Influence of the three RN genotypes on chemical composition, enzyme activities, and myofiber characteristics of porcine skeletal muscle.

An experiment was conducted to evaluate the effects of the RN genotype on skeletal muscle characteristics in pigs sharing otherwise the same polygenic background. Animals were genotyped for RN on the basis of RTN (Rendement Technologique Napole) records using segregation analysis methods. Samples of longissimus (L) and semispinalis capitis (S) muscles were taken from 39 rn+/rn+, 38 RN-/rn+ and 37 RN-/RN- pigs slaughtered at 108 +/- 8.6 kg live weight. Activities of lactate dehydrogenase (LDH), citrate synthase (CS), and beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) were measured on both muscles to assess glycolytic, oxidative, and lipid beta-oxidation capacities, respectively. Histological examinations and chemical analyses were performed on L muscle. The energetic metabolism of the white L muscle was more oxidative in RN-/RN- than in rn+/rn+ pigs, as shown by increased CS and HAD activities (P < .001), decreased LDH activity (P < .001), larger cross-sectional area of IIA (P < .05) and IIB-red (P < .05) fibers, higher relative area of IIA fibers ( P < .05), and lower relative area of IIB-white fibers (P < .001). No significant difference was found between heterozygous and homozygous carriers of the RN- allele, except for CS activity, which was lower in RN-/rn+ than in RN-/RN- pigs. In L muscle, the RN- allele led to a large increase in glycolytic potential (+3.5 phenotypic SD between homozygotes) and lightness (+.7 SD), and a decrease in ultimate pH, dry matter, and protein contents (-1.7 to -2 phenotypic SD for these three traits), with an almost completely dominant effect. No differences were found between genotypes for intramuscular fat and hydroxyproline contents. In the red S muscle, the presence of RN- had no influence on enzyme activities. These results indicate that the RN genotype greatly influences compositional and histochemical traits and metabolic enzyme activities in a muscle type-dependent manner, with a completely or incompletely dominant effect of the RN- allele.     

Prevalence and clinical implications of anthelmintic resistance in cyathostomes of horses.

OBJECTIVE: To determine the prevalence and clinical implications of anthelmintic resistance in cyathostomes of horses. DESIGN: Prospective study. ANIMALS: 80 horses on 10 farms in a 5-county region of northeast Georgia. PROCEDURE: On each farm, horses were stratified in descending order according to pretreatment fecal egg count (FEC), blocked into groups of 4, and then randomly assigned to 1 of 4 treatment groups: no treatment (controls), and treatment with pyrantel pamoate, fenbendazole, or ivermectin. Fecal samples were collected 24 hours prior to treatment and 2, 4, and 6 weeks after treatment for determination of FEC. Mean percentage of reduction in FEC was then calculated for each treatment group. For horses from each farm, the efficacy of each anthelmintic was categorized on the basis of mean percentage of reduction in FEC at 2 weeks after treatment (< 80% reduction = ineffective; 80 to 90% reduction = equivocal; and > 90% reduction = effective). RESULTS: Pyrantel pamoate was effective at reducing FEC in horses from 7 farms, ineffective in horses from 2 farms, and equivocal in horses from 1 farm. Fenbendazole was ineffective at reducing FEC in horses from 9 farms and equivocal in horses from 1 farm. Ivermectin was effective at reducing FEC in horses from all 10 farms. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cyathostome resistance to fenbendazole is highly prevalent, and resistance to pyrantel pamoate is high enough to warrant concern. Resistance to ivermectin was not detected. On the basis of these data, it appears that ivermectin continues to be fully effective in horses. However, too few farms were used in this study to determine the prevalence of cyathostome resistance to ivermectin. Therefore, the efficacy of ivermectin should continue to be monitored closely.     

Inter-river, -annual and -seasonal variability in fecundity of Atlantic salmon, Salmo salar L., in rivers in Newfoundland and Labrador, Canada

Abstract  Fecundity is an integral component of the calculation of Atlantic salmon, Salmo salar L., egg depositions in rivers. Fecundity determinations can be time consuming and prohibitively expensive in terms of application on a broad scale. Consequently, where river specific and annual data are not available, default means are used in calculations in Newfoundland and Labrador. It is important therefore to know the extent of variability among rivers, years and seasons and the potential error involved in using default values. Annual fecundity data were available for one river in Labrador and nine rivers in Newfoundland. Fecundity was determined from ovaries collected in the recreational fishery in the summer for all 10 rivers. For three of these rivers, fecundity determined from summer sampling was compared with that obtained from sampling at time of spawning in autumn. There was significant variability in fecundity with length as a covariate among rivers, years and seasons. Mean number of eggs per female decreased between 8.3% and 29.0% from summer to autumn while mean number of eggs per cm decreased from 5.0% to 28.5%. Depending on the measure of relative fecundity used (no. of eggs kg⁻¹ or no. of eggs cm⁻¹), results of simulations showed that estimates of egg deposition incorporating defaults can deviate from those obtained by applying year-specific and river-specific values by 50–75%, without adjusting for the seasonal reduction in fecundity, and by 30–50% with an adjustment. A sensitivity analysis revealed that of three parameters used in the calculation of egg deposition (size, percent female and fecundity), fecundity was the most influential.     

