Assessment of luteinizing hormone and prolactin immunoactivity in Asian and African elephant urine using assays validated for serum

Abstract

Analysis of serum hormones is useful for timing artificial insemination (LH) and diagnosing pregnancy (prolactin) in elephants. However, these tests require blood collection, which is not tolerated by all animals, and is impractical for field studies. Thus, developing a means to obtain these measures noninvasively could improve species management. Matched urine and serum was collected from Asian and African elephants daily throughout the follicular phase and after administration of a GnRH analogue for LH determination, and in pregnant and nonpregnant females for prolactin analyses using immunoassays validated for elephant serum. Despite identifying robust increases in circulating hormone concentrations, no concomitant changes in urinary LH or prolactin immunoactivity was detected. Concentration of samples by centrifugal filtration or ethanol precipitation did not increase the ability to measure biologically relevant changes in endogenous urinary LH or prolactin immunoactivity. Sample matrix interference was ruled out following sufficient recovery of exogenous LH or prolactin added to samples, except for samples concentrated >35-fold where some interference was suspected. These results suggest that elephants either do not excrete native LH or prolactin in urine, or concentrations are too low to be measured accurately by standard immunoassay techniques that are valid for serum analyses. Thus, it does not appear feasible or economically viable to use these non-invasive tests for ovulation detection or for pregnancy diagnosis in elephants.