The most important constraint in dairy cattle production in Kenya is the quantity and quality of feed offered to the animals. This problem can addressed if farm by-products such as maize stover, millet and sorghum stovers are treated for utilization by cattle and other domestic ruminants. The idea is to improve the nutritive value of maize stover and straws by use of urea solution which is usually abundant in the farm.
Maize and sorghum stovers are abundant in most farms as a consequence of the crops being the major food crops grown by most farmers. Farmers also grow wheat and rice among and other crops and the straw forms an important by-product. Farmers should therefore learn how best they can utilize the stovers and straws to feed the ruminant livestock especially during the dry season when there are no green fodders.
Of all the crop residues maize stover is the main roughage available during the dry season. You can estimate the amount of stover produced by using a grain to stover ratio which is approximately 2:1. So a farmer producing 10 tons of maize should expect about 5 tons of maize stover in the farm.
However there are limitations in the use of maize stover for animal feeds because some farmers may prefer to use it for cooking so as to save on expenses on fire wood and charcoal. Some use the stover to conserve soil, so there are competing uses and it is up to the farmer to decide which among the uses has more economic returns. But of concern is that where it is used as animal feed, it is usually fed as whole stalk and leaves without chopping or any kind of treatment. This results in high wastage and very low intake.
Maize stover has very low digestibility owing to the high lignin content which inhibits microbial digestion of cellulose and hemicellulose. The low content of nitrogen and deficiency of readily available carbohydrates also limit microbial activity in the rumen. The nutrient level in terms of energy, protein and mineral is very low. Compare 3.7% crude protein against 8.8% in green maize stalk.
Treatment with urea
There are advantages of using urea over other chemical treatments.
- It is easily available as a fertilizer grade urea in small packs of 2 kg
- Urea is cheaper compared to caustic soda and ammonia
- Simple application equipment
- Require low volume of water and energy
- Minimum environmental pollution
- Minimum residual effects to animals
- It is not hazardous to use compared with soda and ammonia
- It has the added advantage of increasing the nitrogen content of the roughage in form of NPN, which could be used by the rumen micro-flora to synthesize microbial protein; other conditions in the rumen being right.
The crude protein content of stovers and straws increases when treated with urea. There is also increased dry matter intake, liveweight gain and milk production from urea treated stovers and straw compared to untreated material.
The simple procedure is to:
- Dissolve urea in water
- Soak material or sprinkle with solution
- Store in air tight container (or cover as in the preparation of silage) for 8 days
- Open material after 8 days and aerate material to rid off excess ammonia.
Use a chaff cutter or ordinary methods of chopping to chop the stover into smaller pieces between 1-2 cm lengths. Batches of 10 kg chopped stover should be sprinkled with urea solution made up of 0.5 kg urea dissolved in 10 litres of water. The treated stover should immediately be put in polyethylene (500 gauge) bags measuring 70 cm x 120 cm.
Alternatively ordinary polyethylene bags that come with fertilizers can be used. Bamboo baskets or papyrus baskets can be used but they should be plastered with a mixture of mud and cow dung and lined with banana leaves. Ordinary silage pits can also be used successfully. Recommended size is 4 x 3 m and about 1.5 m deep. The pit should be lined with banana leaves and the top should be covered with banana leaves or polyethylene sheet, on top of which should be put about 30 cm of soil.
In either case ensiling should be for two weeks. There is no advantage in prolonging treatment beyond two weeks. The ensiled maize stover should be ready for feeding either plain or ideally with a green fodder supplement, molasses or with concentrates.
Crop residues are low in utilizable nutrients. Lignin makes material unavailable by binding with proteins and other compounds. This masks what is in the cell making them impossible to be reached by rumen microorganisms.
Chemicals used are mainly alkalis or acids. In Alkali treatment a portion of cell wall is made soluble by acting on the bond between cellulose and lignin thus weakening the bond between the compounds. The effect is that this increases the digestibility and rate of digestion of the treated material. The ratio of water to material is 1:1.
However there are limitations such as
- The chemicals are corrosive in nature
- There is high residue of sodium in material causing the animal to pass high rates in urine
- Pollution of environment
Materials are soaked in a solution of sodium hydroxide or sprayed with sodium hydroxide and then stored. Ammonium hydroxide can also be used instead of Sodium hydroxide and this has the following advantages
- Treatments raises the protein content by 5 – 7% but this will decreases to 3 – 4% after the release of ammonia.
- Digestibility is increased (up to 10% increase in digestibility) and thus more material is taken up by the animal which leads to a 50% increase in feed intake.
In conclusion, the main objective for keeping and feeding dairy cattle should be to maximize profit. When feeds are scarce as happens during dry weather this objective can change to just keeping the animal alive until conditions improve. A healthy cow can lose up to one fifth of its bodyweight and still remain healthy, and recover its normal weight when it resumes normal diet. If you need to maintain milk production and take advantage of the high milk prices common during the dry season, supplementation with high quality feeds is required. There are a number of tactics and strategies you can use to cope with scarcity of green feeds. An obvious option is treatment of maize stovers and straws. But you need to seek expert advice before adopting this option.