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ISSN (Electronic):
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Volume 30, No. (4), 2020 (August)
(Impact Factor 0.529; JCR 2018) |
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NUTRITIVE VALUE AND IN VITRO DIGESTIBILITY OF NON-CONE HOP (HUMULUS
LUPULUS L.) BIOMASS
L. K. Rutto1,*, V. W. Temu1, G. Ferreira2 and M. K. Kering1
1Agricultural
Research Station, Virginia State University, PO Box 9061, Petersburg, VA 23806,
USA
2Department of Dairy Science, Virginia
Tech, 2100 Litton Reaves Hall, Blacksburg, VA 24061, USA
*Corresponding Author Email: lrutto@vsu.edu
ABSTRACT
More than 50% of
hop (Humulus lupulus L.) biomass is discarded as waste. Potentially,
this by-product, comprising leaves, bines, and unrecovered cones (non-cone
biomass) can be processed into a high value forage. In this study we used
classical forage and hop analysis methods to determine the nutritive and
chemical properties of non-cone biomass from five (Cascade, Chinook, Newport,
Nugget and Zeus) hop cultivars. Cascade had significantly higher crude protein (p≤0.05), while ash, starch and sugar
content were not statistically different among cultivars. Acid and neutral detergent
fiber ranged between 187-295 g·kg-1 and 274-397 g·kg-1 of
DM, respectively, with Cascade recording significantly (p≤0.05)
higher fiber than other cultivars. In vitro, dry matter (604-685 g·kg-1)
and NDF (374-478 g·kg-1) digestibility were significantly
(p≤0.05) higher in Newport, while true dry matter disappearance
(709-793 g·kg-1) was significantly (p≤0.05) lower in Cascade.
Variations were also observed in plant metal content with Ca being
significantly (p≤0.05) lower in Cascade, K in Nugget, and S in
Zeus, while Mg was highest in Newport. Overall, crude protein and
non-structural carbohydrate content in hop biomass were comparable,
respectively, to alfalfa, and to forage grasses like brome and Kentucky
bluegrass, and acid and neutral detergent fiber levels were slightly lower than
in alfalfa and legume-grass hays. Digestibility also compared favorably to
other forages including legume-grass hays and alfalfa silage. Hop biomass can
be a good source of dietary calcium, magnesium, and trace elements, and
furthermore was found to contain low levels of lupulone, a compound in cone
biomass recommended as a natural alternative to synthetic antibiotics. Our
findings suggest non-cone hop biomass may be of significant value as a
supplement in livestock nutrition.
Key
words: Humulus lupulus; Non-cone biomass; Nutritive value; Mineral content; a and b acids.
https://doi.org/10.36899/JAPS.2020.4.0093
Published online April 25, 2020
INTRODUCTION
Hops
(Humulus lupulus L.) is a perennial crop grown for the female
inflorescence that is a source of organic acids and other compounds essential
to beer flavor and aroma. During recovery of the female flowers (cones) for
further processing and marketing to the beer industry, large quantities of
non-cone biomass in form of leaves and woody stems (bines) are generated.
In
commercial hop production, disposal of non-cone biomass is an expensive
nuisance that is compounded by the reluctance of growers to return hop residue
into hop yards for fear of accelerating the spread of pests and disease causing
agents. This means leaf and bine biomass is usually removed from the field and
transported away from the hop yard, an exercise that translates into
significant labor cost and loss of native and added soil nutrients.
Various
studies have examined potential applications for non-cone hop biomass including
utilization as a sorbent in the recovery of lead (Hejazi, 2001;
Gardea-Torresday et al., 2002), cadmium (Partelová et al., 2015)
and gold (López et al., 2005) from aqueous solutions, or conversion into
biofuel by wet torrefaction (Yang et al., 2015) or slow pyrolysis
(Apaydin-Varol et al., 2017). There are also some reports on
alternative use as feed or for supplementation of animal diets. Al-Mamun et
al. (2009) found that inclusion of 15% dried non-cone hop residue or 25%
ensiled hop biomass (Al-Mamun et al., 2011) in a mixed hay diet did not
significantly impact plasma acetate metabolism in sheep. Production of acetate,
an important metabolite in fatty acid and carbohydrate metabolism, largely
depends on feed quality (Sutton et al., 2003) and blood acetate content
is a useful index in animal nutrition (Pethick et al., 1981). In an
earlier study, Statham (1984) found that replacement of Lucerne as a yolk
coloring additive with a similar amount of dried hop leaf residue in the diet
of laying hens resulted in darker colored yolks without affecting feed intake,
egg production, or the taste of eggs and carcasses.
