Agriculture Reference
In-Depth Information
ability of an individual pig to cope when ex-
posed to social stressors'. The mechanism by
which A2C exerts its influence on perform-
ance involves both the animal's ability to at-
tain potential growth and its effect on feeding
behaviour. Socially stressed animals (low
A2C) will have a lower capacity to achieve
potential (protein) growth and their normal
feeding behaviour is disrupted, resulting in
subsequent reduced performance. The main
social stressors that interact with A2C include
stocking density, feeder space and health
The A2C parameter will accommodate
the noticeable variation between individ-
uals in how they respond to social stressors.
Because of the strong correlation between
size and dominance (Tindsley and Lean, 1984;
D'Eath, 2002) it is reasonable to assume that
there is a strong positive correlation between
live weight and A2C. Turner
et al
. (2002) ob-
served a greater reduction in growth rates in
smaller pigs than larger pigs when grown
under more stressful conditions (low feeder
space and large group size). There is likely to
be an increase in within-pen body weight
variation when the level of stress increases.
This was observed by Anil
et al
. (2007) when
pigs kept at acceptable stocking density
levels (>0.74 m
2
/pig) had body weight stand-
ard deviations of 7.6-14.9 kg compared to those
pigs with less space (0.64 m
2
/pig) of 11.7-16.6 kg
Although these differences were not statis-
tically different, they do highlight the possi-
bility that the weight differences between the
small and large pigs in a pen may increase
with higher levels of stress. Tindsley and
Lean (1984) noted that dominant pigs were
generally the heaviest pigs and that the vari-
ation in ability to dominate may be respon-
sible for live weight variations.
Health
Not only are there differences in growth po-
tential, initial body weight and A2C between
individuals within a group, there are also
genetic differences in immune-competence
(Knap and Bishop, 2000; Flori
et al
., 2011).
A2C
Intensity and extent
Health
Stocking density
Potential growth
(genetics)
Express potential
A2C
Desired feed intake
Feeding rate
Time at feederAnimal space
Feeder space
Actual intakes
and growth
Fig. 11.2.
Interactions between an animal's ability to cope (A2C) with social stressors and subsequent
effects on performance.
