14 A
. Tolera, F. Sundstøl Livestock Production Science 68 2001 13 –23
chemical and physical structures of roughages, which of sheep were determined using intact male lambs
define their potential microbial degradation and, 18
61.5 kg live weight of the local sheep from hence, voluntary intake by the host animal, are not
southern Ethiopia in a growth experiment followed easy to measure Hovell et al., 1986, especially in
by a digestibility experiment Tolera and Sundstøl, many developing countries where the necessary
2000. The feeds used in the experiment were maize facilities are not available. Moreover, Ørskov and
stover, harvested at three stages of maturity, and Reid 1989 showed that gross chemical analyses are
desmodium hay. The maize stovers were harvested at inaccurate predictors of animal performance, where-
grain moisture contents of 30, 22 and 12, which as in sacco dry matter DM degradation in nylon
were designated as stages I, II and III, respectively. bags appears to be a more promising biological
The early harvested stovers were sun-dried in the method of feed evaluation.
field, to decrease the stem moisture content for safe Determination of in sacco degradation in nylon
storage. The maize stovers harvested at the three bags is a fairly quick and easy method of assessing
stages of maturity were used as basal diets sup- the nutritive value of feeds. The method was re-
plemented with graded levels 0, 150, 300 and 450 ported to be a promising tool in predicting DM and
g head day of desmodium hay in a factorial ar- digestible DM intakes of cereal straws by cattle
rangement of treatments three maturity stages of Ørskov et al., 1988b, of browse species by goats
maize stover 3 four levels of desmodium hay sup-
Kibon and Ørskov, 1993 and of crop residues and plementation. The chemical composition of the
forages by cattle Shem et al., 1995 from their maize stovers and desmodium hay used in the
rumen degradation characteristics. In general, the experiment is shown in Table 1. The DMI, DMD,
degradation characteristics of feeds, determined by DDMI and body-weight change of sheep from these
the in sacco method, were used in the predictions of experiments are shown in Table 2. Details of the
feed intake, digestibility and animal performance in growth and digestibility experiments were reported
terms of growth rate Ørskov and Ryle, 1990; Kibon by Tolera and Sundstøl 2000.
and Ørskov, 1993; Shem et al., 1995. Ørskov and Ryle 1990 indicated that it would be of great
advantage to be able to predict consumption from the 2.1. In sacco DM degradability of the feeds
characteristics of the feed itself. According to Ør- skov 1994, the solubility or cell content of the
Dry matter degradation of the maize stovers and roughage, the insoluble but potentially degradable
desmodium hay used in the experiment were de- fraction, degradation rate, the speed at which long
termined by incubating about 2.5 g of the dry particles are reduced to small particles and rumen
samples, ground to pass through a 2-mm sieve, in outflow rate are the important factors that affect the
nylon bags in three rumen fistulated mature rams of intake of poor quality roughages.
the Horro sheep from western Ethiopia. The rams The objective of this study was to evaluate the
were fed 500 g of desmodium hay, 400 g of maize possibility of predicting DMI, DMD DM digestibili-
stover, 400 g of green alfalfa forage and 100 g of ty, DDMI digestible DM intake and growth rate of
concentrate mix 50 wheat bran and 50 linseed sheep feeding on maize stover harvested at different
cake, which were offered in equal proportions twice stages of maturity and supplemented with graded
a day. All of the bags were incubated 1 h after the levels of Desmodium intortum cv Greenleaf com-
sheep were offered feed. The bags were withdrawn monly known as desmodium or Greenleaf de-
after 4, 8, 16, 24, 48, 72 and 96 h of incubation, smodium hay based on DM degradability of the
washed for 20 min in a washing machine and dried diets, which was calculated from degradability of the
for 48 h at 60 8C. Washing losses were determined by
individual feeds and their corresponding DM intake. soaking two bags per sample in warm tap water
| 398C for 1 h followed by washing and drying as before.
2. Materials and methods The DM degradation data were fitted to the
2ct
exponential equation p 5 a 1 b1 2 e
Ørskov The DMI, DMD, DDMI and body-weight change
and McDonald, 1979; McDonald, 1981 using the
A . Tolera, F. Sundstøl Livestock Production Science 68 2001 13 –23
15 Table 1
a
Chemical composition of maize stover and Desmodium intortum hay used in the experiment Components
Maize stover Desmodium
intortum hay Stage I
Stage II Stage III
Dry matter DM, 93.4
93.7 93.4
89.2 In dry matter
g kg DM Organic matter
926 931
931 922
Crude protein 36
33 31
138 Neutral detergent fibre
772 790
801 533
Acid detergent fibre 455
483 531
351 Acid detergent lignin
50 68
83 97
Cellulose 405
415 458
254 Hemicellulose
317 307
270 182
a
Adapted from Tolera and Sundstøl 2000.
Neway Excel programme Chen, 1995, where p is slowly degradable, fraction; c
5the rate of degra- DM degradation at time t. Since the washing
dation of B and the lag phase L 5 1 c log [b a 1
e
loss A was higher than the estimated rapidly b
2 A]. The effective DM degradability ED was soluble fraction a, the lag time was estimated
calculated as ED 5 A 1 [Bc c 1 k] where A, B and
according to McDonald 1981 by fitting the model c are as described above and k is the rumen outflow
2ct
p 5 A for t t , and p 5 a 1 b1 2 e
for t . t .
rate Dhanoa, 1988. The rumen outflow rate was The degradation characteristics of the feeds were
assumed to be 0.03 h for the maize stovers and defined as A
5washing loss readily soluble fraction; 0.05 h for the desmodium hay Ørskov et al.,
B 5 a 1 b 2 A, representing the insoluble, but
1988a.
