Use of glucose or BTS"! combined with DMSO or methylglycol under two different freezing protocols for the cryopreservation of sperm from the common curimatã (Prochilodus brevis)

Abstract

This study evaluated the effect of glucose or Beltsville Thawing Solution (BTS™) combined with dimethyl sulfoxide (DMSO) or methylglycol (MG) under two different freezing protocols on the kinetics and morphology of cryopreserved Prochilodus brevis sperm. The semen samples were diluted using one of four different treatments (glucose+DMSO, glucose+MG, BTS™+DMSO, and BTS™+MG), loaded into 0.25-ml straws and subjected to two different freezing processes (programmed freezing machine and dry shipper). After 10 days, the semen samples were thawed, and the sperm morphology and kinetics were evaluated. The physicochemical parameters of the semen in natura were similar to those observed in other studies of Characiformes, indicating the feasibility of semen cryopreservation. Glucose, when used as a diluent with the cryoprotectant MG (glucose+MG), yielded higher percentages of mobile spermatozoa after freezing in a dry shipper (76.88 ± 4.84%) and in a programmed freezing machine (70.95 ± 1.76%) compared with the combination of glucose and DMSO. Moreover, the glucose+MG treatment yielded a higher sperm velocity (curvilinear velocity: 79.52 ± 2.88 µm s- 1 ; straight-line velocity: 45.46 ± 3.01 µm s-1 ; average path velocity: 67.92 ± 3.08 µm s-1 ) than the other studied treatments, and a higher amount of normal sperm (74.56 ± 0.77%) was observed in the semen samples cryopreserved using a programmed freezing machine. The sperm abnormalities observed included a bent tail morphology. Therefore, the use of glucose+MG in combination with either a dry shipper or a programmed freezing machine is recommended for the cryopreservation of P. brevis sperm because these methods yielded high numbers of motile and morphologically normal spermatozoa.