Influence of level of supplemental whole flaxseed on forage intake and site and extent of digestion in beef heifers consuming native grass hay.

Abstract

The objectives of this study were to evaluate the influence of supplemental whole flaxseed level on intake and site and extent of digestion in beef cattle consuming native grass hay. Nine Angus heifers (303 ± 6.7 kg of BW) fitted with ruminal and duodenal cannulas were used in a triplicated 3 x 3 Latin square. Cattle were given ad libitum access to chopped native grass hay (9.6% CP and 77.5% NDF, OM basis). All animals were randomly allotted to 1 of 3 experimental treatments of hay plus no supplement (control); 0.91 kg/d whole flaxseed (23.0% CP, 36.3% NDF, and 25.5% total fatty acid, OM basis); or 1.82 kg/d whole flaxseed on a DM basis. Supplemental flaxseed tended to decrease (linear, P = 0.06) forage OM intake. However, total OM intake did not differ (P = 0.29) with increasing levels of flaxseed. Total duodenal OM flow increased (linear, P = 0.05) with additional flaxseed in the diet, and no differences (P = 0.29) were observed for microbial OM flow. True ruminal OM disappearance was not affected (P = 0.14) by supplemental flaxseed. Apparent lower tract OM digestibility increased (linear, P = 0.01) with level of whole flaxseed. Apparent total tract OM digestibility was not different (P = 0.41) among treatments. Nitrogen intake increased (linear, P < 0.001) with supplemental flaxseed. In addition, total duodenal N flow tended (P = 0.08) to increase with additional dietary flaxseed. However, true ruminal N digestibility did not differ (P = 0.11) across treatment. Supplemental whole flaxseed did not influence ruminal (P = 0.13) or total tract (P = 0.23) NDF digestibility. Ruminal molar proportion of propionate responded quadratically (P < 0.001) with increasing levels of whole flaxseed. An increase in the duodenal supply of 18:3n-3 (P < 0.001), total unsaturated fatty acids (P < 0.001), and total fatty acids (P < 0.001) was observed with additional dietary whole flaxseed. Apparent postruminal 18:3n-3 disappearance tended to decrease (P = 0.07) as intake of flaxseed increased. Overall, the inclusion of 1.82 kg/d of flaxseed does not appear to negatively influence nutrient digestibility of a forage-based diet and therefore can be used as an effective supplement to increase intestinal supply of key fatty acids important to human health.

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Proceedings, Western Section, American Society of Animal Science

Vol. 58, 2007

INFLUENCE OF SUPPLEMENTAL WHOLE FLAXSEED LEVEL ON FORAGE INTAKE AND SITE AND
EXTENT OF DIGESTION IN BEEF HEIFERS CONSUMING NATIVE GRASS HAY

