Effect of diluent type and storage time on the pregnancy rate of ewes inseminated laparoscopically with chilled ram semen

J.F. Smith, J. Parr, G. Murray, J.E. Oliver, S. Beaumont, G.C. Upreti

AgResearch Dairy and Beef Division, Ruakura Research Centre, Private Bag 3123, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1995, 55: 245-247

Five trials involving 879 ewes were conducted in November, December 1993, February, March and April 1994. Ewes were synchronised with CIDRΠtype G devices for 14 days and in the November and December trials ewes received 400 iu PMSG (Pregnecol) at the time of device removal. Semen from Dorset x Romney rams was diluted to a concentration of 200 x 10 6 sperm/ml in either a milk diluent or with a synthetic ram semen diluent RSD-1 supplemented with carboxymethyl cellulose (CMC) to prevent sedimentation. The diluted semen was cooled to 15 C and packaged in 0.25 ml straws. Semen was used either on day of collection (D 0 = 6-18 hr after collection) or the following day (D 1 = 30-42 hr). Ewes were inseminated intrauterine using a laparoscopic technique on a time basis 53-56 hr after CIDR removal. Pregnancy was determined by ultrasonic scanning 45-50 days later.

There was no significant difference between diluents (milk = 57.3% and RSD-1 + CMC = 57.8%). There was a significant effect of length of storage at 15 C (D 0 = 62.2% vs D1 = 52.3%; P<0.01) and a significant effect of season (between trials; P<0.001) with an increase from November (39.5%) up to March (72.3%). There was also a seasonal difference in the proportion of ewes showing oestrus prior to insemination (November = 32.3% to April 80.8%; P<0.001) and oestrous status at time of insemination had a significant effect on pregnancy rate (66.6% oestrus vs 41.0% not oestrus; P<0.001). There was no significant difference between operators.

These results indicate acceptable levels of fertility can be obtained with the intrauterine insemination of chilled stored semen up to 42 hr after collection. They also highlight the important effects that season and ewe synchrony can have in insemination programmes.

Keywords: NZSAPAB; semen diluents; laparoscopic AI; chilled semen; storage time; oestrous status; pregnancy rate

Download abstract in text format
Last Updated 25-01-1997