812

Asian-Aust. J. Anim. Sci.

Vol. 22, No. 6 : 812 - 818
June 2009
www.ajas.info

Effect of Live Yeast and Mannan-oligosaccharides on Performance of

Early-lactation Holstein Dairy Cows
M. Bagheri*, G. R. Ghorbani, H. R. Rahmani, M. Khorvash, N. Nili and K. -H. Sdekum1
Department of Animal Sciences, Isfahan University of Technology, Isfahan 84156, Iran
ABSTRACT: This study evaluated the effects of live yeast and yeast cell-wall mannan-oligosaccharide supplementation on
performance and nutrient digestibility during early lactation in cows fed a diet based on a mixture of corn silage and alfalfa hay as forage
sources. Eight multiparous Holstein dairy cows (average days in milk, 276) were used in a replicated 44 Latin square design. Diets
contained 45% forage and 55% concentrate on a dry matter (DM) basis and treatments were: i) basal diet without additive (Control), ii)
basal diet with 32 g/d of mannan-oligosaccharides (MOS), iii) basal diet with 1.21010 colony forming units per day (cfu/d) of live yeast
(Saccharomyces cerevisiae CNCM 1-1077; SC), and iv) basal diet with a mixture of MOS (32 g/d) and SC (1.21010 cfu/d; MOS+SC).
Treatments had no effect (p>0.05) on DM intake and yields of milk, 3.5% fat-(FCM) and energy-corrected milk (ECM), and on milk fat
percentage, body condition score and blood metabolites. Compared with the Control, only supplementation of SC resulted in
numerically higher yields of FCM (41.9 vs. 40.1 kg/d) and ECM (41.8 vs. 40.3 kg/d), and milk fat percentage (3.64 vs. 3.43%). While
the MOS diet had no effects on performance compared to the Control, the combination treatment MOS+SC increased milk protein
percentage (p<0.05). Also, the MOS supplementation, both alone or in combination with SC, numerically increased milk fat percentage.
The SC supplementation increased apparent digestibility of DM and crude protein while the MOS supplementation did not affect
digestibility. Concentrations of total volatile fatty acids (VFA) and ruminal pH were similar across treatments. Overall results indicated
that supplementation of MOS produced variable and inconsistent effects on rumen metabolism and performance, whereas SC
supplementation improved nutrient digestibility and numerically increased FCM and ECM yields, which could not be enhanced by the
combined supplementation of MOS+SC. According to our experimental condition, there was no effect of MOS alone or in combination
with SC on dairy cow performance. (Key Words : Feed Additive, Yeast, Mannan-oligosaccharides, Dairy Cow, Performance)

INTRODUCTION
During early lactation, cows experience huge negative
energy balance and insufficient dry matter intake (DMI)
that may increase the incidence of energy-related metabolic
disorders. As achieving maximum potential intake is
difficult during this critical stage, a promising approach is
to use additives that increase the digestibility of the diet,
especially fiber fractions, and consequently increase energy
and nutrient supply. Live yeasts are among those additives
that have been shown to increase digestibility of fiber and
CP (Erasmus et al., 1992; Wohlt et al., 1998) in some but
not all (Arambel and Kent, 1990; Wohlt et al., 1991) studies.
As an alternative, some forms of complex oligosaccharides
* Corresponding Author: M. Bagheri. Tel: +98-311-3913506,
Fax: +98-311-3913501, E-mail: m.bagheri@ag.iut.ac.ir
1
Institute of Animal Science, University of Bonn, Bonn 53115,
Germany.
Received September 30, 2008; Accepted February 2, 2009

