J T K Munthali, C N Jayasuriya and A N Bhattachrya
Chitedze Agricultural Research Station
PO Box 158
Lilongwe, Malawi
ABSTRACT
Maize stover is an important feed resource in Malawi, but it is poorly utilised. Simple methods of processing and/or treating the stover to optimise its utilisation by stall-fed cattle are being sought. An experiment was conducted at the Chitedze Agricultural Research Station during October to mid-December 1990 to assess the effects of water or urea treatment of maize stover and supplementation with urea-molasses blocks or different levels of maize bran on the growth of yearling steers and heifers.
Animals fed water-treated stover without supplementation lost weight and had the lowest crude-protein intake, indicating that this diet was deficient in nitrogen. Urea treatment increased the crude-protein content of maize stover four-fold compared with untreated stover. Water or urea treatment of maize stover did not affect stover dry-matter or total dry-matter intake. Supplementing urea-treated stover with high levels of maize bran significantly (P<0.01) increased liveweight gains.
RESUME
Performances de bouvillons et de génisses en croissance alimentés avec de la paille de maïs traitée avec de l'urée et complémentée avec du son de maïs ou un concentré de mélasse-urée
Bien qu'elle constitue l'une des principales sources d'aliments du bétail rencontrées au Malawi, la paille de mais est peu utilisée dans ce pays. Les efforts déployés actuellement visent entre autres, à mettre au point des méthodes simples de transformation et/ou de traitement de ces résidus de récolte afin d'en optimiser l'utilisation dans l'alimentation des bovins à l'étable. A cet effet, un essai a été effectué d'octobre à la mi-décembre 1990 à la station de recherche de Chitedze en vue de déterminer l'effet, sur la croissance de bouvillons et de génisses âgés de 1 an, d'un régime alimentaire composé de paille de mais traitée avec de l'eau ou de l'urée et complémentée avec un concentré mélasse-urée ou différents niveaux de son mais.
Les animaux recevant uniquement de la paille traitée avec de l'eau perdaient de poids et consommaient moins de protéines brutes que ceus soumis aux autres régimes alimentaires, ce qui signifie que cette ration présentait une carence en azote. Le traitement avec de l'urée permettait de quadrupler la teneur en protéines brutes de la paille. Par ailleurs, le traitement avec de l'eau ou de l'urée n'avait aucun effet sur l'ingestion de paille brute ou de matière sèche totale. Enfin, la paille traitée avec de l'urée et complémentée avec des niveaux élevés de son de mais entraînait un accroissement significatif (P<0,01) des gains de poids vif.
INTRODUCTION
Maize stover is the largest animal feed resource in Malawi following harvests. Although it is widely acknowledged to be a useful feed, it is not utilised efficiently; it is grazed in situ and so is subjected to trampling, soiling, termite damage and fires. As a result, less than 50% of the available stover is actually consumed by livestock.
Acute cattle feed shortages occur at the peak of the dry season (September through November). The animals hardest hit are the stall-fed dairy cows and their followers or fattening steers which, by regulation, are not supposed to graze freely in order to avoid diseases and indiscriminate mating. For this group-of animals, improvements in the utilisation of maize stover and other crop residues are essential in order to maintain productivity. In addition to proper storage of maize stover, attempts are being made to integrate forage legumes in maize crops and to find simple methods of processing and/or treating the stover to optimise its utilisation by stall-fed cattle. Urea was chosen for treating maize stover because, apart from its ability to increase the nitrogen content of the treated stover, it is being vigorously promoted as a fertiliser, and hence is readily available in the country, and farmers can handle it safely.
An experiment was conducted at the Chitedze Agricultural Research Station, Malawi, during October to mid-December 1990 to assess the effects of water or urea treatment of maize stover and supplementation with maize bran or urea-molasses block on the growth of yearling steers and heifers. Specifically, the objectives were to compare water-treated maize stover with urea-treated maize stover, water-treated maize stover with and without urea-molasses block supplementation, and urea-treated maize stover supplemented with three levels of maize bran.
MATERIALS AND METHODS
Animals
The experimental animals were 40 yearling crossbred (Friesian x Malawi zebu) cattle (22 steers and 18 heifers) that had been previously grazed as a group on Rhodes grass (Chloris gayana) standing hay, maize stover and unimproved dambo grasses. All animals were dewormed with Thibenzole at the start of the experiment. They were then randomly allocated to five feeding treatment groups (eight animals each), taking into account sex and initial liveweight differences.
Feeds
The animals were fed maize stover (treated with water or urea), groundnut tops, Rhodes grass hay, maize bran, urea-molasses blocks and a mineral mixture.
