RESUMO
Fixed-time post-cervical artificial insemination (FTPCAI) allows a wider use of high indexing boars and a considerable reduction in labour requirements in swine production. The aim of this study was to evaluate fixed-time artificial insemination (FTAI) efficiency using different artificial insemination protocols and porcine luteinising hormone (pLH) to induce ovulation. A total of 597 weaned sows in which oestrus detection was performed once daily (08:00 am) was allocated to three groups: FTPCAI1 (n=199) - sows received a 5-mg (4 ml) intramuscular injection of pLH at oestrus onset, and were inseminated 24h later; FTPCAI2 (n=199) - sows received 5mg of pLH and were inseminated at oestrus onset (0 h) and 24h after; and MultPCAI (n=199) - sows did not receive pLH, and the first AI was performed at oestrus onset (0 h) and repeated every 24h during oestrus. Homospermic doses (1.5 × 10(9) total sperm cells/50 ml) were used in post-cervical artificial insemination (PCAI) in all the treatments. Hormonal treatment did not affect (P>0.05) the interval between oestrus onset and ovulation (overall 32.4h) and there were no differences (P>0.05) in farrowing rate (overall 91.6%) or litter size (overall 12.6 piglets born) among treatments. In sows treated with pLH at oestrus onset, a single PCAI with 1.5 billion sperm cells did not compromise reproductive performance compared with a double PCAI at 24h intervals.