Experimental reproduction of ovine vulvitis with bacteria of the haemophilus/histophilus group

Ovine vulvitis was experimentally reproduced by intravaginal inoculation of a mixture of bacterial strains of the histophilus/haemophilus group isolated from field cases. Grossly, the experimental vulvitis was identical to the field condition, and bacteria indistinguishable from the inoculated strains were reisolated.     

Clinical and immunologic response of cattle to administration of a vaccine containing modified-live bovine respiratory syncytial virus

Healthy yearling beef and dairy cattle were inoculated with a vaccine containing modified-live bovine respiratory syncytial virus (ML-BRSV), and sequential changes in clinical signs of disease, blood leukocyte subsets, BRSV-specific antibody titer, and in vitro lymphocyte blastogenic responses were monitored. Vaccination with ML-BRSV did not cause pyrexia, local or systemic hypersensitivity reaction, or respiratory tract disease. Episodes of leukopenia, abnormalities in lymphocyte subsets, or depression of phytomitogen-induced blastogenic responses were not observed subsequent to vaccination. Exposure to ML-BRSV resulted in at least a 16-fold increase in serum neutralizing antibody titer, with no increase seen in nonvaccinated contact controls. Significant BRSV-specific lymphocyte blastogenic responses were not detected, using one dose of several BRSV antigen preparations in a whole blood culturing system.     

Toxoplasmosis in a calf.

Gross post mortem and histopathological changes are described in a calf with toxoplasmosis. The major pathological changes were restricted to the lungs and kidneys and comprised interstitial pneumonia with multifocal necrosis, and glomerular necrosis. Many pseudocysts were present in both organs. The calf had been in close contact with young cats, one of which was killed and examined and shown to have a high antibody titre to Toxoplasma gondii, although there was little histological evidence of infection. No antibodies to toxoplasma were detected in serum from the dam of the calf, and accordingly, it is suggested that the cat was the source of infection for the calf.     

Effect of salicylates on intestinal secretion in calves given (intestinal loops) Escherichia coli heat-stable enterotoxin

The inhibitory effect of salicylates on intestinal secretion in 1- to 5-day-old calves given Escherichia coli heat-stable enterotoxin (ST)-induced intestinal fluid response was investigated. Purified ST was diluted in isotonic saline solution to obtain 1:10, 1:25, 1:50, 1:75, and 1:100 dilutions. Each dilution (1 ml) was inoculated into ligated loops in the distal part of the jejunum of each calf. Acetylsalicylic acid (aspirin) given orally (100 mg/kg) at 4 hours before ST was inoculated did not substantially alter the intestinal fluid response to ST. Sodium salicylate (IV) infusion, begun simultaneously when, or at 1 hour after, ST was inoculated, significantly (P less than 0.05) decreased fluid accumulation in those loops inoculated with ST dilutions of 1:25 or greater. The sodium and potassium concentrations of the accumulated fluid did not differ significantly between or within treatment groups. These results indicate that sodium salicylate infusion may be beneficial in treating enterotoxic colibacillosis in calves. Aspirin given orally at the dose used in the present study, would not have any beneficial effect.     

Bovine genital campylobacteriosis (vibriosis): vaccination of experimentally infected bulls

The therapeutic efficacy of a Campylobacter fetus subsp venerealis bacterin was determined in experimentally infected bulls. Ten of twelve 5-year-old Angus bulls became infected after being infused intrapreputially with C fetus subsp venerealis. Of the 10 bulls, 6 were vaccinated with 5 ml of C fetus subsp venerealis vaccine on 2 occasions 4 weeks apart. Preputial washings of the vaccinated bulls were culturally negative by the 8th week after primary vaccination. None of the 18 heifers exposed to the vaccinated bulls became infected. The 4 infected, nonvaccinated bulls remained culturally positive to C fetus (P less than 0.002), and each bull infected at least 1 heifer (P less than 0.001). Two noninfected, nonvaccinated bulls remained culturally negative and did not infect any heifer. The 4 infected, nonvaccinated bulls were then vaccinated. Two bulls remained infected 9 weeks after primary vaccination, as determined by the virgin heifer test and cultural examination of preputial washings. Serologic data from 7 sampling periods were different (P less than 0.001) for vaccinated vs nonvaccinated bulls at 4 (against K antigen) or 6 (against O antigen) weeks after primary vaccination. Vaccination was effective in eliminating the infection in most of the infected bulls, but cannot be recommended as the sole measure of control in infected herds.     

