EFFECTS OF IN-VITRO TREATMENT OF BOAR SPERMATOZOA WITH TEPA ON THE FERTILIZATION AND DEVELOPMENT OF PIG EGGS

Numerous studies have demonstrated the value of using heterospermic inseminations for comparing the fertilizing capacity of males (Edwards, 1955; Beatty, 1957, 1960; Beatty et al., 1969; Stewart et al., 1974; Overstreet & Adams, 1971; Martin & Reimers, 1973) and for assessing sperm treatments (Roche et al., 1968; Miller et al., 1969; Dziuk, 1970; O'Reilly et al., 1972). Overstreet & Adams (1971) and Bedford & Overstreet (1972) showed that X-irradiation of rabbit spermatozoa in vitro effectively 'marked' the sperm nucleus without affecting the fertilizing capacity. Ova fertilized by the 'marked' spermatozoa have retarded cleavage. The 'marked' spermatozoa were mixed with unmarked spermatozoa from the same ejaculate and used to test the comparative fertilizing capacity after different sperm treatments were superimposed on the two sperm populations. Taber & Borkovec (1969) found that in-vitro treatment ofhoney bee spermatozoa with the chemosterilant TEPA (Tris(l-aziridinyl)phosphine oxide) caused death of all eggs fertilized by the treated spermatozoa. The research reported in this paper was conducted to determine whether TEPA could effectively 'mark' boar spermatozoa in vitro for use in competitive fertilization experiments involving frozen spermatozoa. Preliminary results showed that the addition of 0-1-10 mg TEPA/ml boar semen had no adverse effect on sperm motility or acrosome morphology. Subsequently, 9 gilts were inseminated with boar spermatozoa that had been treated with 0-1, 1-0 or 5-0 mg TEPA/ml semen (Table 1). Fertilized eggs were recovered from 8 gilts 144-168 hr after oestrus, but the cleavage rate of the fertilized eggs was severely retarded. Whereas morulae or blastocysts were expected (Hancock, 1961), single-cell eggs with pronuclei and twoto eight-cell eggs were found (Table 1). The number ofblastomeres decreased as the levels of TEPA increased ( 2 = 25-36; P<0-005). To test whether TEPA-treated boar spermatozoa could compete equally with untreated boar spermatozoa, gilts were inseminated intracervically with (1) 6xl09 untreated frozen spermatozoa (U); (2) 6xl09 TEPA-treated fresh spermatozoa (T); or (3) 3xl09 untreated frozen spermatozoa and 3xl09 TEPA-treated frozen spermatozoa (U + T) from the same boar or from the same pool of semen from two or more boars. Each gilt received two inseminations of