E. Scholljegerdes* and S. Kronberg
Northern Great Plains Research Laboratory, USDA-ARS, Mandan, ND, USA

ABSTRACT1: The objectives of this study were to
evaluate the influence of supplemental whole flaxseed level
on intake and site and extent of digestion in beef cattle
consuming native grass hay. Nine Angus heifers (avg. BW
303 ± 6.7 kg) fitted with ruminal and duodenal cannulas
were used in a triplicated 3 × 3 Latin square. Cattle were
fed ad libitum chopped native grass hay (8.7% CP and
70.0% NDF, DM basis). All animals were randomly
allotted to one of three experimental treatments being either
no supplement (Control); 0.91 kg whole flaxseed; or 1.82
kg whole flaxseed on a DM basis. Supplemental flaxseed
tended to decrease (linear, P = 0.06) forage OM intake.
However, total OM intake did not differ (P = 0.29) due to
flaxseed inclusion. Total duodenal OM flow increased
(linear, P = 0.05) with additional flaxseed in the diet and no
differences were observed for microbial (P = 0.29) OM
flow. True ruminal OM disappearance was not affected (P
= 0.14) by supplemental flaxseed. Apparent lower tract OM
digestibility was greater for supplemented versus Control
cattle (P = 0.03) and increased (linear, P = 0.01) with level
of whole flaxseed. Apparent total tract OM digestibility was
not different (P = 0.41) among treatments. Nitrogen intake
increased (P < 0.001) with supplemental flaxseed. Total
duodenal N flow tended (P = 0.08) to increase with
additional dietary flaxseed. Therefore, true ruminal N
digested (g/d) tended (P = 0.07) to be greater for flax fed
cattle, however, true ruminal N digestibility did not differ
(P = 0.11) across treatment. Supplemental whole flaxseed
did not influence ruminal (P = 0.13) or total tract (P = 0.14)
NDF digestibility. An increase in the duodenal supply of
18:3n-3 (P < 0.001), total unsaturated fatty acids (P <
0.001) and total fatty acids (P < 0.001) was observed with
additional dietary whole flaxseed. Overall, the inclusion of
1.82 kg of flaxseed does not appear to negatively influence
nutrient digestibility of a forage-based diet and therefore
can be used as an effective supplement to increase intestinal
supply of key fatty acids important to human health.
Key Words: Beef cattle, Digestion, Fatty acid, Forage,
Flaxseed
Introduction
Feeding beef cattle diets high in n-3 fatty acids is
warranted for livestock producers interested in enhancing
the human healthfulness of meat products (Weill et al.,
2002) or reducing reproductive losses (Ambrose et al.,
2006). Feeding flaxseed is a viable option for bolstering n-

