Neospora caninum and/or Toxoplasma gondii Seroprevalence: Vaccination against PCV2 and Muscle Enzyme Activity in Seropositive and Seronegative Pigs

Neospora caninum and Toxoplasma gondii affect both humans and animals worldwide. To investigate their seroprevalence and differences in seropositivity between pigs vaccinated and unvaccinated against porcine circovirus 2 (PCV2), as well as differences in muscle enzyme activity between seropositive and seronegative pigs, blood samples were collected from 380 sows. Antibodies against T. gondii and N. caninum were detected by an indirect immunofluorescence antibody (IFA) assay, while the activities of creatine kinase (CK) and aspartate aminotransferase (AST) were biochemically assessed. Out of the 364 sows finally included in the study, 4.4%, 3.5%, and 0.5% were seropositive to T. gondii, N. caninum, or both. A significantly higher percentage of seropositivity against T. gondii and/or N. caninum in PCV2 unvaccinated pigs compared with vaccinated pigs was observed. Increased serum activities of CK and AST were detected in 71.43% and 100% of only against T. gondii (T+) and 63.64% and 90.91% of only against N. caninum (N+) seropositive sows, respectively, and were significantly higher compared to seronegative animals. T. gondii and N. caninum seropositivity, especially in presumed immunocompromised pigs, and the evidence of muscle damage highlight their importance as a zoonotic pathogen and animal model of human infection, respectively.

Carcass traits, meat quality and muscle enzyme activity in strains of Merino wether hoggets

The carcass characteristics, meat quality and specific muscle enzyme activity were studied in 342 Merino wether hoggets representing 7 bloodlines comprising 2 superfine lines, 2 fine wool lines, 2 medium wool lines and 1 broad wool line over 2 years. All animals were supplemented at pasture for 5 weeks before slaughter with high energy pellets. Fat levels in the superfine bloodlines based on total tissue depth over the 12th rib, 110 mm from the midline were much greater than in other lines. This also applied to fat depth measured over the longissimus thoracis et lumborum (LL) muscle for one of the superfine bloodlines when adjusted to the same carcass weight. Differences in LL muscle dimensions were minor, although the broad wool bloodline had a lower depth which translated into a smaller cross-sectional area. Significant differences were detected between bloodlines for muscle pH with superfine animals having the highest values for the LL. The differences for the semitendinosus muscle were less consistent between bloodlines, but of the bloodlines the broad wool line had the lowest pH levels in both muscles. There were few differences between bloodlines for the meat colour parameters measured on the LL. In the second year, muscle samples were taken to determine the activity of fructose 1,6-bis-phosphatase, lactate dehydrogenase (LDH), isocitrate dehydrogenase (ICDH) and the concentration of myoglobin, indicators of anaerobic and aerobic metabolism. Samples from 50 carcasses were selected from a medium wool and a superfine bloodline (2 × 25) based on LL muscle pH values. Of the enzymes, only ICDH activity was different between the 2 bloodlines, with muscle from the medium wool bloodline having a significantly higher activity than muscle from the superfine bloodline. This indicates a greater aerobic capacity in the muscle of the medium wool bloodline. The significantly lower muscle pH for medium wool bloodline was mirrored by a lower glycolytic capacity expressed as the LDH/ICDH ratio with a correlation of 0.46. Thus in this dataset, a high pH is related to a change in energy metabolism as reflected by the aerobic/anaerobic capacity of the muscle and this may be a reflection of a change in fibre type frequency, but this remains to be validated.

Muscle enzyme activity in humans: role of substrate availability and training

To study the effect of nutrient intake (substrate flux) and training on muscle enzyme activities, 36 untrained healthy men adapted for 7 wk to a fat-rich or a carbohydrate-rich diet. Ten of the 18 subjects on each diet completed an endurance training program, and the remaining 8 served as controls. Maximal oxygen uptake was increased (11%) in the trained groups (P < 0.05). Irrespective of training, beta-hydroxyacyl-CoA-dehydrogenase activity in the vastus lateralis muscle was significantly increased by an average of 25% after adaptation to a fat-rich diet and was unchanged after adaptation to a carbohydrate-rich diet. In contrast, irrespective of diet, muscle citrate synthase activity and hexokinase activity were increased (P < 0.05) after adaptation to training by 17 and 18% in the group fed the carbohydrate, rich diet and by 17 and 12% in the group fed the fat-rich diet, respectively, and were unchanged in the two control groups. We suggest that diet can affect muscle enzymatic adaptation, presumably through an effect on the substrate flux.