Potential
for on-farm utilization of hop non-cone biomass as forage or feed supplement is
of particular interest to hops growers in Virginia and the greater mid-Atlantic
who have taken up hop production in response to demand from a growing craft
beer industry. According to statistics from the Brewers Association (an
organization representing small and independent craft brewers), beer production
by craft brewers in the United States (U.S.) has increased by more than 200% in
the last 10 years with most growth being observed among regional and
microbreweries (Brewers Association, 2018). Owing to small-scale operations and
strong regional identity, craft breweries are open to sourcing key ingredients
from local suppliers provided quality, quantity and pricing are satisfactory.
In Virginia, the state is supportive of the craft beer industry and many
landowners have started or are considering growing hops or specialty grains to
meet demand by local craft breweries. In a survey conducted by Virginia
Cooperative Extension (Siegle and Scoggins, 2017), a majority of respondents
have been growing hops for less than three years. Unlike in the Pacific
Northwest (PNW), Virginia hop yards are small (1-2 acres on average) and most
hop production takes place on farms with mixed crop/animal operations. Such
farms would benefit from information on the potential for on-farm utilization
of non-cone hop biomass as forage or value addition for sale to neighboring
farms. Furthermore, the hop plant lends itself to adoption as a forage source
because harvesting (cone separation) is usually done at a central location with
non-cone biomass easily stockpiled for further processing and handling.
Nationally, value addition to non-cone biomass would greatly benefit major PNW
hop growers whose acreage almost solely accounts for production levels
(>44,000 tons in 2017) that make the U.S. the world’s top hop producer (International Hop Growers’ Convention, 2017).
Here,
we report results on nutritive value, in vitro digestibility, and organic acid
chemistry of non-cone forage sampled from five hop cultivars.
MATERIALS AND METHODS
Animal care and
use: The
Institutional Animal Care and Use Committee of Virginia Tech approved all
procedures involving dairy cows for collecting rumen contents (protocol
15-234).
Experimental site
and conditions: The
data presented here is from the 2017 growing season for materials grown at the
Virginia State University Research and Demonstration hop yard located in
Randolph Farm (37o13’46” N; 77o26’02” W). Climatic data
(Table 1) was recorded on-site using a weather station equipped with HOBO smart
sensors and a HOBO RX3000 remote monitoring datalogger (Onset Computers,
Bourne, MA).
Plant materials: Non-cone hop
biomass was recovered at cone maturity from five cultivars (Cascade, Chinook, Newport, Nugget and Zeus) established
in the spring of 2016 using certified rooted cuttings purchased from Great
Lakes Hops (Zeeland, MI). The hop yard consists of an 18ft (5.5m) tall trellis
system with primary lines running north to south and secondary support lines
running east to west. Plant rows are spaced 3.0 m, and plants 1.0 m apart
within rows for a population of approximately 3330 plants per hectare. All
cultivars received similar fertilizer, irrigation, and pest and disease
management treatments in 2017 with nitrogen (N) applied at a rate equivalent to
110 kg·ha-1 N.
Sampling and
sample processing: At
cone maturity (August – September), bines were cut and transported to a central
location where cones were separated from non-cone biomass with the help of a
Hopster 5P hops harvester (Hopsharvester LLC, Honeye, NY). A tarp was used to
trap all non-cone biomass generated during harvest and both leaf and bine
material was consolidated per crown (plant) with four replicates per cultivar
based on a completely randomized sampling design. Fresh biomass from individual
plants was weighed then transferred into labeled burlap sacks and dried to
constant weight at 72oC using a Grieve® oven. Dry matter
(DM) yield was recorded before samples were rough-ground to pass a 4mm sieve.
Subsamples were further ground with a Wiley mill to 2mm before transfer to the
lab for analysis.
Forage analysis: Ash concentration
was determined following AOAC method 942.05 (AOAC International, 2016) by
combusting samples in a furnace for 3 h at 600°C. Crude protein concentration
was calculated as a percentage (N × 6.25) after N determination by combustion
(method 990.03; AOAC International, 2016) using a Vario El Cube CN analyzer
(Elementar Americas Inc., Mount Laurel, NJ). Neutral detergent fiber (NDF) and
acid detergent fiber (ADF) concentrations were determined using an Ankom 200
Fiber Analyzer (Ankom Technology, Macedon, NY) with sodium sulfite and
α-amylase included for NDF analysis. Starch concentrations were determined
using the acetate buffer method (Hall, 2009) with α-amylase from Bacillus licheniformis (Ankom
Technology) and amyloglucosidase from Aspergillus niger (E-AMGDF;
Megazyme International, Wicklow, Ireland). Sugar concentrations were determined
as total ethanol/water-soluble carbohydrates as described by Hall et al.
