Livestock Research for Rural Development 25 (4) 2013 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Cost-effective preservation technique of green fodder and its impact on quality of silage

Z H Khandaker and M J Uddin*

Department of Animal Nutrition, Bangladesh Agricultural University, Mymensingh
* Department of Animal Nutrition, Sylhet Agricultural University, Sylhet, BANGLADESH
jasimsau@gmail.com

Abstract

Four types of silos (pit, bamboo mat, synthetic nylon bag and concrete silo) were prepared to investigate the cost effective preservation method of green fodder and its impact on quality of silage.

The physical properties (color, fermented aroma and acidic taste) were better  in pit and concrete types while moderate was bamboo mat type except synthetic nylon bag case with a watery taste and moderate fermentative  odor. The lowest (3.99) pH was found in concrete type. The temperature at 1ʺ, 6ʺ, 12ʺ and onward vertically depth was found from 96-820F. The synthetic nylon bag lost a bit higher moisture, increased the protein loss and increased the fiber. The pit type conserved more CP in comparison to others. Digestibility of DM and other nutrients (CP, CF and NFE) were found higher (p<0.01) for Synthetic poly bag category followed by bamboo mat and concrete type. Conservation techniques have the great impact on preservation of nutrients. The most economic and effective method was found the silo pit (0.37 Tk/kg) followed by bamboo mat (0.62 Tk/kg), synthetic poly bag (0.75 Tk/kg) and concrete type (7.15 Tk/kg). It can be suggested that the effluent farmers can use the concrete type for long lasting fermentative reserve but the temporary system (pit) might be the easy and economic means of poor farmer.

Key words: conservation, fermented product, green fodder


Introduction

It is customary that forages are consumed by domestic animals either in grazing land or stall seasonally. However, it is possible to serve the animals round the year conserving the forage properly. The availability of green grass is mostly seasonal, only in monsoon, when plant growth is high. The green grass is highly deficient in dry season and during flood. The seasonal deficiency can considerably be reduced by conserving the surplus forage during high fodder availability period. The preservation of fodder by ensiling can be done using fresh or preferably wilted (Catchpoole and Henzell 1971) forage. Silage making offers to secure feeds of high production, preservation and storage as well as also later use in the drought period of relative feed shortage (Koon 1993). It has been reported that a positive use for silage in the tropic is as a means of increasing land productivity (Cowan et al 1999).  

Preservation of fodder is achieved under anaerobic condition when microbes use the fermentable sugars of fodder to produce organic acids, mainly lactic acid (Bolsen et al 1996). Several techniques have been developed to preserved surplus fodder for future use. A gunny-bag ensiling technique has been evolved for small holder farmers in western Kenya by Otieno et al (1999). Chin and Idris (1999) adopted low cost silage making activities in Malaysia since 1960s. Lane (1999) summarized the development of Little Bag Silage (LBS) in Pakistan and Nepal during 1988-1992 with strong, high density plastic poly bag. Very little works (Khaleduzzman et al 2011) have been done in Bangladesh to look upon the low cost and quality forage preservation technique. However, there is a need to develop silage making method under local conditions giving particular emphasis for smallholders in Bangladesh. Keeping this view, the present experiment was conducted to develop cost effective technique and its effect on value of silage.


Materials and methods

This work was done at Shahjalal field laboratory, department of Animal Nutrition, Bangladesh Agricultural University, Mymensingh, Bangladesh from Februrary to December 2012.  

Preparation for ensiling 

Four types of silos (pit, bamboo mat, synthetic nylon bag and concrete tower silo) were prepared. The pit type silo (3.5 ft X 2.0 ft X 1.0 ft) was prepared making hole in the earth wrapped with polythene sheet. Bamboo mat silo was manufactured with mat of bamboo, making cylindrical shape (12 ft diameter and 5 ft depth) keeping open upside and sealed the bottom with another mat wrapped with polythene sheet. The synthetic nylon bags (40 kg capacity) were purchased from the local market and used as individual sac by closing the mouth.  The concrete silo which was prepared earlier by using sand, cement and bricks (Khaleduzzman 2011) was used.

