Plasma vitamin E and blood selenium concentrations in Norwegian dairy cows: regional differences and relations to feeding and health.

Plasma alpha-tocopherol (vit E) and blood selenium (Se) concentrations in February were determined in samples from 314 dairy cows in Norway, selected to provide a representative subset of the Norwegian dairy cow population. Each sample was followed by a questionnaire with information about feeding of the cow at the time of sampling. The results were correlated to herd data and to calving and health data for each cow from the Norwegian Dairy Herd Recording System and the Norwegian Cattle Health Recording System. The mean concentrations were 6.9 microg vit E per ml plasma and 0.16 microg Se per g blood. Both levels were highest in mid lactation. Plasma vit E varied with the amount of silage fed to the cow, while blood Se varied with the amount of concentrates and mineral supplements, and with geographical region. No differences in vit E or Se levels were found between cows with recorded treatments for mastitis, parturient paresis or reproductive disorders in the lactation during or immediately prior to sampling, and those without such treatments. For ketosis, a small difference in blood Se was found between the groups with or without recorded treatments. It is concluded that winter-fed lactating cows in Norway had an adequate plasma level of vit E and a marginal-to-adequate level of Se.

Effects of diets with graded levels of naturally deoxynivalenol-contaminated oats on immune response in growing pigs.

A trial was conducted to evaluate the effect of including different levels of deoxynivalenol (DON)-contaminated oats in the complete diets of growing pigs on immune response and performance. The diets contained 0.6, 1.8 and 4.7 mg DON/kg, and both restricted and ad libitum feeding were used. Performance was recorded as weight gain, feed intake, efficiency of feed utilization and carcass quality. Immune response parameters recorded included primary and secondary antibody titres after injections of five different antigens: Human serum albumin (HSA), sheep red blood cells (SRBC), paratuberculosis vaccine (MPT), tetanus toxoid (TT) and diphteria toxoid (DT). A johnin test was also performed. Lymphocyte stimulation response was measured with three different mitogens (PWM, ConA and PHA). A significant, DON dose-dependent reduction in secondary antibody response to tetanus toxoid was observed. A slightly higher mitogen response after PHA stimulation in lymphocytes from the medium and high DON groups compared to the low DON group after 9 weeks was considered inconclusive. No other indication of dose-dependent immune response inhibition or stimulation was found. Significantly reduced feed intake with increased levels of DON was observed in groups fed restricted rations according to weight, but not in animals fed ad libitum.

Immunosuppression in sheep experimentally infected with Ehrlichia phagocytophila.

The effect of tick-borne fever (TBF) on antibody formation and lymphocyte proliferation in sheep was studied following experimental infection with Ehrlichia phagocytophila. All infected sheep developed fever within three to four days. The sheep recovered clinically within eight days. Both infected and non-infected control sheep were immunised twice with different antigens, that is, on days 9 and 35 following the experimental infection. The levels of antibodies produced against tetanus toxoid and influenza virus in the infected sheep were significantly lower than in the control animals. The findings indicated that a TBF-infection may impair both primary and secondary antibody responses for up to six weeks. Immunisation with Actinomyces pyogenes resulted in significantly higher antibody titres in the TBF-infected group than in the control group, as measured by an enzyme-linked immunosorbent assay (ELISA). It is believed that TBF-induced neutropenia may lead to increased exposure to A pyogenes-antigens and thereby enhance antibody production. Antibodies to E phagocytophila were measured by the indirect fluorescent antibody test and by an ELISA. The inoculated sheep responded with the formation of antibodies to E phagocytophila at one week (P < 0.025), and showed a peak response at four weeks (P < 0.0005) after inoculation. The antibody titre decreased between four and six weeks, but was still high at six weeks (P < 0.0005). The lymphocyte responses to phytohaemagglutinin (PHA) concanavalin A (Con A) and pokeweed mitogen (PWM) were lower than in the control group and this difference was significant at most time points after infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Suspected Lyme borreliosis in sheep.

