Management and Utilisation of Mulberry for Forage in Japan

1. Productivity of mulberry-pasture association system and nutritive value of mulberry

N. Kitahara, S. Shibata and T. Nishida

Department of Grassland Management, National Grassland Research Institute, Japan


Introduction

The pastures in Japan are mainly composed of temperate species such as orchard grass, tall fescue, timothy, white clover, etc., which are native of the Asia Minor/South Europe region. The climatic conditions of Japan, unlike Europe, are not always suited to the growth of these temperate grasses and pastures based on them create some problems. One of the most serious concerns is seasonal forage production, remarkably uneven compared to Europe. Summer forage production in particular decreases to an extreme low due to high summer temperatures. Consequently, there is insufficient forage for grazing animals from summer to autumn in general.

On the other hand mulberry (Morus sp.) was once widely planted for sericulture purposes in Japan. But since the industry has been on the decline for the last few decades, there are a lot of abandoned mulberry farms all over the country. There is an opportunity to utilise those farms for other purposes, especially for mixed pastures.

In view of the above situation, the authors started research on the use of mulberry in temperate grass pastures in order to reduce the summer-autumn forage shortage and to find alternative uses to the abandoned sericulture farms.

The productivity of mulberry-pasture mixtures and the nutritive value of mulberry leaves and shoots are presented in this paper.


Materials and methods

This trial was carried out from 1997 to 1999 on a volcanic ash soil at the National Grassland Research Institute (Nishinasuno, Tochigi) located at 36o 55' latitude north, 139o 55' longitude east and at 320m above sea level.

The mulberry varieties were Shinkenmochi (M. bombycis) and Aobanezumi (M. alba). Mulberry-pasture association was established as follows: Mulberry was planted at a spacing of 3m-between rows and 0.7m between plants (4,762 plants/ha) in spring of 1996. A mixture of five temperate species: orchard grass, tall fescue, perennial ryegrass, red top and white clover, was sown among mulberries rows the following autumn. The association was compared with a sward of those species and with mulberry in pure stand. The design was a randomised complete block with three replications. In all three treatments plot size was 84m2(7m x12m). Four mulberry rows, two of each mulberry variety, were used in both the association and the pure stand. Harvest times were for 1997: 30 April, 10 June, 11 August, 3 October and 10 November; for 1998: 30 April, 9 June, 10 August, 5 October and 5 November; and for 1999: 30 April, 11 June, 9 August, 6 October and 2 November. As mulberry began sprouting at the end of April and stopped shooting about the middle of October, it was harvested three times during from June to October. Mulberry plants were trimmed at 1m high when they were planted and the new shoots harvested by cutting approximately 1cm above old shoots. Swards were cut at 5cm above ground. Fertiliser was applied at the rate of 68kg/ha/year of each N, P and K.

Forage production and nutritive value was determined in the three treatments. Forage samples from September were used to determine crude protein, Acid Detergent Fibre (ADF), Neutral Detergent Fibre (NDF), ash, Organic cellular Content (OCC), Organic Cell Wall (OCW), High Digestible Fibre Fraction (Oa), Low Digestible Fibre Fraction (Ob), Ca, P, Mg, and K. The K/(Ca+Mg) ratio was calculated.


Results and Discussion

Productivity of mulberry-pasture association

Table 1 shows the results of the DM production of three treatments from 1997 to 1999.


Table 1.
The productivity of mulberry and temperate sward in the three treatments (kg of DM/10a)

1997

30/04

10/06

11/08

03/10

10/11

Total

Association:            
Sward

531

394

223

162

69

1,380

  Mulberry:            
    Leaves  

83

86

71

 

239

    Shoots  

26

38

23

 

86

  Subtotal  

109

124

94

 

325

Total

531

503a

347a

256a

69

1,706a

             
Sward

588

434a

232b

203a

57

1,514a

             
Mulberry pure stand            
  Leaves  

111

152

86

 

349

  Shoots  

48

84

24

 

156

Total  

160b

236b

110b

 

505b

             
1998

30/04

09/06

10/08

05/10

05/11

Total

Association:            
Sward

228

213

192

172

36

841

  Mulberry:            
    Leaves  

43

72

58

 

173

    Shoots  

14

21

16

 

51

  Subtotal  

57

93

74

 

224

Total

228

271Aa

285Aa

246Aa

36

1,065a

             
Sward

181

203Bab

196Bab

183Ba

44

807b

             
Mulberry pure stand:            
  Leaves  

90

126

51

 

267

  Shoots  

32

50

15

 

97

Total  

122Cb

177Bb

66Cb

 

364c

             
1999

30/04

11/06

09/08

06/10

02/11

Total

Association:            
Sward

128

286

183

85

39

722

  Mulberry:            
    Leaves  

31

84

101

 

216

    Shoots  

7

34

35

 

75

  Subtotal  

38

118

136

 

291

Total

128

324Aa

301A

221Aa

39

1,013a

             
Sward

121

194Bab

206B

93Bb

32

647b

             
Mulberry pure stand            
  Leaves  

63

111

94

 

268

  Shoots  

18

39

24

 

82

Total  

82Cb

150B

118Bab

 

350c

Statistical comparisons were among treatments within same year. Values with the same letter do not differ (A<0.05, a<0.01).


