Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol87.Issue3-4.Oct2000:
Animal Feed Science and Technology
87 (2000) 163±171
Associative effects of supplementing barley straw
diets with alfalfa hay on rumen environment and
nutrient intake and digestibility for ewes
S.G. Haddad*
Department of Animal Production, Faculty of Agriculture, Jordan University of Science and Technology,
P.O. Box 3030, Irbid 22110, Jordan
Received 18 February 2000; received in revised form 5 July 2000; accepted 16 August 2000
Abstract
The objectives of these experiments were to study the positive associative effects of supplementing
barley straw-based diets with different levels of alfalfa hay on nutrient intake, rumen environment, and
nutrient digestibility and to evaluate the minimal amount of alfalfa hay needed to produce such an effect
in ewes. In experiment one, 15 Awassi ewes (®ve ruminally ®stulated; body weight 54 kg 1:5)
were fed ®ve barley straw-based diets in a 5 5 Latin square design with 3-week periods. Dietary
treatments were as follows: diet 1, barley straw (no supplement), diet 2, barley straw supplemented with
1% urea (dry matter basis), diets 3, 4, and 5 barley straw supplemented with 150, 300, and 450 g of
alfalfa hay, respectively. In experiment 2, the same experimental diets were fed to 50 ewes (10 ewes/diet)
for 50 days in a complete randomized design. In experiment 1, dry matter intake (DMI) was increased
(P < 0:05) by the addition of alfalfa hay compared with diets that had no alfalfa. Metabolizable energy
intake (MEI) increased linearly (P < 0:05) with the increasing amounts of alfalfa hay, being highest
(P < 0:05) for diet 5. Diets that contained alfalfa hay had greater (P < 0:05) dry matter (DM), organic
matter (OM), neutral detergent ®ber (NDF), and crude protein (CP) digestibilities. The extent of barley
straw NDF digestibility was also increased (P < 0:05) with the alfalfa addition (67 versus 60.5%).
Rumen ammonia and VFA concentrations were higher (P < 0:05) in diets that contained alfalfa,
however, rumen pH was not affected by the diet (avg. 6.64). In experiment 2, the effect of alfalfa hay
addition to barley straw-based diets had similar effects on DMI as observed in experiment 1. Straw
intake increased (P < 0:05) with the 150 g addition of alfalfa hay compared with unsupplemented diet
(725 versus 650 gÿd per day) with no further improvement with the higher amounts of alfalfa. It seems
that the minimal amount of alfalfa hay needed to produce the positive associative effect on barley straw
is 150 g per day for maintenance diets of ewes. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Straw; Alfalfa; Associative effects
*
Tel.: 962-2-7095111/ext. 22220; fax: 962-2-7095123.
E-mail address: [email protected] (S.G. Haddad).
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 2 0 3 - 0
164
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
1. Introduction
Barley and wheat straws are the two major forage sources for ruminants in Jordan.
However, the nutritive value of these crop residues is poor due to their higher
concentration of both ®ber and lignin. Furthermore, if nutritive value is de®ned as the
product of consumption and digestibility, then the low protein, high cell-wall content and
high lignin concentrations of straws have important implications in animal nutrition
(Anderson, 1978).
Improving digestibility and intake are the two major factors for improving the
nutritive value of straws. Methods for improvements have largely dealt with physical
(Welch, 1982), chemical (Haddad et al., 1995, 1998), and manipulation of forages
(Klopfenstein et al., 1979). One way for improving straw utilization is to increase
microbial activity by providing needed nutrients. Maeng et al. (1976) improved microbial
growth rate and cellulose digestion in vitro when low levels of amino acids were added
to the media.
Positive associative effects for alfalfa addition to low quality forages were observed on
in vitro fermentation (Hunt et al., 1985), dry matter intake and NDF digestibility
(Paterson et al., 1982; Brandt and Klopfenstein, 1986a) and animal gain (Brandt and
Klopfenstein, 1986b). Similarly, positive associative effects of alfalfa±wheat straw
combination diets fed to sheep were observed for NDF intake with no effect on DM and
NDF digestibility (Ndlovu and Buchanan-Smith, 1985).
Many of the reported research on alfalfa±straw combination diets have dealt with the
associative effects themselves rather than the minimal amount of alfalfa needed for such
effects to occur. The objectives of these experiments were to study the associative effects
of alfalfa hay addition to barley straw-based diets on rumen environment, DMI, and
nutrient digestibility, and to evaluate the minimal amount of alfalfa hay needed to
positively improve the utilization of barley straw by ewes.
2. Materials and methods
Barley straw and alfalfa hay used in experiment 1 and 2 were obtained from a local
source and chopped using a hammer mill ®tted with a 15 mm screen. The chemical
composition and the 48 h in sacco dry matter (DM) and neutral detergent ®ber (NDF)
digestibility of the forages is shown in Table 1.
2.1. Experiment 1
Fifteen Awassi ewes (®ve ruminally ®stulated; body weight 54 kg 1:5) were
assigned randomly to ®ve dietary treatments in a 5 5 Latin square with 3-week periods.
Dietary treatments were as follows: diet 1, barley straw (no supplement), diet 2, barley
straw supplemented with 1% urea (DM basis), diet 3, 4, and 5 barley straw supplemented
with 150, 300, and 450 g of alfalfa hay, respectively. All vitamins and minerals were
added to the diets to meet or exceed the NRC (1985a).
165
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 1
Chemical composition and 48 h in sacco digestibility of barley straw and alfalfa hay used in experiments 1 and 2
Dry matter (%)
Organic matter (% of DM)
Crude protein (% of DM)
Neutral detergent ®ber (% of DM)
Acid detergent ®ber (% of DM)
48 h in sacco digestibilitya
Dry matter
Neutral detergent fiber
a
Barley straw
Alfalfa hay
91.5
89.9
4.6
81.1
61.3
89.3
88.5
17.8
43.2
21.5
0.41
0.43
0.66
0.44
Determined as described in text.
