78 Evaluation of extended hair sheep ram semen stored as liquid at 5°C

Abstract This study was designed to evaluate the quality of extended hair sheep ram semen stored as a liquid at 5°C. St Croix White (STX; n = 6) and Dorper x STX (DRPX, n = 5) rams were collected weekly for 3 wk using estrus ewes fitted with an intravaginal collection vial. Semen was kept at 32°C during transport to the lab and during processing. Semen was evaluated for percent motility (MOT), viability (LIVE) using eosin-nigrosin stain and concentration using a hemocytometer counting chamber. Semen was extended to a final concentration of 250 x 106/mL in a one-step dilution with a skim UHT milk extender with 10% egg yolk by volume and packaged into 0.5 mL straws. Straws were stored in a styrofoam box in a refrigerator at 5°C for 96 h, or in an Equitainer® set up using the manufacturer’s instructions, for 24 h at which time they were transferred to the styrofoam box in the refrigerator for 72 h. Semen was evaluated for MOT and LIVE at -1, 0, 24, 48 72 and 96 h relative to cooling. Semen traits were analyzed using GLM of SAS for repeated measures with ram, time, breed and cooling method in the model. There was no difference (P > 0.10) in MOT or LIVE over time between breeds or cooling method. One STX ram did not produce any samples that survived extension; one STX and four DRPX rams produced at least one sample that did not survive extension and all were removed from analysis. The MOT decreased (P < 0.0001) from 81.7 ± 2.9 % at -1 h to 52.2 ± 2.9% at 96 h. The LIVE decreased (P < 0.0001) from 83.1 ± 3.6% at -1 h to 50.4 ± 3.6% at 96 h. These results show that ram semen stored as a liquid at 5°C can maintain motility and viability for 96 h. Further studies will be conducted to evaluate cooling of extended ram semen and fertility after artificial insemination.