including mannan-, galacto-, and fructo-oligosaccharides,

which recently have been used as prebiotics in monogastric
feeding regimens (Shafey et al., 2001; Yang et al., 2007),
may also be examined in ruminant diets to test whether or
not these compounds act as agents that selectively attach to
bacteria and may thus ultimately modify ruminal
metabolism. At the intestinal level, irreversible attachment
of fructo- and mannan-oligosaccharides to pathogens,
which thereby reduce the chance of pathogen attachment to
intestinal mucosa, has been documented (Sohn et al., 2000).
In sheep and cattle, galacto-oligosaccharides (GOS) have
been used with the objective of reducing methanogenesis or
improving nitrogen utilization efficiency through decreased
urinary N excretion (Mwenya et al., 2004; Sar et al., 2004b;
Mwenya et al., 2005b). Very limited data is available about
the ruminal effects of oligosaccharides when they are
supplemented to diets of dairy cows. Mwenya et al. (2005a)
observed that GOS lowered ruminal pH, increased VFA
concentrations and had minor effects on ruminal DM

Bagheri et al. (2009) Asian-Aust. J. Anim. Sci. 22(6):812-818

degradation profile and microbial nitrogen supply. However,
information regarding the consequences of using selected
oligosaccharides on performance is scarce. In terms of
microbe-attaching properties and also as a nutrient source
for some selected microorganisms, it seems limited studies
have been conducted on ruminal effects of mannanoligosaccharides (MOS). We hypothesized that MOS may
also modify ruminal fermentation by selective inhibition or
stimulation of microbial activity, thus they may also have an
influence on milk production or composition. Examining
the feeding of a mixture of yeast and MOS in diets of
lactating cows would be of interest because the stimulatory
impact of SC (Chaucheyras-Durand et al., 2008) may
interact with possible inhibitory effects of MOS, at least on
certain ruminal populations, and would alter the net
products of rumen metabolism.
MATERIALS AND METHODS
Animals and treatments
Eight multiparous cows in early lactation and averaging
276 days in milk were used in a replicated 44 Latin
square experiment. Cows were housed in individual pens
(2.02.2 m) and fed the experimental diets as a total mixed
ration (TMR) in equal allocations at 09:00 and 16:00 h. The
basal diet consisted of (% DM): 29.96 alfalfa hay, 14.98
corn silage, 28.70 barley grain, 3.88 corn grain, 1.68 fat
supplement, 10.86 soybean meal, 5.22 canola meal, 2.38
cotton seed meal, 0.63 calcium carbonate, 1.32 micro
mineral-vitamin premix, and 0.42 salt. Energy and nutrient
concentrations (DM basis) were; 6.82 MJ/kg NEL, 17.1%
CP, 31.6% NDF (22.4% forage-NDF), 21.9% ADF, 3.6%
ether extract, 0.8% calcium, and 0.4% phosphorus. Values
for NEL, calcium and phosphorus were taken from NRC
(2001) tables. The TMR was offered for ad libitum intake
and feed consumption was monitored daily to ensure 5 to
10% refusals. Fresh water was continuously available and
cows were milked at 05:00, 12:00, and 21:00 h. Each
experimental period was 21 d in length, allowing 14 d for
adaptation and 7 d for sampling and data collection.
Treatments were Control, basal diet without additive; MOS,
basal diet with 32 g/d of MOS (Agrimos, Lallemand,
Blagnace, France); SC, basal diet with 1.21010 colony
forming units per day (cfu/d) of Saccharomyces cerevisiae
CNCM 1-1077 (Levucell SC, Lallemand, Blagnace,
France); and MOS+SC, basal diet with a mixture of MOS
(32 g/d) and SC (1.21010 cfu/d). The study was conducted
at the Dairy Facilities of the Lavark Research Station
(Isfahan University of Technology, Isfahan, Iran) from
October to December, 2007. Animals were cared for
according to the guidelines of the Iranian Council of Animal
Care (1995).

