Influence of different planes of energy supply prior to the breeding season on blood metabolites in female mink (Mustela vison).

Metabolic blood profiles were studied in a total of 30 female mink (Mustela vison) at different planes of nutrition prior to the breeding season in a control (CON; n = 10), a flushed (FLUSH; n = 10) and a negative energy balance group (NEG; n = 10). The animals were kept in metabolism cages or under normal farm conditions, respectively. The experiment, which was divided into six 1-week periods, started on 6 February and continued until 20 March. Flushing was performed by restricted feeding in periods 2 and 3 and refeeding in periods 4 and 5. The animals were weighted weekly and blood sampled at the end of periods 1, 2 and 4, 1 week after changes in the food supply of the FLUSH group. Plasma was analysed for insulin, insulin-like growth factor-1, total triiodothyronine, total thyroxine, free thyroxine, glucose and fructosamine. Generally, within the FLUSH group, animal live weights and blood metabolites were strongly influenced by energy supply, these variables remained almost constant in the CON group. In the NEG group the live weight, total triiodothyronine, total thyroxine, insulin and glucose concentrations decreased significantly. Differences in blood metabolites between the FLUSH and CON groups were non-significant, reflecting only small differences when considered over the total experimental period, thus reflecting an acute response to a varied energy supply, while the differences between the NEG group and the CON and FLUSH groups were significant, indicating a considerable chronic response in all metabolites to a constantly low energy supply.