Infection of bovine fetuses at 120 days' gestation with virulent and avirulent strains of bluetongue virus serotype 11.

Bluetongue virus infection in sheep and cattle during fetal development causes neuropathology. Two strains of bluetongue virus serotype 11 designated as UC-2 and UC-8 have different virulence patterns in newborn mice. These viruses have distinctly different electropherotype patterns on polyacrylamide gel electrophoresis indicating a genetic difference in these two viruses of the same serotype. Four bovine fetuses each were inoculated intramuscularly with either UC-2 or UC-8, and one fetus was inoculated with placebo. The inoculation was made intramuscularly through the uterine wall at 120 days' gestation, and the bovine fetuses were recovered by cesarean section 12 or 20 days after inoculation. Fetal blood was collected for virus isolation and serology. Virus was reisolated from brain, blood, lung and liver. Both strains, UC-2 and UC-8, cause severe lesions in the 120 day fetuses. The encephalomalacic lesions occurred earlier and were more severe in fetuses inoculated with UC-8 as compared to those inoculated with UC-2. The subtle differences observed in the fetuses inoculated with the two different strains suggest that there is a difference in pathogenic potential of the two viruses. These differences do not appear to be completely dependent upon the host species.     

Effect of initial restraint, weaning, and transport stress on baseline and ACTH-stimulated cortisol responses in beef calves of different genotypes.

The productivity and well-being of animals can be substantially affected by stress. This is particularly true in the case of beef calves that are subjected to a multitude of stressors over a short period during the first year of life. Perhaps the most often studied stress-responsive variable has been blood corticosteroid concentrations. Factors such as age, gender, genetics, and degree of prior experience, can influence how an animal perceives and responds to a given stressor. Few studies have tried to control these variables, and accordingly, many conflicting results have been published regarding the impact of various stressors on cortisol response. We measured baseline plasma cortisol concentration over a 44-day study in Bos indicus and Bos taurus calves. Plasma cortisol values in Bos indicus calves were higher (32.60 +/- 0.66 ng/ml) than values in calves of Bos taurus (25.81 +/- 0.76) breeding. A precipitous decrease in cortisol concentration was observed 7 days after transport stress in all calves. Baseline cortisol concentration did not provide any indication of the intensity of the various stressors. However, significant differences were readily observed after ACTH administration. On the basis of cortisol secretion, stresses of transport and weaning were similar and were the most stressful to calves, regardless of genotype.     

A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants

AIM: To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.

METHODS: Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000?cells/mL at the first herd test after calving.

RESULTS: Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000?cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000?cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40–1.30).

CONCLUSIONS AND CLINICAL RELEVANCE: In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.     

Evaluation of azathioprine on lesion severity and lymphocyte blastogenesis in dogs with perianal fistulas

Fourteen dogs with perianal fistulas were entered into a prospective clinical study to investigate the effects of long-term azathioprine on clinical outcome and to determine if the clinical results correlated with lymphocyte blastogenesis tests. Complete remission of perianal fistulas was seen in eight (57%) of 14 dogs; partial remission occurred in one (7%) dog; and no response was detected in five (36%) dogs. The results of lymphocyte blastogenesis assays did not correlate with therapeutic response.     

New insights into the structural characteristics of the arabinogalactan-protein (AGP) fraction of gum arabic

The structural characteristics of the gum exudate of Acacia senegal (gum arabic) have been investigated by monitoring the composition and physicochemical properties before and after treatment with proteolytic enzyme and various alkaline systems. Molecular mass ( M w) and radius of gyration ( R g) measurements were performed using gel permeation chromatography (GPC) coupled to refractive index, UV absorbance, and multiangle light scattering detectors and indicated that the macromolecules present have a compact structure. It was found that treatment with proteolytic enzyme caused the arabinogalactan-protein component (AGP) with average molecular mass approximately 2 x 10 (6) Da to degrade, yielding material of molecular mass approximately 4 x 10 (5) Da, whereas the bulk of the material corresponding to the protein-deficient arabinogalactan component (AG) with molecular mass 4 x 10 (5) remained unaffected. Barium hydroxide was found to hydrolyze the polysaccharide component (AG) itself in addition to the proteinaceous component as demonstrated in control experiments using dextran. However, sodium borohydride/sodium hydroxide treatments were unable to hydrolyze dextran and were assumed to hydrolyze only the proteinaceous component of gum arabic. The AGP component was completely degraded, yielding material of molecular mass approximately 4.5 x 10 (4) Da. It has been concluded, therefore, that the enzyme did not fully hydrolyze all of the protein present and that the AGP component of gum arabic consists of carbohydrate blocks of approximately 4.5 x 10 (4) Da linked to a polypeptide chain consistent with the wattle blossom structure. Because the AGP was degraded to differing extents using a mild and more severe sodium borohydride/sodium hydroxide treatment, it was concluded that the polysaccharide moieties were linked through both O-serine and O-hydroxyproline residues. The gum arabic sample was deglycosylated by treatment with anhydrous hydrogen fluoride and revealed the presence of two putative core proteins of approximately 3 x 10 (4) and approximately 5 x 10 (3) Da, respectively, which correspond to proteins of approximately 250 and 45 amino acids in length. A new model for the structure of the AGP component has been proposed.