(1999).
In
vitro dry matter digestibility (IVDMD), in vitro true DM disappearance
(IVTDMD), and in vitro NDF digestibility (IVNDFD) were determined using a DaisyII
rotating jar incubator (Ankom Technology, Macedon, NY) following procedures
described by Ferreira and Mertens (2005).
For
mineral content, non-cone biomass samples were analyzed by inductively coupled
plasma atomic emission spectrometry (ICP-AES) for calcium (Ca), potassium (K),
sulfur (S), and magnesium (Mg) following AOAC Official Method 953.01 (AOAC
International, 2016).
Alpha and β-acid
analysis: Analyses
of a and b-acid content in non-cone hop
biomass was done by spectrophotometry. Briefly, 15 g (± 0.01) samples of ground
non-cone biomass were transferred into 1000 ml extraction bottles to which 300
ml of toluene was added. The vessels were stoppered and shaken for 30 min on a
rotary shaker. After 30min, samples were centrifuged at 2000 rpm for 5 min and
allowed to settle for 10 min before a 5 ml clear aliquot was drawn. Samples
were diluted and absorbance determined using a spectrophotometer as described
in methods published by the American Society for Brewing Chemists (ASBC, 2011).
Absorbance readings were used to compute a and b acid content in
DM for the different samples.
Statistical
analysis: A
one-way analysis of variance using the Proc-ANOVA function in SAS (v 9.4) was
performed on all variables. Variety was taken as a factor with five levels and
mean comparisons were done using Tukey’s HSD test (p≤0.05).
RESULTS
Dry matter yield
and partitioning: Biomass
yield ranged from a projected maximum 4.1 Mg·ha-1 in Zeus to a low
of 1.8 Mg·ha-1 in Newport (Figure 1). Statistically, total biomass
in Zeus was significantly higher per unit area than in the other four cultivars
and significantly lower in Newport, with no significant differences observed
between Cascade, Chinook and Nugget. Non-cone biomass followed a similar trend
with Zeus recording significantly higher yield than all the other cultivars
(Figure 1). Non-cone biomass DM yield ranged between 230-290 g·kg-1 of
fresh biomass, which was slightly higher than the 220-230 g·kg-1 (data
not shown) recorded for cone biomass at harvest (Table 2).
For
all cultivars, DM partitioning favored non-cone over cone biomass. With only
18% cone biomass, the proportion of non-cone biomass was significantly higher
in Newport than in Cascade, Nugget, and Zeus, but similar to Chinook (28%).
Nugget and Zeus at 36% and 37% cone biomass, respectively, recorded
significantly lower non-cone biomass than the other three cultivars (Figure 2.)
Nutritive value of
non-cone hop biomass: Crude protein (CP) in non-cone biomass was
significantly higher in Cascade, while readings for Zeus were significantly
lower than for all other varieties. There were no significant differences in
ash content (129-146 g·kg-1) among the five cultivars (Table 2). Water soluble carbohydrates (sugar and starch) levels in non-cone
hop biomass was also variable. Sugar content ranged from a high of 78.7 g·kg-1 of DM in Nugget to a low of 49.7 g·kg-1 in Cascade with no
significant difference in content among the top four varieties. Starch content
was much lower ranging from 11.9-21.6 g·kg-1 of DM with no
significant differences observed among varieties (Table 2). Acid detergent fiber and aNDF ranged between 187-295 g·kg-1 and 274-397 g·kg-1 of DM, respectively. For both ADF and aNDF,
Cascade had significantly higher fiber than all the other cultivars, while
fiber content in Nugget was numerically the lowest among all five cultivars (Table 2). For plant metals measured, content ranged
between 29.1-37.8 g·kg-1 of DM for Ca, 19.5-26.6 g·kg-1 for K, 1.9-2.6 g·kg-1 for S, and 6.9-8.4 g·kg-1 for Mg.
Among cultivars, significant variations in metal content were observed with Ca
being significantly lower in Cascade, K in Nugget, and S in Zeus, while Mg was
highest in Newport (Table 2).
