Assessment of Sperm Morphology in Zebu Bulls, under Field Conditions in the Tropics

Abstract

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 air-dried 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 < 0.05) of knobbed acrosomes (4.0 versus 0.9%), head defects [specifically, nuclear invaginations and heads with abnormal shapes and sizes (27.6 versus 4.0%)], abnormal tails (11.2 versus 4.7%), and proximal droplets (8.4 versus 1.6%), compared with bulls considered sound for breeding. In these latter bulls, the abnormality most commonly seen was the presence of single bent tails with an entrapped cytoplasmic droplet (3.0 +/- 3.7%). Young Zebu bulls (i.e. bulls under 2 years of age) showed a higher percentage of missing acrosomes, and proximal cytoplasmic droplets, than older sires (12.1 versus 2.4%, and 23.9 versus 3.6%, respectively; p < 0.05), interpreted as an indication of low ejaculation frequency and sexual immaturity, respectively. Bulls with a long scrotum and soft testicular consistency (TC) at palpation showed higher percentages of abnormal sperm heads in the ejaculate than bulls with a normal scrotal length (SL) and a normal TC (32.7 versus 12.8% and 30.7 versus 10.3%, respectively; p < 0.05). In addition, Zebu bulls with a scrotal circumference (SC) < or = 30 cm showed a higher prevalence of proximal cytoplasmic droplets than bulls whose SC was > 30 cm (9.8 versus 2.6%, p < 0.05). A higher mean percentage of abnormally sized and shaped heads, especially undeveloped and narrow at the base, was more frequently found in stained smears than in unstained samples (26.0 versus 9.9%, p < 0.05), which clearly underlines the importance of using both stained and wet smears when assessing sperm head morphology. However, for a quick assessment of sperm morphology under field, tropical conditions, phase-contrast microscopy provides useful information for the spermiogramme evaluation.

Morphological Features of Spermatozoa of Swamp Buffalo AI Bulls in Thailand

“…(1982). Moreover, the knobbed acrosome shape was the most common type of mis‐shaped acrosome among the present bulls, in agreement with previous findings in both Bos taurus and Bos indicus sires (Cran and Dott, 1976; Barth and Oko, 1989; Chacon, 2001). Acrosome defects are indicative of abnormal spermatogenesis, but rarely affect large numbers of bulls (Barth and Oko, 1989).…”

Impact of proximal cytoplasmic droplets on quality traits and in-vitro embryo production efficiency of cryopreserved bull spermatozoa

“…In a recent study on spermatozoal quality at spermiation in humans, two different kinds of proximal cytoplasmic droplets were described: proximal droplets that reflect epididymal and accessory sex gland alteration and spermatozoa with notable residual cytoplasm (not a cytoplasmatic droplet), indicating an immature cell with improper or incomplete spermiogenesis [4,5]. High percentages of PCDs can be found in the semen of prepubertal bulls, while in mature bulls, high levels of sperm with PCDs are considered a sign of abnormality in spermiogenesis or epididymal sperm maturation [3,6,7]. …”

Bull and boar sperm DNA integrity evaluated by sperm chromatin structure assay in the Czech Republic

“…Morphology evaluation is widely used for predicting fertility potential in farm animals (Johnson et al, 1998;Chacon, 2001) and in humans (Kruger et al, 1986;Vawda et al, 1996).…”