Maize stover from the station was collected and chopped, using a forage harvester, into pieces up to 14 cm long. The stover was ensiled in circular pits, 1.5 m in diameter and 2.0 m deep, with a seepage pit at the bottom. Weighed batches of chopped stover were placed in the pit and sprayed (using a garden watering can) with either plain water or a urea solution at the rate of 1.5 litres of water/solution to 1 kg of stover. (Previous work (Munthali et al, 1990) had shown that spraying at the rate of 1 litre of water to 1 kg of stover DM resulted in inadequate wetting of the stover and hence poor chemical reaction.) The amount of urea used was calculated to give a treatment of 4 g urea to 100 g stover (de, 4% urea-treated stover). The stover was mixed and trampled by two to three people to compress it. More batches of stover were then added and treated until the pit was filled. Finally, the pit was covered with polythene sheets and a thick (about 45 cm) layer of soil.
Groundnut tops were also collected at the station and either baled or kept loose in stooks under a barn. Hay was made from fully mature Rhodes grass, baled and kept in a barn. Maize bran was purchased either from families in and around the station or from Grain and Milling Company as a hominy chop (maize germ meal).
Urea-molasses blocks were manufactured using fertiliser grade urea (45% nitrogen) and type C cane molasses. The characteristics of the molasses and the compositions of the urea-molasses block and of the mineral mixture (also included in the urea-molasses blocks), are given in Table 1.
Feeding
Animals were fed in palm at 0800 and 1400 hours.
During the first 10 days, animals were fed hay ad libitum and maize bran (1.0 kg/animal per day). Thereafter, all animals were fed the experimental diet - a daily allowance of 1 kg groundnut tops, 0.5 kg hay and 0.05 kg mineral mixture plus one of the following treatment diets:
· Diet 1: ad libitum water-treated maize stover plus 1.0 kg maize bran· Diet 2: ad libitum water-treated maize stover plus 1.0 kg maize bran plus urea-molasses block for three hours
· Diet 3: ad libitum 4% urea-treated maize stover plus 1.0 kg maize bran
· Diet 4: ad libitum 4% urea-treated maize stover plus 2.0 kg maize bran
· Diet 5: ad libitum 4% urea-treated maize stover plus 3.0 kg maize bran
Table 1. Characteristics of type C cane molasses and compositions of urea-molasses-mineral block and mineral mixture
|
Molasses a |
Molasses-urea-mineral block |
Mineral mixture | |||
|
|
Value (% DM) |
Component |
Content (g/kg) |
Component |
Content (g/kg) |
|
Dry solids |
78.8 |
Molasses |
370 |
Meat and bone meal |
600 |
|
Brix |
77.4 |
Urea |
100 |
Common salt |
350 |
|
Sucrose |
32.8 |
Maize bran |
300 |
Magnesium sulphate |
35 |
|
Polarisation |
30.0 |
Salt |
50 |
Copper sulphate |
6 |
|
Total invert |
50-56 |
Cement |
130 |
Zinc oxide |
8.5 |
|
Ash |
13.7 |
Mineral mixture |
50 |
Cobalt sulphate |
0.2 |
|
Purity |
38.8 |
|
|
Potassium iodide |
0.3 |
a
Source: Sugar Corporation of Malawi (SUCOMA), Personal communication, 1991
The experimental diets were first fed for a 22-day acclimatisation period, during which time the animals on diet 2 were exposed to the urea-molasses block for only one hour daily. The experimental period was 56 days, ending at the onset of the rainy season.
Data collection
Quantities of feed offered and refused were recorded daily. Feed intake was calculated from daily intakes on four consecutive days weekly. Urea-molasses block intake per animal was calculated from the total number of blocks consumed by each treatment group during the 56-day experimental period.
Initial and final liveweights were calculated as a mean of three consecutive daily weights taken after depriving animals of water for approximately 16 hours.
RESULTS AND DISCUSSION
The chemical compositions of the feeds are shown in Table 2.
Table 2 Chemical compositions of feeds
|
Feed material |
Dry matter (%) |
Crude protein (% DM) | |
|
Maize stover |
|
| |
|
|
Untreated |
91.7 |
2.8 |
|
|
Water-treated |
43.3 |
3.5 |
|
|
4% urea-treated |
35.9 |
14.4 |
|
Maize bran (madeya) |
90.1 |
9.6 | |
|
Groundnut tops |
90.6 |
7.8 | |
|
Rhodes grass hay |
91.8 |
5.6 | |
The chemical compositions of groundnut tops, hay and maize bran were similar to those commonly found in samples collected on the station. However, crude-protein (CP) content of untreated stover was lower than that previously reported by Munthali (1987). The stover used in the present experiment was collected late in the dry season and exposure to varying climatic conditions may have led to nitrogen degradation (Berger et al, 1979).
Urea treatment increased the CP of the maize stover more than four-fold. Similar increases in CP content of forages following urea treatment have been reported elsewhere (Jackson, 1978; Klopfenstein, 1978; Sundstol et al, 1978; Kiangi, 1981). Therefore, urea treatment is a practical method of increasing the nitrogen content of low quality roughages.
The observed differences in dry-matter (DM) content of the water- and urea-treated maize stover may be attributed to sampling errors.
The performance of growing steers and heifers is shown in Table 3.
