Agriculture Reference
In-Depth Information
milk ejections get established at about 12 h after the onset of parturition, and piglets then
compete over early possession of a productive teat rather than over the number of teats
suckled. During the second phase (approximately the first three days), piglets jockey for
possession of individual teats and piglets that acquire high teat fidelity early on benefit
from more frequent nursing participation and faster early growth (de Passillé
et al.
, 1988a).
Teats used in the previous lactation give more milk on the average than previously unused
teats (Farmer
et al.
, 2012). Anterior teats tend to be preferred by piglets and produce
somewhat more milk than posterior teats, but this is more due to their more consistent and
more intensive use by the heavier piglets rather than due to inherent higher productivity
(Fraser and Rushen, 1992; Orihuela and Solano, 1995). During the first, and to a lesser
extent during the second, competition phase sibling competition contributes strongly to
the disproportional mortality of low birth weight piglets, especially in litters with a high
variation in birth weight (Milligan
et al.
, 2002). Once the teat order is established, by the
fourth day, direct competition vanishes and indirect competition can then take place.
At this time piglets can possibly get extra milk at the expense of littermates if they are
able to boost milk production in their teat, e.g. through more complete milk withdrawal
or more intense teat massage. Within litters, piglets differ widely in their milk intake,
and hence in body weights, but only about 20% of this variation can be explained by
differences in teat fidelity and teat position (Fraser and Thompson, 1986). The fact that
within-litter coefficient of variation in body weights does not increase from birth until
weaning (Milligan
et al.
, 2002) indicates that competition of piglets for teats does not
exacerbate the initial differences in body weights among littermates.
13.4.4
Securing mother-young bond, allo-suckling regulation
Although lactating sows are housed individually in most commercial settings and thus do
not encounter alien piglets, this is not the setting in which pig nursing behavior evolved.
In natural wild boar groups, several females lactate at the same time and therefore allo-
suckling (non-offspring nursing) is possible. If several domestic sows are housed in
indoor group pens or outdoor parks, allo-suckling occurs regularly (Kim
et al.
, 2001;
Maletínská and Špinka, 2001; Newberry and Wood-Gush, 1985). From a functional
point of view, a certain degree of non-offspring nursing may be, at least in some cases,
adaptive to the mother (Roulin, 2003; Roulin and Heeb, 1999), for instance if the allo-
sucklers are progeny of a genetically related female as is often the case in wild boar groups
(Kaminski
et al.
, 2005). Nevertheless, the non-offspring young will, due to their low
genetic relatedness to the foster mother, demand more frequent allo-suckling than is
optimal for the dam. Therefore, it is beneficial for the sow to distinguish her own from
alien piglets and to regulate the access of the latter to her milk supply.
The early sow-piglet interactions serve to quickly establish the maternal bond with
the piglets. Through sniffing the piglets, the sow quickly imprints into her memory
the olfactory identity cues of individual piglets within 24 h postpartum. This can be
accomplished actively during the brief activity bouts at parturition or when piglets come
to the snout of the lying sow during teat sampling or cyclic suckling, or later when the
sow regains activity between nursings (Maletínská
et al.
, 2002). The recognition of her
own piglets via individual smell signatures enables the sow to identify alien piglets and