Diets were offered once daily. In diets 3, 4, and 5 alfalfa hay was offered prior to straw
feeding. No barley straw was offered in these diets before the complete consumption of
the hay. Amounts of barley straw offered and refused were recorded daily. Body weight
was recorded weekly before feeding. Experimental periods were 21 days in which the last
6 days of each period were used for sample collection.
Forages used were sampled daily during the collection phase of each period. For
the digestibility measurements, total fecal collection was carried out for 6 days, and
a 10% representative sample was dried for further analysis. Composite samples of
the forages and feces were oven-dried (608C), ground through 1 mm screen and analyzed for crude protein (CP) (AOAC, 1984), amylase-modi®ed NDF (Van Soest et al.,
1991), acid detergent ®ber (ADF), and permanganate lignin (Robertson and Van
Soest, 1981).
Samples of ruminal ¯uid were collected on day 2 of each collection phase at 4 h
intervals for 24 h. The pH was determined immediately using a portable pH meter and
concentrations of VFA were determined by GLC (Erwin et al., 1961). Ruminal ammonia
concentration was determined according to the procedure of Broderick and Kang (1980)
using an autoanalyzer. Fractional rate of NDF digestion of wheat straw was measured
using the in situ bag technique in which dacron bags containing 2 g of straw were
incubated within the rumen of each ewe for 0, 6, 12, 24, 72, and 96 h. Prior to ruminal
incubation, dried straw was ground through a 2 mm screen using a Wiley mill. After
removal from the rumen and rinsing, all bags were dried at 608C and weighed. Contents
were analyzed for ash-free NDF (Van Soest et al., 1991). The kinetics of ruminal NDF
digestion and apparent extent of ruminal NDF digestion were calculated as described by
Grant (1994).
2.2. Experiment 2
The objective of experiment 2 was to evaluate the effect of the experimental diets on
dry matter intake (DMI) and body weight change in a longer-term study. In this
experiment, 50 Awassi ewes were fed the same ®ve experimental diets as described
earlier (10 ewes per diet) in a complete randomized design. The same experimental
166
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
approach used in experiment 1 for the determination of DMI and body weight change.
The experimental period lasted for 50 days.
2.3. Statistical analysis
Data from experiment 1 were analyzed as a 5 5 Latin square using the general linear
models procedure of SAS (1985). For experiment 2, means for the 50 days period were
analyzed as a completely randomized design using the general linear models procedure of
SAS (1985). Differences among treatment means, for both experiments, were detected by
least signi®cant difference (SAS, 1985). Unless otherwise stated, signi®cance was
declared at P < 0:05 for both experiments.
3. Results
The chemical composition and the 48 in sacco digestibility of the forages used in
both experiments are typical of those found in the Middle East area as shown in
Table 1.
In experiment 1, barley straw intake was not affected (P < 0:05) by the addition of
urea, however, it was increased (P < 0:05) by the supplementation with alfalfa being
highest for the 150 g per day alfalfa diet as shown in Table 2. Dry matter intake increased
by the supplementation of alfalfa being highest (P < 0:05) for the 450 g per day (1125 g
per day) alfalfa diet compared with the other levels of alfalfa and the straw diets.
Crude protein intake increased linearly (P < 0:05) with the increasing levels of alfalfa
Table 2
Effect of the diets fed to ewes in experiment 1 on nutrient intake and body weight changea
Dietb
1
2
3
4
5
S.E.
Dry matter intake (g per day)
Straw
Alfalfa
Total
595 c
0
595 c
606 c
0
606 c
720 a
150
970 b
690 ab
300
1001 b
675 b
450
1125 a
35.6
±
34.3
Organic matter intake (g per day)
Crude protein intake (g per day)
Neutral detergent ®ber intake (g per day)
Acid detergent ®ber intake (g per day)
MEIc (Mcal per day)
Weight gain (kg)
535 c
25.9 d
480 c
364 c
0.89 d
ÿ0.79 d
544 c
66.1 c
492 c
371 c
0.90 d
ÿ0.65 d
864 b
62.3 c
649 b
472 b
1.37 c
0.61 b
a
892 b
86.1 b
689 ab
486 ab
1.63 b
0.95 ab
1003 a
27.2
109.2 a
5.3
740 a
30.1
510 a
21.3
2.01 a 0.1
1.15 a 0.1
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
c
MEI metabolizable energy intake; calculated using the NRC (1985a).
b
167
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 3
Effect of the diets on total tract nutrient digestibility and digestive kinetics of barley straw ®ber in ewes used in
experiment 1a
Item
Dietb
1
Digestibility (%)
Dry matter
Organic matter
Neutral detergent ®ber
Acid detergent ®ber
Apparent crude protein
43.3
45.1
49.0
46.8
35.6
2
d
d
b
bc
d
42.9
44.3
50.1
45.4
37.8
3
d
d
b
c
d
Digestive kinetics of barley straw Neutral detergent ®ber
Lag (h)
5.2
4.9
Rate (%/h)
1.65 b
2.05 a
Extent (%)
60.1 b
61.2 b
50.4
51.2
54.3
47.5
45.6
4
c
c
a
ab
c
3.5
2.17 a
67.3 a
54.6
54.8
55.2
47.9
55.3
5
b
b
a
ab
b
3.7
2.20 a
67.7 a
57.3
57.1
54.6
49.5
60.7
S.E.
a
a
a
a
a
3.9
2.18 a
68.1 a
0.9
0.8
1.3
1.2
2.1
1.3
0.4
0.8
a
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
b
(109.2, 86.1, 62.3, and 25.9 g per day) in diets 5, 4, 3, and 1, respectively as shown in
Table 2.
Metabolizable energy intake (MEI) showed a linear increase (P < 0:05) with the
increasing level of alfalfa supplementation. Diet 5 had the highest (P < 0:05) MEI
(2.01 Mcal per day) compared with the rest of the other levels of alfalfa (avg. 1.5 Mcal
per day) and the unsupplemented diet (0.89 Mcal per day). Ewes fed the straw diet and
the urea-supplemented straw diet lost weight (avg. 0.73 kg per experimental period).
However, ewes fed the alfalfa supplements gained weight (avg. 0.9 kg per experimental
period). The highest (P < 0:05) weight gained (1.15 kg per experimental period) was
obtained with the 450 g per day alfalfa diet.