Table 2 Feed intake, DM digestibility total diet and body-weight change of sheep feeding on a basal diet of maize stover harvested at three stages
a
of maturity and supplemented with different levels of Desmodium intortum hay Stover
Level of DM intake
DM Digestible
Body wt
21 0.75
stage of supplement
g kg W
digestibility DM intake
change
21 0.75
21
maturity g head d
g kg W
g day Stage I
54.2 34.6
22.3 222.7
150 62.4
53.8 35.7
9.2 300
71.9 60.4
43.3 33.8
450 68.4
69.6 46.5
40.5 Mean
64.2 54.6
36.3 15.2
S.E.M. 3.3
4.5 4.3
5.7 Stage II
46.4 24.4
16.6 232.4
150 57.6
49.3 31.2
6.0 300
60.8 58.7
36.4 33.6
450 65.2
71.1 44.7
47.0 Mean
57.5 50.9
30.8 13.5
S.E.M. 3.3
5.9 4.3
6.8 Stage III
45.6 25.9
14.4 242.2
150 52.7
52.0 28.5
10.7 300
58.5 53.1
31.7 34.1
450 70.8
67.7 46.9
45.5 Mean
56.9 49.8
29.7 12.0
S.E.M. 3.3
5.0 4.1
7.2
a
Adapted from Tolera and Sundstøl 2000.
16 A
. Tolera, F. Sundstøl Livestock Production Science 68 2001 13 –23
2.2. Estimated DM degradability of the diets experiments. The in sacco DM disappearance after 4
and 8 h of incubation was significantly higher P ,
The estimated in sacco DM degradability of the 0.05 in maize stover harvested at stage I than at
maize-stover-based diets with graded levels of de- stage III. The desmodium hay had significantly
smodium hay supplements were determined assum- higher P
,0.05 DM disappearance than the maize ing additive effects of the maize stovers and de-
stovers after 4, 8, 16, 24 and 48 h of incubation. The smodium hay as follows.
washing loss A value was highest in desmodium hay and lowest in maize stover harvested at stage III.
MSDMI 3 MSISDMD 1 DiDMI 3 DiISDMD
In general, the washing loss showed a significant
]]]]]]]]]] EISDMD
5 3 100
TDMI
decrease P ,0.05 with increasing stage of maturity
where EISDMD
5estimated in sacco DM de- of the stover. The insoluble but potentially degrad-
gradability of the diet ; MSDMI 5maize stover
able fraction B value was significantly lower DM intake; MSISDMD
5in sacco DM degradability whereas the degradation rate was significantly higher
of maize stover; DiDMI 5Desmodium intortum hay
P ,0.05 in the desmodium hay than in the maize
DM intake; DiISDMD 5in sacco DM degradability
stovers. The maize stover harvested at stage III of Desmodium intortum hay; TDMI
5total DM showed an unexpectedly higher P
,0.05 degra- intake.
The EISDMD of the diets was used for prediction
Table 3
of DMI, DMD, DDMI and growth rate of sheep
In sacco DM degradability and degradability characteristics
feeding on these diets based on the intake, diges-
of maize stover and Desmodium intortum hay used in the growth
tibility and body-weight change data obtained from
and digestibility experiments
the growth and digestibility experiment reported by
Parameters Maize stover Desmodium
Tolera and Sundstøl 2000.
intortum hay Stage I
Stage II Stage III
6S.E.
b bc
c a
DMD 19.9
18.5 17.1
29.1 0.5
2.3. Statistical analysis
4h b
bc c
a
DMD 20.4
19.5 17.7
32.6 0.6
8h b
b b
a
DMD 27.1
26.7 28.1
44.4 1.4
16h
Analysis of variance was carried out on the in
b b
b a
DMD 37.3
36.1 35.7
54.4 1.4
24h b
b b
a
sacco DM degradation of the individual feeds using
DMD 51.1
49.3 51.7
65.1 1.4
48h a
a a
a
a completely randomized design and on the esti-
DMD 60.6
62.8 59.9
65.8 1.8
72h a
a a
a
DMD 67.5
65.4 63.8
67.2 1.4
mated DM degradability of the diets using factorial
96h b
c d
a
A 14.6
12.9 11.9
23.6 0.0
arrangement of treatments. Significant differences
a a
a b
B 63.8
67.0 59.9
44.4 2.2
between means were tested using Duncan’s New
ab a
bc c
A 1 B
78.4 79.9
71.8 68.0
2.2
c c
b a
Multiple Range test SAS, 1985; Montgomery,
c 0.018
0.017 0.022
0.05 0.001
ab b
ab a
1991. Correlation as well as simple and multiple
L 1.1
0.7 1.8
2.2 0.4
b b
b a
ED 38.0
37.3 37.7
45.8 0.9
linear regression analyses were performed on the
R.S.D. 2.4
2.5 2.6
2.3
data to examine the relationships of DMI, DMD,
a,b,c
DDMI and growth rate of the sheep with estimated
Means with one or more similar superscripts within a row are not significantly different P
.0.05.
in sacco DM degradability of the diets SAS, 1985.
DMD 5DM disappearance after 4 h of incubation ;
4h
DMD 5DM disappearance after 8 h of incubation ;
8h
DMD 5DM disappearance after 16 h of incubation ;
16h
3. Results
