Agriculture Reference
In-Depth Information
closure. The second is between the time of declining antibody concentrations in the sow's
milk and the transition from passive to active immunity in the piglet (Gaskins and Kelley,
1995), which is impaired by low colostrum intake in early postnatal life.
Gender
There is evidence that female piglets have a greater chance of surviving from birth to
weaning than males (Baxter
et al.
, 2012; Hales
et al.
, 2013; Lay
et al.
, 2002). Baxter
et
al.
(2012) demonstrated that, despite being born heavier than females, male piglets
showed impaired thermoregulation compared with females, having significantly lower
rectal temperatures at 24 h. Moreover, piglets from male-biased litters showed reduced
thermoregulatory abilities, were slower to suck colostrum and were more likely to die
from disease-related causes. These results suggest male-biased mortality reflecting an
intrinsic, gender-related susceptibility to causal factors. This may be masked when
competition for resources favours the larger, more dominant individuals, but the males
may be less able to cope if they can obtain only sparse resources.
Thermoregulatory abilities
The neonatal piglet is born virtually hairless, with no brown adipose tissue to facilitate
metabolic heat production (Herpin
et al.
, 2002). It operates at the limits of its physiological
capabilities and, consequently, has poor thermoregulatory capacity (Herpin
et al.
, 2002;
Mellor and Stafford, 2004). The capacity of newborn piglets to produce heat is crucial
to their survival and is dependent on the co-ordinated functions of various organs
and processes. These are vital when the piglet is experiencing hypothermia as a result
of excessive heat loss due to a cold environment or depressed heat production ability
(Herpin and Le Dividich, 1995). If low body temperature becomes irreversible, then the
piglet will die directly from hypothermia or indirectly from a secondary factor such as
increased susceptibility to crushing (Curtis, 1970). Smaller piglets are at a greater risk
from hypothermia because heat loss per unit of body weight is inversely related to body
size (Herpin
et al.
, 2002). Pattison
et al.
(1990), by taking sequential rectal temperatures
during the early postnatal life of piglets, demonstrated the effects of birth weight on the
temperature profiles of piglets over a 36 h period post-partum (Figure 11.2).
All piglets experience chilling as they enter the extra-uterine environment, taking into
account the 15-20 °C drop in ambient temperature. The metabolic capability of the
neonate and its behavioural abilities affect the extent and duration of the resulting drop
in body temperature. The initiation and sustainability of the thermogenic response to
cold (i.e. a continuing increase in metabolic rate) is dependent on intake and metabolism
of colostrum (Herpin
et al.
, 1994).
Early postnatal behaviour
The piglet's behaviours that predispose crushing often occur as a result of physiological
challenges such as hypoxia, starvation or hypothermia, which may increase lethargy.
There is a trade-off between the innate need of the piglet to be at the warm udder, gaining