Dry matter digestibility of the diets was improved with the addition of alfalfa, being
highest (P < 0:05; 57.3%) for the 450 g per day alfalfa diet compared with diets 1 and 2
(avg. 43.1%) as shown in Table 3. The rest of the diets showed intermediate values (avg.
52.5%). Organic matter digestibility showed a similar response (Table 3). Neutral
detergent ®ber digestibility was highest (P < 0:05) for the diets that contained alfalfa
(avg. 54.7%) compared with the rest of the diets (avg. 49.5%) as shown in Table 3.
Apparent CP digestibility increased linearly (P < 0:05) with the increasing levels of
alfalfa in the diets, being highest for the 450 kg per day diet (60.7%) compared with
the diet 1 (35.6%). The extent of wheat straw digestion was greatest (P < 0:05) for the
alfalfa diets (avg. 67.7%) compared with the rest of the diets (avg. 60.6%) as shown in
Table 3.
Rumen ammonia concentration increased (P < 0:05) with urea and alfalfa supplementation to straw, being highest (P < 0:05) with the highest level of alfalfa used as
shown in Table 4. Total rumen VFA concentration increased (P < 0:05) with the alfalfa
supplemented diets (avg. 88.9 mmol/l) compared with the rest of the diets (avg.
168
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 4
Effect of diets fed in experiment 1 on rumen environmenta
Dietb
Ammonia (mg/l)
Total VFA (mmol/l)
Molar proportions (%)
Acetate
Propionate
Butyrate
Others
Rumen pH
1
2
3
4
5
S.E.
55 c
59.8 c
91 b
58.8 c
95 b
77.3 b
115 ab
81.1 b
136 a
108.2 a
13.5
7.6
74.5
17.5
5.8
2.2
6.62
72.6
17.1
8.2
2.1
6.75
75.3
16.7
6.1
1.9
6.66
69.6
19.5
8.2
2.7
6.58
66.9
23.6
7.5
2.0
6.59
7.5
4.9
1.1
0.7
0.9
a
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
b
59.4 mmol/l; Table 4). Molar proportions of VFA and rumen pH were not affected by the
diet as shown in Table 4.
In experiment 2, the effect of alfalfa hay addition to barley straw-based diets had
similar effects on DMI, organic matter intake (OMI), crude protein intake (CPI), and
neutral detergent ®ber intake (NDFI) as observed in experiment 1. Straw intake increased
(P < 0:05) with the 150 g addition of alfalfa hay compared with unsupplemented diet
(725 versus 650 gÿd) with no further improvement with the higher amounts of alfalfa as
shown in Table 5.
Table 5
Effect of the diets fed to ewes in experiment 2 on nutrient intake and body weight changea
Dietb
1
2
3
4
5
S.E.
Dry matter intake (g per day)
Straw
Alfalfa
Total
650 b
0
651 d
703 ab
0
710 d
725 a
150
875 c
736 a
300
1035 b
718 ab
450
1168 a
27.2
±
37.1
Organic matter intake (g per day)
Crude protein intake (g per day)
Neutral detergent ®ber intake (g per day)
Acid detergent ®ber intake (g per day)
MEIc (Mcal per day)
Initial weight (kg)
Final weight (kg)
Weight gain (kg)
580 a
29.5 d
528 c
398 c
9.6 e
55.8
51.2 d
ÿ3.6 e
638 d
76.8 bc
581 b c
428 c
1.1 d
55.2
53.8 c
ÿ1.6 d
783 c
62.3 c
615 b
481 b
1.3 c
55.3
56.1 b
0.8 c
a
921 b
1052 a
25.4
87.6 b
114.3 a
4.7
658 b
767 a
21.4
521 a
541 a
19.5
1.7 b
1.99 a 0.1
55.2
54.9
1.2
57.8 ab
58.8 a
1.7
2.6 b
3.9 a
0.4
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
c
MEI metabolizable energy intake; calculated using the NRC (1985a).
b
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
169
4. Discussion
Urea supplementation of straw did not affect intake or nutrient digestibility. The only
associative effect of urea supplementation to barely straw was observed for the rate of
NDF digestion. However, no overall improvement in ewe performance was observed.
This is consistent with the ®ndings of Dias-Da-Silva and Sundstol (1986) who observed
no difference in DMI, cellulose, and hemicellulose digestibilities of wheat straw
supplemented with urea at feeding time.
In experiment 1, a positive associative effect of alfalfa addition to barley strawbased diet was observed on feed intake. This is consistent with the ®ndings of Hunt
et al. (1987) who also observed a linear relationship between level of alfalfa in the
diet and DMI and NDFI when similar diets were fed to sheep. The intake of straw
was increased with the supplementation of 150 g per day alfalfa; however, no
further improvement in straw intake was noted at the higher levels of alfalfa. These
®ndings are consistent with Hunt et al. (1988) who fed steers 100% wheat straw
diets supplemented with 0, 25, 50, 75, and 100% alfalfa hay. These researchers
observed that the highest straw intake was with the 25% alfalfa diet (lowest level of
alfalfa used).
Dry matter and organic matter (OM) digestibilities increased linearly with the
increasing levels of alfalfa. This is due to the higher digestibility of alfalfa compared with
the straw (66.5 versus 41.3%, 48 h in sacco) as shown in Table 1. As the level of alfalfa
increased, the alfalfa portion of the diet increased as well, which would ultimately
increase DM and OM digestibility. At the same time, rate and extent of straw NDF
digestion was increased with the alfalfa supplementation which would also explain the
increase in DM and OM digestibilities. Lag time of barley straw NDF digestion was not
affected by the alfalfa supplementation, which is consistent with the ®ndings of Haddad
et al. (1998) using wheat straw.
The effect of alfalfa supplementation on rumen function is presented in Table 4.
Rumen ammonia was increased with the increasing levels of alfalfa, which is primarily
due to the higher CP intake. Total VFA were also higher due to the higher fermentability
of the diets that contained alfalfa. Ruminal proportions of VFA and ruminal pH remained
unaffected by the diet.
