Nursing behavior - The Gestating and Lactating Sow - page 288

into durable teat ownership. By the first day, between 5% and 50% of piglets establish a
stable ownership of one specific teat while the other piglets fight over teat ownership as
they switch between several teats (de Passillé et al. , 1988a; Puppe and Tuchscherer, 1999).
Teat fighting decreases and teat order stability increases steadily until it reaches the level
of 85-95% by the 4 th day. Teat ownership means that piglets return to the same teat at
successive sucklings and fiercely defend it against siblings (de Passillé et al. , 1988a; Puppe
and Tuchscherer, 1999).

Piglets who fail to acquire a teat early pay a double cost; they expend energy in attempts
to displace others from their teat and they often consume less colostrum that is vitally
important both as the initial source of energy and for immunity (Farmer and Quesnel,
2009). Competition, rather than a general inability to thrive, appears to be the cause of
much starvation death (Andersen et al. , 2011; Drake et al. , 2008). Litter size is important
in determining the seriousness of the consequences of teat competition. Although it is
unclear whether the intensity of fighting among siblings increases with litter size (D'Eath
and Lawrence, 2004; de Passillé and Rushen, 1989; Scheel et al., 1977) the consequences
of the competition are graver in large litters (Andersen et al. , 2011). Piglets in large litters
have lower birth weight, and the amount of colostrum ingested per piglet decreases by
about 10% with each additional piglet born because the total colostrum yield is constant
across different litter sizes (Devillers et al. , 2007). Piglet's birth weight is another important
factor because heavier piglets win more fights over teats (Scheel et al. , 1977), gain more
weight (Milligan et al. , 2001) and experience lower mortality (Tuchscherer et al. , 2000).
Mortality of piglets due to crushing or starvation occurs mostly within the first days of
postnatal life and affects mainly the low-weight piglets in large litters. This is often in
direct relation to their inability to secure teat access and, therefore, to their insufficient
colostrum and early milk intake.

13.3 Nursing during the established lactation

This second part of the chapter describes the features and the structure of sow nursing
behaviour beyond the colostrum period, i.e. from the time when cyclic nursing is
established until weaning.

13.3.1 Structure of the typical pig nursing

A pig nursing episode ('a nursing') typically consists of five main phases (Figure 13.1):
nursing initiation, pre-ejection teat massage, milk ejection, post-ejection teat massage
and nursing termination (Fraser, 1980; Schön et al. , 1999; Špinka et al. , 2002).

Nursing initiation occurs in two ways. First, sows can spontaneously assume the
lateral lying nursing position, thereby widely exposing their udder, and start to grunt
rhythmically. In reaction to these stimuli, piglets assemble at the udder and start the teat
massage. Second, individual piglets can approach the sow, vocalize near the mouth of
the sow and start massaging the teats with their snouts. This behaviour recruits further
piglets to join the stimulation until the sow assumes the nursing position and starts