Effects of additives and storage positions on in-bag grass silage quality under smallholder farmer conditions in Mvomero district Tanzania

E J Mtengeti, B J Lyimo and N A Urio

Department of Animal Science and Production, Sokoine University of Agriculture, P.O.Box 3004.Tanzania
emtengeti@yahoo.co.uk

Abstract

Appropriate technologies for conserving excess fodder grasses as silage in the wet season so as to reduce scarcity of feed in the dry season are still lacking among the smallholder dairy farmers in Tanzania. In order to understand the effects of different additives and storage sites (thatched barn and earth pit) on elephant grass(Pennisetum pupureum) silage quality ensiled in shopping plastic bags (silos) a study was conducted among the smallholder dairy farmers in three villages in Mvomero district. The additives were molasses, maize bran and fresh leucaena leaves at a rate 5 % and 10 %, respectively, of ensiling materials. These were reconstituted into six treatments:  elephant grass alone  as control (CONTROL),   elephant grass with 10% maize bran (MB),  elephant grass  5% molasses (MOL),  elephant grass with 10% fresh leucaena leaves (LL),  elephant grass  with10% leucaena and 10% maize bran (LL+MB),  elephant grass with 10% fresh leucaena leaves and 5% molasses (LL+MOL). The treatments were repeated twice in each village. One set of the treatments was stored in a thatched barn and another in an earth pit.

Only control treatment had dry matter content < 17 %, pH >5, crude protein < 10%, digestibility < 50 % in both barn and earth pit silages. However, dry matter and crude protein contents of silages were not significantly (P > 0.05) affected by neither treatment nor the storage site. On the other hand ammonium nitrogen was significantly lower in molasses treated silages (< 4 % of total nitrogen) than all other silages. The pH values of molasses treated silages from the earth pit remained < 5 up to the fourth day of feeding out. From this study it can be concluded that locally available additives such as maize bran and fresh leucaena leaves could be used to improve the quality of fodder grass silages. Moreover, farmers may avoid expenses of digging earth pits every year by building only once a thatched barn for storing in-bag grass silages.  

Keywords: fresh leucaena leaves, maize bran, molasses, shopping plastic bags, thatched barn and earth pit

Introduction

Dairy production has contributed significantly to poverty alleviation and reduction of malnutrition particularly among the smallholder dairy farmers in rural areas (Kayunze et al   2001, Kurwijila et al 2002). However, the productivity of dairy cattle in the country is rather low, producing on average about 6 –7 liters of milk per day in the wet season and decline to nearly 3 liters per day in the dry season (Msangi and Kavana 2002). This is attributed mainly by inconsistent supply of forages throughout the year. It is well known that during the wet season there is a flush growth of both natural forages and a notable increase in biomass of the fodder gardens around the smallholder dairy farmers’ homestead (Mtengeti et al 2001).  The smallholder dairy farmers however, are not able to utilize most of the forage biomass present in the wet season because they lack appropriate and simple technologies for conserving these excess fodder grasses. If these fodder grasses are left in the field to mature they loose nutritive value thereby resulting in wastage of valuable feed resource.

The fodder grasses can best be conserved as silage but most tropical grasses have low water soluble carbohydrates and protein (Sarwatt et al 1992). Changes during ensiling reduce grass silage nutritive value even further. There is an extensive degradation of forage protein to non protein nitrogen which normally occurs during ensiling (McDonald et al 1991). High degradability of protein during fermentation often lowers the crude protein content of the silage (Tesha 1999). Quite often molasses has been used as water soluble carbohydrate additive in making fodder grass silage. However, increased uses and price of molasses, and its inability to reduce effluent in succulent fodder grasses bring an urge to find alternative locally available additives.  Maize bran and fresh leucaena leaves are feed supplement materials that are locally available within most smallholder dairy farmers reach and could be used as low cost additives to improve the grass silage quality. Another problem of ensiling fodder grasses within smallholder’s fodder garden is the available biomass at a particular time that may be enough to use trench or earth pit silos which may require at least half a tone of ensiling forage materials. In solving this problem plastic bags having capacity from 5 kg fresh chopped fodder grass have been used elsewhere (Mtengeti and Urio 2006, Delacollete et al 2005 and Ashbell et al 2001). More problems to solve are where to store the intermittent ensiled plastic bags and how long can the silage quality be maintained during feeding out? The objective of this study was therefore to determine the effects of maize bran in combination with fresh leucaena leaves as additives, shopping plastic bags (as silos), and storage positions (earth pit and thatched barn) on the quality of elephant grass silage.  

