Agriculture Reference
In-Depth Information
39
37
35
33
>1.5 kg
1.0-1.5 kg
<1.0 kg
31
0
10
20
30
40
50
60
70
80
90
2
3
4
5
6
7
8
9
10
24
36
Minutes after birth
Hours after birth
Figure 11.2. Relationship between piglet birth weight and rectal temperature profiles over the first 36 h period
post-partum (Pattison
et al
., 1990).
valuable colostrum and establishing teat fidelity, against the risk of being crushed by the
sow. Weary
et al.
(1996) concluded that crushings are partly the result of the nutritional
challenge facing newborn piglets; a piglet with slow weight gain spends more time in
risky areas underneath the sitting or standing mother. If the piglet's energy reserves are
low, it will also be too weak to escape a moving sow. Since reduction of heat loss at
birth is mainly achieved by behavioural adjustments, including huddling and postural
adaptations (Hrupka
et al.
, 2000), the location where a piglet chooses to lie in the nest
site may be crucial for its survival. For a piglet with low viability that faces demanding
physiological challenges, it is just as dangerous to lie away from the udder and siblings
because, although the risk of crushing is reduced, the risks of starvation and hypothermia
become much greater. Environmental factors contribute to these risks.
11.2.3
Environmental factors
Thermoregulation
The lower critical temperature of newborn piglets is approximately 34 °C (Mount, 1968)
and is not achieved on entry into the extra-uterine environment. Heating the environment
to 34 °C would negatively impact on the sow's thermal comfort zone (Mount, 1968),
which ranges from 12-22 °C (Black
et al.
, 1993) and is thus markedly different from that
of the newborn piglet. Therefore, rapid heat loss via conduction, convection, radiation
and evaporation is experienced by the piglet immediately post-partum (reviewed
by Curtis, 1970). These heat loss processes are affected not only by the physical and
behavioural factors already discussed, but also by the environment. Early work on
