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The objective was to assess the effect of adding various concentrations of dimethylformamide on characteristics of canine semen diluted in powdered coconut water (ACP-106C; ACP Biotecnologia, Fortaleza, CE, Brazil) and frozen at -196°C. Fifteen ejaculates were collected by manual stimulation from five adult Boxer dogs. The sperm-rich fraction was diluted in ACP-106C (ACP Biotecnologia) containing 10% egg yolk and divided into four aliquots. The cryoprotectants used for each aliquot were 6% glycerol (control group; CG) or 2%, 4%, or 6% dimethylformamide (DF2, DF4, and DF6, respectively). After thawing, total motility (mean ± SEM) for CG (58.4 ± 24.6) was higher (P < 0.05) than that of the other groups (2% dimethylformamide, 24.4 ± 12.3; 4% dimethylformamide, 26.5 ± 16.1; and 6% dimethylformamide, 21.7 ± 17.9). Furthermore, there was a greater percentage of fast, average, and slow moving sperm (assessed with computer-aided semen analysis; CASA) in CG in comparison with the other three groups. Therefore, based on concentrations tested in this study, dimethylformamide, together with ACP-106C (ACP Biotecnologia) and 10% egg yolk as a diluent, yielded unsatisfactory in vitro results for freezing canine semen.

We aimed to compare fresh sperm and sperm cooled to 4ºC that had been recovered from the epididymides of cats using powdered coconut water (ACP-117c) and Tris extenders. Sixty epididymides were divided into 6 groups: 10 fresh epididymides were recovered using Tris (T0h); 10 were kept at 4°C/2h and recovered using Tris (T2h); 10 were kept at 4°C/4h and recovered using Tris (T4h); 10 fresh were recovered using ACP-117c (A0h); 10 were kept at 4°C/2h and recovered using ACP-117c (A2h), and 10 were kept at 4°C/4h and recovered using ACP-117c (A4h). The testis-epididymis complexes (TEC) control were not cooled. The others were cooled at 4°C for 2 or 4h. The epididymis was separated and the sperm was recovered by the modified flotation method. Sperm kinetic parameters were evaluated by a computer-system analysis, and vigor, viability, concentration, membrane function and morphology of the sperm were assessed under a light microscope. The progressive motility with ACP-117c declined after 2h of cooling, but did not differ between fresh and 4h. The vigor and membrane function were higher in A4h than A0h. The vigor at T2h and T4h were decreased compared to T0h. T0h was higher than A0h for vigor and sperm membrane function. However, after 4h of cooling, ACP-117c maintained a higher percentage of living cells. Feline epididymal sperm quality can be maintained to the degree necessary for artificial breeding programs following cooling and ACP-117c may be successfully used to recover cat sperm that have been cooled for up to 4h.

Standardized sperm concentration and volume:volume extension were compared as dilution rates for canine semen freezing. Six proven stud dogs were submitted to two seminal collections by manual stimulation. Semen was evaluated and extended in tris plus egg-yolk and glycerol according to two different dilution rates. The first one was based on a standardized sperm concentration of 200x10 6 spermatozoa/ml and the second was a volume:volume extension at a proportion of one part semen to one part extender. Semen was frozen, stored in liquid nitrogen and thawed after one week. Sperm motility and vigor were appraised after each stage of the process and at 15 and 30min post-thawing. Sperm morphology was analyzed after collection and thawing. No differences were observed between treatments after thawing regarding sperm motility and vigor, normal sperm morphology rate or longevity. Both dilution rates can be efficiently used for canine semen freezing.