Adrenocortical and thyroid function, hormone and metabolite profiles and the onset of ovarian cyclicity in dairy cows suffering from various forms of ketosis

Abstract

The involvement of adrenocortical and thyroid hormones in the pathogenesis of ketosis, as well as the ovarian consequences of this metabolic disorder, were studied in >2 parity cows (n=199) in 3 large scale dairy herds. To compare the plasma/serum concentrations of certain hormones [cortisol, thyroxin (T 4 ), triiodothyronine (T 3 ), insulin, insulin-like growth factor-1 (IGF-1)] and metabolites [glucose (G), acetoacetic acid (ACAC), βOH-butyrate (BHB), non-esterified fatty acid (NEFA), trigliceride (TG), total cholesterol (TCh)], and the activity of aspartate aminotransferase (AST), blood samples were taken 1 to 3 days after calving and again 4 times 7 days apart. The ACTH-challenged cortisol responsiveness and the TRH-induced T 4 /T 3 increase were determined between days 1 to 3 and again between days 28 to 35. The resumption of ovarian cyclicity was followed up by individual progesterone (P4) profiles based on milk samples taken 3 times a week for about 80 to 85 days. BHB level of 1 mmol/L was estimated as a border line between hyper- (>1 mmol/L) and normoketonaemic (<1 mmol/L) conditions. Five different ketone patterns were distinguished: (1) non-ketotic (n=98; normoketonaemia in all samples), (2) early type ketosis (n=45; hyperketonemia was detected only in the first week after calving), (3) late type (lactational) ketosis (n=11; after a normoketonaemic period increasing hyperketonaemia was detected in the 5 th , or in the 4 th and 5 th weeks), (4) temporary ketosis (n=11; hyperketonaemia was detected for 1-2 weeks in the 2 nd and 3 rd or in the 3 rd and 4 th weeks); (5) long-lasting ketosis (n=34; hyperketonaemia has been detected since calving for 4 to 5 weeks or until dying/ emergency slaughtering). Simultaneously with the hyperketonaemic stage increased NEFA, ACAC, depressed TCh, glucose and decreased insulin, IGF-1, T 4 and T 3 concentrations were detected in almost all the cases. Obvious metabolic and endocrine alterations were found, however, only in long-lasting ketosis. The TRH-stimulated T 4 and T 3 responses remained almost unaffected proving intact thyroid function in early and late type as well as in temporary ketosis. Depressed thyroid response and delayed onset of cyclic ovarian function were detected only in cases of long-lasting ketosis. The cows characterized by lower than normal (