Transmission studies with bovine malignant catarrhal fever

The intravenous administration of whole blood from a pathologically confirmed field case of bovine malignant catarrhal fever (MCF) resulted in the appearance of the disease in three of five experimental calves 18 to 28 days later. Infection was maintained by serial calf transmissions, and produced clinical and pathological changes identical to those of the field disease for a total of 10 passages. The sixth passage involved the simultaneous infection of 10 calves from a single donor animal; six of the 10 recipients developed the typical disease after incubation periods ranging from 20 to 36 days and in each of these MCF was confirmed by pathological examination. In addition, clinical and pathological changes in the four other calves which were slaughtered either seven or 14 days post-infection suggested that they too would have developed typical clinical signs had they been allowed to survive for the necessary length of time. The results of a detailed study of the onset, progress and duration of the clinical signs of experimentally induced MCF are presented and the opportunity has been taken to discuss the available information regarding the transmission of MCF under experimental conditions and in the field.     

THE IDENTIFICATION OF BABESIA EQUI IN AUSTRALIA

A Babesia parasite, isolated from the blood of a horse at Bowral, New South Wales, was identified on the basis of its morphological features, host specificity and serological reactions, as Babesia equi (Laveran 1901). The case was originally reported by Churchill and Best (1976, Aust. vet. J. 52: 487) and is the first record of equine babesiosis in Australia. In preliminary studies, the organism produced only a mild disease in an intact horse, but caused the typical clinical syndrome of acute babesiosis in a splenectomised horse, which died 19 days after the intravenous inoculation of the parasites.     

Variation in seed protein digestion of different pea (Pisum sativum L.) genotypes by cecectomized broiler chickens: 1. Endogenous amino acid losses, true digestibility and in vitro hydrolysis of proteins

The aim of this study was to investigate the cause of variation in the digestibility of pea protein in poultry and to find a tool to select genotypes with high digestibility potential by using an in vitro hydrolysis assay. Eight pea genotypes were selected for their difference in seed protein content and composition. To reduce the variation due to tannins and particle size, seeds from these 8 genotypes were dehulled and micro-ground. They were incorporated as the only protein source in 8 different experimental isoproteinaceous diets with similar metabolisable energy content. The amino acid digestibility was studied in cecectomized chickens. A balance method was used to obtain apparent digestibility, and the isotope dilution technique was used to determine endogenous losses and true digestibility, after feeding a double labelled test meal containing chromic oxide and ¹⁵N-labelled peas. The 8 diets showed differences in apparent amino acid digestibility. The average apparent digestibility for all amino acids varied between 79.5 and 86.3%, with the highest values for arginine (85.2 to 90.8%) and glutamic acid (85.2 to 90.5%), and the lowest values for cystine (63.3 to 69.7%) and tryptophan (69.1 to 80.3%). This variability of apparent amino acid digestibility was due to variations in endogenous losses and true digestibility among the 8 pea genotypes. The average endogenous losses as determined for 9 amino acids ranged from 3.6 to 5.4% of ingested amino acids, with the highest value for threonine (8.0 to 11.0%). The average true digestibility varied between 84.4 and 90.2%, with the highest values for lysine (89.0 to 95.0%), and the lowest for isoleucine (81.0 to 88.7%) and valine (82.4 to 88.7%). In vitro hydrolysis of protein from micro-ground seeds was performed for the 8 pea genotypes using three proteases (pepsin, trypsin and chymotrypsin). The quantity of small peptides (< 3 kDa) that appeared after the combined hydrolysis with pepsin (3 h) followed by trypsin and chymotrypsin (15 min) was significantly correlated with the average true digestibility of the 8 genotypes (R = 0.74; P < 0.05).     

THE EFFECTS OF HEAVY DRESSINGS OF POTASH APPLIED TO THE SEEDBED OF A LEY COMPARED WITH ANNUAL DRESSINGS

Two experiments were established to compare the effect on the yield of continuously cut herbage of varying amounts of potassium fertilizer applied either in one large dose to the seedbed, or as 3 equal dressings applied to the seedbed and in the summer of the 2 following years. Responses in dry–matter yield were recorded up to the higher rates of potassium fertilizer applied. Establishment and yield in the first 12 months were improved by seedbed applications of up to 4 cwt/ac of muriate of potash (60% K₂O). Although total yields over the whole period were similar, whether the potassium was applied to the seedbed only or in annual dressings, yields from "all–in–seedbed" dressings declined towards the end of the period. Soil analysis indicated that annual dressings left behind higher residues of K.     

Analysis of southern Ontario Actinobacillus (Haemophilus) pleuropneumoniae isolates by restriction endonuclease fingerprinting.

Isolates of Actinobacillus (Haemophilus) pleuropheumoniae were studied by restriction endonuclease fingerprinting (REF) analysis using the enzymes BamHI and HindIII. Restriction fragments were resolved by polyacrylamide gel electrophoresis and visualized by silver staining. Except for serotypes 1 and 9, reference strains of A. pleuropneumoniae serotypes 1 to 10 had clearly distinguishable REF profiles. Analysis of REF profiles of southern Ontario field isolates revealed limited heterogeneity amongst isolates of serotype 1 or serotype 5. The REF profiles of the serotype 7 isolates studied showed greater variation. Heterogeneity could not be correlated with the presence of plasmids nor with antibiotic resistance. Limited heterogeneity could also be detected amongst REF profiles of A. pleuropneumoniae isolates recovered from a closed herd suggesting that there is a small amount of genetic variation within clonal populations.     

Prevalence of benzimidazole resistant nematodes in sheep flocks in Yucatan,Mexico

Thirty-eight sheep flocks, located in three municipalities in the Eastern Yucatan, Mexico, were surveyed for gastrointestinal nematodes resistant to benzimidazole (BZD) anthelmintics (AH). On each flock, 30 sheep were randomly distributed into two groups of 15 animals: albendazole group (5mg/kg BW) and untreated control group. Animals were refrained from any food (either browsing/grazing or supplement) for a period of 16 h prior to treatment. Faecal egg counts (FEC) and larval cultures were performed 10 days after anthelmintic treatment. Percentage reduction and 95% confidence intervals were determined. Anthelmintic resistance (AR) was declared when the percentage reduction in FEC was <95% and the 95% confidence interval was <90%. AR was suspected when only one of the two criteria was met. The survey indicated that AR occurred in 15.8% (n=6) (95% confidence interval=+/-11.6%) and was suspected in 23.7% of the farms (n=9) (95% confidence interval=+/-13.3%). Post-treatment larval cultures indicated that Haemonchus was the only resistant genus. The questionnaire survey showed that most farmers (92%) considered their sheep a secondary activity to cattle production. The majority of farmers (97.4%) treat their animals according to visual appreciation of weight. However, most farmers (79%) treat their flocks at very low frequencies (<3 times per year). Drug rotation was performed every 12 months or more by 84.2% of farmers. Anthelmintics used were: macrociclic lactones (47.4%), BZD (39.5%), levamisol (10.5%) and 1 farmer used closantel.