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fibrous diets based on oat hull and oat hull/alfalfa compared with a low-fibre concentrate
diet (Bergeron
et al.
, 2002). Amongst studies, factors such as the age or the parity of sows
varied, suggesting stronger effects of fibrous diets on the feeding motivation in young
sows compared with multiparous sows.
5.4.2
Non feeding oral activity and stereotyped behaviour
The occurrence of oral activities directed towards substrates within the pen (e.g. rooting,
licking or biting bars, chain, feeder, floor, walls, or bedding material) or self-directed oral
activities (sham-chewing, tongue playing, teeth-grinding, head waving) in pregnant sows
is generally associated with unfulfilled feeding motivation, due to the feed restriction
(insufficient feed to produce satiety), and with the frustration of feeding/foraging
behaviour due to a lack of substrate. Water consumption above the normal physiological
needs has also been associated with feeding frustration (Douglas
et al.
, 1998). Such oral
activities are interpreted as a sign of stress and impaired welfare (Mason, 1991; Lawrence
and Rushen, 1993). In many cases, these activities are performed in a stereotypic manner
mainly around the meal (from before the meal until 3 h after the meal), and different
forms of stereotypies are found before and after feeding (Blackshaw and McVeigh, 1985;
Robert
et al.
, 2002; Rushen, 1985). For instance, object biting has been described to
occur almost exclusively prior to feeding and is performed at high frequency in response
to feed anticipation, while vacuum chewing and chain manipulation generally were
the most common stereotypies after feeding. These results are in accordance with the
argument that pre-feeding stereotypies are likely associated with frustration (e.g. foraging
behaviour), whereas post-feeding stereotypies are rather related to the persistence of
feeding motivation (Robert
et al.
, 2002).
Numerous studies reported a decrease in the occurrence of oral activities immediately
after the meal with the inclusion of fibre in the diet of pregnant sows. Nevertheless, the
effectiveness of fibre supply to reduce oral stereotyped activity depends on the nature
of the fibre, its incorporation rate and the feeding conditions(De Leeuw
et al.
, 2008; Le
Gall
et al.
, 2009; Meunier-Salaün
et al.
, 2001; Philippe
et al.
, 2008). Indeed, the reduction
of stereotypies appeared stronger when incorporated at the rate of around 300 g NDF/
kg of feed vs. a lower level (Bergeron
et al.
, 2000; Ramonet
et al.
, 1999; Robert
et al.
,
1993, 1997), while keeping net energy (NE) at a similar level. Following ingestion of
high NSP diets, major effects on the incidence of stereotypies have been reported,
especially with incorporation of sugar beet pulp, oat hulls, or wheat bran (Cerneau
et
al.
, 1997; Courboulay and Gaudré, 2002; Paboeuf
et al.
, 2000; Ramonet
et al.
, 2000a;
Robert
et al.
, 1997). Ramonet
et al.
(2000a) emphasized that the reduction of stereotyped
activity in sows fed fibrous diets might be partly due to the longer duration of eating,
leaving less time for non-feeding activities, which may explain the stronger effects of
dietary sugar beet pulp compared with wheat bran. Nevertheless, De Leeuw
et al.
(2008)
highlighted that even when correcting for eating time, dietary fibres reduce non-feeding
oral activities immediately after a meal. This postprandial effect of dietary fibres seems
to occur regardless of the source or level of bulkiness (De Leeuw
et al.
, 2008). Even
resistant starch, which has a low bulkiness, was recently shown to reduce stereotypies in
sows (Souza da Silva
et al.
, 2013). It is important to specify, however, that fibrous diets