Materials and Methods

Study area 

This study was carried out in Turiani division, about 100 km North of Morogoro municipality and located at about 37° 36´ E and 5° 7’ S. The division lies along the north-western part of the Wami river flood plain about 300-500 metres above sea level and receiving 900 mm of rain per year. The rainfall pattern experienced in the division is a bimodal with long rains period between March and May and short rains period beginning in November to December. The division has an average temperature ranging between 25 °C and 33 °C per annum and June being the coolest month. In open bushland areas the flood plain is covered by tall tufted grasses such as Panicum maximum, Hyparrhenia rufa and Pennisetum pupureum. Among the crops grown in the area are rice, sugarcane, maize, lablab, pigeon pea and vegetables 

Treatments of ensiling material 

Six different treatments was administered by mixing the chopped elephant grasses with additives and then immediately filled into the bags. Molasses was added at a rate of 5% as water soluble carbohydrates additive while maize bran was added at a rate of 10% and used as both absorbent and water soluble carbohydrate additive. Green Leucaena leaves was added at a rate of 10% and used as protein additive. The treatments were therefore:   a) Elephant grass  alone as a control (CONTROL)  b) Elephant grass and 10% Maize bran (MB)  c) Elephant grass and 5% Molasses (MOL)  d) Elephant grass  and 10% Leucaena (LL)  e) Elephant grass ,10% Leucaena and 10% Maize bran (LL + MB)  f) Elephant grass, 10% Leucaena  and 5% Molasses (LL + MOL). 

The ensiling procedures 

The ensiling materials were chopped using a bush knife to 2.5 cm particles and carefully packed into the plastic bags so as to avoid making any holes in the bags. Strong, high density shopping plastic bags with a capacity to carry 10 kg of chopped elephant grass was used in this study. Only 5 kg of ensiling material was carefully packed in each shopping plastic bag. Each bag was gently squeezed by hand to expel air, while compressed; the neck of each bag was twisted then turned over and tied with a rubber band thereafter labeled with treatment identity. Each bag was then inverted into a second empty shopping plastic bag which was also tied and labeled and put in a hessian bag to protect it from rupturing. For each treatment there were two hessian bags each containing three shopping bags filled with ensiling materials. One hessian bag was placed in a thatched barn and another hessian bag was placed in earth pit 90cm deep x 75 cm wide x 500 cm long. In total therefore, six hessian bags (each having three shopping bags filled with ensiling materials) were placed in the thatched barn while the other six hessian bags were placed in earth pit. In the thatched barn, the hessian bags were carefully stacked on a wooden rack to allow ventilation so as to maintain the  temperature to about 23 -25 ^oC as high temperatures than these could spoil the silage. The wooden rack was surrounded by a chicken wire mesh all over so as to protect the bags against rats, mice and birds especially crow that would view the bags as bin bags full of kitchen waste to consume. In the earth pit the hessian bags were covered by a plastic sheet to protect them from termites and then the pit was re-filled with the soil to form an earth mound over the earth pit so as to clear rain water away from the pit.  

Sampling procedures 

The silages were opened at 60 days after ensiling. Silages showing spoilage spots were insignificant showing that the bags were airtight water proof as much as possible. Four samples each 200g were taken from each ensiling bag. First sample was used to analyse pH, the second to analyse ammonium nitrogen (NH₃N), and the third sample to analyse dry matter (DM), crude protein (CP), water soluble carbohydrate (WSC), neutral detergent fibre (NDF) and determination of in vitro dry matter digestibility.  The fourth sample was used for determining the duration of stability of the silage during feeding out.  

Data collection 

The pH of silages was recorded by using a pH meter. Samples were analyzed for Dry matter (DM), crude protein (CP), Ammonium nitrogen (NH₃N) and Ash according to AOAC (1995) procedure .Water-soluble carbohydrate was determined according to Thomas (1977). The Neutral detergent fibre (NDF) values were analyzed according to forage fibre analysis by Van Soest et al (1991). The two stages technique of Tilley and Terry (1963) was used to determined IVDMD and IVOMD. The organoleptic test was done using panel score method while duration of stability of silage during feeding out was determined by sub-dividing the sample into seven lots placing them in small beakers and exposed them at room temperature and recording pH from the first sub-sample in the first day and up to the seventh sub-sample in the seventh day. 

