Assessing the fertility potential of equine semen samples using the reducible dyes methylene green and resazurin.

The objective of this study was to determine if spermatozoal reduction of the dyes methylene green to colorless and resazurin to pink or colorless was associated with the fertility potential of an equine semen sample. Fifty samples from 38 stallions were evaluated for the number of spermatozoa per milliliter and number of motile sperm per milliliter. Methylene green (20 micrograms/mL of semen) or resazurin (85 micrograms/mL of semen) was added to 3-mL aliquots of semen. Semen samples were identified as having low fertility potential (< 200 x 10(6) total cells/mL and < 140 x 10(6) motile cells/mL) or high fertility potential (> or = 200 x 10(6) total cells/mL and > or = 140 x 10(6) motile cells/mL). The sensitivities were 80% for the methylene green, 68% for the resazurin to pink, and 60% for the resazurin to colorless tests. The specificities were 80% for the methylene green, 79% for the resazurin to pink, and 92% for the resazurin to colorless tests. The overall accuracies were 80% for the methylene green test, 74% for the resazurin to pink test, and 76% for the resazurin to colorless tests. The methylene green and resazurin reduction tests can provide valuable information on the fertility potential of an equine semen sample.

Modified resazurin reduction test for determining the fertility potential of bovine spermatozoa.

The objective of this study was to determine if reduction of the dye resazurin by bovine sperm is associated with the concentration of motile and progressively motile sperm. Metabolically active sperm reduce resazurin (blue color) to resorufin (pink color) and upon further reduction to dihydroresorufin (white color). A total of 68 semen samples from 20 Limousin bulls were collected using electroejaculation. The concentration of motile and progressively motile sperm was determined. Resazurin was added to each semen sample (8.8 microgram/mL semen), samples were then incubated at 37 degrees C for a maximum of 15 min, and visual color changes indicative of dye reduction were noted. Samples were identified as having either low fertility potential (< 200 x 10(6)/mL motile sperm and < 100 x 10(6)/mL progressively motile sperm) or high fertility potential (> or = 200 x 10(6)/mL motile sperm and > or = 100 x 10(6)/mL progressively motile sperm). Assessment of the reduction of resazurin from blue to pink (< or = 3.5 min) allowed identification of 88% of the low and 94% of the high fertility potential samples. In addition, the reduction of resazurin from blue to white (< 15 min) resulted in identification of 82% of the low and 76% of the high fertility potential samples. The modified resazurin reduction test is useful for determining the fertility potential of bovine spermatozoa.