Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol82.Issue3-4.Dec1999:
Animal Feed Science and Technology
82 (1999) 261±269
Short communication
Comparison of diet and faecal collection methods for
assessment of seasonal variation in dry matter intake
by sheep maintained on a Cenchrus ciliaris pasture
S.K. Sankhyan*, A.K. Shinde, R. Bhatta, S.A. Karim
Central Sheep and Wool Research Institute, Avikanagar 304 501, Rajasthan, India
Received 14 August 1997; received in revised form 28 April 1998; accepted 24 August 1999
Abstract
Four diet collection methods: clipping(C), mouth grab (MG), plucking (P) and oesophageal
extrusa (OE) and two faecal output estimation methods: faecal bag (FB) and Cr2O3 marker (I) were
compared to assess seasonal changes in nutrient composition of diet and dry matter intake of sheep
on Cenchrus ciliaris pasture. Crude protein (CP) and lignin contents of OE were higher than C, MG
and P during all the seasons. Fiber fractions were lowest in MG, highest in C and intermediate in
OE and P methods. Pooled CP contents of diet samples declined (P < 0.01) from 12.7% in monsoon
to 9.3 and 7.9% in winter and summer while ADF, cellulose and lignin increased from monsoon to
summer. Clipped samples had lower NDF, ADF, cellulose, hemicellulose and gross energy
digestibility compared to P, MG and OE methods in all the seasons. Nutrient digestibility declined
from monsoon to winter and summer in all the diet samples collected by the four techniques. CP
digestibility showed marked depression from 63.1% in monsoon to 44.1 and 14.4% in winter and
summer. Faecal collection bag and Cr2O3 marker methods estimated similar faecal outputs in all the
seasons. The OE method estimated a lower DM intake of the animals (mean 960 g/day) compared
to C, P and MG methods (mean 1381 g/day). Animals consumed more dry matter during winter
(mean 1706 g/day) than during monsoon and summer (mean 1030 g/day) seasons.
It is concluded that diet sampling method and season had an influence on the estimated diet
composition and DMI of sheep on semi-arid pastures. Both methods of faecal collection, however,
estimated similar daily faecal output in sheep. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Sheep; Grazing; Pasture; Diet sampling; Faecal sampling; Seasonal changes; Nutrient utilization
*
Corresponding author. Fax: 91-1437-28163
E-mail address: sankhyan@cswri.raj.nic.in (S.K. Sankhyan)
0377-8401/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 0 4 - 2
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S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
1. Introduction
Sheep in the semi-arid region of India mainly depend on rangeland to meet their
nutritional requirement, the seasonal change in forage yield is reflected in their
production performances (Shinde and Singh, 1995). Assessment of dietary nutrient
content of forage and dry matter intake by sheep on such grazing resources is necessary to
formulate suitable range management strategies to identify the seasonal factors that limit
animal production. Basic prerequisite in determining dry matter intake of sheep on
pasture is to collect representative samples of forage consumed by the animals accurately
and precisely. Oesophageal cannula is widely used for collecting diet sample of grazing
animal (Goddard and Fraser, 1994). Various other methods viz. hand plucking, clipping
and mouth grab sampling are also used to collect diet samples of animal. Similarly the
accurate estimation of total faecal output is essential to determine the nutrient
digestibility and intake of grazing animals. Faecal bag or Cr2O3 marker is commonly
used methods for estimation of total faecal output in grazing studies (Holechek et al.,
1982). However, each of these diet and faecal collection method has its own advantages
and disadvantages. In view of inconsistencies in using these collection methods, an
experiment was planned to investigate the effect of seasons and sampling techniques on
the diet composition and dry matter intake of sheep on cenchrus pasture.
2. Materials and methods
2.1. Site
The study was conducted at the Central Sheep and Wool Research Institute,
Avikanagar, India located at 728280 E latitude and 268170 N longitude, 320 m above mean
sea level. Climate of the region is typical semi-arid with yearly mean minimum and
maximum temperature of 8 and 418C and 257 mm of annual precipitation of which 93%
is distributed between June and September and remaining 7% in form of short showers
from January to March.
2.2. Season
The animals were introduced in the pasture in the month of August, 1995 and
continued till July, 1996. Three digestion trials on four rams, one in each season of
monsoon (August), winter (December) and summer (June) were conducted.
2.3. Pasture
Field research was conducted on 5.0 ha plot of pasture dominated by perennial grass
(Cenchrus ciliaris), native grasses and forbes (Commelina forskalaei, Eleusine aegypticae
and Crotalaria burhia), shrubs (Zizyphus nummularia and Dicrostachys nutans) and
fodder trees (Ailanthus excelsa, Azardirachta indica, Albezia lebbeck and Prosopis
cineraria). Average yield of pasture in monsoon, winter and summer season was 1.68,
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
263
3.24 and 1.89 ton DM/ha, respectively. Pasture vegetation was lush green and dense in the
monsoon, long and stalky in the winter and dry and patchily distributed in summer.
Animal diets constituted of perennial grasses, forbes and few browse species during the
digestion trials. The contribution of fodder trees and tall shrubs was negligible in the diet
of the animals, as these species were lopped and fed to the grazing sheep only after
completion of digestion trials in each season.
