Chilled Storage of Ram Semen Improves with the Addition of Egg Yolk and Glycerol to Milk‐Based Extenders

Abstract

This study aimed at comparing in vitro, ultra-heat-treated (UHT) skim milk and INRA-96(®) -based extenders supplemented or not with 5% egg yolk and/or 2% glycerol on sperm quality parameters along 72 h of preservation at 5 °C, using a factorial design. Semen from six healthy mature Merino rams was pooled and extended in each medium using a split sample procedure (six replicates) and chilled. Subjective motility (SM) (%), membrane integrity (MI) (%) and uncapacitated spermatozoa (US) (× 10(6) spermatozoa/AI dose) were used to assess the semen quality at 0, 12, 24, 48 and 72 h of preservation. UHT-based extenders yielded better (p<0.05) SM and MI than INRA-96(®) -based extenders (59.7% vs 57.9%; 60.2% vs 55.8%, respectively) but similar numbers of US (64.2% vs 62.3 × 10(6) sperm/AI dose, respectively) along the preservation time. Egg yolk-glycerol or just egg yolk as additives improved (p<0.05) the results compared with the base extenders without additives or just with glycerol. The sperm parameters assessed decline slowly from 0 to 48 h, with a sharp decline (p<0.05) at 72 h of preservation. In conclusion, UHT and INRA-96(®) were similar as base extenders, and the addition of 5% egg yolk plus 2% glycerol or just 5% egg yolk improved the quality of ram semen preserved at 5 °C, at least for 48 h. The combination of egg yolk-glycerol might provide extra protection in case of fluctuation of temperatures below 5 °C, commonly seen under field conditions.

Conception Rates in Ewes after AI with Ram Semen Preserved in Milk–Egg Yolk Extenders Supplemented with Glycerol

“…Egg yolk improves the protective properties of milk‐based extenders (Salamon and Maxwell 2000), and a previous in vitro study (Gil et al. 2010) confirmed that UHT and INRA‐96 ® were improved by this additive.…”

“…(2010) did not find significant differences in sperm viability for UHT supplemented with egg yolk compared to INRA‐96 ® without egg yolk. Gil et al. (2010) found that UHT‐based extenders were significantly better than those based on INRA‐96 ® assessed by subjective sperm motility and sperm membrane integrity, but behaved similarly for the number of uncapacitated spermatozoa in the AI dose.…”

“…UHT‐ and INRA‐96 ® ‐based extenders have been compared previously in vitro (O’Hara et al. 2010; Gil et al. 2010), but not in vivo .…”

“…2010). We compared in vitro the performance of INRA‐96 ® and ultra‐heat‐treated (UHT) skim milk, either supplemented or not with egg yolk and/or glycerol (Gil et al. 2010).…”

Viabilidad de espermatozoides ovinos mantenidos a 5º y 15ºC en diferentes sistemas de refrigeración

“…Gil et al (2011) describieron una disminución en la motilidad e integridad de membrana de espermatozoides mantenidos en medio diluyente a 5 ºC después de 48 horas de refrigeración, diferente de lo encontrado en este estudio, donde la integridad de la membrana (hipo-osmótico y de coloración con eosina) fue evaluada. Sin embargo no se alteró hasta las 72 horas (en torno de 75%), cayendo bruscamente a las 96 horas de refrigeración en las muestras mantenidas en medio diluyente, exceptuando las muestras mantenidas a temperatura ambiente que a las 72 horas no presentaron viabilidad y por tanto no fueron evaluadas para este parámetro durante este momento.…”