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Comparison of digestibility and metabolizable energy between nilegrass and pangola grass

Jeng-Bin Lin2, Mei-Chu Lee3, Shyh-Rong Chang 4 and F.H. Hsu5

1Contribution paper no.1228 from Livestock Research Institute, Council of Agriculture, Executive Yuan, Taiwan.
2
Livestock Research Institute, Council of Agriculture, Executive Yuan, Taiwan, www.tlri.gov.tw Email jblin@mail.tlri.gov.tw
3
Diwan College of Management, Taiwan, www.dwu.edu.tw Email mclee@mail.dwu.edu.tw
4
Livestock Research Institute, Council of Agriculture, Executive Yuan, Taiwan, www.tlri.gov.tw
Email srchang@mail.tlri.gov.tw
5
Livestock Research Institute, Council of Agriculture, Executive Yuan, Taiwan, www.tlri.gov.tw Email Fhhsu@mail.tlri.gov.tw

Abstract

Nilegrass (Acrocras macrum Stapf) and pangola grass(Digitaria decumbens Stent)are perennial C3 and C4 forage grasses, respectively, that produce high forage yield and quality in Taiwan. The objectives of this study were to measure aspects of the quality (metabolizable energy [ME], acid detergent fibre [ADF], neutral detergent fibre [NDF], crude protein [CP]), and observe changes in cell wall digestion, of nilegrass and pangola grass sampled after 4, 6, 8 and 10 weeks of regrowth in spring and fall crops. The contents of ADF and NDF of nilegrass were lower than those of pangola grass in both spring and fall crops. The 4-week crude protein content of both nilegrass and pangola grass were higher than those of the 6, 8 and 10-week growth stages. The ME content of the 6 and 8-week cuts of nilegrass were higher than those of 4 and 10-week cuts in both seasons. After 72 hours in the rumen, both stem and leaf of nilegrass up to 8 weeks growth stage had been digested by rumen micro organisms. For comparable samples of pangola grass the leaf had been digested while the stem tissue was mostly undegraded. The results showed that nilegrass has a higher quality and is more easily digested than pangola grass when grown under the same conditions and is a potential replacement for pangola grass in Taiwan.

Media summary

Both nilegrass and pangolagrass had the highest metabolizable energy at 6 week growth stage. Nilegrass was more easily digested and had better forage quality than pangola grass.

Key words

Nilegrass (Acrocras macrum Stapf), Pangola grass(Digitaria decumbens Stent), digestibility, anatomy.

Introduction

Nilegrass (Acroceras macrum Stapf) is a perennial C3 forage grass (Oliveira et al., 1973) and has been proposed by Shaug et al., (1999) as an alternative to pangola grass (Digitaria decumbens) for Taiwan. A study to compare the growth and forage quality of these grasses has been reported by Hsu et al. (2004). Plant samples from that study were used to develop a more comprehensive understanding of the morphological characteristics and quality attributes of these grasses.

Methods

Chemical contents and metabolizable energy: The contents of metabolizable energy (ME), ether extract (EE) , nitrogen-free extract (NFE), 24hr gas production (Gb24), crude protein (CP), acid detergent fibre (ADF) and neutral detergent fibre (NDF) were determined following the methods presented by Close and Menke (1986) and Olsen and Dean (1965) for oven-dried samples of Nilegrass cv. Taishi No. 1 and pangola grass line A254. Samples were taken from cuts at 4, 6, 8 and 10 week intervals in fall (October) and spring (April) in the second year of the experiment, with four replicates per grass per cutting interval.

Digestibility: Fresh samples of Nilegrass and pangola grass cut at 4, 6, 8 and 10 week intervals were collected at the spring (April) harvest. Fresh samples were enclosed in nylon bags (20 micron mesh) and suspended in the rumen of a cannulated dairy cow. The bags were removed from the rumen after 24, 48 and 72 hours for observation of changes in plant anatomy. Sections were obtained using the paraffin-cut technique reported by Lin and Yeh (1996).

Results

Chemical contents and metabolizable energy: The contents of ADF and NDF in nilegrass were lower than those of pangola grass in both spring and fall crops (Table 1). For both grasses and in both seasons, the highest ME was achieved at the 6 and 8 week growth stages (Table 2, 3).

Effects of different growth stages on digestibility of nilegrass and pangola grass

After 72 hours in the rumen, both stem and leaf of nilegrass had been mostly digested for the 4, 6 and 8 week cuts, while only the leaves of pangola grass cut at 4 and 6 weeks were easily digested (Fig. 1 A, B, C and D). Both stem and leaf of pangola grass cut at 8 and 10 weeks were not easily digested (Fig.1 F and H). The anatomical observations of plant tissues digested by rumen microorganisms, showed that most of the cell wall structure of nilegrass was degraded 72 hours after digesting in rumen of dairy cow. However, the cell wall of pangola grass was not completely degraded during the same period (Fig. 1).

Conclusion

In almost every measure of in vitro quality nilegrass was superior to pangola grass. The complete rumen digestion of both leaf and stem for samples of nilegrass cut up to 8-week intervals was in shape contrast to that for pangola grass.

References

Bourquin, LD and Fahey GC (1994). Ruminal digestion and glycosyl linkage patterns of cell wall components from leaf and stem fractions of alfalfa, orchard -grass, and wheat straw. J. Anim. Sci.72, 1362-1374.

Cassab GI and Varner JE (1987). Immunocy tolocalization of extensin in developing soybean seed coats by immunopgold-silver staining and by tissue priting on nitrocellulose paper. J. Cell Biol. 105, 2581-2588.