Experiment 2 was conducted to evaluate experiment 1 on a larger number of animals
for a longer experimental period. The author felt that the Latin square design does not
offer enough time in each period to accurately measure the effect of the experimental
diets on DMI and animal performance. The results in experiment 2 were similar to those
obtained in experiment 1; however, DMI, OMI and straw intake were higher in
experiment 2 compared to experiment 1.
The author major objective was to evaluate the minimum amount of alfalfa hay needed
to produce the desired associative effects for barley straw-based maintenance diets for
ewes. Hunt et al. (1988) stated that 25% alfalfa is minimal to produce these associate
effects when they fed similar diets to steers. A similar ratio (27% alfalfa) was also
mentioned by Atwell et al. (1991) using dairy heifers fed treated wheat straw±alfalfa
combination diets. In this study 150 g per day of alfalfa seems to produce such an effect
in sheep. This would correspond to a 17% of diet DM. This research demonstrates that
170
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
only a small quantity of alfalfa hay is needed to produce a positive associative effect for
ewes fed barley straw diets.
5. Conclusion
No positive associative effects were observed for barley straw-based diets when
supplemented with urea, however; alfalfa hay did produce such an effect. For ewes fed
maintenance diets based primarily on barley straw, 150 g per day alfalfa hay was needed
to promote positive associative effects for maximum straw intake.
References
Anderson, D.C., 1978. Use of cereal residue in beef cattle production systems. J. Anim. Sci. 46, 849±861.
Association of Of®cial Analytical Chemists, 1984. Of®cial Methods of Analysis, 14th Edition. Association of
Of®cial Analytical Chemists, Washington, DC.
Atwell, D.G., Merchen, N.R., Fahey Jr., G.C., Berger, L.L., Titgemeyer, E.C., Bourquin, L.D., 1991. Intake,
digestibility, and in situ digestion kinetics of treated wheat straw and alfalfa mixtures fed to Holstein heifers.
J. Dairy Sci. 74, 3524±3534.
Brandt, R.T., Klopfenstein, T.J., 1986a. Evaluation of alfalfa-corn cob associative action. I. Interaction between
alfalfa hay and ruminal escape protein on growth of lambs and steers. J. Anim. Sci. 63, 894±901.
Brandt, R.T., Klopfenstein, T.J., 1986b. Evaluation of alfalfa-corn cob associative action. II. Comparative tests of
alfalfa hay as a source of ruminal degradable protein. J. Anim. Sci. 63, 902±910.
Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acid in
ruminal ¯uid and in vitro media. J. Dairy Sci. 63, 64±75.
Dias-Da-Silva, A.A., Sundstol, F., 1986. Urea as a source of ammonia for improving the nutritive value of wheat
straw. Anim. Feed Sci. Technol. 14, 67±79.
Erwin, E.S., Marco, C.J., Emery, E.M., 1961. Volatile fatty acid analysis of blood and rumen ¯uid by gas
chromatography. J. Dairy Sci. 44, 1768±1771.
Grant, R.J., 1994. In¯uence of corn and sorghum starch on the in vitro digestion kinetics of forage ®ber
digestion. J. Dairy Sci. 77, 1563±1563.
Haddad, S.G., Grant, R.J., Klopfenstein, T.J., 1995. Digestibility of alkali-treated wheat straw measured in vitro
or in vivo using Holstein heifers. J. Anim. Sci. 73, 3258±3265.
Haddad, S.G., Grant, R.J., Kachman, S.D., 1998. Effect of wheat straw treated with alkali on ruminal function
and lactational performance of dairy cows. J. Dairy Sci. 81, 1956±1965.
Hunt, C.W., Paterson, J.A., Williams, J.E., 1985. Intake and digestibility of alfalfa±tall fescue combination diets
fed to lambs. J. Anim. Sci. 60, 301±312.
Hunt, C.W., Klopfenstein, T.J., Britton, R.A., 1987. The effects of alfalfa quality and wheat straw ammoniation
on intake and digestibility of alfalfa±wheat straw combination diets fed to sheep. Nutr. Rep. Int. 36, 1219±
1228.
Hunt, C.W., Klopfenstein, T.J., Britton, R.A., 1988. Effect of alfalfa addition to wheat straw diets on intake and
digestion in beef cattle. Nutr. Rep. Int. 38, 1249±1257.
Klopfenstein, T., Berger, L., Paterson, J., 1979. Performance of animals fed crop residues. Fed. Proc. 38, 1939±
1948.
Maeng, W.J., Van Nevel, C.J., Baldwin, R.L., Morris, J.G., 1976. Rumen microbial growth rates and yields:
effects of amino acids and protein. J. Dairy Sci. 59, 68±79.
Ndlovu, L.R., Buchanan-Smith, J.G., 1985. Utilization of poor quality roughages by sheep: effect of alfalfa
supplementation on ruminal parameters, ®ber digestion and rate of passage from the rumen. Can. J. Anim.
Sci. 65, 693±703.
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
171
National Research Council, 1985a. Nutrient requirement of sheep, 6th Revised Edition. National Academy of
Sciences, Washington, DC.
Paterson, J.A., Klopfenstein, T.J., Britton, R.A., 1982. Digestibility of sodium hydroxide-treated crop residues
when fed with alfalfa hay. J. Anim. Sci. 54, 1056±1066.
Robertson, J. B., Van Soest P. J., 1981. Permanganate and sulfuric acid lignin, ADF, hemicellulose, cellulose,
cutin and Si. In: James, W.O.T., Theander, O. (Eds.), The Analysis of Dietary Fiber in Food. Marcel Dekker,
NY, pp. 123, 158.
SAS, 1985. SAS User's Guide: Statistics, Version 5 Edition. SAS Inst. Inc., Cary, NC.
Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary ®ber, neutral detergent ®ber, and
nonstarch polysaccarides in relation to animal nutrition. J. Dairy Sci. 74, 3582±3597.
Welch, J.G., 1982. Rumination, particle size, and passage from the rumen. J. Anim. Sci. 54, 885±894.
