Agriculture Reference
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However, the level of fearfulness also increased with parity number of the sows so that the
effects of fearfulness vs. parity could not be dissociated. Indeed, the incidence of crushing
of piglets is also known to increase with parity due to increased bodyweight and lameness
of sows (Prunier
et al.,
2014; Weary
et al.,
1998b).
Several experiments were conducted to test the hypothesis that a high level of fear
stimulates the adrenal axis which will, in turn, inhibit the hypothalamo-pituitary-ovarian
axis. Development of the adrenals (measured as the surface area of the cortex or weight
of the glands), and plasma concentrations of cortisol (free or total) in basal situation or
in response to a stressor or to an adrenocorticotropic hormone (ACTH) injection were
measured in growing pigs submitted repeatedly (0.5 to 5 min/d during 3 to 5 d/wk and
3 to 12 wks/pig) to various types of human handling (Gonyou
et al.,
1986; Hemsworth
and Barnett, 1991; Hemsworth
et al.,
1981a, 1986a, 1987, 1996a). Results indicate clear
signs of chronic activation of the adrenal axis when pigs are submitted to an aversive
treatment including electric shocks. However, when comparing minimal interactions
with positive interactions (due to tactile stimulations such as rubbing or stroking) or
negative interactions (due to daily intra-muscular injections), differences related to the
adrenal axis were rarely significant (Gonyou
et al.,
1986; Hemsworth
et al.,
1986a, 1987,
1996a). In early pregnant gilts, free and total cortisol concentrations were greater in
aversively- than in positively-treated gilts (Pedersen
et al.,
1998). When measured in
gilts having minimal contacts with humans, cortisol concentrations were generally closer
to those of positively- than aversively-treated gilts. Nevertheless, the negative influence
of hormones from the adrenal axis on the various components of the reproductive axis
has not been clearly established (Turner
et al.,
2005; Von Borell
et al.,
2007). Therefore,
the impact of the quality of the human interactions on the reproductive performance of
gilts and sows should be researched in situations that are not extreme in terms of repeated
aversive interactions imposed by humans.
It can be assumed that a high level of fear of humans by pigs complicates many husbandry
tasks and renders them less efficient. For example, if sows have a high level of fear, they
will get excited at the approach of humans during farrowing which will increase piglet
mortality via longer farrowing or greater crushing incidence. Indeed, comparing outdoor
herds with a low (<16.5%) or high (>16.5%) piglet mortality rate during lactation, Berger
et al.
(1997) observed that the percentage of farmers watching sows at parturition was
greater in the group of herds with the higher mortality. This may be interpreted as a
negative influence of the human presence disturbing the farrowing process. It may also
be assumed that farmers with a herd having a higher mortality rate make more efforts
to reduce it and hence are more present at farrowing in order to assist the sows. If both
hypotheses are true, a negative vicious circle will be established.
Finally, it can be postulated that the behaviour of stockpersons towards pigs is positively
related to their technical skills (Figure 12.1). Such behaviours of the stockpersons were
found to be related to their general beliefs and attitudes about pigs (Hemsworth, 2003).
Significant relationships between personality traits (e.g. self-assured, self-disciplined or
emotionality) and reproductive performance of sows were also demonstrated (Ravel
et
al.,
1996). In addition to those personal features, it is very likely that the organization
