P.J.M. Snijders and A.P. Wouters
E-mail: [email protected]
On behalf of the National Dairy Development Project, several ensiling experiments were conducted at the National Animal Husbandry Research Centre (NAHRC) at Naivasha, Kenya, in the period 1983-1989. The aim of the experiments was to develop methods and techniques suitable for smallholders for the ensiling of Napier grass, Columbus grass and maize stover to overcome feed shortages during the dry season.
MATERIALS AND METHODS
Six series of ensilage experiments were conducted:
- Series A: 2 silages of chopped, wilted Napier grass with or without addition of molasses, ensiled in an number of netted nylon bags and placed inside a larger silage clamp.
- Series B: 6 pits of wet, long or chopped Napier grass with addition of no, 3.5% or 6% molasses.
- Series C: 4 pits of wet, long or chopped Napier grass with addition of 3.5% molasses or molasses/urea mixture (MUM).
- Series D: 6 pits of wet, long or chopped Napier grass with addition of 3% molasses.
- Series E: 4 pits of wet, long or chopped Columbus grass with addition of 3% molasses.
- Series F: 3 pits of chopped maize stover or maize stover mixed with lablab, without additive.
Silages were made in small earthen pits in quantities varying from 1 000 to 2 000 kg fresh material, thus more or less representing conditions typical for small-scale farmers. Sides and top of the pit were covered with 2-m-wide polyethylene plastic sheets covered with a layer of about 50 cm of sand on the top and sides.
The percentage of inedible silage (mouldy or rotten silage) varied from negligible to 2.5%, indicating that sealing with polyethylene sheet and soil cover was good. Levels of butyric acid and contents of ammonia nitrogen were often below 0.3% and 12% respectively for silages of wilted Napier grass and wet-chopped Columbus grass with the addition of molasses and for silage of maize stover. These fermentation characteristics indicate good silage quality. Smell was also good. For some wet Napier grass silage and for silages made with addition of MUM to unchopped Columbus grass, results were less good.
Long, unchopped Napier grass wilted for one or two days to about 30% DM, with the addition of molasses and with proper compaction, also often resulted in good silage.
DM losses due to ensiling of Napier grass averaged between 15.2 and 4.2%. Losses were lower for silages made of grass wilted for one or two days and higher for silages made of wet, unchopped grass and grass with the addition of MUM. For wet Columbus grass, there was also a clear positive effect from chopping. Average DM loss for ensiled maize stover was 8.1%.
CP losses averaged 16.9%, but variation was large, partly due to sampling errors. Losses were lower for wilted silages and much higher for silages with the addition of MUM.
In vitro organic matter digestibility decreased due to ensiling and was more than 10 units lower in the case of poor quality silages. For well-preserved silages, the decrease in digestibility was often limited to 5 units or less. Losses of digestible organic matter for Napier silages averaged between 28.5 and 7.9%. Losses were lower for wilted silages and much higher for wet silages of Series D and silages made with the addition of MUM.
Results show that under smallholder conditions, good silage can be made. However, poor quality silages of poorly digestible Napier grass will not meet maintenance requirements of animals.
CONCLUSIONS AND PRACTICAL RECOMMENDATIONS
1. Under small-scale farming conditions, good silage can be made, provided that airtight sealing with plastic (polyethylene) sheets is used, with at least a cover of 50 cm of soil on top and sides of the pit, and with good drainage of rain water. Ensiling and covering has to be completed within one day.
2. As shown by good fermentation characteristics and smell, wilting one or two days to reach a DM content of 30% often results in good silage, especially when molasses is added. Wilting to a DM content of more than 30%, or wilting of old stemmy material, are not recommended, because of the higher weather risks and difficulties with compaction.
3. DM losses due to ensiling of wilted or wet-chopped Napier grass with the addition of molasses could be limited to 15%.
4. DM losses of silages made of wilted, unchopped long Napier grass are probably slightly higher than from chopped Napier grass. Provided proper compaction, addition of molasses, airtight sealing and covering with at least 50 cm of soil, making silage from long, wilted Napier grass may be a good alternative for small-scale farming conditions.
5. Although it is not very clear from the limited experience provided by these experiments, addition of 3% molasses to wet and long wilted Napier grass will probably be sufficient to obtain good quality silage, especially when hand-mixed through chopped silage. To increase chances for good quality silages, addition rates of up to 6% are suggested when molasses is applied in the silage pit on layers of grass. For chopped, wilted Napier grass and for chopped Columbus grass, addition of molasses can be lower.
6. MUM as an alternative additive for molasses does not produce good silages.
7. Silages of chopped Columbus grass with molasses and chopped maize stover without molasses made good silage. DM losses appeared to be lower compared to Napier grass.
8. Because of a greater risk of leaching, dilution of molasses with water in order to ease application should not exceed a 1:1 ratio. A relatively small quantity of molasses should be used in the bottom layers of the pit, and more to be added to the middle and top layers.
9. Losses of crude protein and digestible organic matter were not accurately measured in these experiments, because of the limited number of samples and because of sampling errors. Based on good quality silages in these experiments, losses are about 15% and 25% for crude protein and digestible organic matter respectively.
10. Poor silages of overgrown Napier grass will - at best - supply sufficient energy for maintenance. Feeding overgrown Napier grass as standing hay, or mulching might then be a better alternative. Proper storage and utilization of crop residues like maize stover and preserving feeds like sweet potato vines, fodder beets, cassava or fodder trees may prove better in those situations.