This study was carried out to evaluate the effects of the sperm cell dose and semen backflow on the pregnancy rate and number of embryos of sows inseminated once at 0-24 h before ovulation, using an intrauterine technique. The results were analysed from a total of 211 sows assigned to three groups inseminated with doses of 0.25 x 10(9) (T1), 0.5 x 10(9) (T2) and 1.0 x 10(9) (T3) spermatozoa. Semen backflow was observed in 95% of the females (143/151) evaluated for this purpose. The percentage of semen backflow is close to two-third of the volume and the percentage of sperm is around 15% of the infused sperm dose. Intrauterine insemination can be successfully performed provided that at least 0.5 billion of sperm cell dose is infused at an interval of 0-24 h before ovulation.

Resumo -O desempenho reprodutivo de fêmeas suínas foi avaliado com o objetivo de comparar duas técnicas de inseminação. Foram inseminadas, em delineamento inteiramente casualizado, 608 fêmeas com ordem de parto de dois a quatro, em dois tratamentos: inseminação intra-uterina com 1,5 bilhão de espermatozóides em 60 mL e inseminação tradicional, com 3 bilhões em 90 mL. Foi possível introduzir o cateter intra-uterino em 97,4% das fêmeas e houve sangramento em 9,5%, as quais apresentaram retorno ao estro superior (p<0,05). O porcentual de volume refluído até duas horas após a inseminação foi maior (p<0,05) na inseminação intra-uterina do que na tradicional, enquanto o porcentual de espermatozóides refluídos foi semelhante. Não houve influência do porcentual de espermatozóides refluídos sobre a taxa de parto e tamanho da leitegada. Não houve diferença nas taxas de retorno ao estro (3,6% e 4,3%), de prenhez aos 21 dias (99,5% e 97,2%), de parto ajustada (94,9% e 94,3%) e tamanho da leitegada (11,6 e 11,8 leitões) entre os dois tratamentos, respectivamente. A inseminação intrauterina permite a obtenção de desempenho reprodutivo semelhante ao observado na tradicional, porém com uso de menor número de espermatozóides.Termos para indexação: número de espermatozóides, parto, refluxo de sêmen, reprodução, tamanho da leitegada, taxa de prenhez. Reproductive performance of swine females inseminated by intrauterine or traditional techniqueAbstract -The reproductive performance of sows was evaluated aiming at the comparison of two insemination techniques. In a completely randomized design, 608 females of 2-4 parities were inseminated in two treatments: intrauterine with 1.5x10 9 spermatozoa/60 mL or traditional insemination with 3x10 9 spermatozoa/90 mL. It was possible to insert the intrauterine catheter in 97.4% of females and bleeding was observed in 9.5%, which had a higher probability to repeat estrus (p<0.05). The percentage of semen backflow volume, during two hours after insemination, was significantly higher (p<0.05) in intrauterine insemination than traditional, whereas sperm backflow percentage was similar. The sperm backflow percentage did not influence the farrowing rate and the litter size. There was no difference in the return to estrus rate (3.6%; 4.3%), pregnancy rate at 21 days postinsemination (99.5%; 97.2%), adjusted farrowing rate (94.9%; 94.3%) and average litter size (11.6; 11.8 piglets) between treatments, respectively. The intrauterine insemination ensures a reproductive performance similar to traditional, but with a lower sperm number.

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