Trials undertaken at Rotomahana in 1984 and 1985 examined factors involved in sheep AI and provided a link between Rotomahana and a commercial AI programme. Semen collected and diluted by the New Zealand Dairy Board gave similar conception rates (46%) to semen collected at Rotomahana (42%). Results in 1984 indicated that there was a small but non-significant decrease in conception rate with semen storage time up to 15 hours (5 h 68%, 10 h 61%, 15 h 57%). In 1985 there was a highly significant difference between 5 and 20 h storage (46% v 25%) and this result was consistent over ewe ages and dose rate. In 1985, 200x10 6 sperm dose was compared to 100x10 6 dose in 3 subtrials. The overall conception rates were 45.7% and 37.5% respectively (P<0.05). In 1984 diluted semen stored in glass and inseminated using a fine glass pipette gave a higher, but not significant, conception rate than semen stored in mini straws and inseminated using a standard cattle pistollet (66% v 58%). In 1985 all semen was stored in glass and inseminated with either a glass pipette (conception rate of 49.8%) or a cattle pistollet (43.2%). This difference was non-significant, although there was a significant interaction of insemination equipment with dose rate. A significantly higher conception rate was achieved for cervical (52.8%) than blind insemination (29%) when ewes were inseminated 'on time' in 1985 and this effect was consistent over dose rate. There was no difference in conception rate when 'on-oestrus' insemination was compared to 'on-time' (63% v 61%). All first-order interactions among the effects of storage time, insemination method and 'on-oestrus' v ' on-time' were non-significant in the 1984 trial.
Proceedings of the New Zealand Society of Animal Production, Volume 46, , 215-218, 1986
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