Pregnancy Rate Obtained with Short-term Protocol for Timed Artificial Insemination in Goats A Menchaca 1 and E Rubianes 2 1 Departamento de Fisiologı´a, Facultad de Veterinaria, UdelaR; 2 Departamento de Produccio ´n Animal y Pasturas, Facultad de Agronomı´a, UdelaR, Montevideo, Uruguay Contents Recent studies demonstrated that the Short-term Protocol of 5 days of progestogen treatment plus one dose of prosta- glandin F 2a and equine chorionic gonadotrophin (eCG) resulted in a close synchronized ovulation (60 h after the end of treatment approximately). In addition, oestradiol benzoate (ODB) is effective in synchronizing ovulation in goats and could be an alternative to eCG. This study was performed to determine the pregnancy rate using the Short- term Protocol comparing: (i) two different moments of timed artificial insemination (TAI) after eCG treatment (trial 1) and (ii) ODB as an alternative to eCG treatment (trial 2). In trial 1, 250 IU of eCG was given at the end of progestogen exposure, and cervical TAI with fresh semen was performed 48 h (n ¼ 156) or 54 h (n ¼ 168) later. In trial 2, 250 IU of eCG was given at sponge withdrawal (eCG group, n ¼ 154) or 200 lg of ODB was given 24 h later (ODB group, n ¼ 119). TAI was performed 54 h after the end of progestogen treatment. Pregnancy rate was determined by transrectal ultrasonography. In trial 1, the pregnancy rate for goats with TAI performed at 54 h (107/168, 63.7%) was higher than for those with TAI performed 48 h (77/156, 49.4%; p < 0.05) after sponge withdrawal. In trial 2, pregnancy rate was higher in eCG (94/154, 61.0%) than in ODB (49/119, 40.3%; p < 0.05) treated goats. In conclusion, the highest pregnancy rate was achieved using Short-term Protocol associated with eCG and TAI performed 54 h after treatment. Introduction Timed artificial insemination (TAI) requires hormonal treatments that ensure an adequate control of both follicular development and luteal activity to synchronize ovulation. These two aspects are controlled in goats by the Short-term Protocol (Menchaca and Rubianes 2004; Menchaca et al. 2006), of 5–6 days of progesterone/ progestogen plus prostaglandin F 2a (PGF 2a ) and equine chorionic gonadotrophin (eCG) treatment. Conven- tional TAI protocols (i.e. 11–17 days of treatment; Corteel et al. 1968, 1988) induce low serum progestogen concentrations during the end of treatment (Greyling et al. 1994; Rubianes et al. 1998). Low progestogen concentrations have a deleterious effect on sperm transport (Pearce and Robinson 1985) and induce inadequate follicular development, affecting ovulation, oocyte health and/or fertility in ruminants (cattle: Adams et al. 1992; Savio et al. 1993; Mihm et al. 1994a,b; Revah and Butler 1996, sheep: Leyva et al. 1998; Vin˜oles et al. 1999; Flynn et al. 2000, goats: Menchaca and Rubianes 2001, 2002). Different studies comparing new short-term treatments with conventional protocols were conducted in sheep and goats (Rubianes et al. 1998; Ungerfeld and Rubianes 1999; Vin˜ oles 2000; Ungerfeld 2001; Vin˜oles et al. 2001; Menchaca and Rubianes 2004). The Short-term Protocol achieves supraluteal levels of progesterone concentrations with an acceptable pregnancy rate with TAI 54 h after treatment. Recently, we determined that the Short-term Protocol induces LH peak at 40 h and ovulation occurs 60 h after the end of progesterone treatment (Menchaca et al. 2006). However, AI performed at different times before the 60 h need to be investigated. Moreover, the use of eCG after progestogen exposure to promote ovulatory follicular growth and ovulation is inquired as repeated eCG treatment is known to affect pregnancy rate in goats (Baril et al. 1992, 1996; Roy et al. 1999; Drion et al. 2001). This detrimental effect is associated with an immunogenic response induced by repeated eCG treatment, which is frequent in goats under intensive breeding programmes. In cattle, oestra- diol benzoate (ODB) is widely used after progesterone treatment nowadays to synchronize ovulation (Bo´ et al. 2003). Recently, we conducted a study on the endocrine profiles, follicular development and ovulation induced by the Short-term Protocol associated with ODB in goats (Menchaca et al. 2006). In this study, 200 lg of ODB given 24 h after the Short-term Protocol induced an LH surge and ovulation in all treated goats, in a similar way to that in eCG-treated goats. However, the pregnancy rate obtained with ODB after the Short-term Protocol has not yet been evaluated. This study was designed to determine the pregnancy rate obtained with the Short-term Protocol comparing: (i) two different times of TAI (trial 1) using eCG and (ii) the use of ODB as an alternative to eCG for TAI in goats (trial 2). Materials and Methods Animals and trials Two trials were performed with a total of 597 goats on three commercial dairy farms (Uruguay, 34°S), main- taining the same experimental design performed during the breeding and non-breeding season. Alpine, Saanen and Anglo Nubian lactating goats were used with more than 60 days of postpartum period and a body condi- tion score above 2.5 (scale 1–5). In both trials, the experimental groups were balanced considering the breed, the postpartum period and the body condition score. Goats were maintained under a typical semi- intensive grazing system on improved pastures, supple- mented with alfalfa hay at night and a commercial concentrate at the time of milking. Reprod Dom Anim 42, 590–593 (2007); doi: 10.1111/j.1439-0531.2006.00827.x ISSN 0936-6768 Ó 2007 The Authors. Journal compilation Ó 2007 Blackwell Verlag