Effect of sepiolite on pellet durability in feeds differing in fat and fibre content

Sepiolite is a hydrated magnesium silicate clay with binder properties. The effect of sepiolite on pellet durability was studied using feeds varying in the level of fat and fibre. A 2 × 2 × 3 factorial arrangement was designed with two levels of sepiolite (0 and 20 g kg−1), two levels of added fat (5 and 40 g kg−1) and three levels of fibre (40, 70 and 140 g kg−1). Four samples of feed pellets were obtained from each combination of factors in order to measure durability using the Pfost durability tester. Temperatures at three points of the pelleting process, and percentage of broken pellets and of fines in the cooler and cyclone were measured. Durability of pellets varied between 81.9% and 98.0%. Results of durability indicated that fat accounted for 45% of the total variability, sepiolite for 19.2% and fibre for 15.5%. There was a significant interaction (P < 0.001) between sepiolite and fat, indicating that sepioliteʹs effect was more pronounced when the fat level was high. Thus, durability of the pellets at a level of 5 g kg−1 was 95.8% without sepiolite and 96.8% with sepiolite. At a fat level of 40 g kg−1, durability was 86.5% without sepiolite and 93.6% with sepiolite. The interactions between fibre and sepiolite, and between fibre and fat were less important and accounted for only 4% of the variation. Percentages of broken pellets and of fines in the cooler and cyclone were reduced by sepiolite addition.