2.4. Animals
Twenty adult Malpura rams (3±4 years old) with average body weight of 37.0 kg were
adopted from the Institute flock. They were solely maintained on cenchrus pasture under
continuous grazing system at a stocking density of four sheep per hectare. The animals
were allowed 9 h of grazing extending from 08:00±17:00 h under supervision of a
shepherd. Two rams were fitted with oesophageal cannulas following the technique of
Karim et al. (1997) and maintained on stall-feeding with ad lib. Cenchrus hay and 300 g
concentrate mixture per day individually. The fistulated animals were taken to pasture 21
days before the digestion trials in each season to make them acclimatized to prevailing
pasture conditions and during this period they were not offered other feeds.
2.5. Pasture and diet sampling
Diet samples of grazing sheep were collected during 5 consecutive days of the
digestion trial in each season by four methods:
1. clipping: ten 1 m2 quadrate of grazing area (two quadrate per hectare) were clipped 2±
3 cm above the ground level for estimation of pasture yield and collection of diet
samples (C);
2. mouth grab: daily 30±35 bites from the mouth of 20 sheep were snatched before
swallowing by a operator and the samples with excessive salivary contamination were
discarded immediately (MG);
3. plucking: daily 25±30 samples of forage species were collected by the same operator,
simulating the animal's dietary preference from a flock of 20 animals (P) and;
4. oesophageal extrusa: extrusa samples were collected from two fistulated animals
during first 3 h of active grazing. Samples were squeezed in muslin cloth to remove
saliva (OE).
Diet samples collected by the four methods were dried at 608C for 48 h in an oven. The
representative samples of diets were drawn for chemical analysis by pooling the daily
samples of 5 days collection.
2.6. Faeces sampling
Four rams from the flock were identified for faecal collection. The same animals were
used in all the three seasons to avoid individual variations. Average body weight of these
rams in monsoon, winter and summer were 47.8, 51.9 and 45.8 kg, respectively. They
were harnessed with faecal bags and dosed for 10 days with 1 g Cr2O3 in a paper capsule
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S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
twice daily at 08:00 and 17:00 h. Out of 10 days, the initial 5 days were allotted to
acclimatization of animals for harness and uniform chromic oxide excretion and the later
5 days were used for collection of diet and faeces samples. Faecal bags were emptied in
the morning (08:00 h) and evening (17:00 h) to estimate daily faecal output (FB) and at
the same time faecal pellets from rectum were also collected for indicator method (I).
Representative samples (10%) of faeces collected by the two techniques (Faecal bag and
Cr2O3 marker) were pooled separately for 5 days collection period and representative
samples were dried in oven at 608C for 48 h.
2.7. Laboratory analysis
Dried forage, diet, and faeces samples were ground to pass through 1 mm sieve in a
Wiley mill and stored in polyethylene bags for further analysis. Diet and faeces samples
were then analyzed for dry matter (DM), crude protein (CP) and ash (Association of
Analytical Chemists, 1984) and acid detergent fiber (ADF), neutral detergent fiber (NDF)
and lignin (Van soest et al., 1991). Gross energy (GE) content was determined by Ballistic
Bomb Calorimeter (Gallenkamp). Dry matter intake and digestibility in sheep were
estimated individually from four diet and two faecal sampling methods by the lignin ratio
technique (Wallace and Van Dyne, 1970).
2.8. Statistical analysis
The data were analyzed according to a factorial split plot design with animal as a main
plot and sampling methods as subplots. Animal variations were removed by arranging
animals and seasons in factorial design and seasonal effects were tested against the error
source of animal X season interaction, while sampling methods and their interactions
were tested against the residual variance using following model with four replications.
Yijkl u Al Si ASli Dj Fk SDij DFjk SFik SDFijk
ADSijkl eijkl
Where A: Animals; S: Seasons; D: Diet sampling methods; and F: Faecal collection
methods.
i 1; 2; 3;
j 1; 2; 3; 4;
k 1; 2;
1 1; 2; 3; 4;
Significance was declared where P < 0.05. No statistical analysis was performed on
data of chemical composition of diet samples collected by four methods as pooled
samples were used for chemical analysis.
3. Result and discussion
3.1. Diet composition
Oesophageal extrusa compared to MG, P and C methods estimated higher CP content
of the samples in winter and summer except monsoon season. Similar higher CP content
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
265
in extrusa samples over plucked and clipped samples in sheep by 3.6 and 4.8% units have
been reported by Forbes and Beattieg (1987). Salivary contamination has contributed to
higher value of CP in OE compared to MG samples (Bhatta et al., 1996). In spite of this
fact, lower value of CP in OE compared to MG in monsoon season is a consequence of
collection of tender portion of forage containing higher CP value while snatching from
the mouth of the animals. Such effect was not observed in winter and summer because of
the age and maturity of forage. Thus, lower estimate of CP value in MG compared to OE
method was recorded. Higher lignin content of extrusa samples compared to other three
methods (MG, P and C) indicated that maceration of plant cell by animal in extrusa
samples might have caused an increase release of tannin which have elevated lignin value
as result of tannin±protein reactions (Osbourn et al., 1971). Papachristou and Nastis
(1994) also reported higher value of lignin in extrusa sample when compared to hand
plucked sample. Higher NDF, ADF, cellulose and hemicellulose content estimated by C
over OE and MG methods was obvious, as clipping method of diet sampling represented
the pasture forage at offer without considering forage selection by the animals while MG,
P and OE method represented the diet sample of preferred forage. Progress in age and
maturity of pasture forage was reflected in decline of CP content from 12.7% in monsoon
to 9.3 and 7.9% in winter and summer and increase of ADF, cellulose and lignin content
of diet. NDF content was highest in monsoon (67.1%), lowest in winter (57.4%) and intermediate in summer (62.4%) season. Moreover, the hemicellulose and gross energy content
of diet also showed declining trend from monsoon to winter and summer (Table 1).
