title: In vitro fermentation characteristics of diets with different forage/concentrate ratios: comparison of rumen and faecal inocula.
abstract: BACKGROUND
  The aim of this trial was to evaluate the replacement of rumen fluid with faeces as inoculum in studying the in vitro fermentation characteristics of diets for ruminants using the in vitro gas production technique. Six iso-protein diets with different forage/concentrate ratios were incubated with rumen fluid (RI) or faeces (FI) collected from sheep.
  
  
  RESULTS
  Most of the fermentation parameters were influenced by diet and inoculum (P < 0.01). With both inocula, organic matter degradability (dOM), cumulative gas production (OMCV) and maximum fermentation rate (R(max) ) increased as the amount of concentrate in the diet increased. R(max) was lower with FI vs RI (P < 0.01); dOM was higher with FI vs RI and the diet × inoculum interaction was significant. As expected, with both inocula, R(max) increased as the neutral detergent fibre content of the diet decreased. Significant correlations were obtained using both inocula between OMCV/dOM and gas/volatile fatty acid (VFA), while the correlation VFA/dOM was significant only with FI. The microbial biomass yield calculated by stoichiometric analysis for all diets was higher with FI vs RI. With FI the organic matter used for microbial growth showed an overall decreasing trend as the amount of concentrate in the diet increased.
  
  
  CONCLUSIONS
  The results indicate that both faeces and rumen fluid from sheep have the potential to be used as inoculum for the in vitro gas production technique.
authors.affiliation: Department of Animal Science and Food Control, University of Naples Federico II, 80137 Napoli, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Zicarelli
authors.forename: Serena
authors.initials: S
authors.lastname: Calabrò
authors.forename: Monica I
authors.initials: MI
authors.lastname: Cutrignelli
authors.forename: Federico
authors.initials: F
authors.lastname: Infascelli
authors.forename: Raffaella
authors.initials: R
authors.lastname: Tudisco
authors.forename: Fulvia
authors.initials: F
authors.lastname: Bovera
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Piccolo
mesh_terms: D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000254:growth & development*; D018533:Biomass; D004032:Diet / Q000662:veterinary*; D004043:Dietary Fiber / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000032:analysis; D005243:Feces / Q000382:microbiology*; D005285:Fermentation; D005740:Gases / Q000378:metabolism; D012417:Rumen / Q000737:chemistry / Q000382:microbiology*; D012418:Ruminants / Q000382:microbiology*; D012756:Sheep
chemical_list: D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D005740:Gases