87 (2000) 163±171
Associative effects of supplementing barley straw
diets with alfalfa hay on rumen environment and
nutrient intake and digestibility for ewes
S.G. Haddad*
Department of Animal Production, Faculty of Agriculture, Jordan University of Science and Technology,
P.O. Box 3030, Irbid 22110, Jordan
Received 18 February 2000; received in revised form 5 July 2000; accepted 16 August 2000
Abstract
The objectives of these experiments were to study the positive associative effects of supplementing
barley straw-based diets with different levels of alfalfa hay on nutrient intake, rumen environment, and
nutrient digestibility and to evaluate the minimal amount of alfalfa hay needed to produce such an effect
in ewes. In experiment one, 15 Awassi ewes (®ve ruminally ®stulated; body weight 54 kg 1:5)
were fed ®ve barley straw-based diets in a 5 5 Latin square design with 3-week periods. Dietary
treatments were as follows: diet 1, barley straw (no supplement), diet 2, barley straw supplemented with
1% urea (dry matter basis), diets 3, 4, and 5 barley straw supplemented with 150, 300, and 450 g of
alfalfa hay, respectively. In experiment 2, the same experimental diets were fed to 50 ewes (10 ewes/diet)
for 50 days in a complete randomized design. In experiment 1, dry matter intake (DMI) was increased
(P < 0:05) by the addition of alfalfa hay compared with diets that had no alfalfa. Metabolizable energy
intake (MEI) increased linearly (P < 0:05) with the increasing amounts of alfalfa hay, being highest
(P < 0:05) for diet 5. Diets that contained alfalfa hay had greater (P < 0:05) dry matter (DM), organic
matter (OM), neutral detergent ®ber (NDF), and crude protein (CP) digestibilities. The extent of barley
straw NDF digestibility was also increased (P < 0:05) with the alfalfa addition (67 versus 60.5%).
Rumen ammonia and VFA concentrations were higher (P < 0:05) in diets that contained alfalfa,
however, rumen pH was not affected by the diet (avg. 6.64). In experiment 2, the effect of alfalfa hay
addition to barley straw-based diets had similar effects on DMI as observed in experiment 1. Straw
intake increased (P < 0:05) with the 150 g addition of alfalfa hay compared with unsupplemented diet
(725 versus 650 gÿd per day) with no further improvement with the higher amounts of alfalfa. It seems
that the minimal amount of alfalfa hay needed to produce the positive associative effect on barley straw
is 150 g per day for maintenance diets of ewes. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Straw; Alfalfa; Associative effects
*
Tel.: 962-2-7095111/ext. 22220; fax: 962-2-7095123.
E-mail address: [email protected] (S.G. Haddad).
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 2 0 3 - 0
164
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
1. Introduction
Barley and wheat straws are the two major forage sources for ruminants in Jordan.
However, the nutritive value of these crop residues is poor due to their higher
concentration of both ®ber and lignin. Furthermore, if nutritive value is de®ned as the
product of consumption and digestibility, then the low protein, high cell-wall content and
high lignin concentrations of straws have important implications in animal nutrition
(Anderson, 1978).
Improving digestibility and intake are the two major factors for improving the
nutritive value of straws. Methods for improvements have largely dealt with physical
(Welch, 1982), chemical (Haddad et al., 1995, 1998), and manipulation of forages
(Klopfenstein et al., 1979). One way for improving straw utilization is to increase
microbial activity by providing needed nutrients. Maeng et al. (1976) improved microbial
growth rate and cellulose digestion in vitro when low levels of amino acids were added
to the media.
Positive associative effects for alfalfa addition to low quality forages were observed on
in vitro fermentation (Hunt et al., 1985), dry matter intake and NDF digestibility
(Paterson et al., 1982; Brandt and Klopfenstein, 1986a) and animal gain (Brandt and
Klopfenstein, 1986b). Similarly, positive associative effects of alfalfa±wheat straw
combination diets fed to sheep were observed for NDF intake with no effect on DM and
NDF digestibility (Ndlovu and Buchanan-Smith, 1985).
Many of the reported research on alfalfa±straw combination diets have dealt with the
associative effects themselves rather than the minimal amount of alfalfa needed for such
effects to occur. The objectives of these experiments were to study the associative effects
of alfalfa hay addition to barley straw-based diets on rumen environment, DMI, and
nutrient digestibility, and to evaluate the minimal amount of alfalfa hay needed to
positively improve the utilization of barley straw by ewes.
2. Materials and methods
Barley straw and alfalfa hay used in experiment 1 and 2 were obtained from a local
source and chopped using a hammer mill ®tted with a 15 mm screen. The chemical
composition and the 48 h in sacco dry matter (DM) and neutral detergent ®ber (NDF)
digestibility of the forages is shown in Table 1.
2.1. Experiment 1
Fifteen Awassi ewes (®ve ruminally ®stulated; body weight 54 kg 1:5) were
assigned randomly to ®ve dietary treatments in a 5 5 Latin square with 3-week periods.
Dietary treatments were as follows: diet 1, barley straw (no supplement), diet 2, barley
straw supplemented with 1% urea (DM basis), diet 3, 4, and 5 barley straw supplemented
with 150, 300, and 450 g of alfalfa hay, respectively. All vitamins and minerals were
added to the diets to meet or exceed the NRC (1985a).
165
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 1
Chemical composition and 48 h in sacco digestibility of barley straw and alfalfa hay used in experiments 1 and 2
Dry matter (%)
Organic matter (% of DM)
Crude protein (% of DM)
Neutral detergent ®ber (% of DM)
Acid detergent ®ber (% of DM)
48 h in sacco digestibilitya
Dry matter
Neutral detergent fiber
a
Barley straw
Alfalfa hay
91.5
89.9
4.6
81.1
61.3
89.3
88.5
17.8
43.2
21.5
0.41
0.43
0.66
0.44
Determined as described in text.
Diets were offered once daily. In diets 3, 4, and 5 alfalfa hay was offered prior to straw
feeding. No barley straw was offered in these diets before the complete consumption of
the hay. Amounts of barley straw offered and refused were recorded daily. Body weight
was recorded weekly before feeding. Experimental periods were 21 days in which the last
6 days of each period were used for sample collection.
