Reproduction performances and conditions of group-housed non ...

- Appendix 1 -
Physiological events before and around mating/insemination
To gain pregnancy and a high litter size, onset of oestrus has to appear followed by ovulation,
the number of ovulated eggs have to be high and further, the artificial insemination or
mating has to bee successful resulting in fertilisation and a high number of fertilised eggs.
At luteolysis (around day 16 in oestrus cycle when the luteal phase is replaced by the follicular
phase) or at weaning, 15-25 follicles are recruited and selected to undergo preovulatory
growth and to ovulate 4-7 days later (Prunier & Quesnel, 2000b). A few days after
weaning the sow start to show oestrus. The interval from weaning to onset of estrus (WEI)
and duration of estrus varies to a large degree between farms and also between sows within
farms (see Table 1).
Table 1. Examples of interval from weaning to onset of estrus (WEI) and duration of estrus (ED) reported
in the literature
WEI, hours after weaning ED, hours
X, +/-SD Range X, +/-SD Range
Pedersen & Navntoft, 1996 112+/-11 - 49+/-7 -
Pedersen & Navntoft, 1996 100+/-17 - 61+/-10 -
Nissen et al., 1997 92+/-13 64-134 60+/-14 30-89
The interval from onset of estrus to ovulation is reported to be in the range of 10 to 85
hours for individual sows, with mean values of 15 to 35 hours (review by Kemp & Soede,
1997). The duration of estrus and the interval from onset of oestrus to ovulation is negative
correlated to WEI (Nissen et al., 1997). The duration of ovulation ranges from one to three
hours (Kemp & Soede, 1997). At ovulation the released ova are expelled into the oviduct
and transported to the ampullary-isthmic junction, the site of fertilisation, perhaps in 30-45
min or less (Hunter, 1990). At insemination or mating sperm cells are deposited at the
utero-cervical junction. Sperm cells migrate through the uterine horns to the oviducts where
they are temporarily stored in the sperm reservoir near the utero-tubal junction (Hunter,
1990). This transport is believed to be dependent mainly upon uterine contractions (Scott,
2000). Hunter (1981) found that within 1-2 h after mating there were enough spermatozoa
in the oviduct to promote 100% fertilisation. Before the sperm are capable of fertilisation
they have to undergo capacitation (maturation), which is presumed to happen in the sperm
reservoir (Rodriguez-Martinez et al., 2001). Capacitation is believed to require five to six
hours but can be accelerated to less than two hours if insemination is performed around
ovulation (Hunter, 1990). By the time ovulation approaches, sperm are released from the
reservoir to the oviduct (Hunter, 1981).
The ova are only capable of being fertilised the first eight hours after ovulation (Hunter,
1967) and the sperm needs to be present in the female tract for about two h or longer before
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