Pre-Caecal Disappearance of Starch and Volatile Fatty Acid (VFA) Content in Digesta of Caecum of Growing Pigs Fed with Ripe Hulled Shredded Acorns in Their Diet

Physical properties and chemical composition of caecum chyme, with particular regard to starch pre-caecal disappearance and volatile fatty acid (VFA, C2-C5) content, were determined in 16 growing pigs fed raw acorns in the diet. Pigs were singly housed and divided into two experimental feeding groups (each n = 8). The control group was fed a conventional complete diet for pigs (pelleted; 890 g dry matter (DM)/kg, 435 g starch/kg DM, based on cereals and soybean extraction meal). The acorn-fed group was offered a combined diet, 70% of ripe whole shredded acorns (695 g DM/kg, 447 g starch/kg DM) and 30% of the control diet. After one week, all 16 animals were slaughtered, and contents of the caudal ileum and caecum were analyzed for dry matter, crude ash, and starch. Fresh caecum chyme was analyzed for VFA content and molar proportion of acetic, propionic, n-butyric, n-valeric acid were determined. VFA per kg of organic matter (OM) in the caecum differed significantly between groups (p = 0.047). Pre-caecal disappearance (pCD) of acorn native starch turned out to be high (>95%). Estimated VFA content in caecum in the acorn combined diet resulted in 8.72 g per kg of OM, and the relationship based on molar proportion between acetic:propionic:n-butyric:n-valeric acid was 1:0.2:0.1:0.04, which pointed to higher proportions of n-valeric acid when hulled shredded acorns are fed to pigs.