Replenishment of AI-doses with oestrogens in physiological amounts: effect on sow prolificacy in a field trial.

Basing on results about physiological functions of seminal oestrogens in the genital tract of sows, the effects of an oestrogen replenishment to AI-doses were investigated in a field trial. Each ejaculate was split into two halves, which were either diluted to normal AI-doses (controls, n = 353) or diluted and replenished with oestrogens in physiological amounts (n = 384). Insemination by qualified technicians led to an improvement of the pregnancy rate (82.8% vs. 77.1%; p less than 0.05) and the litter size (10.8% vs. 10.3%; p less than 0.05) in favour of the oestrogen replenishment. These results partly explain the known differences in prolificacy between natural mating and AI and thus provide a basis for improvement of pig AI.