Forages used were sampled daily during the collection phase of each period. For
the digestibility measurements, total fecal collection was carried out for 6 days, and
a 10% representative sample was dried for further analysis. Composite samples of
the forages and feces were oven-dried (608C), ground through 1 mm screen and analyzed for crude protein (CP) (AOAC, 1984), amylase-modi®ed NDF (Van Soest et al.,
1991), acid detergent ®ber (ADF), and permanganate lignin (Robertson and Van
Soest, 1981).
Samples of ruminal ¯uid were collected on day 2 of each collection phase at 4 h
intervals for 24 h. The pH was determined immediately using a portable pH meter and
concentrations of VFA were determined by GLC (Erwin et al., 1961). Ruminal ammonia
concentration was determined according to the procedure of Broderick and Kang (1980)
using an autoanalyzer. Fractional rate of NDF digestion of wheat straw was measured
using the in situ bag technique in which dacron bags containing 2 g of straw were
incubated within the rumen of each ewe for 0, 6, 12, 24, 72, and 96 h. Prior to ruminal
incubation, dried straw was ground through a 2 mm screen using a Wiley mill. After
removal from the rumen and rinsing, all bags were dried at 608C and weighed. Contents
were analyzed for ash-free NDF (Van Soest et al., 1991). The kinetics of ruminal NDF
digestion and apparent extent of ruminal NDF digestion were calculated as described by
Grant (1994).
2.2. Experiment 2
The objective of experiment 2 was to evaluate the effect of the experimental diets on
dry matter intake (DMI) and body weight change in a longer-term study. In this
experiment, 50 Awassi ewes were fed the same ®ve experimental diets as described
earlier (10 ewes per diet) in a complete randomized design. The same experimental
166
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
approach used in experiment 1 for the determination of DMI and body weight change.
The experimental period lasted for 50 days.
2.3. Statistical analysis
Data from experiment 1 were analyzed as a 5 5 Latin square using the general linear
models procedure of SAS (1985). For experiment 2, means for the 50 days period were
analyzed as a completely randomized design using the general linear models procedure of
SAS (1985). Differences among treatment means, for both experiments, were detected by
least signi®cant difference (SAS, 1985). Unless otherwise stated, signi®cance was
declared at P < 0:05 for both experiments.
3. Results
The chemical composition and the 48 in sacco digestibility of the forages used in
both experiments are typical of those found in the Middle East area as shown in
Table 1.
In experiment 1, barley straw intake was not affected (P < 0:05) by the addition of
urea, however, it was increased (P < 0:05) by the supplementation with alfalfa being
highest for the 150 g per day alfalfa diet as shown in Table 2. Dry matter intake increased
by the supplementation of alfalfa being highest (P < 0:05) for the 450 g per day (1125 g
per day) alfalfa diet compared with the other levels of alfalfa and the straw diets.
Crude protein intake increased linearly (P < 0:05) with the increasing levels of alfalfa
Table 2
Effect of the diets fed to ewes in experiment 1 on nutrient intake and body weight changea
Dietb
1
2
3
4
5
S.E.
Dry matter intake (g per day)
Straw
Alfalfa
Total
595 c
0
595 c
606 c
0
606 c
720 a
150
970 b
690 ab
300
1001 b
675 b
450
1125 a
35.6
±
34.3
Organic matter intake (g per day)
Crude protein intake (g per day)
Neutral detergent ®ber intake (g per day)
Acid detergent ®ber intake (g per day)
MEIc (Mcal per day)
Weight gain (kg)
535 c
25.9 d
480 c
364 c
0.89 d
ÿ0.79 d
544 c
66.1 c
492 c
371 c
0.90 d
ÿ0.65 d
864 b
62.3 c
649 b
472 b
1.37 c
0.61 b
a
892 b
86.1 b
689 ab
486 ab
1.63 b
0.95 ab
1003 a
27.2
109.2 a
5.3
740 a
30.1
510 a
21.3
2.01 a 0.1
1.15 a 0.1
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
c
MEI metabolizable energy intake; calculated using the NRC (1985a).
b
167
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 3
Effect of the diets on total tract nutrient digestibility and digestive kinetics of barley straw ®ber in ewes used in
experiment 1a
Item
Dietb
1
Digestibility (%)
Dry matter
Organic matter
Neutral detergent ®ber
Acid detergent ®ber
Apparent crude protein
43.3
45.1
49.0
46.8
35.6
2
d
d
b
bc
d
42.9
44.3
50.1
45.4
37.8
3
d
d
b
c
d
Digestive kinetics of barley straw Neutral detergent ®ber
Lag (h)
5.2
4.9
Rate (%/h)
1.65 b
2.05 a
Extent (%)
60.1 b
61.2 b
50.4
51.2
54.3
47.5
45.6
4
c
c
a
ab
c
3.5
2.17 a
67.3 a
54.6
54.8
55.2
47.9
55.3
5
b
b
a
ab
b
3.7
2.20 a
67.7 a
57.3
57.1
54.6
49.5
60.7
S.E.
a
a
a
a
a
3.9
2.18 a
68.1 a
0.9
0.8
1.3
1.2
2.1
1.3
0.4
0.8
a
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
b
(109.2, 86.1, 62.3, and 25.9 g per day) in diets 5, 4, 3, and 1, respectively as shown in
Table 2.
Metabolizable energy intake (MEI) showed a linear increase (P < 0:05) with the
increasing level of alfalfa supplementation. Diet 5 had the highest (P < 0:05) MEI
(2.01 Mcal per day) compared with the rest of the other levels of alfalfa (avg. 1.5 Mcal
per day) and the unsupplemented diet (0.89 Mcal per day). Ewes fed the straw diet and
the urea-supplemented straw diet lost weight (avg. 0.73 kg per experimental period).
However, ewes fed the alfalfa supplements gained weight (avg. 0.9 kg per experimental
period). The highest (P < 0:05) weight gained (1.15 kg per experimental period) was
obtained with the 450 g per day alfalfa diet.
Dry matter digestibility of the diets was improved with the addition of alfalfa, being
highest (P < 0:05; 57.3%) for the 450 g per day alfalfa diet compared with diets 1 and 2
(avg. 43.1%) as shown in Table 3. The rest of the diets showed intermediate values (avg.