813

Sample collection
Samples of TMR and orts, for individual cows, were
collected from d 15 to 20 of each period. Fecal samples
were collected after the a.m and p.m feeding from the
rectum of each cow for three consecutive days and frozen
at -13C. Milk yield was recorded for three consecutive
days from day 15 to 17 of each period and was sampled at
all milkings for compositional analysis. On d 21, rumen
fluid was obtained via a stomach tube 3 h after morning
feeding, and pH of the squeezed fluid was immediately
determined with a portable pH meter (HI8314, Hanna
Instruments, Cluj-Napoca, Romania); 10 ml of fluid was
preserved with 1 ml of 5% sulfuric acid for later analysis of
volatile fatty acids (VFA) and ammonia nitrogen. Blood
was sampled from the tail vein 2.5 h post-feeding at day 21,
centrifuged at 1,000g for 20 min and serum was stored at
-13C. Cows were weighed at the start and end of each
period after the 12:00 h milking and scored for body
condition using a scale of 1 to 5 according to Ferguson et al.
(1994). Also, a fecal scoring system was used on 3
consecutive days based on the scores; 1 for watery or
extremely loose and 5 for extremely hard feces. We aimed
to visually monitor manure consistency and color to see
whether inclusion of ground barley induced sub-acute
ruminal acidosis and whether additives prevented manure
inconsistency and deformity.
Chemical analysis
After thawing at room temperature, samples were
composited by treatment (TMR) and cow by period (orts
and feces) and DM contents were determined by oven
drying at 55C for 48 h. Dried samples were ground
through a 1 mm screen. The NDF and ADF were
determined on entire diets and fecal samples according to
Van Soest et al. (1991). A heat stable alpha-amylase (A3306,
Sigma-Aldrich, Steinheim, Germany) was used for feed
NDF analysis but sodium sulfite was omitted. The NDF and
ADF were not corrected for ash contents. Crude protein
(976.05), ether extract (954.02), and ash (942.05)
concentrations of TMR were determined according to
AOAC (2002). Acid-insoluble ash of TMR and feces were
determined according to method 942.05 of AOAC (2002),
and was used as an internal marker for the estimation of
apparent nutrient digestibility. Milk composition was
determined by an automated near infra-red reflectance
spectroscopy analyzer (Foss 605B Milko-Scan; Foss
Electric, Hillerd, Denmark).
Ammonia nitrogen was determined by the colorimetric
phenol-hypochlorite method of Broderick and Kang (1980).
The VFA were determined by gas chromatography
(Chrompack, Model CP-9002, Chrompack, Middelburg,
Netherlands) with a 50-m (0.32 mm ID) silica-fused column

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Bagheri et al. (2009) Asian-Aust. J. Anim. Sci. 22(6):812-818

Table 1. Least squares means of dry matter (DM) intake, milk yield, milk composition, fat- (FCM) and energy-corrected milk (ECM),
and feed efficiency for cows fed a diet containing no additive (Control), mannan-oligosaccharide (MOS), yeast (SC),or mannanoligosaccharide plus yeast (MOS+SC)
Treatments
Item
SEM
p<
Control
MOS
SC
MOS+SC
DM intake
kg/d
24.7
24.2
25.0
24.7
0.89
0.29
% of body weight
3.79
3.79
3.79
3.80
0.121
0.96
Yield (kg/d)
Milk
40.5
40.2
40.8
39.6
1.97
0.57
3.5% FCM
40.1
40.6
41.9
39.7
2.02
0.31
ECM
40.3
40.4
41.8
39.9
1.96
0.36
Fat
1.37
1.43
1.55
1.40
0.064
0.21
Protein
1.25
1.21
1.24
1.24
0.040
0.86
Composition (%)
Fat
3.43
3.57
3.64
3.53
0.114
0.20
3.04a
3.09a
3.16b
0.076
0.003
Protein
3.10a
Feed efficiency (kg/kg)
FCM/DMI
1.62
1.68
1.68
1.62
0.058
0.74
ECM/DMI
1.63
1.67
1.67
1.63
0.053
0.81
a, b
Means within a row with different superscripts differ (p<0.05).
3.5% FCM yield calculated as (milk (kg)(0.4255+(16.425milk fat/100)).
ECM yield calculated as (kg of milk0.3246)+(kg of milk fat12.96)+(kg of milk protein7.04); Jenkins et al. (1998).

