**14. Deep intra-uterine insemination (DIUI) (Figure 1b)**

Non-surgical DIUI has been performed in non-sedated pigs using a flexible fiber optic endo‐ scope (1.35 m length, 3.3 mm outer diameter) inserted via the vagina and cervix to reach the upper segment of one uterine horn [84]. The procedure required 3 to 5 min in 90% of the females. After this DIUI, only 1% of the sows showed signs of uterine infection. However, the endoscope is a highly expensive instrument and unpractical for routine use. A flexible catheter was therefore developed on the basis of the propulsion force and flexibility of the fibro-endoscope [85]. The method allows deposition of low sperm doses of either fresh or FT sperm. Moreover, the technology can be successfully used to produce piglets with sex-sort‐ ed sperm [88], or for embryo transfer [89].

Using fresh semen, FR and LS were not statistically different between DIUI with 150x106 sperm per dose and conventional AI with 3x109 sperm, ranging from 83 to 87% FR and 9.2 to 10.4 LS [88]. Nonetheless, LS was always lowest in the DIUI sows. Similarly, although no differences in FR were found (83% and 90% for DIUI and conventional AI, respectively), DIUI sows had less LS (10.5 and 12.9, respectively). The low LS achieved in the DIUI sows inseminated with 150x106 sperm probably resulted from the high incidence of unilateral or incomplete bilateral fertilization, and could be overcome by increasing the number of in‐ seminated sperm to 600x106 sperm per dose [90]. On the other hand, when a single DIUI with 150x106 sperm was performed in hormonally induced ovulating sows, both FR and LS of DIUI sows (83% and 9.7) were not different from those of conventional AI sows (83% and 10) [85]. When FT semen (1x109 sperm per dose) was used for DIUI, promising results were obtained. With hormonally induced ovulation and a single DIUI, the FR was 77.5% and LS was 9.3, while with spontaneous ovulation and two DIUIs, the FR was 70% and LS was 9.3. The lower fertility obtained in the latter group resulted from the suboptimal inseminationovulation period [91]. Bolarin and staff working with spontaneously ovulating sows (n=407) obtained FR of over 80% and about 10 piglets born per litter when two DIUIs, at 6 h interval, with only 1x109 FT sperm per dose were conducted at the peri-ovulatory period [92]. It has been suggested that DIUI should be carried out ≤ 8 h before spontaneous ovulation when FT sperm are used [93].
