Banca de DEFESA: THALLES CLOVES MACIEL DE MOURA

EFFECT OF ADDITION OF QUARBOXYMETHYLCHITOSAN TO STALLION SEMEN FREEZING DILUENT.

Carboxymethylchitosan, molecular weight, spermatozoa, horses.

The objective of this study was to investigate the effects of the addition of medium and low molecular weight carboxymethylchitosan (CQ) on the quality of equine semen after freezing/thawing. Two experiments were carried out, one QC of medium molecular weight (Exp. 1; CQm) and the other with low molecular weight CQ (Exp. 2; CQb). For each experiment, 5 ejaculates of 4 stallions (n= 20) were obtained, being collected twice a week. The samples were diluted (200 x 10⁹) in Botucrio^®, supplemented with CQ, according to the experimental group: 0 (control), 0.75, 1.5 and 3 mg/mL. After leakage in straws (0.5 mL), the samples were submitted to freezing and storage at -196°C.  After thawing (37°C 30s), the samples from each group were analyzed for kinetics in the CASA system, as well as intact plasma membrane (iPM), intact acrosome (iAC), and mitochondrial membrane potential (MMP) under epifluorescence microscope. Exp. 1: The addition of 0.75 mg/mL of CQm did not result in a significant difference (P > 0.05) in TM and VCL, in relation to the control group, but the groups treated with 1.5 and 3 mg/mL of CQm presented lower values (P < 0.05) than the control group. The RAP, VSL and VAP parameters showed no difference (P > 0.05) between the control group and the groups treated with 0.75 and 1.5 mg/mL of CQm, but the values were higher (P < 0.05) than those observed in the group treated with 3 mg/mL of CQm. Regarding the WOB, the control group presented a higher level (P < 0.05) than the groups treated with 1.5 and 3 mg/mL of CQm. Lower percentages of iAC (P < 0.05) were found in the samples of the group treated with 3 mg/mL of CQm. The iMP and PMM parameters did not differ (P > 0.05) between groups. Exp. 2: TM and MP showed no difference (P > 0.05) of the control group with the group treated with 0.75 mg/mL of CQb, but the groups treated with 1.5 mg/mL and 3 mg/mL of Qb presented lower values (P < 0.05) to the control group. While the parameters of VCL, VSL and VAP, at the concentration of 1.5 mg/mL of CQb, presented lower results (P < 0.05), when compared to the control group. The LIN and WOB parameters showed lower values (P < 0.05) in the group treated with 3 mg/mL of CQb, in relation to the control group. The parameters STR, BCF and ALH showed no difference (P > 0.05) between groups. Regarding iMP, the group treated with 3 mg/mL of CQb showed lower percentages (P < 0.05) than the control group, while the iAC and MMP showed no difference (P > 0.05) between groups. It was concluded that both medium and low molecular weight carboxymethylchitosan, at concentrations of 0.75, 1.5 and 3 mg/mL, do not preserve the sperm parameters of garanhōes after freezing/thawing.