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Citation of this paper

Study on ruminal degradability of local plants by using nylon bag technique

Kanpukdee Suchitra and Metha Wanapat

Tropical Feed Resources Research and Development Center, Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand
nunim_su@yahoo.com   ,   metha@kku.ac.th

Abstract

Two, ruminally fistulated crossbred beef steers of 400±15 kg BW were used to evaluate the nutritive value of local plants by using the in sacco nylon bag technique. A Randomized Complete Block Design (RCBD) was used to determine ruminal degradability of DM and OM, and their effects on rumen ecology in cattle. The investigation was carried out with eleven local plants, namely: mangosteen (Garcinia mangostana) peel of fruit (MSP), guava (Psidium guajava) leaf (GVL), siam neem tree (Azadirachta indica) leaf (SNTL), sesbania (Sesbania grandoflora) leaf (SBNL), coral leaf (Eritrina variegate) (CRL), Bai Yanang (Tiliacora triandra) (BY), cassava hay (Manihot esculenta, Crantz) (CH), bitter cucumber (Mormormdica charantia) fruit (BCF), banana (Musa sapientum)  leaf (BNL), mulberry (Morus indica) leaf (MBL), and Plia farn (Macropanax dispermus Ktze) leaf (PFL). Approximately 5 g of feed samples were weighed into duplicated nylon bags (38 µm pore size) and incubated ruminally at 0, 2, 4, 8, 12, 24, 48, and 72 h-post feeding.

The results showed that the mean values of ruminal pH (6.6) and temperature (38.8 ºC) were not different (P>0.05) among different times of incubation. The condensed tannins (CT), and crude saponin (CS) values of local plants were 15.8, 9.8 % for MSP, 14.8, 2.8 % for GVL, 11.0, 2.5 % for SNTL, 4.0, 2.0 % for SBNL, 2.3, 1.8 % for CRL, 2.2, 1.7 % for CH, 2.2, 1.3 % for BY, 2.1, 4.1 % for BCF, 2.0, 1.4 % for PFL, 1.7, 1.3 % for BNL, and 1.6, 2.3 % for MBL, respectively. The highest and lowest of the potential degradability (a+b), and effective degradability of DM and OM of feed sources for PFL and MSP were 97 and 72.3, 98.1 and 73.2, 58.6 and 46.7 and 59.1 and 45.7 %, respectively. It was also shown that PFL had a higher (p<0.01) degradability in the rumen, while MSP had the lowest, thus resulting in higher rumen degradable and undegradable roughage sources, respectively. Based on these results PFL can be used efficiently in the rumen and MSP as a rumen by-pass protein due to its CT and CS contents.  

Key word: Digestibility, In sacco technique, ruminants


Introduction        

Ruminant diets in most developing countries are based on fibrous feeds and crop residues. These feeds are imbalanced and are particularly deficient in protein, minerals, vitamins, and are highly lignified. Efficient supplementation of locally mixed concentrate with grains or protein foliages has been demonstrated to improve rumen ecology, dry matter intake and subsequently meat and milk quantity and quality (Wanapat 1999). Tree leaves have high protein contents (18-26% crude protein), and some of them have low rates of degradability in the rumen (Espinosa 1984). These characteristics, along with those mentioned above, make them an alternative source of by-pass protein to be used as a supplement for ruminant production systems in the tropics.

The extent to which tree foliage protein is degraded in, or escapes from the rumen is extremely important. If the tree foliage protein is totally degraded, it provides ammonia and minerals for microbial growth (Leng 1993). Local feed resources such as cassava root/hay/silage, corn stovers, kapok meal, baby corn, cow-pea, cotton seed meal, leuceana leaves, sweet potatoes, sugarcane, sesbania seed/leaves, mulberry leaves, moringa seed, sapindus fruit, have potential as ruminant feeds to improve  and  increase the efficiency of the production system (Liu et al 2001; Preston 2001;  Hossain and Becker 2002; Hess et al 2003; Lam 2003; Promkot and Wanapat 2003; Vongsamphanh 2003; Wanapat 2003; Anhwange et al 2004; Hristov et al 2004). However, some of these feeds contain secondary plant compounds such as condensed tannins, saponins, gossypol, mimosine, and trypsin inhibitor, which may diminish the effects of these feedstuffs with respect to feed quality and animal production. Comprehensive reviews on the effects of secondary compounds and detoxification methods on animal nutrition and feeding in the tropics have been reported by Reed (1995), Abdullah and Rajion (1997); Makkar and Becker (1999).