In vitro
digestibility of non-cone hop biomass: In vitro dry matter digestibility (IVDMD)
ranged from a high of 686 g·kg-1 in Newport to a low of 605 g·kg-1 in Cascade and Chinook. Newport IVDMD was significantly higher than in all the
varieties except Nugget, although there were no significant differences in
IVDMD among Nugget, Cascade, Chinook and Zeus. True dry matter disappearance
(IVTDMD) in Cascade at 709 g·kg-1 was significantly lower than in the
other four cultivars. In vitro NDF digestibility (IVNDFD) followed a similar
trend as IVDMD with significantly higher digestibility observed in Newport (478
g·kg-1). Digestibility among the other four varieties (374-419 g·kg-1)
were numerically, but not statistically different.
Alpha and β-acid
content in non-cone hop biomass: Different levels of β-acid (lupulone)
were present in non-cone biomass of all five cultivars. However, no
significant differences were observed between cultivars owing to large
within-cultivar variations in β-acid content (Figure 3). Among
cultivars, β-acid content was highest in Nugget and Chinook (1.7
mg·g-1 of DM) and lowest in Newport (0.9 mg·g-1 of DM).
Alpha acids were present in measurable quantities only in Newport and Zeus with
content in Newport (1.1 mg·g-1 of DM) being significantly higher
than in Zeus with 0.2 mg·g-1 of DM (Figure 3).
Figure
1. Total and non-cone biomass yield from five hop (Humulus lupulus L.)
cultivars grown under Virginia conditions. Bars represent standard error of the
mean (n=4) and letters denote significant difference between varieties (within
biomass type) at p≤0.05.
Figure
2. Dry matter distribution between cone and non-cone biomass at cone maturity
in five hops (Humulus lupulus L.) varieties. (NCB: Non-cone biomass; CB:
cone biomass). Bars represent standard deviation (n=4) and letters denote
significant differences between varieties at p≤0.05.
Figure
3. In vitro digestibility of non-cone biomass recovered at cone maturity from
five hops (Humulus lupulus L.) varieties. Bars represent standard error
(n=4) and different letters across varieties denote significant difference (p≤0.05).
Figure 4. Alpha and β-acid content in in none
cone biomass recovered at cone maturity from five hop (Humulus lupulus L.) cultivars. Bars represent standard deviation (n=4). *Significantly different at p≤0.05.
Table
1. Average temperature, precipitation and relative humidity at the research
site during the 2017 growing season
Month |
Temperature (oC) |
Precipitation (mm) |
RH
(%) |
Mean |
Min. |
Max. |
March |
9.5 |
-5.1 |
26.0 |
88.4 |
59.0 |
April |
18.3 |
0.7 |
31.5 |
32.3 |
67.2 |
May |
19.2 |
3.0 |
33.4 |
112.5 |
72.9 |
June |
24.0 |
11.2 |
33.7 |
73.4 |
71.5 |
July |
27.0 |
13.7 |
36.7 |
41.9 |
70.9 |
August |
24.6 |
13.9 |
34.0 |
66.5 |
73.6 |
Sept. |
21.3 |
9.5 |
32.7 |
11.7 |
73.8 |
October |
17.2 |
-5.1 |
31.1 |
80.5 |
74.2 |
Table
2. Nutritional and mineral composition of non-cone biomass recovered at cone
maturity from five hop (Humulus lupulus) cultivars.
Cultivar |
DM |
Ash |
CP |
ADF |
aNDF |
Sugar |
Starch |
Ca |
K |
S |
Mg |
---------------------------------------------------------- g·kg-1 -------------------------------------------------------------- |
Cascade |
286.0ax |
137.4 |
244.3a |
294.6a |
397.2a |
49.7b |
13.0 |
29.1c |
26.6a |
2.6a |
7.5bc |
Chinook |
272.0ab |
145.9 |
186.8c |
212.5b |
296.5b |
65.3ab |
11.9 |
37.8a |
24.8ab |
2.3b |
7.7b |
Newport |
229.7c |
140.3 |
199.8b |
200.1b |
292.5b |
74.3a |
12.7 |
33.9ab |
23.6b |
2.5ab |
8.4a |
Nugget |
245.0b |
129.1 |
204.5b |
187.0b |
273.7b |
78.7a |
21.6 |
32.4bc |
19.5c |
2.4ab |
6.9c |
Zeus |
294.3a |
132.3 |
164.3d |
226.2b |
318.2b |
66.9ab |
13.0 |
35.7b |
25.4ab |
1.9c |
7.3bc |
DM:
Dry matter; CP: Crude protein; ADF: Acid detergent fiber; aNDF: Neutral
detergent fiber. xValues within columns followed by different
letters are significantly different at p≤0.05 (Tukey’s HSD, n=4).
