Effects of duration of salt supplementation of sheep on rumen metabolism and the accumulation of elements

Sheep may adapt rumen function in response to supplementary sodium, potentially affecting the metabolism and accumulation of this element and related elements in target tissues and organs. In this study, sheep were provided with a supplement of sodium added to silage for 3, 6 or 9 weeks. There was no evidence of adaptation of rumen function that would have benefited digestion or element absorption, on the contrary, after 6 and 9 weeks supplementation compared with 3 weeks, the buffering capacity of rumen solids was reduced and their density increased, with long particles that were associated with high dry matter contents. Potassium concentration in kidneys increased after 9 week of supplementation, in conjunction with reduced bone potassium concentration. In addition, the concentration of cadmium, an element known to compete with sodium, increased in rumen contents and its availability decreased. Copper was increased in the brain and eyes after 9 weeks of supplementation with NaCl, and after 6 weeks, copper in blood plasma decreased. It is concluded that there was evidence of a dynamic response to NaCl supplementation, which affected rumen solids and the accumulation of several important elements in key target organs.