Limited information is available on characteristics of DM and OM degradation in the rumen of feed resources locally used for livestock in the tropics with special reference to Thailand eg. mangosteen (Garcinia mangostana), peel of fruit, guava (Psidium guajava) leaf, siam neem tree (Azadirachta indica) leaf, sesbania (Sesbania grandoflora) leaf, coral leaf (Eritrina variegate), Bai Yanang (Tiliacora triandra), etc. These feeds contain high levels of condensed tannins and/or crude saponins and can be used as alternative dietary strategic supplements to improve rumen ecology and act as defaunating sources in ruminants. Therefore, the objective of this study was to determine DM and OM disappearance of tropical feeds of eleven locally available feeds in Thailand on fermentation characteristics using the in sacco technique. 
 

Materials and methods

Location and duration

This experiment was conducted on station at the Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand.

Experimental design
A randomized complete block design (RCBD) with eleven treatments and two replicates per treatments was used.
Feed samples

Eleven local plants were used as substrates in this experiment. Most of them were collected from nearby and some were bought in local markets.  All samples were dried in a forced air oven at 60 oC and ground to pass a 1 mm screen and stored for chemical analysis and the degradability study. The local plant materials investigated were as follows:

1. Mangosteen (Garcinia mangostana), Peel of fruit

2. Guava (Psidium guajava), Leaf

3. Siam neem tree (Azadirachta indica), Leaf

4. Sesbania (Sesbania grandoflora), Leaf

5. Coral leaf (Eritrina variegate)

6. Bai Yanang (Tiliacora triandra)

7. Cassava hay (Manihot esculenta Crantz)

8. Bitter cucumber (Mormormdica charantia), Fruit

9. Mulbery (Morus indica), Leaf

10. Banana (Musa sapientum), Leaf

11. Plia farn (Macropanax dispermus Ktze), Leaf 

Animal and diets

Two ruminally fistulated crossbred beef steers with liveweight 400±15 kg were used as replicates to determine in sacco DM and OM degradability of eleven local plants. Steers were housed in individual pens and fed ad libitum urea-treated rice straw (UTRS) and concentrate (12% CP) at 70:30 ratio. Water and mineral block were available at all times. The diets were offered in two equal meals at 07.00h and 16.00h. The animals were adapted to the basal feed for two weeks prior to suspension of the bags.

Ruminal disappearance study

The DM and OM disappearances in the rumen were estimated for each feed sample using the nylon bag technique (Ørskov and McDonald 1979). The bags (7x 14cm) were made from dacron cloth with a pore size of 38 μm.  Approximately 5.0 g of dried (60ْ C) feed samples were weighed into previously tired the nylon bags. The bags were tied to weight chains and place in ventral rumen sac of steers approximate 2 h after the morning feeding. All feed samples were incubated simultaneously in both steers using duplicates base at each time point and a blank bag containing no sample for each removal time. Bags for each feed sample were removed after 0, 2, 4, 8, 12, 24, 48 and 72 h of incubation. Immediately after removing from the rumen, the bags were washed with cold tap water until clear and dried in forced air oven at 60 ο C for 72 h. The bags were weighed and residues were removed and then analyzed for DM and OM.  All bag feed samples were collected for their corresponding blank. The 0 h incubation samples were washed and dried in similar conditions. The bags were weighed and tested according to the procedure described by Ørskov and McDonald (1979). Samples of rumen fluid were taken through the ruminal canulae at 0, 2, 4, 8, 12, 24, 48 and 72 h of incubation, during each time, and pH and temperature were measured immediately using a portable pH and temperature meter.

Chemical composition analysis 

The samples were analyzed for DM, Ash, and CP according to AOAC (1990). Neutral-detergent fiber (NDF) and acid-detergent fiber (ADF) were determined using the method of Van Soest et al (1991). Condensed tannins (CT) were estimated by the Vanillin-HCL method (Burns 1971 modified by Wanapat and Poungchompu 2001) and saponins were measured by using methanol extraction following the method of Kwon et al (2002) as modified by Wanapat and Ngamsaeng (2004).

