The satiating effects of dietary fiber may depend more on physicochemical properties of the fiber than on total fiber intake. These properties are expected to affect satiety feelings and feeding motivation due to different effects in the gastrointestinal tract. The aim of the current study was to assess the effects of fibers with varying physicochemical properties (bulkiness, viscosity and fermentability) on feeding motivation in adult female pigs. Sixteen pair-housed pigs received four diets: lignocellulose (LC), pectin (PEC), resistant starch (RS), and control (C) without fiber, in four periods in a Latin square design. Each fiber was fed at a low (L) followed by a high (H) inclusion level (7 days each). At 1h, 3h, and 7h after the morning meal, feeding motivation was assessed in an operant test, where turning a wheel yielded multiple food rewards, and in a runway test, where walking a fixed U-shaped track yielded one food reward. Pigs were observed in their home pen for 6h, using 90-s instantaneous scan sampling. In the operant test, throughout the day feeding motivation was higher for pigs on PEC compared with pigs on LC. In the runway, feeding motivation increased particularly at 1h after the meal for pigs on PEC compared with pigs on RS. Also at 7h, feeding motivation tended to decrease for pigs on RS compared with pigs fed other diets. In their home pen, pigs on PEC showed more feeder-directed behavior compared with pigs on RS. In conclusion, PEC was the least satiating fiber. LC and RS, despite a lower supply of available energy, were the most satiating fibers, possibly due to their bulky and fermentation properties, respectively.
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