Two cases of suspected Lyme borreliosis in lambs are described. The clinical signs observed resemble those described for Lyme borreliosis in dogs and horses. The lambs were approximately six months old and came from two different flocks in a district heavily infested with Ixodes ricinus ticks. The lambs had pronounced lameness in one leg, generally bad condition and poor appetite. They had high serum levels of IgG antibodies to Borrelia burgdorferi when tested in an ELISA. The other lambs in the flocks were negative to B burgdorferi antibodies. Attempts were made to isolate spirochaetes from one of the lambs, but were unsuccessful.

Controlling tick infestations and diseases in sheep by pour-on formulations of synthetic pyrethroids. A field study.

The use of synthetic pyrethroids in pour-on formulations reduced tick infestations and the incidence of tick-associated diseases in lambs more than dipping in organophosphate acaricides. Though the use of pyrethroids did not prevent the lambs from being infected with tick-borne fever (TBF), the incidence of lambs with lameness (tick pyaemia) or lambs suddenly found dead (Pasteurella haemolytica septicaemia), which often are seen in association with TBF, was reduced. The use of pyrethroids for three years did not seem to affect the prevalence of TBF.

Immune response after immunization with an experimental Toxoplasma gondii ISCOM vaccine.

Mice were immunized with ISCOM preparations of tachyzoites from two different strains of Toxoplasma gondii. The antibody response and the cellular response, as measured in vitro, were comparable with those found in chronically infected mice. When challenged with virulent T. gondii tachyzoites, all the immunized mice died, whereas all the chronically infected mice survived. However, the immunized mice generally survived longer than non-immunized animals.

Effect of selenium on sheep lymphocyte responses to mitogens.

The effect of selenium (Se) on sheep lymphocyte response to mitogens was studied. In an indoor experiment lambs were fed a basal diet containing 0.13 mg Se kg-1, and supplemented with, respectively, 0.1 or 0.5 mg Se kg-1, either as sodium selenite or as selenomethionine. Enhancement of the proliferative response of lymphocytes to phytohaemagglutinin (PHA), pokeweed mitogen (PWM) and concanavalin A was found in lambs following selenium supplementation at the lower levels. The highest dietary selenium content, however, induced decreased mitogen response. Transient increases in lymphocyte response to PHA and PWM by ewes supplemented with selenium was demonstrated in one field study and a combined effect of selenium and vitamin E was seen in another. There was no stimulatory effect on the mitogen response of lymphocytes from sheep supplemented with dietary vitamin E alone.

Influence of selenium on antibody production in sheep.

Three experiments were carried out, using sheep fed a marginally low selenium diet, to study the effect of selenium supplementation on the antibody response to tetanus toxoid and on the serum IgG concentration. Six groups of three six-month-old lambs were fed a basal diet containing 0.13 mg Se kg-1 supplemented with either 0.1, 0.5 or 1.0 mg Se kg-1, as sodium selenite or as selenomethionine. These animals generally showed enhanced antibody response to tetanus toxoid, parainfluenza-3 virus and Corynebacterium pseudotuberculosis, and their total serum IgG concentrations were higher than in unsupplemented control animals although few responses were statistically significant. In two field studies significantly higher titres to tetanus toxoid were detected in ewes injected with 100 mg selenium as barium selenate, although no influence on serum IgG concentrations was detected. Lambs from selenium supplemented ewes had significantly higher titres to tetanus toxoid than lambs from ewes in the control group. Dietary vitamin E supplementation had a similar effect on the antibody response to tetanus toxoid in ewes, though no additive effect was seen when vitamin E was given together with selenium.

Influence of vitamin E and selenium supplement on antibody production in horses.

Fifteen horses used for serum production were maintained on low vitamin E and selenium diets. They were divided into four groups receiving: Group 1 no supplements, Group 2 vitamin E, Group 3 selenium and Group 4 both vitamin E and selenium. The humoral immune response to novel antigens, such as tetanus toxoid and equine influenza virus, was increased in groups receiving either vitamin E or selenium/vitamin E. No effects were recorded on the titres against Escherichia coli or the levels of immunoglobulin G.