3.2. Faecal output
Faecal output of animals assessed by two methods (faecal bag versus indicator) were
almost similar in three seasons indicating that both the methods were equally effective in
estimating the faecal output of grazing sheep. This observation confirm the finding of
Buntinx et al. (1990) who also reported similar estimation of faecal output in sheep by
faecal bag and chromic oxide release device (CRD) methods.
3.3. Digestibility
Oesophageal extrusa sampling estimated lower (P < 0.05) digestibility of DM, NDF,
ADF, cellulose, hemicellulose and GE except CP in comparison to the C, MG and P
methods (Table 2). It appears from the study that the release of tannin of plant cell in
maceration process have depressed the digestibility estimates of OE samples. It has been
reported that tannins act as inhibitors affecting microbial fermentation and/or enzymatic
digestion (Nastis and Malechek, 1988). Thus, tannins inhibitory properties might be
possible reason for lower estimates of digestibility in OE samples. Secondly, in the
present study lignin was used as a marker for estimation of nutrient digestibility, higher
value of lignin have caused the lower estimation of nutrient digestibility in OE samples
compared to other methods. Papachristou and Nastis (1994) have also reported lower
IVOMD of oven dried extrusa diet sample compared to hand plucked, wherein reduction
in digestibility was up to 11% in hand plucked and 31% in extrusa. Linear decline in
nutrient digestibility assessed by four methods from monsoon to winter and summer was
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S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 1
Chemical composition (on % DM basis) and gross energy (MJ/kg) of diet collected by different methods
Clipping
Mouth grab
Plucking
Oesophageal extrusa
Dry matter
Monsoon
Winter
Summer
20.10
65.65
87.38
16.47
38.49
82.36
17.90
53.00
83.36
a
Crude protein
Monsoon
Winter
Summer
10.18
6.38
4.37
13.96
10.17
8.05
14.48
7.22
6.30
12.15
13.58
13.12
Neutral detergent fibre
Monsoon
Winter
Summer
68.63
68.97
72.70
62.76
49.67
53.50
69.18
57.52
60.92
68.00
53.62
62.45
Acid detergent fibre
Monsoon
Winter
Summer
39.30
42.42
64.80
34.09
35.90
46.26
36.24
39.97
52.16
39.10
40.30
49.73
Cellulose
Monsoon
Winter
Summer
31.21
34.44
41.16
27.99
27.75
31.08
30.16
31.93
35.94
30.76
29.02
30.30
Hemicellulose
Monsoon
Winter
Summer
29.33
26.55
7.90
28.67
13.77
7.24
32.94
17.55
8.76
28.70
13.32
12.72
Lignin
Monsoon
Winter
Summer
3.75
5.91
22.06
5.60
6.05
12.36
4.33
6.30
15.13
7.13
9.13
17.97
Gross energy
Monsoon
Winter
Summer
18.58
17.36
16.94
18.24
17.40
17.32
17.40
17.44
17.36
17.26
17.90
17.90
Total ash
Monsoon
Winter
Summer
13.63
8.01
8.51
11.21
10.39
14.60
11.18
10.10
9.72
12.95
15.80
15.35
a
a
a
DM content of extrusa samples was not estimated due to salivary contamination.
related to maturity and lignification of pasture grasses. Such seasonal trend in nutrient
digestibility in sheep on cenchrus pasture in semi arid region was also reported by Shinde
et al. (1998). Faecal bag or indicator method of total faecal collection in combination
with either of the four diet sampling methods (C, P, MG and OE) estimated similar
digestibility of DM, ADF, hemicellulose, CP and GE except NDF and cellulose.
