By assessing the results of this study, guidance should be provided regarding intramuscular injection volumes of medicines for pigs meeting animal welfare standards.Totally, 252 pigs were included in the trial. Tissue reactions of varying injection volumes were investigated in three groups formed according to age. Group 1 comprised suckling piglets 3 - 28 days of age. Piglets of Group 2 were 4 - 12 weeks old and Group 3 was formed of fattening pigs and sows.
Studying the effect on haptoglobin concentrations of an intramuscular injection of NaCl, Stellamune® Mycoplasma, Suvaxyn® M.hyo, M+PAC® or Myofer® 100, only the vaccine M+PAC® (2 ml dosage) showed an increase above the upper value of the normal range (1.42 +/- 0.6 mg/ml).
The local tolerance of two antibiotics (Terramycin® 100 and Draxxin®) was studied in three age groups. The three mycoplasma vaccines (Stellamune® Mycoplasma, Suvaxyn® M.hyo, M+PAC®) were tested in suckling as well as weaned piglets and the PRRSV-vaccine (Ingelvac® PRRS MLV) only in weaned piglets. The studied criteria comprised the laboratory parameters leukocytes, AST and CK. Additionally, the injection sites were assessed clinically over a period of six day post injectionem as well as pathoanatomically and histologically.
After a single injection of Terramycin® 100 or Draxxin®, determined leukocyte values did not point to any inflammatory reactions in any of the age groups. The injection of Terramycin® 100 resulted in elevated AST enzyme values above the maximum reference standard of 35 U/l in weaned piglets, fattening pigs and sows as well as after application of Draxxin® to suckling and weaned piglets. After administration of Draxxin®, creatine kinase values rose above the limit (2000 U/I) in all age groups while after application of Terramycin® 100, elevated values of CK were only found in the groups of fattening pigs and sows. Comparing the two antibiotics, the clinical investigation of injection sites resulted in significant differences in suckling piglets and partly highly significant differences regarding individual experimental parameters in the age groups of weaned piglets and fattening pigs/sows. Comparing the three age groups and evaluating the injection sites macroscopically, predominantly highly significant differences were observed concerning the parameter “extension score 3D”. Equally, significant or highly significant results were recorded when the two antibiotics were compared separately according to age groups. Histologically, extreme myodegeneration as well as coagulation necrosis were seen. The latter was demarcated by a massive inflammatory vallum with fibroblastic budding. Giant cell formation as well as myofibrillar calcification additionally to adipose cell and vascular necrosis was found in the age groups of the “weaned piglets” and of “fattening pigs/sows”.
After injection of Mycoplasma hyopneumoniae vaccines, AST enzyme values rose above the maximum range limit (8 – 35 U/I) only after application of 4 ml Suvaxyn® M.hyo to suckling piglets and after administration of 2 ml M+PAC® to weaned piglets.
The findings of the clinical investigation of the injection site were either depending on the used vaccine or the applied volume. Predominantly highly significant differences were determined by macroscopic investigation of the injection site comparing the vaccines separately within dose volumes and age groups. Significant differences were seen when comparing dose volumes of Suvaxyn® M.hyo (2 and 4 ml) in the two age groups (suckling and weaned piglets) and of M+PAC® (1 and 2 ml).
The results of the histologic investigation showed that the type of tissue reaction predominantly depends on the composition of the vaccine. Consequently, marked differences were found between the three used mycoplasma vaccines, however, the histological findings were predominantly uniform within the treatment groups.
Concerning the tissue reaction, an obvious difference was observed between the two dose volumes (2 and 20 ml) of the Ingelvac PRRS MLV vaccine. The application of 20 ml Ingelvac® PRRS MLV vaccine caused a marked elevation of the concentration of AST and CK. Contrary, all tested blood parameter were within the range of range standards after injection of 2 ml of the vaccine. No significant differences between the two dose volumes were determined in the clinical investigation of the injection site for any of the assessed parameters.
Macroscopically, highly significant differences were seen between the two dose volumes (2 and 20 ml) for the parameters “tissue alteration”, “extension score” and “extension score 3D”. The histological alteration was very similar in both experimental groups. Only the formation of granular tissue was much more pronounced with the 20 ml dosage.