The effect of age and processing on the in vitro fermentation of fibrous feedstuffs by labrador retriever dogs

Dietary fibre substances in dog foods are composed of cell wall polysaccharides, non-cellulose polysaccharides, and structural non-polysaccharides. The purpose of this study was to determine the effects of dog age and heat-steam pressure (extruding process) on the in vitro fermentation of fibrous feedstuffs (sugar beet pulp, tomato pomace, wheat bran, corn bran, and rice bran) to be included in dog foods. The fibrous feedstuffs were incubated with a fermentation medium mixture and faeces inoculum, which were collected from two 6 month old (puppy), two 2 year old (adult), and two 8 year old (geriatric) dogs. The in vitro cumulative gas production (at 6, 12, 18, 24, 36, and 48 h), true-organic matter disappearance (T-OMd) (at 6, 12, 24, and 48 h), and molarities of short chain fatty acids (SCFA) (acetic, propionic, and butyric acids; AA, PA, and BA) in fermentation fluid (at 24 h) of fibrous feedstuffs were determined. The extruding process increased the in vitro cumulative gas production of rice bran (at 12, 18, 24, and 48 h) and wheat bran (at 6, 12, 24, and 36 h) (P < 0.05). In addition, in vitro cumulative gas production values of tomato pomace (at 12, 18, 24, 36, and 48 h) were reduced by the extruding process (P < 0.05). The extruding process increased the in vitro T-OMd values of sugar beet pulp (at 6, 12, and 24 h), wheat and rice bran (at 6 and 12 h), and the molarities of AA, BA, and total SCFA of the in vitro fermentation fluid of sugar beet pulp and wheat bran (P < 0.05). The in vitro cumulative gas production values of tomato pomace from faecal inoculums of the puppy and adult dogs were higher than that of the geriatric dog (P < 0.05). The in vitro T-OMd of sugar beet pulp (at 48 h) and extruded corn bran (at 6 h) with faecal inoculums of adult dog was higher than those of inoculum from puppy faeces (P < 0.05). The molarity of AA of tomato pomace with adult dog's faecal inoculum was higher than those from puppy and geriatric dog (P < 0.05). The molarities of AA, BA, and total SCFA with corn bran from faeces inoculums of the puppy and adult dog was higher than that of the geriatric dog (P < 0.05). The molarities of AA and total SCFA of the in vitro fermentation fluid of extruded rice bran with faecal inoculums from the geriatric dogs was higher than those with faecal inoculums from the puppy and adult dogs (P < 0.05). As a result, the extruding process positively affected the in vitro fermentation values of sugar beet pulp, wheat bran, and rice bran. Furthermore, the organic acid molarities of the in vitro fermentation fluid of extruded rice bran from the geriatric dog was higher than those from the puppy and adult dogs. Sugar beet pulp, tomato pomace, wheat bran, and corn bran can be used as a source of fibre in food for puppy, adult, and geriatric large dogs