Effects of oocyte activation and treatment of spermatozoa on embryonic development following intracytoplasmic sperm injection in cattle

The objective of this study was to determine the effects of oocyte activation and of different treatments of spermatozoa on cleavage rate and blastocyst production after bovine intracytoplasmic sperm injection (ICSI). In Experiment 1a, matured oocytes were injected without spermatozoa (sham injection) and randomly allocated to 1 of 3 treatments: 1) untreated controls, 2) 50 mu M calcium ionophore A23187, or 3) 7% ethanol. Cleavage rates after A23187 (55%, 41/75) and ethanol treatments (52%, 39/75) were higher (P<0.05) than that of the control (4%, 3/75), but no cleaved oocytes developed into morulae or blastocysts in any of the treatments. In Experiment 1b, each oocyte was injected with 1 spermatozoan that had been incubated with heparin (capacitated) and then randomly allocated to 1 of 3 treatments as in Experiment 1a. Cleavage rates after A23187 (47%, 33/70) and ethanol (50%, 34/68) treatments were higher (P<0.05) than that of the control (25%, 17/68). The A23187 treatment resulted in more blastocysts/oocyte (16%) than ethanol treatment or controls (0 and 6%, P<0.05). :in Experiment 2a, in vitro fertilization with spermatozoa incubated for 2 h with heparin (capacitated) had a higher (P<0.01) cleavage rate (67%, 101/150) than with unincubated (24%, 36/150) or with incubated + A23187-treated spermatozoa (33%, 49/150). Blastocyst formation rates/oocyte did not differ among these treatments (P>0.05). In Experiment 2b, all oocytes were activated with A23187. Cleavage rates for sham-injected, unincubated, incubated, and incubated + A23187-treated spermatozoa after ICSI were 43% (25/58), 40% (24/60), 38% (22/58) and 44% (27/62), respectively (P>0.1). The use of incubated (capacitated) spermatozoa yielded a higher rate (P<0.05) of blastocyst formation/oocyte (10.3%) than that of the sham injections (0%), but did not differ from that of unincubated spermatozoa (3.3%) or of incubated + A23187-treated spermatozoa (6.5%). (C) 1997 by Elsevier Science Inc.