Nursing behavior - The Gestating and Lactating Sow - page 286

postpartum. Nevertheless, this nursing pattern changes gradually from the second week
onwards as sows tend to restrict their nursing investment into the litter, and this process
of 'gradual weaning' is the topic of the third part of this chapter.

13.2 Nursing during the postpartum period

13.2.1 Peri-parturient changes in sow activity

Domestic sows are not particularly active mothers during the parturition itself and the
early postpartum hours. After the conspicuous prepartum nest building activity (Jensen,
1986; hodberg et al. , 1999), sows calm down as parturition approaches. During the
parturition, sows generally lie immobile and rather unreactive in lateral recumbency
(Jarvis et al. , 1999; Jensen, 1986; hodberg et al. , 1999), although in the initial stage
of parturition posture changes may be more frequent than in the later stages (Jarvis et
al. , 1999; hodberg et al. , 1999). Through the lasting lateral recumbency, sows expose
the udder for 'teat sampling' by the piglets, as described below. Sometimes, sows rise
to sniff the first few piglets as they are born (Jensen, 1986). A new increase in activity
coincides with an increase of maternal responsiveness to naso-nasal contacts around 10
h postpartum (Pedersen et al. , 2003). During such contacts the sow responds by sniffing
when a piglet approaches her snout (Illmann et al. , 2001; Jensen, 1988).

13.2.2 Early colostrum availability and milk ejections

During parturition, colostrum (early milk rich in energy and immunoglobulins) is
available almost continuously, as supported by high oxytocin concentrations (Devillers et
al. , 2007; Farmer and Quesnel, 2009). However, individual discrete ejections of colostrum
are already occuring during parturition (Castrén et al. , 1993; de Passillé and Rushen,
1989; Fraser and Rushen, 1992; Rushen and Fraser, 1989). Gradually, more and more of
the colostrum becomes available in cyclic discrete ejections caused by pulsatile oxytocin
bursts separated by periods with little or no release of colostrum. At 5 h after the onset
of birth, these ejections are brief and frequent, occurring at irregular intervals about
three times per hour (Castrén et al. , 1989b; Fraser, 1984). Then they decline in frequency
and from about 8-11 h after the start of farrowing, milk is available only during discrete
ejections occurring at the stable rate of approximately 1.5 per hour. These ejections occur
spontaneously, without the need of piglet teat massaging. As of 12-16 h postpartum, the
piglets start to include teat massaging (rubbing the vicinity of teats with their snouts)
into their suckling behavior, and the milk ejections gradually become dependent on the
tactile stimulation of the udder by piglets.

Teat sampling by piglets and transition to synchronized sucklings

Newborn piglets struggle to their feet within one or two minutes, and move to the udder
mainly by staying in contact with the vertical surface of the recumbent sow. Once a piglet
has suckled a teat, it moves along the udder sampling from different teats and biting or
pushing littermates to obtain other teats (de Passillé and Rushen, 1989). This teat sampling