2006, 2008). Because of this, timed artificial insemination (TAI) programmes have become important tools for the reproductive management at many commercial dairy farms (Pursley et?al. 1997b; Rabiee et?al. 2005; Souza et?al. 2008). Many TAI programmes are based on the original Ovsynch protocol that can be used to synchronize the time of ovulation at first and subsequent AIs in lactating dairy cows (Pursley et?al. 1997b). The Ovsynch synchronization protocol was developed Itraconazole
to synchronize ovulation in cows using GnRH and PGF2�� (Pursley et?al. 1997b). This protocol synchronizes ovulation within an 8-h period from 24 to 32?h after the second GnRH administration. This precise synchrony allows for successful AI without the detection of oestrus. Numerous research reports have compared the Ovsynch, modified Ovsynch and other reproductive management strategies. For instance, in early studies, pregnancy rates were found to be similar or greater in cows inseminated with TAI (Ovsynch) than in cows inseminated after detected oestrus (Pursley et?al. 1997a,b). www.selleckchem.com
Pursley et?al. (1997a) indicated that the conception rate in lactating dairy cows (n?=?310) averaged 38% following the Ovsynch protocol or AI based on oestrous detection with three injections 14?days apart. Similarly, Gumen et?al. (2003) showed that the conception rate after AI was 32% in cows receiving the Ovsynch protocol and 35% in cows inseminated after oestrous detection. Furthermore, the Ovsynch protocol reduced the median days post-partum to the first AI (54 vs 83: p?<?0.001) and days open (99 vs 118: p?<?0.001) in lactating dairy cows compared with the oestrous detection-based synchronization programme (Pursley et?al. 1997b). In 2005, a meta-analysis of 71 trials in 53 research publications with sufficient experimental details for inclusion found that no differences were detected between Ovsynch and various other reproductive <a href="http://www.selleckchem.com/products/Roscovitine.html
">CYC202 cell line management strategies (Rabiee et?al. 2005). However, the variation in conception rates between herds and between trials was substantial (Rabiee et?al. 2005). The other significant advantage of Ovsynch is that it can be applied at a random stage of the oestrous cycle (Pursley et?al. 1997a), although the stage of the oestrous cycle at the initiation of Ovsynch affects fertility in response to the protocol (Bello et?al. 2006; Vasconcelos et?al. 1999). Cows that begin Ovsynch in the late luteal phase (Days 13�C17 of oestrus) and do not ovulate in response to the first GnRH treatment may have premature regression of the CL and undergo oestrus and potentially ovulation prior to the second GnRH treatment of Ovsynch (Vasconcelos et?al. 1999).