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Poster 7.2: Development of ensiling technology for smallholder cattle owners in Zimbabwe - M. Titterton, O. Mhere, T. Kipnis, G. Ashbell, Z.G. Weinberg and B.V. Maasdorp


M. Titterton
Department of Animal Science
University of Zimbabwe
P.O. Box MP 167
Mt. Pleasant, Harare, Zimbabwe
E-mail: [email protected]

O. Mhere
Matopos Research Station
P.B. K 5137
Bulawayo, Zimbabwe



T. Kipnis
Institute of Field and Garden Crops
The Volcani Centre
Bet Dagan, Israel

G. Ashbell and Z.G. Weinberg
Forage Preservation and By-Products Research Unit
The Volcani Centre
Bet Dagan, Israel

B.V. Maasdorp
Department of Crop Science
University of Zimbabwe
Harare, Zimbabwe.

INTRODUCTION

Many smallholder livestock owners in semi-arid areas of Zimbabwe would like to start commercial dairy farming. However, it is not feasible unless one of the major constraints to productivity in their cows is overcome, namely the very poor availability of forage for feed in the dry season. Rain-fed forages are grown to feed in the wet season, but conservation as high quality hay is difficult due to leaching and rotting of the harvested material. Ensilage of forage, can, if done correctly, maintain productivity throughout the dry season. However, storage in a pit or bunker requires expensive machinery for chopping and compaction. Experience has shown, furthermore, that pit silage, through frequent exposure, suffers large spoilage losses. The authors examined the use of low-cost technology to produce silage from semi-arid adapted crops in a small-scale silo, in this case, an easily portable plastic bag. In order to produce a high quality silage, a mix was used of either sweet forage sorghum or Napier grass (Pennisetum purpureum) with a legume, dolichos bean (Lablab purpureus).

METHODS

The crops

Two forage crops were used: sweet forage sorghum (FS) (cv. Sugargraze) and Pennisetum (PS) (cv. SDBN3b) and a legume: dolichos bean (DB).

Ensilage was carried out in each plastic bag with either one of the forage crops mixed on a 50:50 by fresh weight basis with legume to produce 8 kg total fresh weight, or with one of the forage crops alone, also at 8 kg fresh weight. The crop materials ensiled were therefore: FS+DB; FS; PS+DB; PS.

Treatments

Chopping was done in one of two ways: either with the use of a petrol-motor-driven chaffer, producing a chop with an average length of about 2.5 cm, or manually, using pangas, producing a chop with an average length of about 7.5 cm.

Compression was done in one of two ways: either with the use of a manual tobacco press, which comprises a manually driven screw pressing on to a metal plate sitting on the bag of crop material, or by leaning as hard as possible on the bag, using hands to remove as much air as possible.

The silos

The silos were recycled plastic bags used for garbage and of a size that could hold up to 50 kg of material. Upon filling and evacuating the bags of air, they were tightly tied with twine and stored in a closed storeroom.

RESULTS

The fermentation quality of all silages was good, showing pH less than 5.0, ammonia to total nitrogen ratio of less than 10%, DM loss of less than 20%, lactic acid content ranging from 2 to 7%, acetic acid content ranging from 1-2.5% and butyric acid ranging from 0 to 1.8% (Table 1). Visual and sensory evaluation of the silages also indicated good results. However, while treatments of chopping method and compression method had no effect on fermentation, crop type showed significant differences in pH, NH3-N ratio, lactic and volatile fatty acids. Sorghum silages had better fermentation quality than Pennisetum silages, with or without legume. This was probably due to the high levels at ensiling of WSC in sweet forage sorghum (averaging 220 g/kg) compared with Pennisetum (about 75 g/kg).

Nutrition quality of silages showed that addition of legumes produced silage with significantly higher CP content (range: 13 to 14%) compared to sorghum and Pennisetum, and improved digestibility (range 52 to 56%) compared to Pennisetum alone (Table 2).

Table 1. Fermentation quality of different forage crops ensiled after differing treatments

Crop material

DM loss (%)

pH

NH3:N (%)

Lactic acid (%)

Butyric acid (%)

Acetic acid (%)

Ethanol (%)

All sorghum (FS)

9.36

3.70

4.07

5.63

0.05

2.04

2.12

All Pennisetum (PS)

18.00

4.30

4.99

4.25

1.17

1.89

0.97

FS+DB

12.30

3.78

4.37

6.55

0.30

2.34

0.72

FS only

7.15

3.63

3.85

4.76

0.07

1.74

2.81

PS+DB

16.46

4.25

5.26

2.32

1.70

2.42

0.68

PS only

19.79

4.40

4.71

1.92

0.57

1.34

0.72

All materials fine-chopped

12.43

3.84

4.40

4.65

0.50

2.12

1.22

All materials coarse-chopped

15.31

4.20

4.70

4.62

0.72

1.80

1.60

All materials tobacco-pressed

15.04

4.05

4.50

4.18

0.50

1.74

1.38

All materials hand pressed

12.88

4.01

5.20

3.59

0.67

2.13

1.45

Table 2. Nutritional quality of silages made from different crops

Crop

DM (%)

Digestibility (g/kg)

CP (g/kg)

PS

30.55

471.05

66.50

SE

0.41

10.76

1.66

PS+DB

27.50

523.17

133.23

SE

0.76

8.92

9.22

FS

32.80

544.15

64.98

SE

1.34

16.20

7.90

FS+DB

30.10

536.29

144.88

SE

0.94

11.55

12.13

CONCLUSION

Forages and legumes adapted to semi-arid conditions can be mixed and ensiled successfully in plastic bags with only manual chopping and compression. On-farm trials on four farms have subsequently shown the same success.

Forty farmers are currently participating in farmer-controlled, researcher-monitored trials in Gulathi communal area in the semi-arid region of Matabeleland in Zimbabwe.


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