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To improve the boar sperm cryopreservation process, the influence of the sugar (lactose, trehalose) source and the cryoprotectant [glycerol, dimethylformamide (DMF)] on the success of freezing was investigated. Sperm samples were frozen in one of six extenders: lactose plus 3% glycerol (LG); lactose plus 1.5% glycerol and 1.5% DMF (LGD); lactose plus 3% DMF (LD); trehalose plus 3% glycerol (TG); trehalose plus 1.5% glycerol and 1.5% DMF (TGD); trehalose plus 3% DMF (TD). Effects on motility, viability, acrosome integrity and hypoosmotic test (HOST) were measured. The results showed that extender containing 3% glycerol retained the highest motility percentages. In regard to viability and acrosome integrity, all extenders yielded similar rates except for the decreasing values of TD. Endosmosis was diminished in TD and LD at 2 h (P = 0.0018), as compared with the others. The results of the study demonstrated that the use of DMF as a cryoprotectant adversely affected boar sperm quality after cryopreservation.

In an effort to improve the quality of in vitro produced porcine embryos, the effect of progestagens -progesterone analogues -on the in vitro developmental competence of porcine oocytes was studied. A total of 1421 in vitro matured oocytes, from 4 replicates, were inseminated with frozen-thawed spermatozoa. Progestagens were added to late maturation and embryo cultures (10 IU/ml). Fertilisation success (pre-maturation, penetration, monospermy and efficiency) and nuclear maturation were evaluated. There were no differences among prematuration rates between groups (P = 0.221). Penetration rates were higher (P < 0.001) in the presence of progestagens (75.0%) as compared to the control (51.7%). However, no differences were observed in monospermy percentages (P = 0.246). The results indicated that supplementation with progestagens increased the efficiency of the in vitro fertilisation system (P < 0.001). An additional beneficial effect was observed in nuclear maturation with progestagens (P = 0.035). In summary, progestagen supplementation is an important factor to improve the in vitro fertilisation procedure. Key words: In vitro fertilisation, oocyte maturation, progesterone, porcineThe overall efficiency of in vitro porcine embryo production and the quality of embryos are still low when compared with in vivo results (Funahashi, 2003). One of the major problems includes improper in vitro maturation (IVM) of oocytes, in both the nuclear and cytoplasmic compartments (Niwa, 1994;Marchal et al., 2001). While a large percentage of oocytes reached metaphase II after maturation, inadequate cytoplasmic and molecular maturation occurred (Sirard et al., 2006), leading to a lack of subsequent embryo development success. There is a lack of information on ovarian factors that may be important for the maturation and subsequent fertilisation of oocytes.The production of sex steroids by follicular cells is proposed to be influenced by the maturity of oocytes. Oestradiol, progesterone and testosterone are the main steroid hormones that play an essential role during the follicular and