Impact of isothermic and bithermic dilution on quality of chilled boar sperm

ABSTRACT

The use of bithermic dilution protocols is increasing in artificial insemination centres; therefore, it is necessary to guarantee that the quality of insemination doses remain the same when compared to isothermic dilution protocols. Four ejaculates from each of 19 crossbreed PIC® boars were collected and assigned, in a split sample design, in three treatments two-step bithermic dilution two-step isothermic dilutionand one-step isothermic dilution. Temperature curves for the three treatments were recorded using a temperature sensor data logger. Semen doses were prepared with a BTS extender and stored at 16°C and then used to evaluate sperm parameters with the CASA system and sperm morphology for 120 h. The temperature in semen samples submitted to a two-step bithermic dilution reached 24.6ºC after 120 min, whereas one or two-step isothermic dilution samples reached 26.4ºC and 27.4ºC, respectively. Total motility, progressive motility and BCF were influenced (P < 0.05) by the storage time but not by the dilution procedure. Total and progressive motility decreased throughout the storage time (91.0 ± 0.91 to 81.5 ± 1.08% and 74.0 ± 2.48 to 60.4 ± 2.59% from 24 h to 120 h, for MOT and PROG, respectively) whereas BCF differed between 24 and 120 h (28.6 ± 0.76 and 27.3 ± 0.79 Hz). The following motility traits were not affected by the dilution procedure or by the time of storage DAP, DCL, DSL, VAP, VCL, VSL, STR, LIN, WOB, and ALH. At 72 h of storage, sperm morphology was not different among treatments (P > 0.05), showing an overall mean of 9.2 ±0.4 total defects. In conclusion, the bithermic dilution makes the production of artificial insemination doses faster by taking less time to reach a temperature close to that of storage, without impairing semen quality.(AU)