Calving rates in a tropical beef herd after treatment with a synthetic progestagen, norgestomet, or a prostaglandin analogue, cloprostenol

Maiden heifers and lactating cows of known ovarian status and of several breeds were treated with a synthetic prostaglandin, cloprostenol, or a synthetic progestagen, norgestomet, at the start of an artificial insemination (AI) program. Animals in the cloprostenol treatment received 2 injections 10 days apart. Over the next 26 days those animals that showed oestrous behaviour were inseminated. Synchronisation rates and calving rates to insemination over the first 7 days were calculated. Those in the norgestomet treatment received an implant of norgestomet plus an injection of norgestomet and oestradiol valerate. The implant was removed 10 days later and the animals were given an injection of pregnant mare serum gonadotrophin (PMSG). They were inseminated at 48 h (maiden heifers) or 56 h (lactating cows) after implant removal. Calving rates to fixed-time insemination were recorded. After completion of the AI program the animals in both treatments were joined with bulls. Overall calving rates (AI plus bulls) were calculated. By day 7 of the program, 82% of the maiden heifers and 76% of the lactating cows in the cloprostenol treatment had been detected in oestrus. By day 21 the respective figures were 99% and 81% Norgestomet treatment had an immediate and a prolonged effect on ovarian activity in those females classified as having inactive ovaries at the start of the AI program. Calving rates of those females to fixed-time AI and overall were similar to those of the females with active ovaries in both treatments. Their calving rates to fixed-time insemination, and overall calving rates for the lactating females, were significantly higher than the corresponding values of their contemporaries treated with cloprostenol and inseminated on observed oestrus over 7 days. For those females classified as having active ovaries at the start of the AI program, calving rates to first insemination and overall were similar for both treatments. Overall calving rates of lactating cows of each breed were, with one exception, higher in the norgestomet treatment than in the cloprostenol treatment. Although norgestomet treatment was more expensive than cloprostenol treatment, the advantage in calf crop resulted in an overall monetary advantage to the norgestomet treatment.     

Immunisation of pregnant sows with a live Salmonella cholerae suis vaccine

Sows were immunised subcutaneously with a live Salmonella cholerae suis (SCS) vaccine prior to farrowing. Serological tests demonstrated a high level of SCS colostral antibodies at parturition. Piglet sera negative for antibodies at birth contained a high level of SCS antibodies 24 h after the ingestion of vaccinated sow colostrum. Experiments were carried out to establish if these maternally derived antibodies could protect the piglets against an intranasal (IN) challenge with a field isolate of SCS. It was concluded that pregnant sows could be safely immunised with a live SCS vaccine thus providing their piglets with a passive immunity which protected them against an intranasal challenge.     

The effect of artificial photoperiod at the end of the breeding season on plasma testosterone concentrations in stallions

Testosterone concentrations in stallions showed a seasonal trend with peak concentrations in the spring (April and May in Britain) and lowest concentrations in the period from December to February. The effect on this pattern of changing the length of the photoperiod at the end of the normal breeding season (mid-summer's day) was studied in 2 experiments. In the first experiment artificial illumination was organised from 21 June to mimic the effect of transfer to a southern hemisphere spring and summer, that is short days becoming longer. The stallions had low concentrations of testosterone in February and high concentrations in April. Concentrations in July, August and September were extremely low with a return to high values in late November/early December. In the second experiment, illumination was maintained at the equivalent of a 16 1/2-hour day from 21 June to mid December. These stallions had high testosterone concentrations in April, after which they fell until August, later rising to a maximum in October. These results are discussed in relation to transfer of stallions between the northern and southern hemispheres.     

Lack of effect of selenium supplementation on the incidence of weak calves in dairy herds

A double blind controlled trial was carried out on four commercial dairy herds, to investigate the effect of one 50 mg injection of selenium, 10 days before parturition, on the incidence of weak calves. Although the treatment marginally increased the selenium status of treated calves it did not decrease the incidence of the weak calf syndrome.