Hooo-Hooo Volume 11 Nr 3 - Page 9

Post Mortal Mineral Analysis in African Wildlife Dr Rick Last – BVSc; M.Med.Vet(Path) Specialist Veterinary Pathologist Introduction Trace mineral and deficiencies / imbalances are significant contributors to fetal, neonatal and post- natal losses, as well as having important impacts on growth, habitat adaption, species survival, production and reproductive performance in African wildlife. Such micronutrient imbalances or emerging as significant disease entities as intensification in the industry gains momentum. Therefore, evaluation of micronutrient levels is becoming an important component of the routine disease investigation post- mortem in African wildlife. The primary means of mineral analysis in the post- mortem setting is on liver tissue and / or bone. Minerals analyzed on liver tissue include selenium, copper, iron, zinc and manganese. Bone on the other hand is used for analyzing calcium, phosphorus, magnesium and fluoride. Liver analysis Hepatic mineral analysis is currently primarily used in wildlife to determine whether a nutrient deficiency or toxicity possibly exists. With the collation of mineral levels for various species over time recommended guideline levels will start to emerge and then evaluation of endogenous reserves for a specific mineral will be possible. The beauty of this procedure is that it can be performed on formalin fixed liver tissue which has major practical benefits to the wildlife veterinarian performing autopsies in the field. Variou s scientific studies evaluating the effect of preserving liver tissue in formalin on the concentration of trace mineral levels, found no statistically significant difference in the concentrations in formalin fixed liver (stored for up to a month), compared to fresh or frozen liver. Recommendations for the sampling of liver tissue for mineral analysis include the following: • • • • A minimum of 20 g of liver tissue is required (equivalent to a tissue block of 3 cm x 3 cm dimensions). Only 10% buffered formalin should be used for preservation, as mineral dilution can be expected with non-buffered formalin solution. Liver tissue block should be fixed in the 10% buffered formalin for a minimum of 24 hours before the analysis is performed. Submit the sample as per the normal routine procedures for histopathological specimens to the veterinary diagnostic laboratory. Normal micronutrient levels are significantly affected by age, with normal foetus and neonatal levels being significantly higher than post-natal and adults, and so the age of the animal needs to be taken into consideration when analysing levels. The dam preferentially pushes trace minerals into her foetus, so if the neonate has a low trace mineral status, it is due to the mother`s low status. This holds true for Zn, Fe, Cu and Se. It is important to remember that these trace minerals are toxic in excessive amounts and so over supplementation can result in toxicity. The risk of toxicity is obviously far greater where injectable multimineral preparations are used for supplementation in place of balancing of the nutrition provided. There is also growing concerns regarding the sensitivity of certain antelope species 2017 October 9