52.5%). Organic matter digestibility showed a similar response (Table 3). Neutral
detergent ®ber digestibility was highest (P < 0:05) for the diets that contained alfalfa
(avg. 54.7%) compared with the rest of the diets (avg. 49.5%) as shown in Table 3.
Apparent CP digestibility increased linearly (P < 0:05) with the increasing levels of
alfalfa in the diets, being highest for the 450 kg per day diet (60.7%) compared with
the diet 1 (35.6%). The extent of wheat straw digestion was greatest (P < 0:05) for the
alfalfa diets (avg. 67.7%) compared with the rest of the diets (avg. 60.6%) as shown in
Table 3.
Rumen ammonia concentration increased (P < 0:05) with urea and alfalfa supplementation to straw, being highest (P < 0:05) with the highest level of alfalfa used as
shown in Table 4. Total rumen VFA concentration increased (P < 0:05) with the alfalfa
supplemented diets (avg. 88.9 mmol/l) compared with the rest of the diets (avg.
168
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
Table 4
Effect of diets fed in experiment 1 on rumen environmenta
Dietb
Ammonia (mg/l)
Total VFA (mmol/l)
Molar proportions (%)
Acetate
Propionate
Butyrate
Others
Rumen pH
1
2
3
4
5
S.E.
55 c
59.8 c
91 b
58.8 c
95 b
77.3 b
115 ab
81.1 b
136 a
108.2 a
13.5
7.6
74.5
17.5
5.8
2.2
6.62
72.6
17.1
8.2
2.1
6.75
75.3
16.7
6.1
1.9
6.66
69.6
19.5
8.2
2.7
6.58
66.9
23.6
7.5
2.0
6.59
7.5
4.9
1.1
0.7
0.9
a
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
b
59.4 mmol/l; Table 4). Molar proportions of VFA and rumen pH were not affected by the
diet as shown in Table 4.
In experiment 2, the effect of alfalfa hay addition to barley straw-based diets had
similar effects on DMI, organic matter intake (OMI), crude protein intake (CPI), and
neutral detergent ®ber intake (NDFI) as observed in experiment 1. Straw intake increased
(P < 0:05) with the 150 g addition of alfalfa hay compared with unsupplemented diet
(725 versus 650 gÿd) with no further improvement with the higher amounts of alfalfa as
shown in Table 5.
Table 5
Effect of the diets fed to ewes in experiment 2 on nutrient intake and body weight changea
Dietb
1
2
3
4
5
S.E.
Dry matter intake (g per day)
Straw
Alfalfa
Total
650 b
0
651 d
703 ab
0
710 d
725 a
150
875 c
736 a
300
1035 b
718 ab
450
1168 a
27.2
±
37.1
Organic matter intake (g per day)
Crude protein intake (g per day)
Neutral detergent ®ber intake (g per day)
Acid detergent ®ber intake (g per day)
MEIc (Mcal per day)
Initial weight (kg)
Final weight (kg)
Weight gain (kg)
580 a
29.5 d
528 c
398 c
9.6 e
55.8
51.2 d
ÿ3.6 e
638 d
76.8 bc
581 b c
428 c
1.1 d
55.2
53.8 c
ÿ1.6 d
783 c
62.3 c
615 b
481 b
1.3 c
55.3
56.1 b
0.8 c
a
921 b
1052 a
25.4
87.6 b
114.3 a
4.7
658 b
767 a
21.4
521 a
541 a
19.5
1.7 b
1.99 a 0.1
55.2
54.9
1.2
57.8 ab
58.8 a
1.7
2.6 b
3.9 a
0.4
Means within row with different letters differ (P < 0:05).
Diet 1, barley straw (no supplement); diet 2, barley straw supplemented with 1% urea (DM basis); diets 3,
4, and 5 barley straw supplemented with 150, 300, and 450 g of alfalfa hay, respectively.
c
MEI metabolizable energy intake; calculated using the NRC (1985a).
b
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
169
4. Discussion
Urea supplementation of straw did not affect intake or nutrient digestibility. The only
associative effect of urea supplementation to barely straw was observed for the rate of
NDF digestion. However, no overall improvement in ewe performance was observed.
This is consistent with the ®ndings of Dias-Da-Silva and Sundstol (1986) who observed
no difference in DMI, cellulose, and hemicellulose digestibilities of wheat straw
supplemented with urea at feeding time.
In experiment 1, a positive associative effect of alfalfa addition to barley strawbased diet was observed on feed intake. This is consistent with the ®ndings of Hunt
et al. (1987) who also observed a linear relationship between level of alfalfa in the
diet and DMI and NDFI when similar diets were fed to sheep. The intake of straw
was increased with the supplementation of 150 g per day alfalfa; however, no
further improvement in straw intake was noted at the higher levels of alfalfa. These
®ndings are consistent with Hunt et al. (1988) who fed steers 100% wheat straw
diets supplemented with 0, 25, 50, 75, and 100% alfalfa hay. These researchers
observed that the highest straw intake was with the 25% alfalfa diet (lowest level of
alfalfa used).
Dry matter and organic matter (OM) digestibilities increased linearly with the
increasing levels of alfalfa. This is due to the higher digestibility of alfalfa compared with
the straw (66.5 versus 41.3%, 48 h in sacco) as shown in Table 1. As the level of alfalfa
increased, the alfalfa portion of the diet increased as well, which would ultimately
increase DM and OM digestibility. At the same time, rate and extent of straw NDF
digestion was increased with the alfalfa supplementation which would also explain the
increase in DM and OM digestibilities. Lag time of barley straw NDF digestion was not
affected by the alfalfa supplementation, which is consistent with the ®ndings of Haddad
et al. (1998) using wheat straw.
The effect of alfalfa supplementation on rumen function is presented in Table 4.
Rumen ammonia was increased with the increasing levels of alfalfa, which is primarily
due to the higher CP intake. Total VFA were also higher due to the higher fermentability
of the diets that contained alfalfa. Ruminal proportions of VFA and ruminal pH remained
unaffected by the diet.