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S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 2
Digestibility coefficients assessed by different diet and faecal collection methods during three seasons and their
interactions*
Digestibility
coefficients
Diet sampling methods
Faecal sampling methods
Clipping
Mouth
grab
Plucking
Oesophageal
extrusa
SEM
Indicator
Faecal
bag
SEM
Dry matter
Monsoon
Winter
Summer
75.9cB
65.5bB
16.2aA
64.1bB
64.6bB
53.0cA
72.2cB
63.1bB
43.9bA
54.2aB
46.6aB
31.7bA
11.00
11.00
11.00
67.2B
59.8B
36.3A
66.0B
60.1B
36.0A
7.77
7.77
7.77
Crude protein
Monsoon
Winter
Summer
67.6bC
32.5aB
0.0A
64.2bB
56.6bB
24.6A
73.3cC
36.4aB
0.0A
47.7aB
51.0bB
32.7A
1.78
1.78
1.78
63.9C
39.7B
13.4A
62.3C
48.5B
15.2A
1.26
1.26
1.26
Neutral detergent fibre
Monsoon
79.4bB
Winter
71.7aB
Summer
29.0aA
66.4aB
59.8bB
41.9bA
76.4bC
63.9aB
39.1bA
60.6aC
43.8bB
27.7aA
1.81
1.81
1.81
71.4C
58.7B
36.5A
70.6C
60.9B
32.4A
1.28
1.28
1.28
Acid detergent fibre
Monsoon
73.8bC
Winter
62.9bB
Summer
22.5aA
55.0aB
56.4bB
39.2bA
67.2cB
58.1bB
36.1bA
50.4aC
38.7aB
18.4aA
1.68
1.68
1.68
63.1B
54.1B
30.2A
59.9B
53.8B
27.8A
1.19
1.19
1.19
Cellulose
Monsoon
Winter
Summer
85.7bcC
77.0bcB
49.8aA
76.1abB
70.8bB
62.8bA
82.9bB
73.5bB
61.6bA
72.4aC
57.8aB
44.5aA
1.59
1.59
1.59
80.5C
69.2B
49.2A
78.5C
70.3B
60.1A
1.12
1.12
1.12
Hemicellulose
Monsoon
Winter
Summer
86.9cB
85.6bcB
26.4aA
80.1bC
71.6bB
55.9bA
86.6cC
76.8bB
56.5bA
74.9aC
55.8aA
63.5cB
3.52
3.52
3.52
81.6C
69.9B
45.5A
81.6C
74.0B
55.4A
2.48
2.48
2.48
Gross energy
Monsoon
Winter
Summer
78.7cC
67.3bB
18.3aA
66.6bB
66.3bB
55.2dA
72.9bC
65.0bB
46.6cA
55.4aB
50.7aB
37.1bA
1.27
1.27
1.27
68.8B
62.0B
39.8A
67.6B
62.5B
38.9A
0.90
0.90
0.90
*
Unlike superscripts (a,b,c) in a row differ significantly (P < 0.05); Unlike superscripts (A,B,C) in a column
differ significantly (P < 0.05); No significant differences were observed between faecal sampling methods.
3.4. Intake
Oesophageal extrusa sampling estimated lower (P < 0.01) dry matter intake (DMI) of
animals compared to P, MG and C methods and the trend remained similar on its
expression in terms of unit body weight or metabolic body size (Table 3) reflecting under
estimation of digestibility when estimated from extrusa samples, probably due to elevated
value of lignin as a result of tannin±protein reaction. Average DMI of animals was higher
in winter (mean 1706 g/day) than in monsoon and summer (mean 1030 g/day) seasons.
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S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 3
Intake assessed by different diet and faecal collection methods during three seasons and their interactions*
Intake
Diet sampling methods
Clipping
Faecal sampling methods
Mouth
grab
Plucking
Oesophageal
extrusa
SEM
Indicator
Faecal
bag
SEM
49.6bA
96.5bC
78.3dB
64.2cA
92.5bB
65.8cA
39.2aA
76.5aC
53.2bB
5.31
5.31
5.31
56.8A
88.0B
62.9A
53.6A
94.2B
57.3A
3.75
3.75
3.75
Digestible crude protein g/day/kgW0.75
Monsoon
49.9bC
44.5bB
Winter
20.9aB
56.0cB
A
Summer
0.0
0.5aA
68.2cC
24.8aB
0.0A
22.6aA
44.4bB
22.4bA
2.54
2.54
2.54
49.2C
33.6B
9.0A
43.4B
39.5B
9.6A
1.80
1.80
1.80
MJ/day/kgW0.75
0.94dB
0.60bA
cC
1.16
1.12bB
0.13aA
0.74dA
0.82cB
1.05bC
0.52cA
0.38aA
0.59aB
0.53bA
0.07
0.07
0.07
0.70B
0.98C
0.46A
0.67B
0.98C
0.41A
0.05
0.05
0.05
Dry matter g/day/kgW0.75
Monsoon
74.2dB
Winter
98.8bC
Summer
43.3aA
Digestible energy
Monsoon
Winter
Summer
*
Unlike superscripts (a,b,c) in a row differ significantly (P < 0.05); Unlike superscripts (A,B,C) in a column
differ significantly (P < 0.05); No significant differences were observed between faecal sampling methods.
Higher moisture content of vegetation (Minson, 1982) and gut fill limitation of animals
(Yoelao et al., 1970) would have contributed to the lower DMI in monsoon season.
However, the lower DMI in summer compared to winter season was reflection of
prevailing hot environmental conditions (Baile and Forbes, 1974) and depletion in quality
and quantity of pasture forage (Mali et al., 1984). Faecal bag or Cr2O3 marker in
combination with the four diet sampling methods estimated similar DMI for all the three
seasons.
In clipping method higher value DMI and lower value of CP of the diet contributed to
lower DCP and higher DE intake of the animals. Whereas OE method, which was true
reflection of diet selection by the animals showed higher DCP and lower DE intakes.
DCP intake of sheep progressively declined (P < 0.05) from monsoon (82.6 g/day) to
winter (71.0 g/day) and summer (16.4 g/day), while DE intake was highest in winter
(18.94 MJ/day) followed by monsoon (13.31 MJ/day) and summer (7.57 MJ/day). Such
changes are associated with seasonal variation in pasture forage availability, its quality
and preference by the animals.
4. Conclusions
Season had a great influence on diet composition and intake of grazing sheep
maintained on semi arid Cenchrus pasture. Estimates of intake were also influenced by
different methods of diet collection. Faecal bag and Cr2O3 marker methods estimated
similar faecal output, hence, either of the method can be used in digestion trial of grazing
animals.
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269
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Yoelao, K., Jackson, M.G., Saran, I., 1970. The effect of wilting berseem and increase herbage on voluntary dry
matter intake by buffalo heifers. J. Agric. Sci. Camb. 74, 47±51.