Experimental design and statistical analysis 

The data obtained from the experiment were analysed using general linear model of SAS (1990) using a completely randomized design with a 2 x 6 factorial arrangement with three replicates. Least Square Means for treatments were compared between treatments. The model used to study effects of different additives of NP grass and position of storage was:

Yijk = µ + P_i + T_j + (PT) _ij+ e_ijk where:

Yijk= Observation the k^th replication (Observation from the j^th treatment and i^th positions)

µ = General mean common to all observations in the experiment

Pi = Effect of the i^th positions

Tj = Effect of the j^th treatment

(PT)ij = Interaction effect between the i^th positions and

j^{th =} Treatment

eijk = Random effect peculiar to each observation (replication) 

Results and discussion

Effect of additives and storage position on elephant grass silages pH, crude protein and ammonia nitrogen 

Additives improved silage fermentation process as indicated by lower pH and NH₃N    values (Table 1). Similar observations have been reported in the country and elsewhere (Tjandraatmadja et al 1993, Maeda, 1997, Manyawu, et al 2003 and Mtengeti and Urio 2006). In both thatched barn and earth pit the control and LL silages had higher pH values than all other silages, while MOL and LL + MOL silages had the lowest pH values. This could be due to higher available energy from MOL for the fermentation bacteria.  Tesha (1999) obtained nearly similar results from fodder grass silages ensiled with gliricidia and leucaena fresh leaves as additives. All silages, however, except the control had towards acceptable Ph values of good preserved grass silage.  

The CP content of silages with additives was on average slightly higher than that of control silage. The CP content was observed to be relatively high in LL and LL+ MOL in both storage positions, although there was no significant difference between the additives. Moreover the results obtained from this study showed that there was enough DCP g/kg DM for maintenance and milk production in all silages except for the control silages. The result strengthens the possibilities of using locally available additives to improve and conserve nutritious fodder grasses which would otherwise be lost when they are plenty during the rainy season. Silages with additives had lower NH₃N than the control silage. These findings were consistent with the findings reported by Sunarso et al (1995) and Maeda et.al. (1997).

Silages without additives were, however, well preserved despite of slightly high NH₃N. Addition of molasses reduced significantly the pH and NH₃N values, regardless with storage position.  The same NH₃N values were observed for good grass silage by Kung (2009). These similarities could be due to readily available energy provided by molasses to the fermenting bacteria. The implication from this is that there should be a threshold proportion of molasses to be added in the grass material during ensiling for appropriate fermentation. 

Elephant grass silages stored in thatched barn had higher pH value than those stored in earth pit but there were rather much less difference between storage positions in terms of CP and NH₃N values (Table 2). Higher pH values in elephant grass silages stored in thatched barn as compared to those stored in earth pit could be attributed by slightly higher temperature in thatched barn than in the earth pit. These results were in agreement with findings reported by Gonzalez et al. (2003) who found higher silage pH values in higher temperature relative to low temperature environment.

Effects of additives and storage position on the chemical composition of elephant grass silage 

Silage with additives had relatively higher DM content than the control (Table 3). This could be due to the higher DM content of additives as compared to the elephant grass.  Nearly similar results were reported by Tesha (1999). The trend of DM content values was similar for silages from both earth and pit storage positions.  There was insignificant difference between silage with and without additives in terms of Ash content. The variation in Ash content between the treatments was very low but, silages with MOL, MB and LL had relatively higher Ash contents than other silages.  

Silage with MOL alone had the highest WSC content, followed by silage with combination of LL and MOL and then MB and LL alone silages. The control silage from the thatched barn had lower WSC content as compared to the silages with additive. The WSC values of the silages in this study were within those reported earlier by Tesha (1999). Higher NDF contents observed in control silages relative to other treatments could have been attributed to higher NDF content of the grass relative to the additives. Silage treated with MOL had relatively lower NDF content as compared to other additives. Nearly similar results were also reported by Maeda et al (1997) who reported lower NDF content for molasses treated elephant grass silage than untreated one. This could be attributed to increased acidity which stimulated further hydrolysis of linked sugar molecules in the cell wall causing further breakdown of hemicelluloses. Breakdown of up to 50% of hemicelluloses during silage fermentation has been documented by McDonald et al (1991).

There was an insignificant difference between thatched barn and earth pit storage positions in terms of DM, Ash, WSC and NDF contents (Table 4). This might be due to favorable environmental condition for fermentation found in both storage positions, suggesting that farmers may avoid expenses of digging earth pits for storing shopping bags with ensiled grass material every year and thus build only once a thatched barn where they can store silage bags and even hay bales together.