(CP-Wax Chrompack Capillary Column, Varian, Palo Alto,

CA, USA). Helium was used as carrier gas and oven initial
and final temperature was 55 and 195C, respectively, and
detector and injector temperature was set at 250C.
Crotonic acid (1:7, v/v) was used as internal standard.
Blood serum glucose was determined by an enzymatic
procedure with a commercial kit (Pars Azmon, Tehran, Iran).
Serum urea nitrogen was determined colorimetrically
(Technicon Auto Analyzer II; Technicon, Tarrytown, NY,
USA).

repeated over time were analyzed using the REPEATED

statement with time of sampling as a repeated measure. The
compound symmetric (CS) covariance structure was tested
and selected based on the nearest AIC and BIC to zero.
Normality of distribution of response variables was tested
using PROC UNIVARIATE of SAS (SAS Institute, 1996).
Treatment least squares means were compared when the
treatment effect in the statistical model approached
significance (p<0.05) and trends were noted at p<0.10.
RESULTS

Statistical analysis
Data were analyzed using the MIXED procedure of Animal performance and feed intake
Dry matter intake was not affected by supplementation
SAS (SAS Institute, 1999) according to the following
of
additives
(p>0.05, Table 1), yet compared to the control
model;
diet, MOS supplementation slightly reduced (24.2 vs. 24.7
kg/d) and SC supplementation slightly increased (25.0 vs.
Yijk = +Pi+Sj+Tk+Cl (Sj)+eijkl
24.7 kg/d) the DMI (p = 0.29). Expressed as percent of
Where Pi (i = 1 to 4), Sj (j = 1 to 2), Tk (k = 1 to 4) were body weight (BW), DMI was the same for all four diets
fixed effects of period, square, and treatment respectively, (p>0.05).
Treatments had no effect on milk production (p>0.05),
Cl (Sj) was random effect of cow (l = 1 to 4) within square
although
cows on the SC diet had numerically greater milk
and eijkl was pooled experimental error. Data of feed intake,
production.
Cows fed MOS+SC produced milk with a
milk production and composition, and fecal scores that were
Table 2. Least squares means apparent total-tract digestibility (%) of dry matter, neutral detergent fiber and crude protein for cows fed a
diet containing no additive (Control), mannan-oligosaccharide (MOS), yeast (SC),or mannan-oligosaccharide plus yeast (MOS+SC)
Treatments
Item
SEM
p<
Control
MOS
SC
MOS+SC
a
ab
b
b
Dry matter
69.1
71.2
74.1
73.0
1.20
0.02
Neutral detergent fiber
54.8ab
53.8a
59.0b
58.8b
1.79
0.04
72.7ab
75.8b
75.3b
1.40
0.04
Crude protein
70.4a
a, b

Means within a row with different superscript differ (p<0.05).

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Bagheri et al. (2009) Asian-Aust. J. Anim. Sci. 22(6):812-818

Table 3. Least squares means of ruminal pH, ammonia nitrogen, and volatile fatty acid (VFA) profile for cows fed a diet containing no
additive (Control), mannan-oligosaccharide (MOS), yeast (SC),or mannan-oligosaccharide plus yeast (MOS+SC)
Treatments
Item
SEM
p<
Control
MOS
SC
MOS+SC
Ruminal pH
6.32
6.37
6.41
6.25
0.111
0.66
Ammonia nitrogen (mmol/L)
6.8
6.3
6.2
7.3
0.50
0.39
Total VFA (mmol/L)
76.5
89.9
74.6
94.0
8.90
0.29
Acetate (A) (mol/100 mol)
69.7
69.0
69.5
69.6
0.98
0.96
Propionate (P) (mol/100 mol)
18.8
19.5
18.9
18.2
0.97
0.81
Butyrate (mol/100 mol)
9.3
9.4
9.3
9.7
0.34
0.80
Isobutyrate (mol/100 mol)
0.23
0.41
0.34
0.40
0.062
0.31
Valerate (mol/100 mol)
1.24
1.41
1.30
1.27
0.074
0.19
0.57a
0.67ab
0.77b
0.047
0.03
Isovalerate (mol/100 mol)
0.60a
A:P ratio (mol/mol)
3.83
3.74
3.77
3.87
0.261
0.91
a, b

Means within a row with different superscript differ (p<0.05).

higher protein percentage than other cows (p<0.05, Table 1).