82 (1999) 261±269
Short communication
Comparison of diet and faecal collection methods for
assessment of seasonal variation in dry matter intake
by sheep maintained on a Cenchrus ciliaris pasture
S.K. Sankhyan*, A.K. Shinde, R. Bhatta, S.A. Karim
Central Sheep and Wool Research Institute, Avikanagar 304 501, Rajasthan, India
Received 14 August 1997; received in revised form 28 April 1998; accepted 24 August 1999
Abstract
Four diet collection methods: clipping(C), mouth grab (MG), plucking (P) and oesophageal
extrusa (OE) and two faecal output estimation methods: faecal bag (FB) and Cr2O3 marker (I) were
compared to assess seasonal changes in nutrient composition of diet and dry matter intake of sheep
on Cenchrus ciliaris pasture. Crude protein (CP) and lignin contents of OE were higher than C, MG
and P during all the seasons. Fiber fractions were lowest in MG, highest in C and intermediate in
OE and P methods. Pooled CP contents of diet samples declined (P < 0.01) from 12.7% in monsoon
to 9.3 and 7.9% in winter and summer while ADF, cellulose and lignin increased from monsoon to
summer. Clipped samples had lower NDF, ADF, cellulose, hemicellulose and gross energy
digestibility compared to P, MG and OE methods in all the seasons. Nutrient digestibility declined
from monsoon to winter and summer in all the diet samples collected by the four techniques. CP
digestibility showed marked depression from 63.1% in monsoon to 44.1 and 14.4% in winter and
summer. Faecal collection bag and Cr2O3 marker methods estimated similar faecal outputs in all the
seasons. The OE method estimated a lower DM intake of the animals (mean 960 g/day) compared
to C, P and MG methods (mean 1381 g/day). Animals consumed more dry matter during winter
(mean 1706 g/day) than during monsoon and summer (mean 1030 g/day) seasons.
It is concluded that diet sampling method and season had an influence on the estimated diet
composition and DMI of sheep on semi-arid pastures. Both methods of faecal collection, however,
estimated similar daily faecal output in sheep. # 1999 Elsevier Science B.V. All rights reserved.
Keywords: Sheep; Grazing; Pasture; Diet sampling; Faecal sampling; Seasonal changes; Nutrient utilization
*
Corresponding author. Fax: 91-1437-28163
E-mail address: sankhyan@cswri.raj.nic.in (S.K. Sankhyan)
0377-8401/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 0 4 - 2
262
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
1. Introduction
Sheep in the semi-arid region of India mainly depend on rangeland to meet their
nutritional requirement, the seasonal change in forage yield is reflected in their
production performances (Shinde and Singh, 1995). Assessment of dietary nutrient
content of forage and dry matter intake by sheep on such grazing resources is necessary to
formulate suitable range management strategies to identify the seasonal factors that limit
animal production. Basic prerequisite in determining dry matter intake of sheep on
pasture is to collect representative samples of forage consumed by the animals accurately
and precisely. Oesophageal cannula is widely used for collecting diet sample of grazing
animal (Goddard and Fraser, 1994). Various other methods viz. hand plucking, clipping
and mouth grab sampling are also used to collect diet samples of animal. Similarly the
accurate estimation of total faecal output is essential to determine the nutrient
digestibility and intake of grazing animals. Faecal bag or Cr2O3 marker is commonly
used methods for estimation of total faecal output in grazing studies (Holechek et al.,
1982). However, each of these diet and faecal collection method has its own advantages
and disadvantages. In view of inconsistencies in using these collection methods, an
experiment was planned to investigate the effect of seasons and sampling techniques on
the diet composition and dry matter intake of sheep on cenchrus pasture.
2. Materials and methods
2.1. Site
The study was conducted at the Central Sheep and Wool Research Institute,
Avikanagar, India located at 728280 E latitude and 268170 N longitude, 320 m above mean
sea level. Climate of the region is typical semi-arid with yearly mean minimum and
maximum temperature of 8 and 418C and 257 mm of annual precipitation of which 93%
is distributed between June and September and remaining 7% in form of short showers
from January to March.
2.2. Season
The animals were introduced in the pasture in the month of August, 1995 and
continued till July, 1996. Three digestion trials on four rams, one in each season of
monsoon (August), winter (December) and summer (June) were conducted.
2.3. Pasture
Field research was conducted on 5.0 ha plot of pasture dominated by perennial grass
(Cenchrus ciliaris), native grasses and forbes (Commelina forskalaei, Eleusine aegypticae
and Crotalaria burhia), shrubs (Zizyphus nummularia and Dicrostachys nutans) and
fodder trees (Ailanthus excelsa, Azardirachta indica, Albezia lebbeck and Prosopis
cineraria). Average yield of pasture in monsoon, winter and summer season was 1.68,
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
263
3.24 and 1.89 ton DM/ha, respectively. Pasture vegetation was lush green and dense in the
monsoon, long and stalky in the winter and dry and patchily distributed in summer.
Animal diets constituted of perennial grasses, forbes and few browse species during the
digestion trials. The contribution of fodder trees and tall shrubs was negligible in the diet
of the animals, as these species were lopped and fed to the grazing sheep only after
completion of digestion trials in each season.