Data analysis

Data for ruminal disappearance characteristics of DM and OM were fitted to the exponential equation following the procedure described by Ørskov and McDonald (1979) and using the NEWAY program (Chen 1996). P = a+b (1-e-ct) where, P = disappearance rate at time t (%), a = the intercept of the degradation curve at time zero (%), b = the fraction of DM and OM which were degraded when given sufficient time for digestion in the rumen (%), c = a rate constant of disappearance of fraction b (h-1), and t = time of incubation (h). The effective degradability (ED) of DM and OM were calculated by using the following equation. EDDM or EDOM = a+{(bc)/(c+k)} where, k = assuming the rate of particulate outflow from the rumen, k, is 0.05 h-1 by equation of Ørskov and McDonald (1979)

Statistical analysis

Data were analyzed by Analysis of variance (ANOVA) according to a Randomized complete block design (RCBD). It was performed on the data of the same incubation time as a separate set following the ANOVA procedure of SAS (1998). Treatment means were compared using Duncan's New Multiple Range Test (Steel and Torrie 1980). The statistical model was: Yij = m + δi+Tj +eij where; Yij = Observation in block i and treatment j, m = Over all sample mean, δi = Block i, Ti = Effect of treatment i, eij = Error
 

Results

Chemical composition of feedstuffs

The chemical composition of feedstuffs is presented in Table1.


Table 1.  Chemical composition of local feeds resources used in in sacco technique

Substrates

DM

DM, %.

Ash

OM

CP

NDF

ADF

CT1

CS2

Mangosteen peel

95.3

2.6

97.4

21.5

52.5

50.0

15.8

9.8

Guava leaf

94.7

7.7

92.3

14.0

55.0

32.6

14.8

2.8

Siam neem tree leaf

94.8

10.8

89.2

13.3

50.8

33.9

11.0

2.5

Sesbania leaf

94.9

8.0

92.0

30.8

29.4

15.6

4.0

2.0

Coral leaf

95.0

10.4

89.6

23.0

48.9

29.9

2.3

1.8

Bai yanang leaf

93.1

6.8

93.2

17.1

60.2

38.1

2.2

1.3

Cassava hay

93.2

7.0

93.0

25.4

52.3

29.8

2.2

1.7

Bitter cucumber fruit

94.2

9.6

90.4

2.9

52.5

31.6

2.1

4.1

Banana leaf

96.2

7.8

92.2

14.8

73.8

34.8

1.7

1.3

Mulberry leaf

95.4

12.8

87.2

17.2

55.2

22.5

1.6

2.3

Plia fran leaf

95.5

5.1

94.9

12.2

28.2

13.6

2.0

1.4

DM = dry matter, OM = organic matter, CP = crude protein, NDF = neutral-detergent fiber,
ADF = acid-detergent fiber, CT1 = Condensed tannins; CS2 = Crude saponins

All eleven feed sources had similar DM and OM contents. The CP content ranged from 2.9 % in bitter cucumber to 30.8 % in sesbania leaf. More than half of the samples had CP, NDF and ADF contents ranging from 12.2 to 21.5%, 25.4 to 73.8% and 12.6 to 50.0%, respectively. Feed sources could be divided into three groups: high, medium, and low depending on CT concentration, which ranged from 11.4 to 15.8%, 2.1 to 4.6% and 1.6 to 1.7%, respectively. MSP had the highest and MBL the lowest CT values, while BY and BNL had the lowest CS values and MSP had the highest (1.3 % and 9.8 %, respectively).

Ruminal environment

Rumen environment expressed by the level of pH and temperature is shown in Table 2. The average ruminal pH and temperature was 6.6 and 38.8 ºC, respectively. There were no differences of these values among times of incubation.


Table 2.  Ruminal pH and temperature of beef steers during nylon bag study 

h-post suspension

pH

Temperature, ºC

0

6.6

38.8

2

6.7

38.4

4

6.6

38.4

8

6.6

38.9

12

6.6

38.4

24

6.7

39.0

48

6.6

39.5

72

6.8

38.5

Mean±SD

6.6±0.1

38.8±0.4
Ruminal DM and OM disappearance and characteristics

Ruminal DM and OM disappearance and characteristics of ruminal DM and OM disappearance of the eleven feed sources are shown in Figures 1, 2, and Table 3, respectively.



Figure 1.  In sacco dry matter (DM) disappearances of feedstuffs


Figure 2.  In sacco organic matter (OM) disappearances of feedstuffs


Table 3.  Dry matter (DM) and organic matter (OM) disappearances of local plant feedstuffs incubated in the rumen at various times in beef cattle