Feed efficiency, either expressed as FCM or ECM (kg) per
unit of DMI, was not affected by treatments (p>0.05, Table
1).

treatments (p>0.05). Although fecal scores were not

affected, MOS cows had low fecal scores. Serum glucose
and urea nitrogen did not differ between treatments
(p>0.05).

Nutrient digestibility
Digestibilities of DM, NDF, and CP are shown in Table
2. Supplementation of SC and MOS+SC significantly
increased the digestibility of DM and CP of the diets
relative to the Control (p<0.05). Cows fed MOS had lower
NDF digestibility than cows supplemented with SC and
MOS+SC (p<0.05).

DISCUSSION

Ruminal fermentation and pH

Ruminal fermentation variables of cows fed the four
diets are shown in Table 3. Treatments did not affect rumen
pH, which only ranged from 6.25 (MOS+SC) to 6.41 (SC).
The molar proportion of propionate was slightly higher for
the MOS diet. Although isovalerate accounted for less than
1% of total VFA, the MOS+SC supplemented cows had the
highest proportion of isovalerate (p<0.05). No treatment
differences were observed for ammonia concentration.
The BW, body condition score, and blood metabolites
In Table 4, treatment effects on BW, BW change, body
condition score, fecal score, and serum glucose and urea
nitrogen are shown. None of the variables was affected by

Intake and performance

Intake responses of dairy cows to yeast supplementation
have been quite variable ranging from substantial increase
(Erasmus et al., 1992; Piva et al., 1993; Dan et al., 2000) to
no change (Swartz et al., 1994; Robinson, 1997) or even a
numerical decrease (Wohlt et al., 1991; Adams et al., 1995).
When supplemental yeast culture was offered from 14 d
pre-partum to 14 d post-partum, Robinson (1997) reported
only a slight increase in DMI (0.3 kg/d) in fresh cows,
which was very similar to the results of the current trial.
Wang et al. (2001) showed that the potential of live yeast
products to increase intake of fresh cows was more affected
by total NDF concentration of the diet than by forage NDF
intake. In all the above studies, total NDF concentration of
the ration was close to that of our study. Although one
reason for selecting early lactating cows was to test the
ability of SC to increase the DMI of cows in the period
when they are prone to physical or physiological constraints
of intake, only a slight DMI increase was observed for SC
cows. Average DMI of cows (3.80% of BW) was typical for

Table 4. Least squares means of body weight (BW), BW change, body condition score, fecal score, blood urea nitrogen
blood serum glucose for cows fed a diet containing no additive (Control), mannan-oligosaccharide (MOS), yeast (SC),
oligosaccharide plus yeast (MOS+SC)
Treatments
Item
SEM
Control
MOS
SC
MOS+SC
BW (kg)
659
674
666
672
28.6
BW change (kg/d)
0.10
0.39
0.15
0.98
0.285
Body condition score
3.37
3.53
3.59
3.43
0.191
Fecal score
3.0
2.8
3.0
2.9
0.13
BUN (mmol/L)
14.64
14.85
15.53
14.11
0.081
Serum glucose (mmol/L)
3.75
3.86
3.82
3.86
0.135

