Studies on the Use of Persimmon Peel for Ruminant Feeds

概要

Doctoral Thesis

Studies on the Use of Persimmon Peel for Ruminant Feeds
཯ⱄᐙ␆࡟ᑐࡍࡿᰠ⓶ࡢ㣫ᩱ฼⏝࡟㛵ࡍࡿ◊✲

(Summary)

Ainissya Fitri

Graduate School of Biosphere Science
Hiroshima University

September 2020

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Fruit byproducts are abundantly available in Japan, and thus should be considered
as alternative feed resources because of their economic and environmental impact
through the food chain. One example, persimmon peel (PP), is a waste product from the
producers of dried persimmon. The PP contains fiber, non-fiber carbohydrate (NFC), and
protein as well as phenolic compounds, particularly tannins, which gives persimmons
their astringent taste. This astringent taste would decrease palatability if used in animal
feed. Fruit byproducts, especially PP, have a high moisture content, which leads to the
problems of susceptibility to microbial spoilage when used and preserved. Mixing PP
with other feeds when preparing total mixed ration (TMR) reduces these obstacles and
may improve its utilization. Ensiling TMR is a practical method for preserving high
moisture feeds over a long period. However, during the ensiling process, a part of
nutritional compounds in PP can be lost and the tannin in PP would also be insolubilized.
This would reduce the astringent taste because the ethanol and CO2 that are used for the
deastringency treatment of persimmon fruit are also produced during the ensiling process.
Additionally, mixing PP in TMR silage may reduce the ruminal protein degradability
because tannins bind to dietary protein and forms a less degradable complex in the rumen.
Thus, the purpose of the present study was to evaluate the utilization of PP as an
ingredient of TMR silage for ruminant feeds, with a particular focus on changes in the
contents of tannins and nutrients during the ensiling process.
The first experiment (Experiment 1) was conducted using four sheep that each
received four different diets in a 4 × 4 Latin square design with 15 days for each
experimental period. The ingredients of the diets were as follows: 1) a basal non-ensiled
diet containing oat hay, soybean meal, beet pulp, and barley (T1); 2) a basal non-ensiled
diet with 1% Quebracho tannin on a dry matter (DM) basis (T2); 3) a control mixed silage
diet with barley (T3); and 4) a PP mixed silage diet with barley (T4). The control and PP
mixed silages were prepared with oat hay, soybean meal and beet pulp or PP and ensiled
for about 6 months. The sheep were fed diets at 1.5 times their maintenance energy. There
was no difference in the average daily gain and nitrogen balance between sheep fed the
four different diet. The digestibility of DM, organic matter (OM) and neutral detergent
fiber (NDF) in sheep fed the T4 diet was lower than those in sheep fed the other diets.
The methane production in sheep fed the T3 diet was the highest among these diets.
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However, the total VFA concentration and its proportion in the rumen of sheep fed the
T4 diet was similar to those in sheep fed the T3 diet. The ruminal ethanol concentration
was higher for the T4 diet than that for the other diets at 2 hours after feeding. The ruminal
ammonia-N (NH3-N) and plasma urea-N concentrations were higher in sheep fed the T3
and T4 diets than those in sheep fed the T1 and T2 diets. The concentrations of essential
amino acids in the plasma were not affected by the diets. For plasma metabolites, the T4
diet showed the highest concentrations of ketone bodies and triglycerides among the diets.
In conclusion, the mixed silage containing PP showed lower digestibilities of DM and
NDF but reduced methane emission from the sheep. Nitrogen utilization in the sheep was
not affected by feeding the mixed silage although the ruminal protein degradation seemed
to be enhanced by feeding the mixed silages.
To investigate the reasons for the lower digestibility of the PP mixed silages (T4
diet) observed in Experiment 1, the effect of the ensiling treatment on the nutrient
contents and in vitro ruminal fermentation between PP and grape pomace were compared
(Experiment 2.1). The PP, red grape pomace (RGP) and white grape pomace (WGP) were
ensiled for 0, 1, 2, 4 and 8 weeks. Freeze-dried samples of byproducts ensiled for 0 (fresh
byproduct) and 4 weeks were used for the in vitro rumen fermentation with rumen fluid
collected from sheep. For the in vitro study, polyethylene glycol (PEG) was added to
determine the tannin activity because PEG can bind tannins and inhibit its activity. The
NFC content in the byproducts decreased after ensiling, especially for the PP. The total
tannin content was similar among the fresh byproducts. The proportion of soluble tannin
in the PP decreased after ensiling but the grape pomaces were not affected by the ensiling
treatment. The ruminal fermentation, indicated by the gas production, total VFA
concentration and methane production parameters for all byproducts, was reduced by the
ensiling treatment, but was increased by adding PEG, except for the PP silage. The gas
production and VFA concentration for the PP silage was increased less by adding PEG
compared with grape pomaces. In conclusion, reducing the NFC content by the ensiling
treatment decreased the ruminal fermentability of the PP. The insolubilization of tannins
that occurred in the PP during ensiling reduced its inhibitory effect on ruminal
fermentability. In Experiment 2.2, the in vitro fermentability was compared between PP
and beet pulp. Compared with beet pulp, PP silage showed lower gas and methane
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production and DM and NDF digestibility by the in vitro rumen incubation. The replacing
lower digestible PP for beet pulp was the one of the reasons for the lower DM and NDF
digestibility of the mixed silage diets containing PP.
In Experiment 3, the effect of including PP in TMR silages at different levels on
their chemical composition, protein fraction, tannin fractions, and in vitro rumen
fermentation were investigated. Four different types of TMR silage containing PP at 0,
50, 100, 150 g/kg DM were used in this experiment. The TMR silages were prepared in
500-mL plastic bottles then stored for 6 months. Freeze-dried samples of pre-ensiled and
ensiled TMR were used for in vitro rumen fermentation. Increasing the PP level in the
TMR silages decreased the soluble protein and increased the neutral detergent insoluble
protein. The total tannin content in the TMR silage was not affected by the PP level.
However, increasing the PP level in the TMR silages decreased soluble tannin and
increased the insoluble tannin contents. During the ruminal fermentation, the gas and
methane production in the TMR silages was lower than that in the pre-ensiled TMR and
decreased linearly with increasing PP level. The concentrations of NH3-N and total VFA
in the in vitro rumen were not affected by the ensiling treatment or the PP content.
Including PP in the TMR silages affected protein breakdown during the ensiling process
with a negative correlation being observed between the insoluble tannin and soluble
protein contents. Although gas and methane production in TMR could be reduced by
including PP, this decrease was more pronounced in the pre-ensiled TMR.
In conclusion, even though TMR silage containing PP can be preserved well for 6
months, the tannins of PP become inactivated and a part of the NFC of PP is lost during
the ensiling treatment. TMR silage containing PP did not affect the nitrogen balance
parameters in the sheep, even though the tannins in PP can reduce protein solubility in
TMR silages. Furthermore, TMR silage containing PP reduced DM digestibility, which
relates to the reduction of methane emission from animals, although this inhibitory effect
on DM digestibility and methane emission seemed to have occurred through the loss of
NFC during ensiling rather than the tannin activity in PP. The loss of NFC after ensiling
in TMR containing PP means that additional energy sources might be required to cover
this loss and to provide enough energy for the animals.

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