Item

PFL2/

SBNL

MBL

CH

BCF

SNTL

CRL

BY

BNL

GVL

MSP

SEM

a

45.4a

48.7b

39.2cd

36.9ed

33.0f

37.6ed

40.3c

30.8g

35.9e

24.1h

38.2cde

1.13

b

52.5a

45.9b

45.5bc

42.6d

53.6a

43.6cd

30.8f

36.2e

28.7g

42.8d

20.4h

1.03

c

0.052a

0.051a

0.061a

0.086b

0.058a

0.058a

0.059a

0.061a

0.050a

0.056a

0.043a

0.01

a+b

97.9a

94.7b

84.7c

79.5d

86.6c

81.2d

71.1e

67.0f

64.6g

66.9f

58.6h

1.06

1/EDDM,%

72.3a

71.8a

64.2b

63.6b

61.7c

60.8c

56.7e

50.5f

50.2f

47.6g

46.7h

0.40

a

44.6ab

46.5a

43.2b

37.2d

31.2f

27.8g

40.9c

29.1g

34.8e

22.1h

37.6d

0.99

b

53.5a

49.1b

46.0c

44.4c

55.4a

53.1a

33.5e

39.6d

31.3e

44.6c

21.5f

1.13

c

0.058a

0.053a

0.056a

0.076b

0.055a

0.055a

0.051a

0.056a

0.055a

0.056a

0.043a

0.01

a+b

98.1a

95.6b

89.2c

81.6e

86.6d

80.9e

74.3f

68.6g

66.1h

66.7gh

59.1i

0.99

1/EDOM, %

73.2a

71.6b

67.4c

63.8d

60.0e

55.3g

57.7f

49.9i

51.0h

47.5j

45.7k

0.54

a-k Means within rows not sharing a common superscript are different at P<0.01

1/Effective degradability in the rumen (assuming rate of passage of 0.05/h-1), SEM = Standard error of the mean EDDM = effective degradability of dry matter, EDOM = effective degradability of organic matter

2/ PFL = Plia farn leaf, SBNL = sesbania leaf, MBL = mulbery leaf, CH = cassava hay, BCF = bitter cucumber fruit, SNTL = siam neem tree leaf, CRL = coral leaf, BY = Bai Yanang leaf, BNL = banana leaf, GVL = guava leaf , MSP = mangosteen peel 


Ruminal DM and OM disappearances increased with rumen incubation time for all feed sources (0 to72 h). PFL had the greatest degradability in the rumen, while MSP was lowest on DM and OM degradability after suspension in the rumen from 12 to 72 h. However, after suspension of GVL from 2 to 12 h, and for BY from 2 to 8 h in the rumen, the values of DM and OM degradability were lower than that of MSP. DM and OM degradability of feed sources can be divided into three groups, depending on their degradability in the rumen. PFL and SBNL had a high rapid rumen degradability, while BCF, MBL, CH, and SNTL had a medium rumen degradability; CRL, BY, BNL, GVL, and MSP had the lowest rumen degradability (Figure 1 and 2). The amounts of DM and OM degraded after 12 h in sacco were more than 50 % of the total which had been found in SBNL, PLF, CH, MBL, SNTL, BCF, CRL, BY  and BNL respectively, except for MSP and GVL.

The amount of DM and OM disappearance and characteristics ranked from the highest to the lowest degradation rate (c) were as follows: CH, BY, MBL, CRL, BCF, SNTL, GVL, PEL, SBNL, BNL, and MSP, respectively. DM and OM degradation rate constants (c) of CH was significantly highest (p<0.01) as compared with the other feed sources, while BY, MBL, CRL, BCF, SNTL, GVL, PFL, SBNL and BNL were degraded to similar extents. The degraded fraction (a) of DM and OM was significantly highest (p<0.01) in SBNL and lowest in GVL (48.7 and 24.1, respectively). The insoluble degradability fractions (b) and the potential degradability (a+b) of DM and OM were highest (P<0.01) in BCF and PFL (53.6, 55.4, 97.9 and 98.1, respectively), as compared to the other feed sources. Similarly, effective degradability of DM and OM at outflow rate of passage of 0.05/h-1, PFL (72.3 and 73.2 respectively) was higher than the other feed sources.
 

Discussion

Chemical composition

The CP content of cassava hay (25.4%) was similar to the earlier value of 23.6%, reported by Wanapat (2003), and 25.5% in whole cassava plant by Moore and Cock (1985) and was within the range reported by Poungchompu et al (2001) (20.6-22.0%). In addition, Vongsamphanh (2003) also reported that the CP level can increase to 27.3% if harvested at 3 months after planting and growing in soils with higher fertility in Lao, PDR. However, the NDF and ADF values were similar to those reported earlier. The levels of condensed tannins in cassava hay were slightly lower than those reported by Wanapat and Poungchompu (2001) (2.2 and 3.8-4.2 %, respectively) but the values for mangosteen peel, guava leaves and sesbania leaves were similar to those previously reported (Getachew et al 2002; Hossain and Becker 2002; Ngamsaeng and Wanapat 2005). The CT contents of cassava foliage increased with maturity. The cassava foliage in this study was younger (2-3 months), as compared to that previously reported (Wanapat and Poungchompu 2001).  