Close W and Menke KH (1986). Selected topics in animal nutrition, pp. 26-66. 2nd Edition, Animal Nutrition. University of Huhenelm, Germany.

Grabber JH, Jung GA and Hill RR (1991). Chemical composition of parenchyma and sclerenchyma cell walls Isolated from orchardgrass and switchgrass. Crop. Sci. 31, 1058-1065.

Jung HG. and Deetz DA (1993). Cell wall lignification and degradability, pp. 315-346. In Jung, H. G., Buxton, D. R., Hatfield, R. D., Ralph, J. (ed) Forage cell wall structure and digestibility. ASA, Inc., SSSA, Inc., Madison, Wisconsin, USA.

Lee CF, Chen CP and Shiao TF (1999). Feeding values of pangolagrass and bermudagrass hay for lactating dairy cows. Taiwan Livestock Res.32, 353-364.

Lin JB and Yeh MS (1996). Development of embryo and endosperm derived from selfing and interspecific hybridization between Glycine max x G.. tomentella. J. Agric. Associ. China 173, 17-27.

Oliveira BAD, Faria PR, Souto SM, Carneiro AM, Dobereiner J and Aronovich S (1973) Identification of tropical grasses with the C4 pathway of photosynthesis from leaf anatomy. Pesquisa Agrope Cuaria Brasileira, Agronomia 8, 267-271.

Olsen SR and Dean LA (1965). Phosphorus, pp. 1035-1048. In Black, “C. A. (ed) Method of soil analysis” part 2. American Society of Agronomy Inc., Madison, Wisconsin.

Shaug SP, Lo KD and Lin JB (1999). Effects of cutting stages on forage yield and quality of nilegrass. Taiwan Livestock Res. 32, 219-226.

Smith LW, Goering HK and Gordon CH (1972). Relationships of forage compositions with rates of cell wall digestion and undigestibitity of cell walls. J. Dairy Sci. 55, 1140-1147.

Wilson JR (1993) Organization of forage plant tissues, pp.1-27. In. Jung, H. G., Buxton, D. R., Hatfield, R. D., Ralph, J. (ed) Forage cell wall structure and digestibility. ASA, Inc., SSSA, Inc., Madison, Wisconsin, USA.

Table 1. Comparision of the chemical contents between nilegrass and pangola grass at different growth stages in spring and fall crops (%).

Growth stage week

 

Spring

Fall

Species

CP

ADF

NDF

CP

ADF

NDF

4

Nilegrass

12.35a*

35.14b

59.23b

11.96a*

34.41b

61.12b

Pangolagrass

10.48a

39.67a

63.09a

9.39b

39.08a

70.89a

6

Nilegrass

10.58a

36.29b

59.81b

9.33a

35.94b

66.76b

Pangolagrass

9.88a

39.09a

59.83b

7.26b

38.47a

69.96a

8

Nilegrass

6.76a

37.09b

56.72b

8.67a

36.72b

68.96b

Pangolagrass

6.64a

39.48a

68.13a

5.92b

41.50a

73.46a

10

Nilegrass

5.20a

38.04b

59.31b

7.15a

38.13b

69.08b

Pangolagrass

5.15a

39.22a

64.99a

5.68a

42.13a

72.82a

*Means within columns and at the same growth stage with the same letter are not significantly different (P<0.05).

Table 2. Effects of different growth stages on the chemical contents and metabolizable energy of nilegrass and pangola grass in spring crop.

Growth stage

Nilegrass

Pangolagrass

EE@

NFE

Gb24

ME

EE

NFE

Gb24

ME

week

%

%

My/200mg

Mcal/Kg

%

%

My/200mg

Mcal/Kg

4

2.53c*

61.5a

40.3a

9.79c

2.18a

64.7b

40.1a

8.97c

6

1.56b

59.3b

42.2b

10.08a

1.98b

63.3d

40.4ab

9.96a

8

1.77a

62.0a

41.4ab

9.92b

1.41c

65.7b

41.7b

9.20b

10

1.83a

65.9c

41.0ab

9.71d

1.42c

66.5a

39.6a

9.00c

SEM

0.036

0.422

0.570

0.017

0.027

0.410

0.530

0.020

*Means with the same letter in the same column are not significantly different (P<0.05).

Table 3. Effects of different growth stages on the chemical contents and metabolizable energy of nilegrass and pangola grass in fall crop.

Growth stage

Nilegrass

Pangolagrass

EE@

NFE

Gb24

ME

EE

NFE

Gb24

ME

week

%

%

My/200mg

Mcal/Kg

%

%

My/200mg

Mcal/Kg

4

1.42a*

63.2c

42.8a

9.95c

1.99a

61.9a

38.3a

8.01c

6

1.57b

65.6b

49.5b

10.97a

2.06 b

62.1a

44.3b

9.01b

8

1.61b

63.3c

45.5c

10.22b

2.17c

67.6b

42.8b

9.59a

10

1.18c

70.0a

42.7a

9.61d

2.10 d

67.3b

36.5c

8.33d

SEM

0.021

0.400

0.516

0.021

0.012

0.379

0.521

0.019

*Means with the same letter in the same column are not significantly different (P<0.05).

Figure 1. The cell walls of nilegrass (left) and pangola grass (right) internodes at 4 (A, B), 6 (C, D), 8(E, F) and 10 (G, H) weeks after cutting digested by rumen micro-organisms in the rumen for 72 hours observed by transverse section, respectively. (x 100).

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