2.4. Animals
Twenty adult Malpura rams (3±4 years old) with average body weight of 37.0 kg were
adopted from the Institute flock. They were solely maintained on cenchrus pasture under
continuous grazing system at a stocking density of four sheep per hectare. The animals
were allowed 9 h of grazing extending from 08:00±17:00 h under supervision of a
shepherd. Two rams were fitted with oesophageal cannulas following the technique of
Karim et al. (1997) and maintained on stall-feeding with ad lib. Cenchrus hay and 300 g
concentrate mixture per day individually. The fistulated animals were taken to pasture 21
days before the digestion trials in each season to make them acclimatized to prevailing
pasture conditions and during this period they were not offered other feeds.
2.5. Pasture and diet sampling
Diet samples of grazing sheep were collected during 5 consecutive days of the
digestion trial in each season by four methods:
1. clipping: ten 1 m2 quadrate of grazing area (two quadrate per hectare) were clipped 2±
3 cm above the ground level for estimation of pasture yield and collection of diet
samples (C);
2. mouth grab: daily 30±35 bites from the mouth of 20 sheep were snatched before
swallowing by a operator and the samples with excessive salivary contamination were
discarded immediately (MG);
3. plucking: daily 25±30 samples of forage species were collected by the same operator,
simulating the animal's dietary preference from a flock of 20 animals (P) and;
4. oesophageal extrusa: extrusa samples were collected from two fistulated animals
during first 3 h of active grazing. Samples were squeezed in muslin cloth to remove
saliva (OE).
Diet samples collected by the four methods were dried at 608C for 48 h in an oven. The
representative samples of diets were drawn for chemical analysis by pooling the daily
samples of 5 days collection.
2.6. Faeces sampling
Four rams from the flock were identified for faecal collection. The same animals were
used in all the three seasons to avoid individual variations. Average body weight of these
rams in monsoon, winter and summer were 47.8, 51.9 and 45.8 kg, respectively. They
were harnessed with faecal bags and dosed for 10 days with 1 g Cr2O3 in a paper capsule
264
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
twice daily at 08:00 and 17:00 h. Out of 10 days, the initial 5 days were allotted to
acclimatization of animals for harness and uniform chromic oxide excretion and the later
5 days were used for collection of diet and faeces samples. Faecal bags were emptied in
the morning (08:00 h) and evening (17:00 h) to estimate daily faecal output (FB) and at
the same time faecal pellets from rectum were also collected for indicator method (I).
Representative samples (10%) of faeces collected by the two techniques (Faecal bag and
Cr2O3 marker) were pooled separately for 5 days collection period and representative
samples were dried in oven at 608C for 48 h.
2.7. Laboratory analysis
Dried forage, diet, and faeces samples were ground to pass through 1 mm sieve in a
Wiley mill and stored in polyethylene bags for further analysis. Diet and faeces samples
were then analyzed for dry matter (DM), crude protein (CP) and ash (Association of
Analytical Chemists, 1984) and acid detergent fiber (ADF), neutral detergent fiber (NDF)
and lignin (Van soest et al., 1991). Gross energy (GE) content was determined by Ballistic
Bomb Calorimeter (Gallenkamp). Dry matter intake and digestibility in sheep were
estimated individually from four diet and two faecal sampling methods by the lignin ratio
technique (Wallace and Van Dyne, 1970).
2.8. Statistical analysis
The data were analyzed according to a factorial split plot design with animal as a main
plot and sampling methods as subplots. Animal variations were removed by arranging
animals and seasons in factorial design and seasonal effects were tested against the error
source of animal X season interaction, while sampling methods and their interactions
were tested against the residual variance using following model with four replications.
Yijkl u Al Si ASli Dj Fk SDij DFjk SFik SDFijk
ADSijkl eijkl
Where A: Animals; S: Seasons; D: Diet sampling methods; and F: Faecal collection
methods.
i 1; 2; 3;
j 1; 2; 3; 4;
k 1; 2;
1 1; 2; 3; 4;
Significance was declared where P < 0.05. No statistical analysis was performed on
data of chemical composition of diet samples collected by four methods as pooled
samples were used for chemical analysis.
3. Result and discussion
3.1. Diet composition
Oesophageal extrusa compared to MG, P and C methods estimated higher CP content
of the samples in winter and summer except monsoon season. Similar higher CP content
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
265
in extrusa samples over plucked and clipped samples in sheep by 3.6 and 4.8% units have
been reported by Forbes and Beattieg (1987). Salivary contamination has contributed to
higher value of CP in OE compared to MG samples (Bhatta et al., 1996). In spite of this
fact, lower value of CP in OE compared to MG in monsoon season is a consequence of
collection of tender portion of forage containing higher CP value while snatching from
the mouth of the animals. Such effect was not observed in winter and summer because of
the age and maturity of forage. Thus, lower estimate of CP value in MG compared to OE
method was recorded. Higher lignin content of extrusa samples compared to other three
methods (MG, P and C) indicated that maceration of plant cell by animal in extrusa
samples might have caused an increase release of tannin which have elevated lignin value
as result of tannin±protein reactions (Osbourn et al., 1971). Papachristou and Nastis
(1994) also reported higher value of lignin in extrusa sample when compared to hand
plucked sample. Higher NDF, ADF, cellulose and hemicellulose content estimated by C
over OE and MG methods was obvious, as clipping method of diet sampling represented
the pasture forage at offer without considering forage selection by the animals while MG,
P and OE method represented the diet sample of preferred forage. Progress in age and
maturity of pasture forage was reflected in decline of CP content from 12.7% in monsoon
to 9.3 and 7.9% in winter and summer and increase of ADF, cellulose and lignin content
of diet. NDF content was highest in monsoon (67.1%), lowest in winter (57.4%) and intermediate in summer (62.4%) season. Moreover, the hemicellulose and gross energy content
of diet also showed declining trend from monsoon to winter and summer (Table 1).
