High-Fibre feeding in gestation - The Gestating and Lactating Sow - page 87

the sensory phase of the satiety cascade can be illustrated by the increased chewing
activity of gestating sows during the ingestion of a diet with sugar beet pulp, which has
a high water-binding capacity, as a major fibre component (Ramonet et al. , 1999). he
enhanced chewing activity induces a longer sensory exposure time in the mouth known
to enhance satiation, or meal termination, in humans (Zijlstra et al. , 2009). Reduced
feeding motivation recorded short term after the meal, may also illustrate the satiation
signals associated with dietary fibre (Meunier-Salaün et al. , 2001; Souza da Silva et al. ,
2012). Several putative effects of dietary fibres associated with the post-ingestive phase
of satiety have been reported throughout the gastrointestinal tract (Brownlee, 2011): an
increased production of saliva and gastric juice thereby promoting gastric distention,
a delayed gastric emptying, afferent vagal signals of fullness, a prolonged transit time
which may result in increased secretion of satiety-related hormones and prolonged
chemoreception, and, finally, an increased production of short-chain fatty acids (SFCA)
related to fermentation in the distal part of the intestine, mainly in the colon (Sappok,
2012). The post-absorptive factors relate to the metabolic changes that follow the meal.
The biomarkers for satiety that have been shown to be affected by ingestion of dietary
fibres are glucose, insulin and SCFA. Indeed, the incorporation of fibres in the diet results
in lower postprandial glucose and delayed insulin responses, reflecting a decreased influx
of glucose by enzymatic digestion, and an increased production of SCFA after the meal
(Farmer et al. , 2002; Ramonet et al. , 2000a) which might stimulate the release of satiety-
related hormones such as PYY or GLP-1 (De Leeuw et al. , 2008) and prolong the energy
supply to the body, thereby promoting the duration of satiety.
The current literature on post-prandial changes in metabolic and hormone profiles
induced by dietary fibres in pregnant sows, shows variations due to fibre sources and level
of dietary fibre tested in the studies (De Leeuw et al. , 2004; Farmer et al. , 2002; Guerin
et al. , 2001; Quesnel et al. , 2009; Ramonet et al. , 2000a; Serena et al. , 2008). For instance,
studies with diets containing sugar beet pulp as the main fibre source showed stronger
effects on the sensory phase, by increasing mastication time, and on the post-absorptive
phase, with delayed glucose and insulin peaks and lower levels of glucose and insulin,
compared with diets containing wheat bran (Ramonet et al. , 2000a). Brouns et al. (1995)
also reported lower palatability of diets containing sugar beet pulp compared with diets
using others fibre sources.
In summary, dietary fibres have an impact on the mechanisms involved in the satiety
process. However, depending on the fibre source and its physicochemical properties,
including bulkiness, viscosity, gelling or fermentability, the efficiency of dietary fibre used
in diets of pregnant sows to induce satiety is variable (Le Gall et al. , 2009; Serena et al. ,
2008, 2009; Slavin and Green, 2007). Studies on the impact of the main physicochemical
properties suggest a stronger effect of bulkiness during and immediately following a meal
whereas fermentable fibres prolong postprandial satiety for many hours after a meal
(Benelam, 2009; De Leeuw et al. , 2008; Souza da Silva et al. , 2012). Besides the satiating
effects, dietary fibres may also have beneficial effects on colonic health and microbiota
composition (Haenen et al., 2013a,b). These effects are beyond the scope of this chapter,
but will be discussed in Chapter 15 (Le Huërou-Luron and Ferret-Bernard, 2015).