Physical characteristics and fertility of fractionated donkey semen cooled at 5°C

Abstract

The aim of this study was to evaluate the effect of two different extenders (Skimmed Milk Glucose -SMG or Lactose -Egg Yolk -LEY) on physical characteristics and fertility of fractionated donkey semen cooled at 5°C. For this, four Pêga donkeys were used as semen donors. The sperm rich fraction of the ejaculate was diluted preparing insemination doses containing 400 x 10 6 motile spermatozoa in a volume of 22 mL, cooled to 5°C and stored up to 48 hours in a container proposed by Palhares (1997). Sperm motility and vigor were assessed in fresh semen, after first semen dilution, before insemination, at 24 and 48 hours after storage. For the fertility evaluation, 44 mares were inseminated with semen stored for a period between 12 and 24 hours. The mares were inseminated on fixed days (Mondays, Wednesdays, and Fridays) after the detection of a follicle greater than a 30mm diameter in one of the ovaries through ovulation. Pregnancy diagnosis was performed on day 12 post-ovulation, using transrectal ultrasonography. Semen diluted in SMG showed superior sperm motility than LEY, at the Pre-AI evaluation (P<0.05). At 48 hours of storage, all donkeys had motility values between 45 and 53% for semen diluted in SMG, while only one donkey showed motility greater than 30% in the LEY treatment. The pregnancy rate/cycle for mares inseminated with semen diluted in SMG was superior than that obtained using LEY (56.52% vs 4.76%, respectively).Keywords: donkey, fractionated collection, cooled semen, fertility RESUMO Objetivou-se com o presente experimento avaliar o efeito de dois diferentes diluidores (leite em pó desnatado glicose -SMG ou lactose gema de ovo -LEY) sobre as características físicas e a fertilidade do sêmen asinino coletado de forma fracionada e resfriado a 5ºC. Para isso, quatro jumentos da raça Pêga foram utilizados como doadores de sêmen. A fração espermática rica do ejaculado foi diluída preparando-se doses inseminantes contendo 400 x 106 espermatozoides móveis em um volume de 22 mL, resfriadas a 5ºC e armazenadas por até 48 horas em contêiner proposto por Palhares (1997)

Ability of donkey sperm to tolerate cooling: Effect of extender base and removal of seminal plasma on sperm parameters and fertility rates in mares

“…However, although centrifugation improved the ability of donkey semen extended in SM to tolerate cooling in the present study, it did not yield comparable sperm analytical parameters and fertility to SC- and EY-extended semen. Interestingly, Carvalho et al reported that the sperm-rich fraction of jack semen cooled in a SM-based extender resulted in superior motility parameters and fertility in horse mares compared to a lactose-egg yolk extender ( 13 ). These results may illustrate the interaction between the seminal plasma and sperm cooling tolerance with SM extenders in donkeys.…”

“…Even though some studies have reported fertility rates of cooled donkey semen ranging from 21 to 76% using extenders with different bases, the average period of storage in the majority of studies has been short (e.g., 2–8 h) ( 24 – 26 ) or mares were inseminated several times in the same estrous cycle ( 13 , 63 ). Therefore, in our previous study with cooled donkey semen ( 14 ), the authors deliberately mimicked conditions in equine practice where semen is often shipped over long distances for 24–48 h ( 2 ).…”

“…However, donkey semen does not clinically appear to tolerate cooling in these same commercially available milk-or milk-protein-based extenders (2). Additionally, even though few studies have compared semen extenders for cooling donkey sperm, there is presently no gold standard protocol for this species (4)(5)(6)(7)(8)(11)(12)(13). Clinical experience and previous studies suggest that donkey sperm needs an additional source of cholesterol to preserve sperm characteristics after cooling (2, 14).…”

Effect of egg yolk-based extender and seminal plasma removal on sperm viability of cooled donkey semen

“…Milk-based extenders supplemented with egg yolk preserved equine sperm motility and fertility for 24 h at 5° to 8 °C (Varner et al, 1989;Jasko et al, 1992). Likewise, egg yolk added to the milk-based extender is frequently used to cool donkey semen, preserving progressive motility, vigor, and acrosome integrity (Cottorello et al, 2002;Rota et al, 2008;Carvalho et al, 2017;Wu et al, 2018). However, their undefined chemical composition constitutes a relevant disadvantage.…”