(BUN), and
or mannanp<
0.11
0.15
0.21
0.82
0.34
0.99

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Bagheri et al. (2009) Asian-Aust. J. Anim. Sci. 22(6):812-818

high producing dairy cows. Therefore, intake might have

not been limited by physical constraints caused by fiber
form or content in our study.
Due to numerically higher milk fat percentage, SC cows
produced 1.8 kg more FCM per day. Similarly, Putnam et al.
(1997) showed that 4% FCM of cows in early lactation
tended to increase (28.4 vs. 26.5 kg) when diets were
supplemented with 10 g/d of a yeast culture. Also in the
study of Wang et al. (2001), amounts of milk and FCM
during the first 30 days in milk were 2.5 kg higher in cows
receiving a yeast culture supplement in diets containing
21% forage NDF. Numerical increases in milk fat
percentage have been observed after yeast supplementation
in some trials with dairy cows (Piva et al., 1993; Robinson,
1997; Erasmus et al., 2005). Increased digestibility of NDF
in the SC treatment explains the 0.2 percentage unit
increase in milk fat percentage observed in this trial.
The MOS supplementation decreased whereas
MOS+SC increased milk protein percentage. Information
regarding the effect of MOS or similar compounds on milk
protein is scare. Nocek et al. (2007) reported a significant
increase in milk protein percentage when they compared
cows fed an enzymatically hydrolyzed yeast product (a nonlive product that may be comparable to MOS) to those fed
yeast culture or no additive. On the other hand, data
confirming the result of the current work regarding the
inefficiency of yeast products to increase milk protein
percentage are abundant (Piva et al., 1993; Robinson, 1997).
Given increased crude protein digestibility in SC-fed cows,
no change in milk protein in this treatment is unexpected
and the reason remains unclear.
Nutrient digestibility
The short duration of periods usually puts some
limitations on Latin squares that may require the results to
be interpreted with caution. Nevertheless, short terms of
yeast supplementation may practically be applied in tight
price situations or during early post-calving periods,
therefore, it was hoped that results of this trial would aid in
demonstrating the potential of SC and/or MOS to favorably
alter the performance or metabolism of cows within a short
time frame. We observed that digestibility of all of the
measured nutrients were affected by one or more of the
additives. In agreement with these results, Nocek and Kautz
(2006) found that potentially degradable DM of forage was
significantly higher for corn silage and mixed haylage when
cows received direct-fed microbials containing 11010 cfu/d
of live yeast. Also in supplemented cows, in situ
undegraded forage DM was consistently lower from 12 to
72 h ruminal incubation, than in un-supplemented cows.
Significant increases in digestibility of CP (Erasmus et al.,
1992; Wohlt et al., 1998) and cell wall constituents (Wohlt
et al., 1998) have also been observed with yeast

supplementation. In this trial, digestibility of nutrients was

higher for SC and MOS+SC supplemented cows than for
other cows and the higher DM digestibility probably was
the result of higher digestibility of CP and NDF. Since the
digestibility of MOS+SC cows did not exceed the
digestibility of SC cows, it could be inferred that SC was
responsible for the increased digestion in both treatments.
This conclusion is confirmed by unchanged, or only slightly
changed, digestibility of nutrients in MOS relative to the
control. As a consequence of improved NDF digestion, it
was expected that lipogenic precursors would be more
available for SC-fed cows. We observed that a numerical,
but biologically meaningful, increase occurred in BW, FCM
and milk fat percentage suggesting that lipogenicity was
stimulated. However, small number of cows and short
experimental period probably did not allow for completion
of SC effect on performance.
Ruminal fermentation
Yeast products are often claimed to smooth rumen pH
fluctuations and increase pH nadir of the rumen
(Chaucheyras-Durand et al., 2008). While some studies
reported a positive effect (Mwenya et al., 2004), others
reported no effect (Erasmus et al., 1992; Putnam et al.,
1997; Robinson and Garret, 1999) of yeast or yeast cultures
on rumen pH. In our study, samples of rumen fluid were
taken 3 h post-feeding that was expected to represent the
period of peak fermentation and consequently the lowest pH
values. However, pH values were high on average and did
not indicate a severe acidic condition. This may be due to
incorporation of 45% forage DM in the diet of which twothirds were alfalfa hay (30% DM) having a high intrinsic
buffering capacity to neutralize fermentation acids
(McBurney et al., 1983). Stabilized ruminal conditions led
to a balanced metabolism in the rumen, thereby no change
in fecal scores, including color and consistency, was
observed.
Concentrations of total VFA were similar with slightly
higher values for cows fed MOS and MOS+SC compared to
the control. In sheep and cattle, feeding GOS did not alter
VFA production (Mwenya et al., 2004; 2005b); however,
GOS plus nitrate increased total VFA in sheep relative to
the control diet (Sar et al., 2004a). In dairy cows, a
combination of GOS and yeast decreased while GOS alone
increased total VFA concentrations (Mwenya et al., 2005a).
Similar to total VFA, molar proportions of individual VFA
have also been variable, ranging from significant change
(Mwenya et al., 2005a) to no change (Mwenya et al.,
2005b), in studies with GOS on cattle and sheep,
respectively. Molar proportion of isovalerate, a product of
the fermentation of branched-chain amino acids in the
rumen, was significantly increased after MOS+SC
supplementation. The SC and MOS might have provided