Ruminal environment

The ruminal pH and temperature were not different among different times of incubation. The results were similar to the values reported by Chanjula et al (2003) and Promkot and Wanapat  (2003) in which ruminal pH and temperature ranged from 6.5 to 7.0, and 39 to 41 ºC, respectively. These ranges are considered to be optimal for the microbial digestion of fiber and also for protein (Hoover 1986; Firkins 1996; Wanapat 1990).

In sacco DM and OM degradability of feed

Different roughage digestibility in the rumen could be attributed to their chemical composition, especially CP and NDF contents, which could be more easily attacked by micro-organisms in the rumen (Mahadeevan et al 1980). There is a decrease in the proportion of CP and increase in the concentration of cellulose, hemicelluloses and lignin, which are normally associated with a depression in DM digestibility. The cell wall content and the magnitude and nature of lignification of these cell walls are amongst the most important factors which govern the degradability and the rate of passage of forage. Promkot and Wanapat (2003) reported that palm seed meal is low in protein and high in neutral-detergent fiber (NDF), and was lowest in DM and CP digestibility. PFL had lower NDF and ADF contents, which gave the highest values of DM and OM digestibility.

Preston (1986) reported that the rate of degradation (c) was an important parameter in the assessment of the fermentation in the rumen. The low EDDM and EDOM contents of the feed resources in this study, despite high potentially degradable values, are most likely a result of the low rate degradation observed, suggesting therefore that they could have high fill values hence low intake and animal productivity (Mgheni et al 2001). In addition, in this study the rate of degradation (c) was highest in CH as compared to the other treatments. Therefore, it could result in low gut fill hence higher intake and animal production achieved.

Higher levels of tannins may reduce cell wall digestibility by binding bacterial enzymes and/or forming indigestible complexes with cell wall carbohydrates (Reed et al 1990). As shown, DM and OM degradability of MSP were characterized by a slow rate of degradation, as compared to the other treatments. Digestibility of OM and fiber fractions was lowest for sheep fed A. cyanophylla, the supplement with the highest CT content and soluble phenolics (Reed et al 1990). High levels (5-9 %) of tannins become highly detrimental (Barry 1983) as they reduce digestibility of the fiber in the rumen (Reed et al 1985) by inhibiting the activity of bacteria and anaerobic fungi (Chesson et al 1982). High levels also reduce feed intake (Akin and Rigsby 1985), and levels above 9 % tannins may be lethal to an animal that has no other feed (Kumar 1983). Condensed tannins facilitate the by-pass of protein that might otherwise be lost through microbial deamination in the rumen (Barry et al 1986; Tanner et al 1994). This by-pass is made possible by reactive components of CTs, which complex with soluble proteins, making them insoluble at rumen pH (5.8–6.8) but soluble and released at the more extreme pH conditions found in the abomasum (pH 2.5–3.5) and small intestine (pH 7.5–8.5) (Barry and Manley 1984). This process increases the absorption of essential amino acids in the small intestine (Waghorn et al 1987). In this study, MSP had the highest level of condensed tannins, which resulted in slower DM and OM degradability as compared to the other feed resources (Figures 1 and 2).

It is clear from a consideration of the rumen bag technique that the absolute value of the results depends on the way in which the forage is prepared and the pore size of the material from which the bag is made (Promkot and Wanapat, (2003). In this experiment SBNL had a higher proportion of fine dusty particles, which would easily escape from the bag in the rumen. However, as this technique is gravimetric, the extent and rate of digestion are obtained assuming that dry matter loss equals fermentation, which is not normally the case because considerable substrate is lost from nylon bags (Rodrigues et al 2002). Pearce et al (1987) have found quite different levels of fermentability of the soluble fraction of wheat straw, a fraction which would be lost from the nylon bag or upon filtration and so overestimating digestibility. The considerable DM and OM from feed resources would escape from the rumen degradation and be available for intestinal digestion. These would differ among feed sources and the possibility of an overprotection effect could be further investigated in studies of intestinal digestibility using the mobile bag technique (De Boer et al 1987).  
 

Conclusions and recommendations

Acknowledgements 

The authors would like to express their most sincere thanks to all who have assisted and supported the research in this study, particularly the MEKARN project financed by SIDA-SAREC, and the Tropical Feed Resources Research and Development Center (TROFEC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand, for their kind facilitation in the use of the equipment, laboratory and analyses.
 

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