 Photo 1: Ensiled forage in the silos

The harvested maize fodder of 75 days maturity was chopped (3 cm) using a locally manufactured grass chopper and wilted under sunshine for several hours to attain desirable DM level (30 – 35%). The pit, bamboo mat and concrete silos were filled by wilted fodder with continuous compression and trampling. Finally, the upper surface was wrapped with polythene and sealed to make it totally air tied by putting bricks on over the sealing materials.  In other hand, all the synthetic fiber bags were filled accordingly with high compression and closed the mouth tiding with rope. All the sacs were stacked wrapping together with polythene sheet and kept for anaerobic fermentation up to 4 weeks. 

Evaluation of silage 

After 4 weeks of ensiling the silos were opened and the silages were visually assessed. The physical parameters (color, odor, mould infestation) were recoded. Besides, temperature of the fermented product in different sorts of depth i.e upper surface (0.5˝-1˝ depth), 6 inches beneath, 12 inches depth and onwards were observed and recorded using the compost thermometer (Holland and Kezar 1995). The pH of the silage from different silo pits were measured. To determine the pH of silage, 30 g of representative sample was taken in a beaker and 200 ml of distilled water was added and mixed well (Khaleduzzman 2011). After well mixing, the silage extract was filtered and pH of the silage sample was determined using a laboratory pH-mV meter (inoLab, Germany). A representative silage sample from pit, bamboo mat, synthetic poly bag and concrete silo were taken into labeled poly bag for chemical analysis (DM, CP, CF, NFE, EE, TA) using AOAC (2000) method. During sampling, the silages were visually assessed and compared the silages of different silo types in terms of physical properties (Otieno et al 1999). The cost for the preparation of different silos were calculated considering the cost for materials, labour and transport as per market price of the materials in July 2012 and cost of concrete silo was taken in the price of 2009 (Khaleduzzaman 2011). 

Digestibility trial 

A biological trial (digestibility) was done to determine the nutritive value of different types of silage. Twelve growing indigenous bull calves of around 1year age with 100kg live weight were selected and divided in to 4 groups having 3 animals in each. The animals were offered the 4 types of silage (Pit, Bamboo mat, Synthetic poly bag and concrete) considering 14 days adjustment period followed by 5 days collection period. At the onset of the trial, ad-libitum silage was provided daily at 7.0 am and 4 pm. Silage intake and faeces voided were recorded and the representative samples of silage and  faeces were stored for further analysis following method of AOAC (2000). For data analysis Statistical Analysis System (SAS 9.1.3) was followed.


Results and discussion

Physical and chemical evaluation of silages 

Morphological characters of 4 types of silage are shown in Table 1. The upper surface color was a bit fate green with a black yellow on account of air contamination that reflected some mould infestation especially in synthetic poly bag and bamboo mat type (Photograph 2). Meanwhile in 6ʺ deeper and onwards, the standard color (green yellowish) was found in all types. Likewise the fermented aroma and acidic taste were observed in all types except synthetic poly bag case with a watery taste and moderate fermentative odor. The tabulated data reflect the index of high quality silage apart from synthetic poly bag bears the good quality may be due to excessive penetration of air. However, well protection with continuous monitoring may reduce the nutritive loss of ensiled period. Khaleduzzaman 2011 conducted an experiment and found yellow green (Yg), brown green (Bg), and blackish (B) color and for odor lactic acid (La), lactic + acidic (L+A) and butyric (Bu). The lowest pH was found in concrete type followed by pit and bamboo mat type. Khaleduzzman (2011) stated the silage pH value of bamboo mat fenced chamber (BFC), Synthetic fiber bag (SFC), Concrete Tower silo (CTS) were 4.11, 4.92 and 4.62 respectively. Otieno et al (1999) also observed the pH with in 3.0-4.0 for good silage using gunny bag ensiling technique that support the present findings. High acidic condition (lactic acid) maintains the non-fermentative condition for long life with a real fermentative taste and aroma.  

