Failure of hair analysis to reflect excessive sodium chloride ingestion by Holstein heifers.

Mineral analysis of hair samples was to assess its value as an indicator of excessive salt ingestion. Ten pregnant Holstein heifers averaging 499 +/- 32 kg were group-fed 9 kg of alfalfa hay cubes and 2 kg of a 14% dairy concentrate mix per head per day. Salt and dicalcium phosphate were available free choice. Prior to treatment animals received fresh water containing 450 ppm total dissolved salts. During treatment, sodium chloride was added to the fresh water at 3500 ppm. Hair samples together with blood and urine were taken immediately prior to start of the experiment and at 30 and 60 days after initiation. Hair samples from two previously marked areas were composited, washed with hot detergent, rinsed, dried with ethanol and then acetone, and wet-ashed. Blood electrolytes and hair and urinary minerals were measured by atomic absorption spectrophotometry. Analysis yielded no significant treatment effects for sodium, potassium, calcium, magnesium in hair and blood serum, and no correlations between hair, blood serum, and urinary minerals. Only urinary sodium reflected the increased sodium ingestion.