces at tracks in the United States and Canada. DESIGN: Cross-sectional study. ANIMALS: All Thoroughbreds (n = 22,589) that finished a race on dirt surfaces at tracks in the United States and Canada between June 28 and July 13, 1997 in jurisdictions that allowed the use of furosemide. PROCEDURE: Race records were analyzed by use of multivariable ANOVA procedures and logistic regression analyses to determine the effect of furosemide on estimated 6-furlong race time, estimated racing speed, race earnings, and finish position. Principal component analysis was used to create orthogonal scores from multiple collinear variables for inclusion in the models. RESULTS: Furosemide was administered to 16,761 (74.2%) horses. Horses that received furosemide raced faster, earned more money, and were more likely to win or finish in the top 3 positions than horses that did not. The magnitude of the effect of furosemide on estimated 6-furlong race time varied with sex, with the greatest effect in males. When comparing horses of the same sex, horses receiving furosemide had an estimated 6-furlong race time that ranged from 0.56 +/- 0.04 seconds (least-squares mean +/- SE) to 1.09 +/- 0.07 seconds less than that for horses not receiving furosemide, a difference equivalent to 3 to 5.5 lengths. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the pervasive use of furosemide and its apparent association with superior performance in Thoroughbred racehorses, further consideration of the use of furosemide and investigation of its effects in horses is warranted.