Abstract

RODRIGUEZ-ALMEIDA, Felipe A. et al. Sperm capacitation induced by conservation of diluted, refrigerated, or frozen ram semen. Agrociencia [online]. 2008, vol.42, n.4, pp.399-406. ISSN 2521-9766.

Refrigeration and cryopreservation of spermatozoa reduce or interrupt their metabolic activity and prolong their viability, but sperm capacitation (CE) induced in ram semen may reduce its fertility. In order to determine the degree of CE induction and the effect on progressive motility (MP) fresh semen samples were assessed [double boiler water bath at 36 °C for 3 (F3) and 6 h (F6)]; refrigerated [5 °C for 3 (R3), 6 (R6), and 24 h (R24)]; and frozen [(CON) in liquid N]. Five ejaculates of each of three young rams and three adults per breed (Pelibuey and Blackbelly) were diluted in citrate-yolk extender and divided proportionally in three aliquots. Percentages of MP and of capacitated spermatozoa with intact acrosome (B pattern) and acrosomal reaction (RA pattern) were determined, the two latter in duplicate with chlortetracycline assay. The statistical model for evaluating MP included fix effects of type-time preservation (PRE), breed, age, and their interactions; and random effects of ram and its interaction with PRE within breed and age. For B and RA patterns, the model included also the random effects of ejaculate and ejaculate by PRE within ram, breed and age. The means for B pattern were 23.9, 30.8, 32.8, 42.5, 44.5, and 36.6 % (E.E.=2.3; p<0.01) for F3, F6, R3, R6, R24, and CON. There was interaction of PRE with age for RA pattern; it was greater (p<0.01) in young rams than in adults only in R24 (27.8±1.6 vs 19.8±1.6%) and CON (33.9±1.6 vs 26.3±1.6%). MP was more reduced (p<0.01) in F6 and CON than in the other levels of PRE. With refrigeration at 5 °C ram semen motility was maintained, but when it was kept until 24 h, the same as with cryopreservation, the induced CE levels change fertility.

Keywords : Chlortetracycline; cryopreservation; ram semen.