Epsilon Archive for Student Projects

Abstract

Boar semen can be successfully frozen -highly packed- in small containers (medium-straw, MS or multiple FlatPack, MFP). The use of deep intrauterine artificial insemination (DIUAI) can make possible the deposition of small volumes of this thawed, non re-extended semen deeply intra-cornual. The fertility achieved after single or double DIU-AI per oestrus was hereby studied, with special attention to the interval between AI and spontaneous ovulation. Semen from two boars of proven fertility was frozen in MS or MFP holding 1x109 total spermatozoa. Multiparous (n=42) crossbred sows were checked for oestrous behaviour after weaning and the occurrence of spontaneous ovulation was checked with transrectal ultrasonography (TUS) to establish the interval between onset of oestrus (OO) and ovulation. Sows were subjected to DIU-AI in the following oestrus using thawed semen (MS=20 or MFP=22), inseminated without further re-extension. Sows were randomly allotted to one of 3 groups: (1) Single DIU-AI 8 h before expected ovulation (Control group, n= 19), (2) Single DIU-AI 4 h before expected ovulation (Treatment group S, n=15) and (3) Double DIU-AI 12 and 4 h before expected ovulation (Treatment group D, n=8).

Pregnancy was confirmed by TUS 28 days after OO in those sows not returning to oestrus. These sows were later slaughtered (day 30 to 45 of pregnancy), noting the appearance of the reproductive tract and ovaries, numbers of live foetuses, implantation sites and of CL.

Some sows (n= 9) returning to oestrus were re-inseminated (either once [n=4] or twice [n=5]) in the following oestrus with either MFP (n=5) or MS (n=4) and slaughtered 12 to 14
h post-ovulation for recovery of spermatozoa from the utero-tubal junctions (UTJ, sperm reservoir) and of tubal oocytes, to disclose the effectiveness of sperm transport. Post-thaw sperm motility was 44.3±3.21% in MFP and 42.8±0.72 % for MS (LSMean±SEM, n.s.), and did not significantly change from thawing to AI. The DIU-AI could be performed in all sows, but insertion was slow (>5 min) in 5/42 sows of which 4 returned to oestrus.

Pregnancy rate averaged 35% (Group D: 25%, Group S: 40%, Control: 36%, n.s.). The interval between DIU-AI and ovulation varied largely (group C: between -13 and -3 h , for S-group: between -11 and +3h , for group D: between -17 and -4 h). Pregnancy rates clearly related to the interval DIU-AI and ovulation, being highest (60%, 12/20) when AI occurred between 8 and 4 h before ovulation. Numbers of apparent implantation sites ranged 6 to 22 and of live foetuses 2 to 11 (n.s. among groups), while fertilization rate (total number of implantations/CL) ranged 48.0 to 69.7%, being highest in group D (P<0.05). The examination of the open sows slaughtered 12 to14 h post ovulation showed low sperm numbers (approx 4,000) in the UTJs. Only 40% of oocytes had spermatozoa bound to the zona pellucida, not more than 2 spermatozoa per oocyte, and only 10 % of recovered oocytes were fertilized, irrespective of using one or two DIU-AI (n.s.). The highest (p<0.05) values for these variables were recorded when DIU-AI (either single or double [second AI]) was done between 4 to 8 h before ovulation, especially when MFP-semen was used (P<0.05). In conclusion; (1) DIU-AI can be easily performed in most sows, (2)pregnancies can be obtained by the DIU-AI of low volumes of highly concentrated frozenthawed boar semen, once or twice during oestrus, but fertility is still low, probably owing to an incomplete replenishment of the sperm reservoirs, and (3) fertility is mainly related to the interval DIU-AI and ovulation -which should be -8 to -4 h of spontaneous ovulationand to the package, MFP having shown better results in vivo.