Assessment of sperm morphology in Zebu bulls, under field conditions in the tropics

Sperm morphology was studied in 302 extensively managed Zebu bulls (aged 1.5-9 years), classified as sound (n = 166) or unsound (n = 136) for breeding, under field conditions in the dry tropics of Costa Rica. Single semen samples were collected by electro-ejaculation and fixed in formol-saline solution immediately after collection. Sperm morphology was determined in the field on wet smears using a microscope equipped with phase-contrast optics, and further determined in the laboratory on airdried smears stained with carbol-fuchsin. The frequencies of sperm abnormalities (such as abnormal acrosome, head, neck, mid-piece, tail, and presence of cytoplasmic droplets) were recorded as a percentage of the total number of counted spermatozoa (400 cells). Zebu bulls considered unsound for breeding showed a higher mean prevalence (p 30 cm (9.8 versus 2.6%, p 30 cm (9,8 frente a 2,6%, p < 0,05). En los frotis teñidos se encontró con mayor frecuencia un porcentaje medio de cabezas de tamaño y forma anormales, especialmente no desarrolladas y estrechas en la base, que en las muestras sin teñir (26,0 frente a 9,9%, p < 0,05), lo que subraya claramente la importancia de utilizar tanto frotis teñidos como húmedos al evaluar la morfología de las cabezas de los espermatozoides. Sin embargo, para una evaluación rápida de la morfología de los espermatozoides en condiciones tropicales de campo, la microscopía de contraste de fase proporciona información útil para la evaluación del espermiograma.Universidad Nacional, Costa RicaEscuela de Medicina Veterinari