1 Mention of a proprietary product does not constitute a guarantee or
warranty of the product by USDA or the authors and does not imply its
approval to the exclusion of other products that may also be suitable.
USDA, ARS, Northern Plains Area, is an equal opportunity/ affirmative
action employer. All agency services are available without discrimination.
3 fatty acid concentration in livestock diets. Unfortunately,
there are limitations as to the level which fat can be added
to ruminant diets due to reductions in intake and
digestibility (Jenkins, 1993) however, flaxseed seems to be
unique in this regard. Because, Zhang et al. (2005)
observed an increase in DM digestibility for lactating ewes
fed a silage-based diet that contained 8% flaxseed
compared to diets that contained no oilseed or Canola. In
feedlot diets, flaxseed has been reported to not affect
(Maddock et al., 2006) or increase (Drouillard et al., 2004)
dietary intake with an overall improvement in ADG when
included at 5 – 8 % of the diet. However, little information
exists regarding the use of flaxseed in hay-based diets. Our
objectives were to evaluate site and extent of digestion in
beef heifers fed increasing amounts of whole flaxseed and
consuming native grass hay.
Materials and Methods
Animals and diets
Nine Angus heifers (avg. BW 303 ± 6.7 kg) fitted with
ruminal and duodenal cannulas were used in a triplicated 3
× 3 Latin square. Cattle were fed ad libitum chopped native
grass hay (8.7% CP and 70.0% NDF, DM basis). Previous
to the initiation of the experiment heifers were given ad
libitum access to both forage and whole flaxseed for 21 d in
an effort to determine the level at which the animal would
chose to consume flaxseed. It was determined that the
average maximal amount of whole flaxseed consumed was
approximately 1.82 kg/d. Therefore, all animals were
randomly allotted to one of three experimental treatments
being either no supplement (Control); 0.91 kg whole
flaxseed; or 1.82 kg whole flaxseed on a DM basis. All
experimental procedures were reviewed and approved by
the Northern Great Plains Research Laboratory, Animal
Care and Use committee. Animals were housed in a
temperature controlled barn within a 3.3 m × 2.7 m pen
equipped with cup waterers. Heifers were fed twice daily at
0600 and 1800. Hay and flax was fed in a separate feeders
and hay was fed at a level to achieve 5% orts each day. As
a marker of digesta flow, boluses containing 5 g of TiO2
were dosed intraruminally at each feeding. Each
experimental period was 21 d with 17 d adaptation to
ensure adequate adjustment of the gastrointestinal tract to
the new dietary treatment and 4 d of intensive sampling.
Sampling and laboratory analysis
Beginning at 0400 on d-18 of each sampling period,
duodenal (200 mL) and fecal (50 mL) samples were taken
every 4 h. On d-19, collection times were advanced 2 h so
that samples were collected to represent every 2 h in a 24 h
period. Fecal samples were dried in a 55° C forced-air
oven, ground (Wiley mill, 1-mm screen), and composited
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within heifer for each period. Duodenal digesta samples
were composited (equal vol.) within heifer for each period
and immediately frozen. Duodenal digesta samples were
then lyophilized (Freezemobile 25SL Freeze Dryer, The
VirTis Co., Gardiner, NY) and ground (Wiley mill; 1-mm
screen).
Immediately before the 0600 feeding and again every 3
h on d 20 until d 21 approximately 200 mL of whole
ruminal contents were collected. Immediately after each
collection whole ruminal contents were processed for
subsequent isolation of ruminal bacteria and analysis of
purines as described by Scholljegerdes et al. (2004).
All feed, microbes, duodenal digesta and fecal samples
were analyzed for DM and ash (AOAC, 1990). Nitrogen
content of feed, microbes, duodenal digesta, and feces were
determined using a Carlo Erba Model NA 1500 Series 2
N/C/S analyzer (CE Elantech, Lakewood, NJ). Neutral
detergent fiber of feed, duodenal digesta and feces were
determined using an ANKOM 200 fiber analyzer (ANKOM
Technology, Fairport, NY). Duodenal and fecal samples
were analyzed for Titanium dioxide according to the
procedures of Myers et al. (2005).
Feed was prepared for fatty acids analysis via direct
transesterification (Whitney et al., 1999) with methanolic-
HCl (Kucuk et al., 2001) and duodenal digesta fatty acids
were prepped for fatty acid analysis as outlined by Lake et
al. (2006). Separation of fatty acid methyl esters was
achieved by GLC (Model CP-3800, Varian Inc., Palo Alto,
CA) with a 100 m capillary column (SP-2560, Supelco,
Bellefonte, PA) and H2 as a carrier gas at 1.0 mL/min for
feedstuffs and 1.5 mL/min for duodenal digesta. Oven
temperature was maintained at 120° C for 2 min and then
ramped to 210° C at 6° C/min. Oven temperature was then
ramped to 250° C at 5° C/min. Injector temperature was
260° C and flame ionization detector temperature was 300°
C. Identification of peaks was accomplished using purified
standards (Sigma-Aldrich, St. Louis, MO; Nu-Chek Prep,
Elysian, MN; Matreya, Pleasant Gap, PA). Furthermore,
based on the chromatogram published by Loor et al. (2004)
the identification of 18:1trans 13+14 peak was based on
peak location relative to a peak identified and confirmed as
18:1cis-9 using a commercially available standard.
Statistical analysis
All data were analyzed using the MIXED model of
SAS (SAS Inst. Inc., Cary, NC) as a triplicated 3 × 3 Latin
square experiment. The model included animal as the
random variable. Single degree of freedom orthogonal
contrasts were used to compare effects of Control vs.
supplemented and orthogonal polynomial contrasts were
used to compare linear and quadratic responses to level of
flax intake (Steel and Torrie, 1980).
Results and Discussion