DISCUSSION
Hops
are grown for the unfertilized female flowers (also referred to as hop cones),
used in brewing, and our data shows less than average yield for this key
ingredient among tested cultivars. Ranging
from a low of 0.3 Mg·ha-1 for Newport to a high of 1.6 Mg·ha-1 in
Zeus, cone biomass yields were much lower than estimates for Michigan and the
Pacific Northwest (Sirrine et al., 2014). This was further reflected in
higher non-cone to cone biomass ratios among all varieties with the least cone
production being observed in Newport (18%) and the highest in Nugget and Zeus
at 36% and 37%, respectively. These numbers are contrary to those reported by
Thomas (1967) who observed that cone biomass accounts for about 50% of
above-ground dry matter accumulation at harvest.
The
overall lower yield coupled with a higher proportion of non-cone biomass may be
attributed to location. The VSU hop yard is located at a lower latitude with a
shorter growing season compared with the north western states of the U.S. where
hops are most productive. Failure by most bines to reach the top of the trellis
and thus break apical dominance may also account for less side-arm growth and
lower cone yield. Although dry matter partitioning is likely to change as the
yard matures, these results underline the need for more work to identify
varieties and agronomic practices most suited to Virginia and the
mid-Atlantic.
The
nutritive value of non-cone hop biomass and its potential for use as forage was
considered from the perspective of dairy nutrition (Hoffman and Shaver, 2004;
Hoffman, 2005; Paulson et al., 2008; Brown et al., 2017). Even at
the lower end, non-cone biomass CP compares favorably with averages recorded
for legume-grass hay (Hoffman and Shaver, 2004), suggesting it can be a good
source of protein in livestock rations. Crude protein is a function of N
content in forage and the generally high CP levels in hop biomass may be
associated with the higher than average amounts of N fertilizer applied in the
production of the crop (Neve, 1991). Recommended N rates for hops are 112-300
kg·ha-1 in the UK, Germany and the U.S., while P and K are supplied
at 0-100 kg·ha-1 and 0-150 kg·ha-1, respectively,
depending on residual levels in the soil (Mahaffee et al., 2009). This
implies that processing of hop residue for use as livestock forage would
represent significant value addition to minerals sequestered in non-cone
tissues.
Ash
represents the total mineral content in forage and is found to range between
60-160 g·kg-1, 70-160 g·kg-1, and 30-140 g·kg-1 of DM in legume-grass silages, legume-grass hay, and corn silage, respectively
(Hoffman and Shaver, 2004). The relatively high ash content in non-cone hop
biomass implies a lower proportion of non-fiber carbohydrates, a negative
attribute in forage. Higher than normal ash in grass and legume forages is
usually associated with silica from soil and other external contamination
(Hoffman, 2005), but our hop forage samples were mostly free of non-plant
contaminants suggesting high mineral sequestration in hop tissues. Results from
forage and petiole (data not included) analysis relative to recommended
sufficiency ranges for hop (Sirrine, 2016)
show Ca and Mg concentrations to be slightly higher, and P, K and S to be
comparable to content in legume-grass hay. These levels are slightly lower that
values recorded for alfalfa hays (Orloff and Putnam, 2007) and legume/grass
silages (Hoffman and Shaver, 2004). Trace element data also shows that hop
forage can be a good source of Cu, Mn, Fe and Zn.
Sugar
content in non-cone hop biomass ranged from a high of 78.7 g·kg-1 of
DM in Nugget to a low of 49.7 g·kg-1 in Cascade with no significant
difference in content among the top four varieties (Table 2). Starch content
was much lower ranging from 11.9-21.6 g·kg-1 of DM with no
significant differences observed between varieties. However, plant carbohydrate
content has been shown to vary during the day due to imbalances in sugar
synthesis and utilization (Bowden, 1968), and within-cultivar carbohydrate
content in hop biomass may vary depending on time of harvest. Starch and sugars
comprise non-structural carbohydrates that are readily available to rumen
microbes and are reported to improve N use efficiency in dairy cattle
(Pelletier et al., 2010a). Compared to levels reported for other
species, sugar content in non-cone hop biomass (49.7-78.7 g·kg-1 DM)
is similar to that in forage grasses like reed canarygrass, brome grass, and
Kentucky blue grass, and slightly higher than in alfalfa and red clover.
