Animals
2021, 11, 1248
2 of 19
1. Introduction
Fibrous roughages account for 40 to 100% of the basic ration of dairy cows. Despite
its low energy and nutrient density, there are physiological and economic reasons for
increasing the percentage of forage in lactating cow’s diet. However, if higher forage-based
diets are to be realized, then increasing the rate and extent of fiber digestion is critical to
meet the energetic requirements of copious milk production. Diet fungal products can
enhance rumen fermentation and alter ruminal digestive processes; thus, they may improve
animal health and energy status in early lactation [
1
]. Aspergillus oryzae and Aspergillus niger
fungi have been chosen for production in food science in a low-cost medium [
2
–
5
] and both
have a long history concerning strain improvement to optimize enzyme production [
6
–
9
].
Thus, A. oryzae and A. niger co-cultivation extract (AOAN) has potential as a feed additive,
but their use has long been ignored in dairy feeding.
Several studies have investigated the efficacy of A. oryzae or A. niger on improving
the nutritional quality of grape seed [
10
], palm kernel cake [
11
], ginkgo leaves [
12
], and
common feeds [
13
,
14
] through fermentation. However, inconsistent results have been
obtained from animal experiments when fed A. oryzae or A. niger extract alone [
15
–
17
].
These results may be due to different diet types, which may provide limited substrate
for enzymes secreted from A. oryzae or A. niger to degrade. The effects of A. oryzae on
rumen fermentation and microbial populations have been proven to be determined by
the roughage type [
13
]. In addition, the single enzyme secreted by only one fungus
may also contribute to inefficient results from animal experiments. The different strains
enhance the nutritional composition in varying degrees [
10
]. Digestion of plants occurs
extracellularly for fungi. Hence, it is important for the natural degradation of plant biomass
by enzymes produced by several Aspergilli spp. Hu et al. [
18
] reported that co-cultivation of
A. oryzae and A. niger resulted in improved production of β-glucosidase, cellobiohydrolase,
β
-xylosidase, and laccase. However, studies are lacking on the effects of AOAN on nutrient
digestibility, fermentation characteristics, and bacterial composition using the 16s rRNA
sequencing approach, which is widely used in dairy nutrition to characterize prokaryotic
communities [
19
–
21
].
A common issue with all in vitro experiments is the paucity of in vivo data. However,
it must be noted that in vitro techniques can provide satisfactory accuracy for comparative
purposes and precludes unnecessary in vivo experimentation [
22
,
23
]. Therefore, we used
an in vitro experiment to investigate the effects of supplementation of AOAN on nutrient
degradation of a total mixed ration (TMR), three different roughages (corn silage, oat
hay, and alfalfa hay), at four-time points (7 h, 24 h, 30 h, and 48 h). The fermentation
characteristics, gas production, and bacterial composition at 48 h were also determined.
We hypothesized that AOAN could affect the microbiome, and subsequently affect dietary
degradation. The current study will provide fundamental information about AOAN and
investigate the potential of AOAN as a feed additive, which to date has been ignored in
the dairy industry.
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