The microbial fermentation fortifying agent (temperature) was observed vertically (Table 2) at different levels (1ʺ surface, 6ʺ depth, 12ʺ and onwards) and was found 96 - 820F. It is clear that low temperature (≤950F) may stop the activity of proteolytic and acid forming bacteria that made it conceal. It was also observed that temperature and pH had the positive relationship both downwards and upwards. Bamboo mat silage maintained the lowest temperature followed by pit, concrete and synthetic poly bag type (table 2). Holland and Kezar (1995) stated that aerobic fermentation, temperature increases from 69 to 900F (6-6.5 pH) then in hetero fermentative fermentation temperature decreases from 900F to 700F with reducing pH up to 5.0 and thereafter homo-fermentative fermentation temperature. Stabilizes near 65 to 700F with 4.5 to 4.0 pH, the stable condition that match with this outcome. However, the temperature for all categories of silos were lower than ambient temperature. Elevated temperature above the ambient temperature may be due to oxidative respiration by mould & fungi and feed instability. Temperature more than 1200F is the reflection of aerobic oxidation potential for heat damage and  also mould growth can often result in excess of 1000F (Van Saun and Heinrichs 2008).

Table 1. The physical characters and pH of silages

Parameters

silage type

Pit

Bamboo mat

Synthetic poly bag

Concrete

Surface color

Greenish yellow

Greenish yellow

Blackish yellow

Greenish yellow

6̋̋ beneath and onward color

Green yellowish

Green yellowish

Greenish yellow

Green yellowish

Odor/aroma

Fermented

Fermented

Moderate

Fermented

Taste

Acidic

Acidic

Watery

Acidic

Mould infestation

No

Very negligible

More in surfaces

No

pH

4.04

4.07

7.49

3.99


Table 2. Temperature (0F) at different layer of silages

Level of depth

Temperature(0F)

Pit

Bamboo mat

Synthetic poly bag

Concrete

Surface

95.5

96.5

96

95

6ʺ beneath

94

92

95

94

12ʺ and onward beneath

83

82

85

84


High moisture silages are unstable with respect to pH and a wide range is found (Rotz 1995). High pH at high water content is associated with proteolysis and low pH with lactic acid production (Holland and Kezar 1995).  

In high DM silage pH is a less useful criterion of quality since deficiency of water restricts fermentation and acid production that causes a negative association between water content and pH over the high DM range.

Photo 2: Four types of silage

Conservation techniques have the great impact in preservation of nutrients. Dry matter content of silage (Table 3) from concrete, pit and bamboo mat contained lower (p<0.001) DM  compared with synthetic poly bag type. The synthetic polybag lost a bit higher moisture, increased the protein loss and increased the fiber. The pit type conserved more CP in comparison to others even though concrete type may be due to appropriate reduction of air by trampling with big outer surface that was absent in others. Degeneration of protein is the sign of worse quality increase the feeding cost subject to addition of protein supplementation.  

 Silage fermentation quality is a qualitative term describing the extent to which the silage has been preserved by the desired lactic acid fermentation. Lactic acid is the dominant fermentation product maintains the minimal breakdown or degradation of protein. Poorly preserved silage has poor fermentation quality; unpalatable to stock and interrupt the intake. It also likely to suffer excessive degradation of protein, resulting in poor utilization of the silage nitrogen by animals. Pilipaviciu et al (2003) reported 34 % DM, 7.8% CP and 19% CF in maize silage (concrete). 

Table 3. Proximate component of different silages

Parameters

(%)

Types of silage

SEM

P

Pit

Bamboo mat

Syn. nylon bag

Concrete

DM

42.4b

41.3c

45.0a

34.5d

0.01

<0.01

CP

6.73a

5.88b

5.92b

6.05b

0.18

<0.01

CF

30.1ab

30.4a

30.4a

29.9b

0.14

<0.01

NFE

55.0a

53.4b

52.2b

50.4c

0.44

<0.01

EE

0.64c

0.88b

0.23d

1.64a

0.04

<0.01

TA

7.55c

9.39b

11.3a

12.0a

0.29

<0.01

 DM: dry matter; CP: crude protein; CF: crude fiber; NFE: nitrogen free extract; EE: ether extract; TA: total ash.

a,b,c Means in the same columns for each parameter with different superscript are different at P<0.01

SEM: standard error of the means.