The addition of whole flaxseed tended to reduce OM
intake (P = 0.10) compared to Control and tended to be
linearly reduced (P = 0.06) with increasing levels of
flaxseed (Table 1). However, total OM intake did not differ
(P = 0.29) across treatments due to the addition of whole
flaxseed. Likewise, increasing the level of supplemental
flaxseed linearly increased (P = 0.05) total duodenal OM
flow. A depression in forage intake with fat
supplementation has been well documented by others
(Palmquist and Jenkins, 1980; Jenkins and Palmquist, 1984)
and is generally attributed to a reduction in ruminal
digestibility. However, in the current trial, no differences
(P = 0.14) were observed in true ruminal OM digestibility.
Therefore, the reduction in forage intake may have been
due to the increase in cholecystokinin (CCK) observed with
an increase in fat intake (Chelikani et al., 2004).
Specifically, these authors observed an increase in
circulating levels of CCK with a decrease in intake when
canola oil was fed or infused into the abomasums of dairy
cows. Apparent lower tract OM digestibility was increased
(P = 0.03) with flaxseed supplementation and increased
linearly (P = 0.01) with level of flaxseed. Apparent total
tract OM digestibility did not differ (P = 0.38) across
treatment due to the lack of differences in ruminal
digestibility combined with differences observe for lower
tract OM digestibility. Contrary to this result, Ueda et al
(2003) reported an increase in total tract OM digestibility
when dairy cattle were fed a 65% forage diet and linseed
oil. In the current experiment, whole flaxseed made up
13.0 and 24.8% of the total OM intake for 0.91 and 1.82
treatments, respectively.
Overall, N intake increased linearly (P < 0.001) with
additional flaxseed. However, additional flaxseed only
tended (quadratic, P = 0.08) to increase the amount of N
reaching the duodenum. Duodenal supply of microbial N
did not differ (P = 0.22) across treatments. Others have
also indicated that duodenal microbial N supply (g/d) was
unaffected by fat feeding (Brokaw et al., 2001;
Scholljegerdes et al., 2004) with forage-based diets.
Whereas, nonmicrobial N flow did not differ (P = 0.25)
between Control and supplemented treatments but did
increase linearly (P = 0.02) with inclusion of whole
flaxseed. Overall, true ruminal N digestibility did not differ
(P = 0.14) across treatments. However, apparent lower
tract N digestibility did increase (P = 0.02) for flax-fed
heifers and increased linearly (P = 0.003) with level of
flaxseed. Thereby indicating that N supplied by whole
flaxseed is readily available in the small intestine.
Apparent total tract N digestibility was greater (P < 0.001)
for heifers supplemented with whole flaxseed.
No differences were observed (P = 0.20 to 0.92) for
NDF intake or duodenal and fecal NDF flow. In turn, the
inclusion of whole flaxseed had no affect on ruminal, lower
tract or total tract NDF digestibility (P = 0.13 to 0.90). This
agrees with Ueda et al. (2003) who fed dairy cows a 65:35
forage:concentrate diet containing 3.0% linseed (4.7% total
fatty acids on an OM basis). The fat levels fed in the
current experiment were 0.91, 4.1 and 6.7% total fatty acids
(DM basis) for Control, 0.91 or 1.82 kg treatments,
respectively.
Due to experimental design, fatty acid intake increased
(P < 0.001) for all dietary fatty acids (Table 2). Duodenal
supply of 16:0 increased (P < 0.001) across treatment
(Table 3). Due to ruminal biohydrogenation of unsaturated
fatty acids duodenal supply of 18:0 increased (P < 0.001)
with inclusion of flaxseed and increased quadratically (P <
0.001) as flaxseed intake went from 0 to 1.82 kg per day.
No differences (P = 0.50) were observed for total 18C
biohydrogenation (data not shown). The approximate 20
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fold increase in intestinal supply of 18:0 compared to intake
was due to biohydrogenation of 18C fatty acids averaging
82.1% across treatments. Previous research has reported as
much as 91% of the total 18C fatty acids from linseed oil
are biohydrogenated (Scollan et al., 2001). It was thought
that feeding whole oilseeds would protect dietary fatty acids
from biohydrogenation (Jenkins, 1993). However, Keele et
al. (1989) reported little to no protection from
biohydrogenation of whole cotton seed, because of
mastication of the seed. Duodenal supply of all 18:1
isomers increased (P < 0.001) in flax-fed cattle compared to
unsupplemented control and there was a quadratic increase
(P < 0.01) for 18:1trans-9,
18:1trans13+14 whereas 18:1n-9 increased linearly (P <
0.001) with increasing levels of whole flaxseed. This
agrees with Loor et al. (2004) who reported an increase in
duodenal supply of 18:1 isomers when linseed oil was
added to either a low concentrate or high concentrate dairy-
type diet. Flax feeding increased (P < 0.001) intestinal
supply of 18:3n-3. The addition of flaxseed to the diet
increased (P < 0.001) duodenal supply of MUFA and
exhibited a quadratic (P = 0.02) response to increasing
levels of flaxseed. Intestinal PUFA and total unsaturated
fatty acid supply increased (P < 0.001) with flaxseed
supplementation.
Implication
Although the addition whole flaxseed up to 1.82 kg per
day did reduce forage intake, the impact on diet digestibility
was minimal. Therefore, adding whole flaxseed at the
levels described herein is a viable option for increasing the
supply of key fatty acids to ruminant tissues in cattle
consuming a forage-based diet.
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on performance, carcass
Effect of linseed oil
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Table 1. Influence of supplemental whole flaxseed level on OM, N, and NDF intake, flow, and digestibility in beef heifers
consuming native grass hay

