Agriculture Reference
In-Depth Information
emphasising the influence of placental quality not only on prenatal survival but also on
postnatal viability.
Other piglet physical characteristics in addition to PI and BMI have been implicated in
postnatal piglet survival (Amdi
et al.
, 2013; Hales
et al.
, 2013). Hales
et al.
(2013) have
developed an IUGR score, based in part on Chevaux
et al.
's (2010) work looking at the
different head morphology of piglets with varying degrees of IUGR. They assigned piglets
a visual IUGR score ranging from normal, through mildly IUGR to severe IUGR based
on whether or not certain characteristics were present or absent. The characteristics were:
(1) steep, dolphin-like forehead; (2) bulging eyes; and (3) wrinkles perpendicular to the
mouth. A score of severe IUGR was given if 2 or 3 of the characteristics were present. A
score of mildly IUGR was given if 1 of the characteristics was present. Finally, if none
of the characteristics were present, piglets were considered normal. Hales
et al.
(2013)
associated early postnatal death with lower BMI, greater levels of growth restriction and
larger litters. Amdi
et al.
(2013) further found that piglets classified as normal had a
greater colostrum intake between 0 and 12 h and between 12 and 24 h post-partum,
had higher birth weight, crown rump length, BMI and PI and had a tendency towards a
higher vitality score than severe IUGR piglets. IUGR piglets can also show differential
organ development, including the 'brain sparing effect,' as part of a fetal adaptive
reaction to placental insufficiency (Roza
et al.
, 2008). Differential organ development can
influence cognitive and immune function (Wu
et al.
, 2006), with demonstrated long-term
detriments to reproductive capabilities (Da Silva-Buttkus
et al.
, 2003) and hypothalamic-
pituitary-adrenal axis function affecting later stress reactivity (Kranendonk
et al.
, 2006).
Thus, the piglet's physical status at birth, whose aetiology stems from the quality of the
placenta, affects its prenatal survival, its physiological and behavioural viability and how
it responds to postnatal challenges.
Farrowing kinetics: the influence of a prolonged birth duration on piglet survival
Prolonged duration of farrowing, delivery in the last third of the birth order, premature
rupture of the umbilical cord, sow behavioural and physiological characteristics,
including parity and blood haemoglobin concentration of less than 9 g/100 ml are all
major influencing factors for stillbirth (Baxter
et al.
, 2008; Fahmy and Friend, 1981;
Randall, 1972a,b; Van Dijk
et al.
, 2005; Van Rens and Van der Lende, 2004; Zaleski and
Hacker, 1993). These factors result in death by asphyxiation (Alonso-Spilsbury
et al.
,
2005; Mota-Rojas
et al.
, 2005; Van Dijk
et al.
, 2005; Van der Lende
et al.
, 2001), or in a less
viable hypoxic piglet with poor survival chances post-partum. The predisposing factors
are not independent (as illustrated in Figure 11.1); for example, prolonged farrowing
duration is influenced by increased litter size (Andersen
et al.,
2011; Van Rens and Van
der Lende, 2004), sow stress associated with fatigue (Vallet
et al.
, 2002; Van Kempen,
2007), restrictive farrowing environments (Oliviero
et al.
, 2006), and high ambient
temperatures (Vanderhaeghe
et al.
,
2010). Piglet size can also influence farrowing
duration and stillbirth rate. There is a quadratic relationship between birth weight and
stillborn mortality (Canario
et al.
, 2006); very small piglets and 'giant' piglets are equally
at risk, though for different reasons, with heavier piglets often being more hypoxic than
lighter littermates as a result of birthing difficulties (Trujillo-Ortega
et al.
, 2007).