3.2. Faecal output
Faecal output of animals assessed by two methods (faecal bag versus indicator) were
almost similar in three seasons indicating that both the methods were equally effective in
estimating the faecal output of grazing sheep. This observation confirm the finding of
Buntinx et al. (1990) who also reported similar estimation of faecal output in sheep by
faecal bag and chromic oxide release device (CRD) methods.
3.3. Digestibility
Oesophageal extrusa sampling estimated lower (P < 0.05) digestibility of DM, NDF,
ADF, cellulose, hemicellulose and GE except CP in comparison to the C, MG and P
methods (Table 2). It appears from the study that the release of tannin of plant cell in
maceration process have depressed the digestibility estimates of OE samples. It has been
reported that tannins act as inhibitors affecting microbial fermentation and/or enzymatic
digestion (Nastis and Malechek, 1988). Thus, tannins inhibitory properties might be
possible reason for lower estimates of digestibility in OE samples. Secondly, in the
present study lignin was used as a marker for estimation of nutrient digestibility, higher
value of lignin have caused the lower estimation of nutrient digestibility in OE samples
compared to other methods. Papachristou and Nastis (1994) have also reported lower
IVOMD of oven dried extrusa diet sample compared to hand plucked, wherein reduction
in digestibility was up to 11% in hand plucked and 31% in extrusa. Linear decline in
nutrient digestibility assessed by four methods from monsoon to winter and summer was
266
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 1
Chemical composition (on % DM basis) and gross energy (MJ/kg) of diet collected by different methods
Clipping
Mouth grab
Plucking
Oesophageal extrusa
Dry matter
Monsoon
Winter
Summer
20.10
65.65
87.38
16.47
38.49
82.36
17.90
53.00
83.36
a
Crude protein
Monsoon
Winter
Summer
10.18
6.38
4.37
13.96
10.17
8.05
14.48
7.22
6.30
12.15
13.58
13.12
Neutral detergent fibre
Monsoon
Winter
Summer
68.63
68.97
72.70
62.76
49.67
53.50
69.18
57.52
60.92
68.00
53.62
62.45
Acid detergent fibre
Monsoon
Winter
Summer
39.30
42.42
64.80
34.09
35.90
46.26
36.24
39.97
52.16
39.10
40.30
49.73
Cellulose
Monsoon
Winter
Summer
31.21
34.44
41.16
27.99
27.75
31.08
30.16
31.93
35.94
30.76
29.02
30.30
Hemicellulose
Monsoon
Winter
Summer
29.33
26.55
7.90
28.67
13.77
7.24
32.94
17.55
8.76
28.70
13.32
12.72
Lignin
Monsoon
Winter
Summer
3.75
5.91
22.06
5.60
6.05
12.36
4.33
6.30
15.13
7.13
9.13
17.97
Gross energy
Monsoon
Winter
Summer
18.58
17.36
16.94
18.24
17.40
17.32
17.40
17.44
17.36
17.26
17.90
17.90
Total ash
Monsoon
Winter
Summer
13.63
8.01
8.51
11.21
10.39
14.60
11.18
10.10
9.72
12.95
15.80
15.35
a
a
a
DM content of extrusa samples was not estimated due to salivary contamination.
related to maturity and lignification of pasture grasses. Such seasonal trend in nutrient
digestibility in sheep on cenchrus pasture in semi arid region was also reported by Shinde
et al. (1998). Faecal bag or indicator method of total faecal collection in combination
with either of the four diet sampling methods (C, P, MG and OE) estimated similar
digestibility of DM, ADF, hemicellulose, CP and GE except NDF and cellulose.