Treatmentsa
Item Control 0.91
OM Intake, g/d
Forage 6358 5771
Total 6358 6636
Duodenal OM Flow, g/d 3963 4275
Microbial OM Flow, g/d 1127 1346
Fecal OM Flow, g/d 2461 2548
OM Digestibility
True ruminal, % intake 54.4 54.5
Lower tract, % of duodenal flow 37.6 40.9
Total tract, % of intake 60.1 61.7

N Intake, g/d 83.6 104.9
Duodenal N Flow, g/d 135.5 146.3
Microbial N Flow, g/d 92.3 108.1
Nonmicrobial N Flow, g/d 44.2 38.2
Fecal N Flow, g/d 48.4 48.6
N Digestibility
True ruminal, % intake 47.0 60.3
Lower tract, % of duodenal flow 64.2 66.0
Total tract, % of intake 40.5 54.3

NDF Intake, g/d 4466 4331
Duodenal NDF flow, g/d 2379 2120
Fecal NDF flow, g/d 1863 1724
NDF digestibility
Ruminal, % intake 44.5 50.4
Lower tract, % of duodenal flow 21.0 19.4
Total tract, % of intake 56.4 60.6
aTreatments = Control = Chopped native grass hay only; 0.91 = Chopped native grass hay plus 0.91kg (DM basis) whole
flaxseed; 1.82 = Chopped native grass hay plus 1.82 kg (DM basis) of whole flaxseed
bn = 9

Table 2. Influence of supplemental whole flaxseed level on fatty acid intake (g/d) in beef heifers consuming native grass hay

Treatmentsa
Fatty acid Control 0.91
16:0 21.1 32.2
18:0 2.62 10.1
18:1n-9 4.98 43.3
18:2n-6 11.9 50.0
18:3n-3 16.4 144.2 272.1
Total saturated fatty acidsc 23.8 42.3
MUFAd 4.98 43.3
PUFAe 28.3 194.3 360.5
TUFAf 33.4 237.6 442.1
Total 60.5 284.6 508.7
aTreatments = Control = Chopped native grass hay only; 0.91 = Chopped native grass hay plus 0.91kg (DM basis) whole
flaxseed; 1.82 = Chopped native grass hay plus 1.82 kg (DM basis) of whole flaxseed
bn = 9
cTotal saturated fatty acids = 16:0 + 18:0
dMUFA = 18:1n-9
ePUFA = 18:2n-6 + 18:3n-3
fTotal unsaturated fatty acids = MUFA + PUFA
Contrasts
Control vs
Supplemented
1.82 SEb Linear Quadratic
5236
6966
4721
1208
2633
435.0
435.8
253.5
138.0
161.3
0.10
0.37
0.11
0.37
0.51
0.06
0.29
0.05
0.67
0.45
0.96
0.96
0.83
0.29
1.0
49.0
44.1
62.1
3.2
1.6
1.7
0.40
0.03
0.38
0.14
0.01
0.41
0.37
0.97
0.75
120.1
161.8
84.7
77.1
47.2
5.8
10.1
13.6
11.2
3.9
0.001
0.15
0.75
0.25
0.88
<0.001
0.08
0.72
0.02
0.75
0.88
0.85
0.22
0.06
0.79
39.3
70.7
63.2
11.4
2.1
3.0
0.80
0.02
<0.001
0.55
0.003
<0.001
0.14
0.38
0.47
4262
2349
1672
307.8
147.2
119.1
0.62
0.44
0.27
0.60
0.89
0.26
0.92
0.20
0.76
43.9
27.3
60.4
3.3
3.4
2.1
0.50
0.59
0.14
0.90
0.22
0.21
0.13
0.28
0.40
Contrasts
Control vs.
Supplemented
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
1.82
43.1
17.6
81.6
88.4
SEb
1.5
0.40
0.78
1.4
1.9
1.8
0.78
3.3
4.1
5.8
Linear Quadratic
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.96
0.98
0.99
0.96
0.99
0.97
0.99
0.98
0.98
1.00
60.7
81.6
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Table 3. Influence of supplemental whole flaxseed level on duodenal fatty acid flow (g/d) in beef heifers consuming native
grass hay