Since, mulberry is a very palatable forage for cattle (Kitahara, 1999) and both new shoots and leaves are well consumed, therefore, mulberry production data shown also includes shoots.

Excellent yearly DM production of mulberry-pasture association was obtained in all three years. DM production of the mulberry-pasture mix was 13%, 32% and 57% above the grass alone in 1997, 1998 and 1999, respectively, due to the contribution of mulberry. In general, grassland productivity in Japan decreases with time. This was the case in this experiment for the temperate sward, which yield remarkably decreased from 1997 to 1999. On the contrary, the productivity of the mulberry-pasture association did not drop. This interesting result seems to be due to protective shading effect of mulberry on the grass sward. Seasonal forage production in the mulberry-pasture association was considerably well distributed compared with other treatments. Consequently, the mulberry-pasture association can be an alternative to solve the problem of the summer-autumn forage deficit in Japan.

None of the mulberry plants were killed by the three-times per year defoliation during the experiment


Nutritive value of mulberry leaves and shoots

Table 2 shows the nutritive value of mulberry leaves and shoots compared with temperate sward and Table 3 the comparative mineral content.


Table 2.
The nutritive value of mulberry leaves and shoots compared with temperate species

 

CP

ADF

NDF

Ash

OCC

OCW

Oa

Ob

Mulberry                
Leaves

25.8

21.0

31.6

11.8

51.8

36.5

10.0

26.5

Shoots

12.1

45.6

60.5

8.8

32.8

58.5

9.4

49.1

Sward

20.4

27.9

53.5

11.6

34.0

54.4

12.3

42.1

Harvesting month: September 1997. The mulberry variety = Shinkenmochi.

 

Table 3. Mineral content of mulberry leaves and shoots compared with the temperate sward

 

Ca

P

Mg

K

K/(Ca+Mg)

Mulberry          
Leaves

2.98

0.44

0.43

2.84

0.41

Shoots

1.01

0.37

0.36

3.78

1.21

Sward

0.28

0.37

0.30

4.99

3.29

Harvesting month: September 1997. The variety of mulberry is Shinkenmochi.


The characteristics of the nutritive component of mulberry were as follows: The contents of crude protein and OCC in the leaves were high, but those of ADF and NDF were low compared with the sward. Mulberry leaves were more digestible than the sward. On the other hand, the contents of ADF, NDF and OCW in the mulberry shoots were relatively high. This shows that mulberry shoots might have low digestibility. As the ratio of DM production of mulberry leaves to the shoots is 3:1, whole nutritional quality of the mulberry foliage, likely to be consumed by cattle, seems to be high.

With regard to mineral content, Ca, P and Mg in mulberry leaves were higher than in the sward. K content and K/(Ca+Mg) in mulberry leaves were markedly lower than in grass.

Grass tetany is one of the important diseases during grazing season. The disease has generally been related to low Mg, high K, and high K/(Ca+Mg) equivalent ratios in the forage (Karlen et al., 1978). Gross (1973) reported that generally accepted values of less than 0.2% Mg, more than 2.5% K, and K/(Ca+Mg) equivalent ratios greater than 2.2 could cause forage to be tetany prone. It is apparent that mulberry has the good mineral component to prevent grass tetany.


Conclusion

This study has demonstrated that the productivity of mulberry-pasture association is very high with even seasonal distribution compared with a sward of temperate species. The nutritive value of mulberry leaves was very high, and moreover, mineral content was excellent. Mulberry-pasture system seems to be a promising grazing method. But it is logical that further studies on this system be conducted since there are still many unsolved practical problems.


References

Gross, C.F. 1973. Managing magnesium-deficient soils to prevent grass tetany. Proc. 28th Annu. Meeting Soil Conserv. Soc. Am., Hot Springs, Ark., p88-92.

Karlen, D.L.; Ellis,R. Jr.; Whitney, D.A. and Grunes, D. L. 1978. Influence of soil moisture and plant cultivar on cation uptake by wheat with respect to grass tetany. Agronomy Journal 70:919-921.

Kitahara, N. 1999. Some cases of available roughage in the riverbank and abandoned arable land. Dairy Journal 4:22-24.