267
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 2
Digestibility coefficients assessed by different diet and faecal collection methods during three seasons and their
interactions*
Digestibility
coefficients
Diet sampling methods
Faecal sampling methods
Clipping
Mouth
grab
Plucking
Oesophageal
extrusa
SEM
Indicator
Faecal
bag
SEM
Dry matter
Monsoon
Winter
Summer
75.9cB
65.5bB
16.2aA
64.1bB
64.6bB
53.0cA
72.2cB
63.1bB
43.9bA
54.2aB
46.6aB
31.7bA
11.00
11.00
11.00
67.2B
59.8B
36.3A
66.0B
60.1B
36.0A
7.77
7.77
7.77
Crude protein
Monsoon
Winter
Summer
67.6bC
32.5aB
0.0A
64.2bB
56.6bB
24.6A
73.3cC
36.4aB
0.0A
47.7aB
51.0bB
32.7A
1.78
1.78
1.78
63.9C
39.7B
13.4A
62.3C
48.5B
15.2A
1.26
1.26
1.26
Neutral detergent fibre
Monsoon
79.4bB
Winter
71.7aB
Summer
29.0aA
66.4aB
59.8bB
41.9bA
76.4bC
63.9aB
39.1bA
60.6aC
43.8bB
27.7aA
1.81
1.81
1.81
71.4C
58.7B
36.5A
70.6C
60.9B
32.4A
1.28
1.28
1.28
Acid detergent fibre
Monsoon
73.8bC
Winter
62.9bB
Summer
22.5aA
55.0aB
56.4bB
39.2bA
67.2cB
58.1bB
36.1bA
50.4aC
38.7aB
18.4aA
1.68
1.68
1.68
63.1B
54.1B
30.2A
59.9B
53.8B
27.8A
1.19
1.19
1.19
Cellulose
Monsoon
Winter
Summer
85.7bcC
77.0bcB
49.8aA
76.1abB
70.8bB
62.8bA
82.9bB
73.5bB
61.6bA
72.4aC
57.8aB
44.5aA
1.59
1.59
1.59
80.5C
69.2B
49.2A
78.5C
70.3B
60.1A
1.12
1.12
1.12
Hemicellulose
Monsoon
Winter
Summer
86.9cB
85.6bcB
26.4aA
80.1bC
71.6bB
55.9bA
86.6cC
76.8bB
56.5bA
74.9aC
55.8aA
63.5cB
3.52
3.52
3.52
81.6C
69.9B
45.5A
81.6C
74.0B
55.4A
2.48
2.48
2.48
Gross energy
Monsoon
Winter
Summer
78.7cC
67.3bB
18.3aA
66.6bB
66.3bB
55.2dA
72.9bC
65.0bB
46.6cA
55.4aB
50.7aB
37.1bA
1.27
1.27
1.27
68.8B
62.0B
39.8A
67.6B
62.5B
38.9A
0.90
0.90
0.90
*
Unlike superscripts (a,b,c) in a row differ significantly (P < 0.05); Unlike superscripts (A,B,C) in a column
differ significantly (P < 0.05); No significant differences were observed between faecal sampling methods.
3.4. Intake
Oesophageal extrusa sampling estimated lower (P < 0.01) dry matter intake (DMI) of
animals compared to P, MG and C methods and the trend remained similar on its
expression in terms of unit body weight or metabolic body size (Table 3) reflecting under
estimation of digestibility when estimated from extrusa samples, probably due to elevated
value of lignin as a result of tannin±protein reaction. Average DMI of animals was higher
in winter (mean 1706 g/day) than in monsoon and summer (mean 1030 g/day) seasons.
268
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
Table 3
Intake assessed by different diet and faecal collection methods during three seasons and their interactions*
Intake
Diet sampling methods
Clipping
Faecal sampling methods
Mouth
grab
Plucking
Oesophageal
extrusa
SEM
Indicator
Faecal
bag
SEM
49.6bA
96.5bC
78.3dB
64.2cA
92.5bB
65.8cA
39.2aA
76.5aC
53.2bB
5.31
5.31
5.31
56.8A
88.0B
62.9A
53.6A
94.2B
57.3A
3.75
3.75
3.75
Digestible crude protein g/day/kgW0.75
Monsoon
49.9bC
44.5bB
Winter
20.9aB
56.0cB
A
Summer
0.0
0.5aA
68.2cC
24.8aB
0.0A
22.6aA
44.4bB
22.4bA
2.54
2.54
2.54
49.2C
33.6B
9.0A
43.4B
39.5B
9.6A
1.80
1.80
1.80
MJ/day/kgW0.75
0.94dB
0.60bA
cC
1.16
1.12bB
0.13aA
0.74dA
0.82cB
1.05bC
0.52cA
0.38aA
0.59aB
0.53bA
0.07
0.07
0.07
0.70B
0.98C
0.46A
0.67B
0.98C
0.41A
0.05
0.05
0.05
Dry matter g/day/kgW0.75
Monsoon
74.2dB
Winter
98.8bC
Summer
43.3aA
Digestible energy
Monsoon
Winter
Summer
*
Unlike superscripts (a,b,c) in a row differ significantly (P < 0.05); Unlike superscripts (A,B,C) in a column
differ significantly (P < 0.05); No significant differences were observed between faecal sampling methods.
Higher moisture content of vegetation (Minson, 1982) and gut fill limitation of animals
(Yoelao et al., 1970) would have contributed to the lower DMI in monsoon season.
However, the lower DMI in summer compared to winter season was reflection of
prevailing hot environmental conditions (Baile and Forbes, 1974) and depletion in quality
and quantity of pasture forage (Mali et al., 1984). Faecal bag or Cr2O3 marker in
combination with the four diet sampling methods estimated similar DMI for all the three
seasons.
In clipping method higher value DMI and lower value of CP of the diet contributed to
lower DCP and higher DE intake of the animals. Whereas OE method, which was true
reflection of diet selection by the animals showed higher DCP and lower DE intakes.
DCP intake of sheep progressively declined (P < 0.05) from monsoon (82.6 g/day) to
winter (71.0 g/day) and summer (16.4 g/day), while DE intake was highest in winter
(18.94 MJ/day) followed by monsoon (13.31 MJ/day) and summer (7.57 MJ/day). Such
changes are associated with seasonal variation in pasture forage availability, its quality
and preference by the animals.
4. Conclusions
Season had a great influence on diet composition and intake of grazing sheep
maintained on semi arid Cenchrus pasture. Estimates of intake were also influenced by
different methods of diet collection. Faecal bag and Cr2O3 marker methods estimated
similar faecal output, hence, either of the method can be used in digestion trial of grazing
animals.
S.K. Sankhyan et al. / Animal Feed Science and Technology 82 (1999) 261±269
269
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