Treatmentsa
Fatty acid Control 0.91
12:0 0.74 0.80
14:0 2.77 4.33
14:1 2.64 2.62
15:0 2.53 2.68
15:1 1.83 0.07
16:0 21.3 36.1
16:1 1.03 0.89
17:0 1.38 1.78
18:0 42.6 251.1 365.9
18:1trans-9 0.0 2.46
18:1trans-11 2.65 13.9
18:1trans13+14 0.03 13.7
18:1n-9 5.36 27.3
18:2trans-9 trans-12 0.0 1.14
18:2n-6 3.5 12.7
20:0 2.16 2.27
18:3n-3 3.15 27.2
21:0 0.39 0.67
22:0 1.91 2.22
20:3n-6 0.0 0.0
23:0 0.27 0.35
22:2 0.59 0.31
24:0 1.89 2.42
20:5n-3 0.58 0.65
24:1 0.26 0.02
Other 17.9 39.6
Total saturated FAc 78.0 304.7 466.2
MUFAd 13.9 61.0
PUFAe 8.17 42.2
TUFAf 22.1 103.2 160.0
Total 117.1 446.7 668.6
aTreatments = Control = Chopped native grass hay only; 0.91 = Chopped native grass hay plus 0.91kg (DM basis) whole
flaxseed; 1.82 = Chopped native grass hay plus 1.82 kg (DM basis) of whole flaxseed
bn = 9
cTotal saturated fatty acids = 12:0 + 14:0 + 15: 0 + 16:0 + 17:0 + 18:0 + 20:0 + 22:0 + 23:0 + 24:0
dMUFA = 14:1 + 15:1 + 16:1 + 18:1trans-9 + 18:1trans-11 + 18:1trans 13+14 + 18:1n-9 + 24:1
ePUFA = 18:2trans-9 trans-12 + 18:2n-6 + 18:3n-3 + 20:3n-6 + 22:2 + 20:5n-3
fTotal unsaturated fatty acids = MUFA + PUFA

Contrasts
Control vs
Supplemented
0.11
0.31
0.18
0.71
0.16
0.02
0.07
0.01
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.16
<0.001
0.58
0.74
0.49
0.43
0.60
0.72
0.20
0.47
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
1.82
0.89
3.94
2.39
2.69
0.16
84.5
0.78
1.64
SEb
0.05
1.07
0.08
0.37
0.94
8.40
0.08
0.08
19.3
0.16
1.31
1.28
2.86
0.20
2.13
0.19
6.31
0.13
0.29
0.06
0.06
0.22
0.31
0.32
0.11
2.86
21.2
3.71
8.25
10.7
28.2
Linear Quadratic
0.05
0.45
0.04
0.75
0.23
<0.001
0.05
0.04
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.05
<0.001
0.52
0.76
0.24
0.59
0.92
0.40
0.05
0.77
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.83
0.47
0.26
0.84
0.43
0.12
0.87
0.02
<0.001
<0.001
0.01
0.004
0.66
0.20
0.67
0.46
0.95
0.04
0.25
0.49
0.51
0.23
0.04
0.34
0.07
0.02
0.23
0.02
0.93
0.29
0.14
2.36
15.5
17.5
46.2
1.67
19.9
2.74
50.4
0.27
1.80
0.11
0.32
0.61
1.58
0.13
0.30
43.3
85.3
74.7
343