M A Naga
Faculty of Agriculture, University of Alexandria, Alexandria, Egypt.
Abstract
Introduction
Materials and methods
Results
Discussion
The nutritive value of poor quality by-products may be improved by supplementary sources of easily fermentable carbohydrates, crude protein, minerals and vitamin A-precursor.
The technique described here was found successful in providing most of these requirements at a relatively low price. Grains (one kg) were sown on double their weight of chopped rice straw and irrigated daily with 7 litres of tap water. Some urea and traces of foliar fertilizer were added to the water on the seventh day. One kg grains gave six times its weight of sprouts within two weeks. The sprouts and the rice straw bedding contained 11% crude protein and 55% TDN and was readily consumed by sheep.
Before the recent droughts and human population explosion, feeding animals on pasture and cultivatable land for food crops did not present any problem. Economics demand maximum inclusion of agricultural and agro-industrial by-products in animal diets to save as much cereals and oil seeds for human consumption as possible.
Many successful approaches to improving the nutritive value of these by-products are now practiced either through alkali treatments, feeding with leguminous forage or supplementation of the deficient nutrients by adding urea, molasses, vitamin A and some minerals. Such improved by-product based diets may satisfy the maintenance requirements of animals. Feeding for production or reproduction necessitates supplementing the by-product based diet with some nutritious concentrates to a level around 30% of the diet dry matter. The supplement in this case should be rich in protein, energy and vitamin A. It may, therefore, be expensive, especially under most small farmer conditions.
The present results describe the adaptation of the hydroponic technique to obtain an adequate supplement at a reasonable cost.
The hydroponic technique
Rice straw was chopped and spread over a plastic sheet as a bedding for maize and barley seeds. Used fertilizer bags were spread close together to form the sheet. The grains were sown on the surface of the bedding, and left in the open air. Irrigation was applied frequently by spraying tap water until the seedlings reached a height of 30 cm. The final product, consisting of the bedding and sprouts, was offered to sheep as the sole diet.
The technique was tried in winter with barley and in summer with maize. Mould growth was prevented by adding 4% chlorax in the irrigating water; at the beginning and on the 7th day. The mould disinfectant was not detectable in the bedding four days after application. It did not apparently cause any harm to the animals.
Irrigation frequency, chop length and depth of bedding
The effect of the length of chopped rice straw was investigated, using three lengths (1, 3.5 and 7 cm), and three bedding depths (4, 8 and 12 cm) were also compared. The bedding was irrigated with 7, 14 or 21 litres per m² per day. Irrigation was carried out at three frequencies, once or twice per day and every other day. Foliar fertilizer was dissolved in the irrigating water at one or two parts per million.
The voluntary feed intake (g/head/day) and dry matter digestibility of this products were estimated. An economical evaluation was also carried out.
There were no significant differences between any of the treatments in dry matter production of the sprouts, although increasing depth of the bedding showed a tendency to promote higher production (Table 1), possibly through greater water holding capacity and reduced evaporation. The results also indicated that a grain to bedding ratio by weight of 1:2 was preferable to ratios of 1:1 or 1:4 (Table 2). Perhaps higher grain density caused competition by the sprouts for nutrients in the bedding, while light density may have been inadequate for optimum photosynthetic activity. Although frequency of irrigation and rate of foliar fertilizer application showed no significant effect on the DM yield from sprouts, water tended to be more effective when it was applied at three times the weight of the bedding.
Table 1. Dry matter gains in form of sprouts expressed as percent of the weight of originally added grain.
|
Bedding depth (cm) |
Season (grain type) |
|
|
Winter (barley) |
Summer (maize) |
|
|
4 |
514 |
389 |
|
8 |
641 |
575 |
|
12 |
675 |
680 |
Sheep consumed the product at the rate of 86 g/kgW0.75/day, and the digestibility of DM approximated 57%. Total crude protein content in the shoots ranged between 20 and 25. Three to 10% of the dry matter of the bedding was contributed by the root network of the sprouts.
Table 2. Effect of grain: bedding ratio (W/W) on the dry matter gain of sprouts per m² expressed as percent of the weight of the grain originally added
|
Grain bedding ratio * |
Grain type |
|
|
Barley |
Maize |
|
|
1:1 |
521 |
513 |
|
1:2 |
687 |
530 |
|
1:4 |
641 |
462 |
* The weight of grains was consistently one kg/m².
Tables 1 and 2 indicate that the weight of grains increased about 6 times in two weeks. This would mean that 4.25 tons of grain sown on 8.5 tons of chopped by-products (maize stover or cobs) and irrigated with 450 cubic meters of water, repeated over 20 cropping batches each of 15 days would result in the production of 150 tons of a nutritious feed containing 11% crude protein and 55% TDN. This technique reduces the need for extended land areas for producing animal feed and also cuts down the water demand for cropping 0.5 ha from 14-16 thousand m³/year to only 9000 m³.
If a diet of roughage and concentrate in the ratio of 1:1 is sought it is recommended that 20% maize or barley grains be added to chopped roughage and irrigated for some 14 days. The price of the roughage by-product material may be one sixth of the price of grain. The two week's old sprout is very rich in protein, low in fibre and is high in digestibility. It also contains high levels of carotene.
The sprouts can be fertilized by any nitrogenous fertilizer to improve their true protein content. They supply the by-product based diet with easily fermentable carbohydrates, vitamin A-precursor, true protein and improve its palatability and digestibility. The technology reduces the costs of feed production by reducing rent on land and irrigating water, while maximizing the benefits of photosynthetic activity through such an intensive cropping system.
