Efeito de diferentes tempos de equilíbrio, taxas de congelamento e concentrações espermáticas na fertilidade do sêmen eqüino

Abstract

O objetivo deste estudo foi avaliar a eficiência de diferentes tempos de equilíbrio, as curvas de congelamento e descongelamento e a concentração espermática por dose inseminante sobre a fertilidade do sêmen eqüino. No Experimento 1, foram utilizados cinco ejaculados de três garanhões da raça Mangalarga Marchador, sendo o grupo experimental dividido em três tratamentos: T1 = tempo de equilíbrio de 25 minutos, T2 = tempo de equilíbrio 1h25 min e T3 = tempo de equilíbrio com 2h25 min, em que a qualidade seminal foi avaliada por testes como supravital, teste hiposmótico (Host), motilidade e vigor espermático progressivo no TTR. A motilidade espermática progressiva avaliada no TTR nos tempos de 0, 20 e 40 minutos não diferiu. Não houve diferença na qualidade do sêmen nos diferentes tempos do TTR (P > 0,05). Houve redução de aproximadamente 33% de espermatozóides reativos ao Host após o descongelamento, em comparação aos resultados registrados no sêmen in natura, de onde se conclui que o tempo de equilíbrio não tem nenhuma influência na qualidade espermática do sêmen congelado. No Experimento 2, para teste de fertilidade, foram utilizados cinco ejaculados de seis garanhões da raça Mangalarga Marchador e dois garanhões da raça Bretão-Postier e foram testadas duas concentrações espermáticas por dose inseminante, em que T1 = 300 milhões e T2 = 150 milhões. A taxa de prenhez obtida em 95 estros foi de 54,7% (T1 = 35/64 estros) e 51,6% (T2 = 16/31 estros), e não diferiu das taxas de prenhez registradas nos dois tratamentos (P > 0,05). No Experimento 3 foram utilizados cinco ejaculados de três garanhões da raça Mangalarga Marchador, em que foram testados dois protocolos de congelamento, sendo curva horizontal (CH) com taxa de congelamento de -60 oC/minuto e curva vertical (CV) com taxa de congelamento de -100 oC/minuto e dois protocolos de descongelamento, sendo 37 oC/30 e 75 oC/7 . Comparando-se a porcentagem de espermatozóides móveis pós-descongelamento com o sêmen fresco, observaram-se perdas de motilidades progressiva de 28,6% no T0 do TTR; ao final do TTR (90 minutos) este valor não ultrapassou 50%, independentemente dos protocolos de congelamento e descongelamento. Entretanto, queda acentuada na motilidade espermática e no vigor espermático pós-descongelamento para CH, quando comparada aos 40, 60 e 90 minutos do TTR com a CV (39,7% vs 50,23% e 40,2% vs 50%), (36,7% vs 43,7% e 36,3 vs 43,9) e (27,8 vs 35,9 e 25,44 vs 40,86) tanto no descongelamento quanto a 37 oC e 75 oC, respectivamente (P < 0,05). Resultados superiores foram obtidos para o vigor. A taxa de prenhez obtida em 25 ciclos para a CV foi de 81,8% para a concentração 300 milhões e de 71,4% para 150 milhões de espermatozóides viáveis no descongelamento.

The freezing process cause damages the structural integrity, biochemist and biophysical the plasmatic membrane of the spermatozoon, leading a reduction in the fertility of the semen after the unfreeze. These damages are in consequence the imperfections in the freezing process that it understands since the collection until speed and time of centrifugation; curve of cooling and freezing; balance time; spermatic concentration for inseminated dose and frequency of insemination. The objective of this study was to evaluate the efficiency of alternative method equine semen freezing, as different times of balance, curves of freezing and unfreeze on the fertility of the equine semen. In Experiment 1, five ejaculates of three had been used sires of the race Mangalarga Marchador where the experimental group was divided in three treatments: T1 = time of balance of 25; T2 minutes = 1 time of balance and 25 minutes; and T3 = time of balance with 2 hours 25 minutes, where tests had been evaluated as survival, hypostatic test motilities and vigor in the TTR. The total motilities evaluated by the TTR in the times of 0, 20 and 40 minutes did not differ (P > 0.05) between the T1 and the evaluated semen the cool one. It did not have difference (P > 0.05) enter the treatments how much the evaluated motilities in the different times of the TTR, and evaluated vigor inside of each time. It approximately had a reduction of 33% number of reactive spermatozoa to the Host in the unfreeze, comparison to the results found in the cool semen. The structural integrity of the plasmatic membranes was evaluated using the survival test, being the dead spermatozoa had been approximately 36.15% superior in the frozen semen when compared with the cool semen. In Experiment 2 for fertility test one used five ejaculates ones of six sires of the race Mangalarga Marchador and two of the race Breton. Where a curve of freezing T1 was tested and two spermatic concentrations for inseminated dose T1 = 300 million and T2 = 150 million. The tax of gestation gotten in 95 cycles was analyzed getting tax of 54.7% fertility (T1 = 35/64 cycles) e 51.6% (T2 = 16/31 cycles). It did not have difference (P > 0.05) between treatments between the treatments. In Experiment 3 five ejaculates of three sires of the race Mangalarga Marchador had been used where it was tested two protocols of freezing, CH (horizontal curve) with one tax of freezing of -60 oC/minute and CV (vertical curve) with one tax of freezing of -100 oC/minute (extreme-fast) and two protocols of unfreeze 37 oC/30 and 75 oC/7 . Comparing it mobile percentage of spermatozoa after unfreeze with the cool semen, had observed losses of next motilities to 28.6% in the T0 of the TTR, to the end of the TTR (90 minutes) this value did not exceed to 50%, independently of the procedure of freezing and unfreeze. However, a fall accented in the motilities and vigor after unfreeze for CH when compared with the 40, 60 and 90 minutes of the TTR with the CV (39.7% versus 50.23% and 40.2% versus 50%), (36.7% versus 43.7% and 36.3 versus 43.9) e (27.8 versus 35.9 and 25.44 versus 40.86) in such a way in the unfreeze the 37 oC and 75 oC respectively (P < 0.05). Superior results had been gotten for the vigor. The tax of gestation gotten in 25 cycles for the CV was of 81.8% for the concentration 300 71.4% and million for 150 million viable spermatozoa in the unfreeze.