Crude-protein intake increased when animals were fed 4% urea-treated maize stover. It declined as the amount of maize bran fed increased from 1.0 to 3.0 kg/animal per day because stover intake declined with increased feeding of maize bran. The decline in CP consumption was due to the substitution of high N urea-treated maize stover by maize bran. The intake of the urea-molasses block was calculated to be 200.8 g/animal per day, giving a nitrogen consumption from the block of approximately 90 g/animal per day. The anticipated intake of the block was 300 g/animal per day, so the limited exposure time (three hours) of the animals to the block probably lowered its intake.
Total DM intake did not vary greatly, and all animals appeared to have satisfactory DM intakes of 3% or more of their body weights. Urea treatment of maize stover did not increase DM intake compared with water treatment of the stover. However, Smith et al (1989) reported significant increases in DM intake of urea-treated maize stover compared with dry fresh maize stover, indicating that water treatment followed by ensiling has a similar effect in increasing DM intake to urea treatment followed by ensiling.
Table 3. Performance of growing steers fed maize stover diets a
|
|
Diet 1 |
Diet 2 |
Diet 3 |
Diet 4 |
Diet 5 | |
|
Crude-protein content in diet (% dry matter) b |
5.7 |
5.7 c |
13.2 |
12.3 |
11.7 | |
|
Stover dry-matter intake |
|
|
|
|
| |
|
|
kg/animal per day |
3.56 |
3.71 |
4.46 |
3.46 |
2.99 |
|
|
% of body weight |
1.86 |
1.98 |
2.29 |
1.76 |
1.55 |
|
Total dry-matter intake |
|
|
|
|
| |
|
|
kg/animal per day |
5.80 |
5.95 |
6.70 |
6.58 |
6.99 |
|
|
% of body weight |
3.02 |
3.17 |
3.44 |
3.36 |
3.63 |
|
Mean liveweight at start of experimental period (kg) |
187.1 |
197.1 |
201.0 |
222.7 |
229.2 | |
|
Daily gain during 56-day experimental period (g) |
|
|
|
|
| |
|
|
Mean |
-83.0 |
170.6 |
116.1 |
483.0 |
649.8 |
|
|
SE |
70.0 |
65.3 |
96.3 |
51.9 |
85.8 |
a
Diets were:
Diet 1: ad libitum water-treated maize stover + 1 kg maize bran + 1 kg groundnut tops + 500 g hay + 50 g mineral mixture
Diet 2: ad libitum water-treated maize stover + 1 kg maize bran + 1 kg groundnut tops + 500 g hay + 50 g mineral mixture + urea-molasses block
Diet 3: ad libitum 4% urea-treated maize stover + 1 kg maize bran + 1 kg groundnut tops + 500 g hay + 50 g mineral mixture
Diet 4: ad libitum 4% urea-treated maize stover + 2 kg maize bran + 1 kg groundnut tops + 500 g hay + 50 g mineral mixture
Diet 5: ad libitum 4% urea-treated maize stover + 3 kg maize bran + 1 kg groundnut tops + 500 g b hay + 50 g mineral mixture
b Crude-protein content in maize stover was determined using fresh samples
c Urea N from urea-molasses block not included, but intake of nitrogen was 90 g/animal per day
The highest liveweight gain (P<0.01) was achieved by animals on diet 5, the treatment with the highest level of maize bran supplementation. Animals fed unsupplemented water-treated stover (diet 1) lost weight; these animals showed the lowest crude-protein intake, indicating that diet 1 was deficient in nitrogen. Supplementation of the water-treated stover with urea-molasses block (diet 2) or treatment of the stover with urea (diet 3) was enough to support maintenance and slight liveweight gains of the animals, further showing that nitrogen could have been the limiting nutrient in diet 1. The improvement in liveweight gain by animals on diets 4 and 5 could be attributed to the increased intake of energy and an accompanying improvement in the utilisation of non-protein nitrogen in the 4% urea-treated maize stover. Early work by Pearson and Smith (1943), Arias et al (1951) and Belasco (1956) showed that starch induced better utilisation of non-protein nitrogen than any other carbohydrate source, and the maize bran used in the present study is rich in starch.
CONCLUSIONS
Treatment of maize stover with water followed by ensiling gave comparable DM intakes to that obtained when the stover was treated with 4% urea and ensiled, although animals fed unsupplemented water-treated stover lost weight. Supplementing water-treated stover with urea-molasses block, or treating the stover with urea, was sufficient to support maintenance plus small liveweight gains in cattle. Supplementing urea-treated stover with a suitable source of energy (such as starch, as in maize bran) promoted high liveweight gains.
The experiment has demonstrated that an adequate supply of nitrogen is essential to maintain cattle fed basal diets of maize stover, and that farmers could supplement their animals with energy to promote faster liveweight gains, even when the sole diet is treated maize stover.
ACKNOWLEDGEMENTS
We are grateful to Mr H K Chikhawo and Mrs C H Jere and their staff for the daily management of the experiment and to the nutrition laboratory staff at the Central Veterinary Laboratory for analysing the feed samples and for manufacturing the urea-molasses blocks. We are also very grateful to Ms D Fatch for typing the manuscript.
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