Effects of additives and storage position on elephant grass silage digestibility, metabolizable energy and digestible crude protein contents  

The IVDMD and IVOMD of the elephant grass silages were improved by addition of additives (Table 5). The IVDMD was highest in silages treated with MOL and   LL + MOL, followed by silage with LL + MB and then MB alone. The LL alone and control silages had the lowest IVOMD. Higher IVOMD values were observed in silages with MOL as compared to silages with LL. Reduced digestibility of silages with LL could have been contributed by the presence of digestibility depressants such as tannins. Reduction of organic matter digestibility by tannin content in browse species has been documented by Msangi, (2005). In particular, presence of tannis up to 10% in LL leaves has been documented by Norton, (1994). The digestibility results reported in this study were in agreements with those reported by Tesha, (1999) who found an improvement of the IVDMD and IVOMD of the elephant grass silage with addition of molasses. This could be attributed to the provision of useful energy substrate for ruminal microbes and thus improve their effectiveness in digesting feed particles. The importance of molasses as useful energy substrate for ruminal microbes have been documented by McDonald et al (1973).

Silages with additives had better ME than the control.  Metabolizable Energy tended to increase with increase in IVDMD and IVOMD values. The ME results in this study were relatively lower than those suggested by NRC (1989) for a 350 kg l wt dairy cow (10.0 MJ, ME/kgDM). This means the farmers have to supplement their dairy cows with some energy concentrates especially when fed those silages with nitrogenous additives such as LL. Additives improved DCP of silages at all different combinations. Silage treated with MB and LL + MB had the highest DCP values at both storage sites. Except for the control silage, all other silages from earth pit met the required DCP (60 g/kgDM) by a dairy cow producing 8 lts of milk/day (NCR,1989).This improvement could be attributed to the high protein content in MB and LL additives.

There was insignificant difference between storage positions in terms of IVDMD and IVOMD values of the elephant silage (Table 6).Storage positions seemed to have insignificant effect on fermentation patterns. Therefore, silages in shopping bags could be stored in thatched barns and thus avoid digging the earth pits for ensiling fodder grasses every season. 

Effect of different additives and storage positions on the stability of silage quality during feed out 

Results of the effect of different additives and storage positions on stability of elephant grass silage quality during feed out for seven days are shown in Tables 7.  There was variation of deterioration rate among the silages during the feeding out period. The control silages had pH values greater than 5 even before the feed out trial. Four silages from the thatched barn (i.e. those with MB, MOL, LL + MB and LL + MOL) had pH values less than 5 up to the second day of feeding out. This indicate that silage from thatched barn should be fed within two days after opening the silo, thereafter deterioration becomes unbearable and the silage becomes unsuitable for feeding the animals. On the other hand the four silages (i.e. those with MB, MOL and  LL + MB, LL + MOL) from the earth pit maintained their pH values less than 5 up to the third day, while those with MOL and  MOL + LL maintained the pH values < 5 to the fourth day of feeding out. This means that additives and storage sites have an influence on the stability of the silage quality during the prolonged feeding out period. This was also noted by‘t Mannetje (2000). The rise in pH as feeding out progress is due to onset of deterioration due to the degradation of preserving organic acids by yeast and occasionally rises in environmental temperature‘t Mannetje (2000). Aerobic spoilage occurs in almost all silages that are opened and exposed to air (Woolford, 1990) where the activity of yeasts moulds and enterobacteria is enhanced. The results from this experiment indicate that during feed-out period spoilage by air in grass silage can be minimized by a sufficiently high feed-out rate.  In addition, silage additives capable of decreasing spoilage losses (e.g. molasses) can be applied at the time of ensiling. Further, the silage should be stored in appropriate site that does not allow fluctuation of temperature such as in the earth pit and silage should be ensiled using small bags rather than large bags just enough to be consumed in each day of feed out.

Conclusions and recommendations

• The results obtained in this study indicate that elephant grass can be conserved well when leguminous tree leaves, molasses and maize bran are included as nitrogenous and carbohydrates additives, respectively. Most of the silage parameters such as DM, CP, NH₃N, ash, WSC, NDF, IVDMD, IVOMD, ME and DCP were insignificantly affected by storage position (i.e. earth pit and thatched barn) suggesting that smallholder farmers can ensile excess elephant grass biomass in small shopping plastic bags and store them in thatched barns thus avoid digging earth pits whenever they want to make silage. However if bigger plastic bags are used for ensiling grass silage it recommended to store them in earth pits so as to improve  stability of the silage quality in terms of maintaining low pH (values < 5) for an extended days of feeding out.

Acknowledgements

The authors extend their sincere thanks to the Programme for Agricultural and Natural Resources Transformation for Improved Livelihoods (PANTIL) of Sokoine University of Agriculture for financial support for this study.  

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Received 1 October 2013; Accepted 7 October 2013; Published 1 November 2013

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