Non-cone hop biomass starch content was found to be higher than in most pasture
grasses and comparable to that in alfalfa and red clover (Pelletier et al.,
2010a & b). These results show that non-cone hop biomass can be an
important source of non-structural carbohydrates in livestock diets.
Feed
supplementation with hop cones or cone extracts to study their effect on
ruminal fermentation and feed utilization have been conducted as discussed
below, but we did not find any reports on controlled feeding to test
palatability and in situ digestibility of non-cone biomass. However, findings
by Al-Mamun et al. (2009; 2011) and reports of widespread sheep grazing
to control sucker regrowth in New Zealand hop yards (Dodds, 2017) suggest
general ruminant acceptance of non-cone hop forage. Furthermore, although the
hop organic acids thought to be responsible for improving feed use efficiency
in ruminants are found primarily in cone biomass, trace quantities are
sequestered in leaf tissue (Čeh et al., 2007). Harvest losses (up
to 10% of cone biomass in our case) may also contribute to elevated levels of
the two organic acids in non-cone biomass. We found 0.9-1.7 mg·g-1 β-acid
in ground non-cone hop biomass after storage at ambient temperature for more
than six months, suggesting long term stability of this compound in forage.
This finding deserves further study as it suggests hop forage may improve feed
utilization in addition to supplying key nutrients and trace elements to
ruminants.
As
mentioned above, the presence of low levels of hop organic acids in feed has
been shown to modify rumen fermentation and to improve feed use efficiency in
ruminants. At least two in vivo studies confirm the efficacy of hop organic
acids as natural alternatives to synthetic growth promoters (ionophores) used
in ruminant nutrition. Wang et al, (2010) found that supplementation of
a steer diet with pelletized hop cones (cv. Teamaker) at a β-acid
inclusion rate of 0-40 mg·kg-1 of DM (growing diet) and 0-80 mg·kg-1 of
DM (finishing diet) resulted in a 6% increase in daily gain among steers
receiving the highest hop treatment relative to the control diet. In fattening
lambs, Blanco et al. (2018) report that inclusion of Nugget hop cones at
a rate of 1.5 or 3.0 g·kg-1 of total mixed ration (TMR), equivalent
to 55.5 mg and 110 mg·kg-1 β-acid of TMR modified rumen
fermentation by increasing the proportion of acetate and decreasing that of
propionate in a dose dependent manner. Higher acetate favors normal rumen pH,
while high propionate is commonly associated with metabolic disorders including
reduced fiber digestion and rumen acidosis.
In
vitro, amendment of rumen cultures with cone biomass from hop cultivars
including Cascade (Narvaez et al., 2013), Willamette (Flythe, 2009), and
Aurora and Dana (Lavrenčič et al.,
2013) or isomerized hop extracts (Flythe, 2009; Flythe and Aiken, 2010)
was observed to modify microbe composition and to regulate fermentation in a
manner similar to synthetic antibiotics used to enhance feed utilization in ruminants.
Furthermore, Harlow (et al., 2014) report that hop β-acids can inhibit fructan fermenting fecal bacteria, commonly associated with hindgut acidosis
and laminitis in horses (Bailey et al., 2004). Based on existing
literature, Flythe et al, (2017) recommend hop β-acids as a
model natural alternative to synthetic ionophores in ruminant nutrition.
Conclusion and
management implications: This report confirms the potential value of hop
non-cone biomass as alternative forage. In addition to being a good source of
protein, non-structural carbohydrates and minerals, hop forage holds great
promise as a natural alternative to synthetic ionophores used to improve feed
efficiency in ruminants by modifying rumen fermentation. This particular
attribute merits further study to determine whether the same benefits deriving
from the inclusion of cone biomass or cone extracts in ruminant rations can be
realized through direct feeding of non-cone forage. Considering the scale of the U.S. hop industry, our findings could have huge
economic implications.
Acknowledgements: We are grateful to
Dr. Anwar Hamama and Ms. Zaid Abraha-Eyob at the VSU Common Analytical lab for
help with various analyses. This study was funded by a grant to the
corresponding author from the USDA NIFA 1890 Institution Capacity Building
Program# 2015-38821-24384. This is a contribution of Virginia
State University Research Station Article No. 363.
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