Intake and nutrient digestibility of silage 

Dry matter intake was higher  in synthetic poly bag type followed by pit and bamboo mat group whilst the concrete type was in the lowest position . Addah et al. (2011) stated that the average DMI of corn was 6.88 kg/d. Wilkins et al (1978) stated that the intake was reduced in silages having high NH3 –N and VFAs (Ruiz et al 1992). Depression in intake was associated with de-carboxilation with de-amination (Barry et al 1978). Khaleduzzman (2011) stated that there was no significantly difference intake among silages of different categories eventhough in Napier silage due to low pH and high NH3 –N of silage than that of fresh grass.   Coefficient of digestibility of DM silage and other nutrients (CP, CF and NFE) were found higher (p<0.01) for Synthetic nylon bag category (Table 4). Significant improvement in intake and digestibility were may be owing to optimum fermentation.

Khaleduzzman (2011), Sarwar and Hasan (2001), Sarwar et al (2003), Yahaya et al (2004) reported that the moisture content and pH of silage negatively affect the intake. The results of this study is in agreement with the findings of Sarwar et al (2005) who reported that the DMI was lower in silage than fresh fodder. The nutrient intake also followed a similar trend as observed in DMI. Khaleduzzman (2011) and Broderick et al (2001) clarified that the lower ash and greater non fiber carbohydrate could be the possible reasons for releasing greater amount of energy and increasing nutrient digestibility during fermentation.  

Table 4. DM intake and Coefficient of Digestibility of nutrients available in different types of silages

Parameters

Types of silage

SEM

p

Pit

Bamboo mat

Syn. Poly bag

Concrete

DMI(kg/d)

2.5b

2.49b

2.71a

2.22c

0.04

<0.01

% on  DM basis

DM

50.9b

48.5b

61.2a

45.8b

2.72

<0.01

CP

53.8a

43.8b

56.5a

41.9b

2.57

<0.01

CF

78.1b

76.7b

82.1a

79.8ab

1.10

<0.01

NFE

39.5b

33.2bc

47.9a

28.5c

1.97

<0.01

EE

8.4c

25.5b

31.3b

52.2a

3.63

<0.01

DMI: dry matter intake; DM: dry matter; CP: crude protein; CF: crude fiber; NFE: nitrogen free extract; EE: ether extract.

a,b,c Means in the same columns for each parameter with different superscript are different at P<0.01

SEM: standard error of the means.

The table 5 shows the physical structure and cost of 4 category silages. It is very much clear that pit form silage was more economic than that of others. Bamboo mat and synthetic nylon bag types. Bamboo mat type was more time consuming but costing moderately among the temporary groups while synthetic poly bag system expensed around 2 folds than that of least cost system (Pit). Khaleduzzman (2011) stated more or less the same trend (bamboo mat 0.62Tk/kg, fiber bag 5.26Tk/kg and concrete 18.5Tk/kg) of manufacturing cost.  

Table 5. Physical structure and costing of different silo types

Parameters

Silo types

Pit

Bamboo mat

Syn. Nylon bag

Concrete*

Physical structure

 

 

 

 

Silo size

3.512

1232

333/2

531

Total space(cft)

7

72

54

15

Bulk density(fresh) Kg/cft

11.4

11.1

7.4

11.7

Costing(BDT)

Polythene sheet

20.0

75.0

50.0

50.0

Bamboo mat

 

275

 

 

Syn. Nylon bag

 

 

150

 

Brick

 

 

 

500

Sand and cement

 

 

 

500

Labor

10

150

100

200

Total cost

30

500

300

1250

Silo cost/cft

4.28

6.94

5.55

83.33

Cost/kg silage

0.37

0.62

0.75

7.15

*Khaleduzzman 2011


Conclusion


Acknowledgement

The authors thank the UGC, Bangladesh for encouragement and financial support. The writer also acknowledge the BAURES and department of Animal Nutrition, Bangladesh Agricultural University providing the research facilities.


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Received 25 February 2013; Accepted 22 March 2013; Published 2 April 2013

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