Abstract
The physical and chemical characteristics of gelatin have been used to justify its inclusion in extenders to preserve the sperm quality and improve results of cervical artificial insemination with cooled semen. The objective of this study was to evaluate the effects of gelatin supplementation in cooling extender on the quality and fertility of ram semen stored at 5°C. Semen samples (n = 24) of Santa Inês rams (n = 6) were diluted in Glycine-Yolk-Milk extender without (control) or with 1.5% of gelatin. The samples were loaded into 0.25 mL straws, cooled to 5°C and stored vertically for 48 and 72 hours. Sample quality was evaluated using straw homogeneity tests based on pH, osmolality and the proportion of spermatozoa (PS) in both upper and lower segments of straws (US and LS), analyses of sperm motility, plasma and acrosomal membrane integrity, and by fertility after artificial insemination. Differences between the US and LS of straws were found for pH and PS (%). They were significant only in the control group at both times: pH – 5.96 vs. 5.71 at 48 h and 6.13 vs. 5.89 at 72 h; PS – 21.66 vs. 78.34 at 48 h and 20.87 vs. 79.13 at 72 h. Storage in gelatin had very little, to no effect on the sperm kinetics or on the sperm membrane integrity evaluations. The addition of gelatin to the extender did not affect the pregnancy rate which ranged from 4.4 to 26.1%. We conclude that gelatin is effective in maintaining the physical and chemical homogeneity of the semen samples. Further research is needed in order to optimize the use of gelatin supplementation and elucidate any potential benefits.
Highlights
Cooled semen has been used for many years as an important tool for the conservation, dissemination and transport of genetic sheep genetics (Evans and Maxwell, 1990; Salamon and Maxwell, 2000)
The sperm quality when stored in an extender may depend on its position in the tube or straw, when the samples are held in a vertical position prior to cooling or freezing
Most manuscript do not specify how the samples are positioned during cooling and transportation, many of the procedures keep the semen in a vertical position in glass or plastic tubes or even in vials such as those cited by Sousa and Bicudo (2003) and Yániz et al (2005)
Summary
Cooled semen has been used for many years as an important tool for the conservation, dissemination and transport of genetic sheep genetics (Evans and Maxwell, 1990; Salamon and Maxwell, 2000). Most manuscript do not specify how the samples are positioned during cooling and transportation, many of the procedures keep the semen in a vertical position in glass or plastic tubes or even in vials such as those cited by Sousa and Bicudo (2003) and Yániz et al (2005). Some automated semen refrigeration and freezing systems arrange the doses upright during processing (Maia et al, 2009; Sicherle et al 2011). All of these procedures and systems can lead to sedimentation of the sperm during sample processing, storage and cryopreservation
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