Experiment 2 was conducted to evaluate experiment 1 on a larger number of animals
for a longer experimental period. The author felt that the Latin square design does not
offer enough time in each period to accurately measure the effect of the experimental
diets on DMI and animal performance. The results in experiment 2 were similar to those
obtained in experiment 1; however, DMI, OMI and straw intake were higher in
experiment 2 compared to experiment 1.
The author major objective was to evaluate the minimum amount of alfalfa hay needed
to produce the desired associative effects for barley straw-based maintenance diets for
ewes. Hunt et al. (1988) stated that 25% alfalfa is minimal to produce these associate
effects when they fed similar diets to steers. A similar ratio (27% alfalfa) was also
mentioned by Atwell et al. (1991) using dairy heifers fed treated wheat straw±alfalfa
combination diets. In this study 150 g per day of alfalfa seems to produce such an effect
in sheep. This would correspond to a 17% of diet DM. This research demonstrates that
170
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
only a small quantity of alfalfa hay is needed to produce a positive associative effect for
ewes fed barley straw diets.
5. Conclusion
No positive associative effects were observed for barley straw-based diets when
supplemented with urea, however; alfalfa hay did produce such an effect. For ewes fed
maintenance diets based primarily on barley straw, 150 g per day alfalfa hay was needed
to promote positive associative effects for maximum straw intake.
References
Anderson, D.C., 1978. Use of cereal residue in beef cattle production systems. J. Anim. Sci. 46, 849±861.
Association of Of®cial Analytical Chemists, 1984. Of®cial Methods of Analysis, 14th Edition. Association of
Of®cial Analytical Chemists, Washington, DC.
Atwell, D.G., Merchen, N.R., Fahey Jr., G.C., Berger, L.L., Titgemeyer, E.C., Bourquin, L.D., 1991. Intake,
digestibility, and in situ digestion kinetics of treated wheat straw and alfalfa mixtures fed to Holstein heifers.
J. Dairy Sci. 74, 3524±3534.
Brandt, R.T., Klopfenstein, T.J., 1986a. Evaluation of alfalfa-corn cob associative action. I. Interaction between
alfalfa hay and ruminal escape protein on growth of lambs and steers. J. Anim. Sci. 63, 894±901.
Brandt, R.T., Klopfenstein, T.J., 1986b. Evaluation of alfalfa-corn cob associative action. II. Comparative tests of
alfalfa hay as a source of ruminal degradable protein. J. Anim. Sci. 63, 902±910.
Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acid in
ruminal ¯uid and in vitro media. J. Dairy Sci. 63, 64±75.
Dias-Da-Silva, A.A., Sundstol, F., 1986. Urea as a source of ammonia for improving the nutritive value of wheat
straw. Anim. Feed Sci. Technol. 14, 67±79.
Erwin, E.S., Marco, C.J., Emery, E.M., 1961. Volatile fatty acid analysis of blood and rumen ¯uid by gas
chromatography. J. Dairy Sci. 44, 1768±1771.
Grant, R.J., 1994. In¯uence of corn and sorghum starch on the in vitro digestion kinetics of forage ®ber
digestion. J. Dairy Sci. 77, 1563±1563.
Haddad, S.G., Grant, R.J., Klopfenstein, T.J., 1995. Digestibility of alkali-treated wheat straw measured in vitro
or in vivo using Holstein heifers. J. Anim. Sci. 73, 3258±3265.
Haddad, S.G., Grant, R.J., Kachman, S.D., 1998. Effect of wheat straw treated with alkali on ruminal function
and lactational performance of dairy cows. J. Dairy Sci. 81, 1956±1965.
Hunt, C.W., Paterson, J.A., Williams, J.E., 1985. Intake and digestibility of alfalfa±tall fescue combination diets
fed to lambs. J. Anim. Sci. 60, 301±312.
Hunt, C.W., Klopfenstein, T.J., Britton, R.A., 1987. The effects of alfalfa quality and wheat straw ammoniation
on intake and digestibility of alfalfa±wheat straw combination diets fed to sheep. Nutr. Rep. Int. 36, 1219±
1228.
Hunt, C.W., Klopfenstein, T.J., Britton, R.A., 1988. Effect of alfalfa addition to wheat straw diets on intake and
digestion in beef cattle. Nutr. Rep. Int. 38, 1249±1257.
Klopfenstein, T., Berger, L., Paterson, J., 1979. Performance of animals fed crop residues. Fed. Proc. 38, 1939±
1948.
Maeng, W.J., Van Nevel, C.J., Baldwin, R.L., Morris, J.G., 1976. Rumen microbial growth rates and yields:
effects of amino acids and protein. J. Dairy Sci. 59, 68±79.
Ndlovu, L.R., Buchanan-Smith, J.G., 1985. Utilization of poor quality roughages by sheep: effect of alfalfa
supplementation on ruminal parameters, ®ber digestion and rate of passage from the rumen. Can. J. Anim.
Sci. 65, 693±703.
S.G. Haddad / Animal Feed Science and Technology 87 (2000) 163±171
171
National Research Council, 1985a. Nutrient requirement of sheep, 6th Revised Edition. National Academy of
Sciences, Washington, DC.
Paterson, J.A., Klopfenstein, T.J., Britton, R.A., 1982. Digestibility of sodium hydroxide-treated crop residues
when fed with alfalfa hay. J. Anim. Sci. 54, 1056±1066.
Robertson, J. B., Van Soest P. J., 1981. Permanganate and sulfuric acid lignin, ADF, hemicellulose, cellulose,
cutin and Si. In: James, W.O.T., Theander, O. (Eds.), The Analysis of Dietary Fiber in Food. Marcel Dekker,
NY, pp. 123, 158.
SAS, 1985. SAS User's Guide: Statistics, Version 5 Edition. SAS Inst. Inc., Cary, NC.
Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary ®ber, neutral detergent ®ber, and
nonstarch polysaccarides in relation to animal nutrition. J. Dairy Sci. 74, 3582±3597.
Welch, J.G., 1982. Rumination, particle size, and passage from the rumen. J. Anim. Sci. 54, 885±894.