50 mL) provide an effective packaging system for freezing boar sperm worldwide. These straws allow uniform ice crystallization and enable the storage of a relatively high number of sperm, achieving good post-thaw sperm survival and acceptable fertility after AI. It is recommended that such straws be thawed at 70 °C/8 s in order to achieve the maximum sperm survival [17]. In peccaries, however, no differences were verified between 0.25 mL or 0.50 mL straws, when considering the same freezing curve and thawing rate as a reference. Similarly, www.selleckchem.com/products/INCB18424.html no difference between straw sizes was also described for agoutis, but sperm from such animals can be thawed either at 37 °C or 70 °C [35]. According to Erickson
and Rodriguez-Martinez [14], spermatozoa have to traverse the critical
temperature zone of −15 °C to −60 °C during freezing and thawing, and both these events are potentially harmful. A fast thawing rate has been reported as resulting in better post-thaw semen quality than a slower thawing rate for several species [29] and [30], including the boar [14]. In collared peccaries, Epigenetics inhibitor however, previous studies had demonstrated that thawing temperatures at 37 °C/1 min or 55 °C/7 s promote similar preservation of semen quality [7] and, as observed in the present study, the increase of thawing rate to 70 °C/8 s was extremely harmful for the peccary sperm. In fact, it is reported that an increase in the thawing rate could reduce the recrystallization of intracellular ice [11] and [15]. On the other hand, it could also induce osmotic stress on the sperm because of the abrupt melting of the extracellular solution that can cause unbalanced rates of water influx and cryoprotectant egress, and can lead to swelling and lyses of cells [3], [16] and [24]. As verified for collared peccaries, thawing temperatures at 37 °C are also recommended for Bama Benzatropine miniature pigs [23]. Indeed, even in domestic
swine, some authors recommend the use of such temperatures according to the protocol adopted for semen cryopreservation [22]. For Badinand et al. [5], thawing at 37 °C is safer than at higher temperatures because the time spent in high temperatures is always critical and could have a lethal influence on the sperm viability. Quantitative data evaluated by CASA has allowed for the detection of subtle changes in sperm motion and velocity, improving accuracy and efficiency in the discrimination between treatments in laboratory studies of new extenders, cryoprotectants, and other processes [1]. Based on this fact, along with the classic evaluation of collared peccaries semen, we can affirm that the results obtained in the present research for different parameters of frozen samples thawed at 37 °C are similar to those previously reported by Castelo et al. [8] and Silva et al. [34], using Tris- and coconut water extenders, respectively.