Abstract
Flow cytometry of testicular and sperm cells was used to evaluate effects of pre-weaning zeranol implants on spermatogenesis. Forty five Angus-Simmental bulls were randomly assigned to three treatment groups of 15 bulls each: 1) no implant, 2) one implant at 30 d of age and 3) two implants, one at 30 and the second at 120 d of age. Prior to slaughter at approximately 15 mo, semen was collected from 30 bulls, 10 of each group. Following slaughter, testes were weighed, and testicular biopsies and vas deferens sperm obtained from the same 30 bulls. Testicular and sperm cells were stained with acridine orange and measured by flow cytometry. Proportions of testicular haploid, diploid and tetraploid cells were determined by relative amounts of green (DNA) and red (RNA) fluorescence. Treatment of sperm at low pH prior to acridine orange staining potentially induces partial denaturation of DNA, detectable by the metachromatic shift from green (native DNA) to red (single-stranded DNA) fluorescence. The effect of this shift was quantified by alpha-t [αt = red/(red + green) fluorescence] . Nonimplanted bulls had heavier (P<.01) testicular weights than treated bulls. The proportion of haploid cells was greater (P<.02) and diploid cells less (P<.03) in testes of nonimplanted bulls. Sperm from implanted bulls had altered chromatin structure, indicated by higher (P<.05) αt values. Flow cytometry is an effective means for detecting changes in testicular cell subpopulations and chromatin structure of sperm. Copyright © 1986. American Society of Animal Science . Copyright 1986 by American Society of Animal Science