1. Introduction
In commercial conditions, the daily energy supply to sows during pregnancy is determined in order to meet the requirement for maintenance, uterine growth and
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maternal gain AFRC, 1990; Noblet et al., 1990 . In fact, the feeding level is adjusted in order to maintain optimal body condition of sows during successive parities and
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maximize their longevity Dourmad et al., 1994 . Consequently, sows are generally restricted fed during pregnancy to a level which amounts to only 50 to 60 of their
voluntary food intake, inducing sustained feeding motivation during most of the day Ž
. Lawrence et al., 1988; Hutson, 1991 . The behavioural expression of feeding motiva-
Ž tion has been recorded from various parameters Lawrence and Terlouw, 1993; Rushen
. Ž
. et al., 1993 including the feeding rate Terlouw et al., 1991; Brouns et al., 1994 and
Ž the level of stereotypic behaviours expressed by sows around meal time Rushen, 1984;
. Robert et al., 1993 . Operant conditioning techniques, used to assess needs andror
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preferences of farm animals Kilgour et al., 1991 , have also been developed to examine Ž
. feeding behaviour. In pigs, Lawrence et al. 1988 demonstrated that feed restricted
boars sustained a high level of feeding motivation, as measured by an operant condition- ing procedure.
The energy dilution of diets by fibre allows the bulk of food eaten by sows during Ž
pregnancy to be increased without changing the daily energy intake Shi and Noblet, .
1993 . It has been previously shown that sows fed high-fibre diets perform less Ž
. stereotyped behaviours Robert et al., 1993; Brouns et al., 1994; Ramonet et al., 1999a
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and more resting behaviour Robert et al., 1993; Ramonet et al., 1999a . High-fibre diets have also been shown to reduce feeding motivation measured by operant conditioning
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tests, especially in the immediate post feeding period, in growing pigs Day et al., 1996 Ž
. and in fed restricted sows Robert et al., 1997 .
Nevertheless, the effect of specific feedstuffs on feeding motivation of food restricted sows is still unclear. In sows fed ad libitum, the nature of the fibrous ingredients has an
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effect on feed intake and time spent in feeding activity Brouns et al., 1995 . In particular, sows fed sugar beet pulp-based diet showed limited spontaneous feed intake
which should be interpreted as a reduced feeding motivation. The aim of this study was to evaluate the incidence of the level and the nature of
fibrous component in diet on the feeding motivation of pregnant restricted fed sows. This was achieved by comparing a low and two high fibre diets differing in their
physico-chemical properties, which have an influence on the profile of metabolic and digestive processes. The potential effects of the fibrous diets were measured after a
medium and a long-term period in order to evaluate the feeding motivation of sows over the day.
2. Materials and methods
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