Failure to spread bovine virus diarrhoea virus infection from primarily infected calves despite concurrent infection with bovine coronavirus

Previous reports on the spread of bovine virus diarrhoea virus (BVDV) from animals primarily infected with the agent are contradictory. In this study, the possibility of transmission of BVDV from calves simultaneously subjected to acute BVDV and bovine coronavirus (BCV) infection was investigated. Ten calves were inoculated intranasally with BVDV Type 1. Each of the 10 calves was then randomly allocated to one of two groups. In each group there were four additional calves, resulting in five infected and four susceptible calves per group. Virulent BCV was actively introduced in one of the groups by means of a transmitter calf. Two calves, susceptible to both BVDV and BCV, were kept in a separate group, as controls. All ten calves actively inoculated with BVDV became infected as shown by seroconversions, and six of them also shed the virus in nasal secretions. However, none of the other eight calves in the two groups (four in each) seroconverted to this agent. In contrast, it proved impossible to prevent the spread of BCV infection between the experimental groups and consequently all 20 study calves became infected with the virus. Following infection, BCV was detected in nasal secretions and in faeces of the calves and, after three weeks in the study, all had seroconverted to this virus. All calves, including the controls, showed at least one of the following clinical signs during days 3-15 after the trial started: fever (> or =40 degrees C), depressed general condition, diarrhoea, and cough. The study showed that BVDV primarily infected cattle, even when co-infected with an enteric and respiratory pathogen, are inefficient transmitters of BVDV. This finding supports the principle of the Scandinavian BVDV control programmes that elimination of BVDV infection from cattle populations can be achieved by identifying and removing persistently infected (PI) animals, i.e. that long-term circulation of the virus without the presence of PI animals is highly unlikely.     

Analysis of factors to predict piglet body weight at the end of the nursery phase

In pig (Sus Scrofa) production, within-batch variation in bw gain of piglets during the nursery period (up to 10 wk of age) can be high and is of high economic importance. Homogeneity of BW within batches of animals is important as it influences the efficiency of use of the grower and finisher facilities, and provides an extra value for the fattening farms. In the current study, factors for a light BW at the end of the nursery period of pigs were determined by analyzing datasets from 3 different swine research centers in the Netherlands and France. The entire dataset contained information on 77,868 individual piglets born between 2005 and 2010. Body weight was determined at different time points over the pre- and post-weaning phase, and sex, season of birth, litter information (litter size at day of birth and after cross-fostering, number of piglets born alive per litter, number of total born littermates, sow parity number), cross-fostered animals (yes or no), and pen group size over the post-weaning period were recorded. A risk factor analysis approach was used to analyze the datasets to determine factors that predict piglet bw at the end of the nursery period. Body weight at the end of the nursery period corrected for age was mainly determined by season (P < 0.001), birth weight (BiW, P < 0.001), weaning weight (WW, P < 0.001), and BW at 6 wk of age (P < 0.001). These variables were consistent among datasets and explained approximately 70% of the overall variation in BW at the end of the nursery period. Litter information did not significantly (P > 0.05) contribute to explaining the BW at the end of the nursery period. To discard the possibility of intrauterine growth retarded piglets (IUGR) being the reason for the influence of BiW as an explanatory factor in the regression model, a further analysis was performed on the effect of this category of piglets on the results of the regression analysis. Overall, it was concluded that the bw of piglets at the end of the nursery phase is mainly determined by season, sex, birth, WW, and BW at 6 wk of age. Piglets with a BiW greater than the mean biw minus 2.5 times the sd have the potential to compensate during the subsequent phases of growth.     

Spatial epidemiology of the Asian honey bee mite (Varroa destructor) in the North Island of New Zealand

We describe the spatial epidemiology of Varroa destructor infestation among honey bee apiaries in the greater Auckland area of the North Island of New Zealand. The study population was comprised of 641 apiaries located within the boundaries of the study area on 11 April 2000. Cases were those members of the study population declared Varroa-infested on the basis of testing conducted between April and June 2000. The odds of Varroa was highest in apiaries in the area surrounding transport and storage facilities in the vicinity of Auckland International Airport. A mixed-effects geostatistical model, accounting for spatial extra-binomial variation in Varroa prevalence, showed a 17% reduction in the odds of an apiary being Varroa infested for each kilometre increase in the squared distance from the likely site of incursion (95% Bayesian credible interval 7–28%). The pattern of spatially autocorrelated risk that remained after controlling for the effect of distance from the likely incursion site identified areas thought to be ‘secondary’ foci of Varroa infestation initiated by beekeeper-assisted movement of infested bees. Targeted investigations within these identified areas indicated that the maximum rate of local spread of Varroa was in the order of 12 km/year (interquartile range 10–15 km/year).     

Nuclear Remodelling in Growing Oocytes of Sheep

Veterinary Research Communications - Russo, V., Martelli, M., Mauro, A., Di Giacinto, O., Nardinocchi, D. and Berardinelli, P., 2007. Nuclear remodelling in growing oocytes of sheep. Veterinary...