Effect of solid storage at 15 °C on the subsequent motility and fertility of rabbit semen

Abstract

We conducted two studies to improve preservation of rabbit semen. The objective of the first study was determine whether a glucose- and fructose-based extender with two different amounts of gelatin would solidify at 15 °C, and to evaluate the influence of gelatin supplementation on sperm motility parameters after storing semen up to 10 days at 15 °C. The fertility of rabbit semen diluted in the best gelatin-supplemented extender established in Study 1 and stored for up to 5 days was evaluated in the second study. In Study 1, semen was collected with an artificial vagina from 40 bucks. Each ejaculate was diluted to (80–100) × 10 6 spermatozoa/mL (1:3, semen/extender) at 37 °C in one of the three following glucose- and fructose-based extenders: control (standard liquid extender), semi-gel or gel (0.7 or 1.4 g gelatin in 100 mL extender, respectively). Pools of semen were allocated among 0.6 mL plastic artificial insemination (AI) guns. Thirty (10 per extender group) AI doses were immediately analyzed (0 h) and the remainder stored in a refrigerator (15 °C) for 12, 24, 36, 48, 72, 96, or 240 h. All doses with gelatin extenders solidified at 15 °C. Semen samples, prewarmed to 37 °C, were evaluated with a computer-assisted sperm analysis (CASA) system. The percentage of motile cells was significantly lower using the liquid compared to the gel extenders during semen storage from 0 to 96 h. Although significance was lost, these differences persisted after 240 h of storage. Motility of spermatozoa in the semi-gel extender was intermediate between that of liquid and gel extender throughout the study. Study 2 was performed on 1250 multiparous lactating does. Five homogeneous groups of 250 does previously synchronized were inseminated using semen previously stored for 120, 96, 72, 48 or 24 h, respectively. Rabbit does receiving 24 h-stored semen (diluted with the control extender used in Study 1) served as controls. The remaining females received seminal doses supplemented with 1.4 g/100 mL gelatin (gel extender used in Study 1). Kindling rates for rabbit does inseminated with gelatin-supplemented (solid) semen doses stored for 48 h (88%) or 72 h (83%) were similar to those recorded for liquid controls stored for 24 h (81%), whereas rates significantly decreased when the semen was solid and stored for 96 h (64%) or 120 h (60%) before AI. In conclusion, rabbit spermatozoa were effectively stored in the solid state at 15 °C, with fertility preserved for up to 5 days. Solid storage of rabbit semen would facilitate commercial distribution.