ORIGINAL ARTICLE
Evaluation of sources of variation on in vitro
fermentation kinetics of feedstuffs in a gas production
system
Juan P. KEIM,
1
Christian ALVARADO-GILIS,
1
Rodrigo A. ARIAS,
1
M onica GANDARILLAS
1
and
Jaime CABANILLA
2,3
1
Animal Production Institute, Faculty of Agricultural Sciences, Universidad Austral de Chile,
2
Graduate School,
Faculty of Agricultural Sciences, Universidad Austral de Chile, Valdivia, Chile; and
3
Department of Animal
Production, Faculty of Veterinary Medicine & Zootechnics, Universidad Agraria del Ecuador, Guayaquil, Ecuador
ABSTRACT
The aim of this study was to evaluate the effect of different sources of variation in gas production technique on the
in vitro gas production kinetics of feedstuffs. Triplicates of commercial concentrate, grass silage, grass hay and grass
pasture were incubated in three experiments: experiment 1 assessed two agitation methods; experiment 2 evaluated
different rumen inocula (pooled or different donor cows for each incubation run); and experiment 3 used Goering-Van
Soest or Mould buffers for media preparation. Gas production data were fitted into the Michaelis–Menten model and
then subjected to analysis of variance. Gas production (GP) at 48 h and asymptote gas production (A) were lower
when bottles were continuously under horizontal movement. Time to produce half and 75% of A, and A were
affected by rumen inocula, while buffer type affected time to produce half and 25% of A and GP. No interactions
between substrates and sources of variation were observed, suggesting that the effects of substrates on GP parameters
were not modified. It is concluded that comparison of numerical data from in vitro experiments that follow different
protocols must be done carefully. However, the ranking of different substrates is more robust and less affected by the
sources of variation.
Key words: buffer type, rumen fermentation, rumen inocula.
INTRODUCTION
The in vitro gas production technique (IVGPT) is a
valuable tool that describes the fermentability of
ruminant feedstuffs, allows the determination of fer-
mentation kinetics (Theodorou et al. 1994), estimates
dry matter (DM), protein and fiber degradation, as
well as rumen volatile fatty acid contents and the
microbial protein synthesis (Dijkstra et al. 2005). The
composition of the headspace gas produced from dif-
ferent feedstuffs has also been analyzed (Xu et al.
2010), especially for methane content, as it is consid-
ered a strong greenhouse gas and represents a loss of
dietary energy for ruminants (Pellikaan et al. 2011).
Kinetics of GP and GP at 24 h have been used to
rank feedstuffs, and also to estimate feed energy value
(Menke & Steingass 1988), and the effectiveness of
different additives on improving the nutritive value
and methanogenic potential of different feedstuffs
(Pirondini et al. 2015; Togtokhbayar et al. 2015). The
popularity of in vitro GP stems mainly from the ability
to exercise experimental control, the capacity to non-
destructively screen a large number of substrates, the
kinetic information obtained, and the relatively low
costs (Dijkstra et al. 2005). Thus, IVGPT offers a
unique tool for researchers to address a wide range of
nutritional issues in ruminants (Getachew et al. 2005)
as well as for non-ruminant species (Coles et al. 2005;
Cone et al. 2005; Williams et al. 2005).
Different batch culture systems have been used,
such as the syringe technique (Menke & Steingass
1988), the pressure transducer method (Theodorou
et al. 1994) and fully automated systems (Cone et al.
1996), among others.
Correspondence: Juan P. Keim, Animal Production
Institute, Faculty of Agricultural Sciences, Universidad
Austral de Chile, PO Box 567, Valdivia, Chile.
(Email: juan.keim@uach.cl)
Received 28 December 2016; accepted for publication
21 March 2017.
© 2017 Japanese Society of Animal Science
Animal Science Journal (2017) 88, 1547–1555 doi:10.1111/asj.12825