Bagheri et al. (2009) Asian-Aust. J. Anim. Sci. 22(6):812-818

factors stimulatory to proteolytic bacteria as suggested by
Mwenya et al. (2004). In addition, greater NDF digestibility,
which in turn causes more protein from the intracellular
spaces of the forage cell-wall to be released and exposed to
microbial attack (Bach et al., 2005), might have also been
involved in elevated proportion of isoacids on diets
containing additives.
Very often, yeast or yeast cultures did not cause any
change in ruminal ammonia nitrogen (Erasmus et al., 1992;
Piva et al., 1993; Mwenya et al., 2004) but in some cases
lowered ammonia nitrogen was observed (Enjalbert et al.,
1999). In addition, limited data on feeding GOS to sheep
and steers have demonstrated a suppressing effect of GOS
on rumen ammonia concentration (Mwenya et al., 2004,
2005b). In our trial, treatments had similar ruminal
ammonia concentrations with only slightly higher values for
MOS+SC. As time of blood sampling preceded rumen
sampling on the same day, the difference between rumen
ammonia and blood urea nitrogen was relatively high. In
other words, blood samples were likely taken at the time
when urea was at its highest concentration but rumen
samples were taken when ammonia concentration had
already passed its peak.
The BW, body condition score and blood metabolites
In some studies, yeast supplementation did not alter BW
(Robinson, 1997) or BW change (Robinson and Garret,
1999), while in another study yeast supplementation
decreased BW loss in early lactation (Dann et al., 2000). In
the current experiment, cows consistently gained BW in the
course of the trial indicating a positive energy balance that
most likely arose from adequate DMI. As discussed earlier,
BW gain was higher in supplemented than control cows
suggesting a higher provision of energy for gain with
additive supplementation.
Blood glucose was similar in feedlot cattle fed high
grain diets without or with probiotic including Enterococcus
plus live yeast (Beauchemin et al., 2003). Opposed to that,
Nocek et al. (2003) and Nocek and Kautz (2006) observed a
significant increase in blood glucose of lactating cows 7 d
post-partum. The GOS fed to steers did not cause any
change in blood glucose (Mwenya et al., 2005b). Similar
propionate production among treatments in the current work
can explain no change in blood glucose.
IMPLICATIONS
Post-partum supplementation with MOS, live yeast, and
the mixture of the two additives resulted in no changes in
cow performance and ruminal metabolism under the
conditions of this experiment. Significant improvement in
digestibility of nutrients in cows fed live yeast suggested
that these products may have the ability to exert their

817

positive effects on digestion processes, but not necessarily

on milk production, in a short duration. The MOS+SC only
significantly increased milk protein percentage, but not milk
protein yield. Using the combination of yeast and MOS did
not show any advantage in ruminal metabolism over using
yeast or MOS alone.
AKNOWLEDGMENT
The authors wish to acknowledge the financial support
given to this project by the Isfahan University of
Technology.
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