RESUMO
In a prospective, longitudinal study ten pregnant dry cows were randomly assigned as either experimentals or controls. The experimental period was from 28 days before expected calving until calving. Experimental cows were allocated 800 g of zeolite A daily during week 2 and 3 before expected calving. The zeolite A was given continuously via a feed dispenser. The daily calcium intake was calculated to be 60 g. Daily urine samples were obtained before, during and after the period of zeolite A supplementation. Urine pH was measured immediately whereas the remaining of samples was stored at C until analysis for calcium and creatinine. Urinary calcium/creatinine ratio was used as a measure of renal calcium excretion. Zeolite A supplementation did not affect urine pH. Renal calcium excretion peaked at the first day of supplementation, whereupon it decreased steadily to a level comparable to pre-exposure level. This could be explained by a sudden draw of calcium from the readily mobilizable pool in the bone. A commercial available water hardness test kit was evaluated as a possible cow-side test for monitoring renal calcium excretion. The repeatability of the analysis was acceptable (CV = 9.3). The accuracy of the test was good. When compared to laboratory derived urinary calcium/creatinine ratios of the same samples, a distinct linear relationship could be shown (Y = 7.9E-7 + 1.9E-8). It was therefore concluded that the water hardness test was able to monitor renal calcium excretion with an acceptable accuracy.