A serum enzyme increasing effect of non-toxic herring meal fed to sheep.

In a series of experiments it was demonstrated that highly increased activities of aspartate aminotransferase (= GOT), total lactate dehydrogenase (LDH), and α-hydroxybutyrate dehydrogenase (HBD) occurred in serum of sheep on herring meal feeding. The alanine aminotransferase (A1AT = GPT) level remained unchanged. The enzyme increase was apparently not related to the liver toxic agent dimethylnitrosamine (DMNA) occasionally occurring in lethal doses in meals produced from raw materials preserved with excesses- of nitrite. Histological changes of the liver or other tissues were never detected in experimental animals killed at a stage with very high serum enzyme values. Diets equivalent in digestible crude protein consisting of vegetable as well as of animal protein sources other than fish meal, did not give rise to elevated serum enzyme values. Electrophoretic separation of the LDH isoenzymes in serum of herring meal-fed sheep showed an increased percentage of the LDH fraction, which is predominant in liver, heart, and kidney. Determination of enzyme activities in various tissues resulted in a markedly higher concentration in livers from herring meal-fed animals than in sheep fed casein at an equal protein level. It is suggested that herring meal may have a special promoting effect on the de novo synthesis of the enzymes concerned. As a practical consequence of the experiments it must be emphasized that serum determinations of these enzymes for diagnostic purposes will give a false picture of the clinical condition of sheep fed even moderate amounts of herring meal.