Lemma Biru*, L.J. Lambourne** and Fana Tesfahunei*
* Institute of Agricultural Research (IAR), Adami Tulu Research Centre, P. O. Box 2003, Addis Ababa
** Formerly JAR, Feeds and Nutrition Consultant.
Abstract
Introduction
Material and methods
Results and methods
Conclusion
Acknowledgements
References
Crossbred exotic × Barka and exotic × Boran milking cows in month 3-5 of lactation (mean initial yield 6-9 kg/d) were fed fresh-cut Sesbania sesban or Leucaena leucocephala to replace part of the concentrate ration normally given during dry season grazing of natural pasture. A concentrate was fed at the rate of 2 kg plus 0.5 kg per kg initial dairy milk yield to a control group of 3 cows; in 4 similar groups either 0.3 or 0.6 of this concentrate allowance was replaced by fresh-cut leucaena or sesbania browse (1 kg browse dry matter per kg concentrate replaced) during 1 week change-over, and 2 weeks experimental feeding with a final week on the original concentrate ration. All cows had access to dry season pastures. Leucaena was eaten more freely (max. 12 kg fresh, 4 kg dry weight per day) than sesbania (max. 8 kg fresh, 2.5 kg dry). Milk yield of the browse-fed groups was significantly higher in the two 7-day browse feeding periods than in the preliminary and final control feeding periods. Milk yield was higher in the experimental than the control periods by 0.45 kg/d in the controls, by 0.85 and 0.30 kg/d in the 0.3 and 0.6 sesbania groups, and by 0.76 and 1.18 kg/d in the 0.3 and 0.6 leucaena groups.
Shortage of feed is the main constraint to livestock productivity in the arid and semi-arid zones. Almost all year round, the annual feed budget would not maintain the feed requirement of livestock rations. A large proportion of the rift valley's grazing lands have dry seasons lasting from six to eight months each year. With the advancing dry season, grazing animals turn more and more to browse to satisfy their daily needs for feed. The advantage of browse is its ability to maintain its feeding value into the dry season. (Sherman, 1977).
Being deep-rooted shrubs or trees, browses offer some drought tolerance and being leguminous they provide forage of higher nutritive value than dry season unimproved pastures. Jones (1979) reviewed the use of Leucaena as forage, while Jones and Jones (1984) reported that inclusion of leucaena in sub-tropical pastures gave better annual weight gains in beef cattle and supplementation with leucaena was shown to maintain production in milking cows (Plucknett, 1970).
As part of a study of the adaptability of browses to a range of environments in Ethiopia, Sesbania sesban and Leucaena leucocephala were established at the IAR cattle research centre at Adami, Tulu in the Rift Valley, 160 km south of Addis Ababa In March 1987. This is a semi-arid zone, with 400-600 mm rainfall in the months of March July. Growth was studied under rainfed conditions and under intermittent irrigation, and sufficient amount of forage was available mainly from the latter area for a short feeding experiment in November - December 1987, the middle of the dry season, using cows in mid-lactation from the crossbreeding herd at the Centre.
Both species were established in April with occasional watering. Sufficient forage was cut each afternoon for that evening and the following morning feeding. Records were kept of the total and of the usable material harvested from both leucaena and sesbania. Samples were taken for dry matter (DM) determination from the feeds offered and from the residues, since the latter contained much stemmy material of higher DM content.
Fifteen cows from the IAR crossbreeding study in months 3 to 5 of lactation were allotted to 5 groups of 3, each including offspring of Barka and Boran dams. Groups were balanced as far as possible for initial milk yields; group means ranged from 6.8 to 8.1 kg/d - and were then allocated at random to the control treatment and 4 experimental feeds.
All cows received the concentrate allowance in 2 feeds, at morning and afternoon milking times. Browse groups were tied for one to one and half hours to eat their browse ration after morning and afternoon milking. After morning milking, cows were allowed to graze. Browse was given to replace 0.3 and 0.6 of the concentrate. A surplus of about 30% was offered to ensure ad libitum intake.
Milk records were taken as part of normal herd routine and yield in the week (November 24-30) was taken as the initial control value for calculation of concentrate entitlement, 2 kg/d plus 0.5 kg per kg of milk. The control group received this amount from December 3 until January 2. Browse was offered to the other groups in small amounts on December 1 and 2; from December 3 to 11 the concentrate was reduced and browse increased to the desired levels and then maintained for 2 weeks until December 25. From December 26 no browse was fed; all cows returned to their initial calculated concentrate entitlement until January 1 and then to normal station feeding.
Browse intakes and milk yields were studied by analysis of variance, milk yields were also adjusted by covariance on yield in the initial week.
Browse intakes results are summarized in Table 1. Intake was generally higher in the second experimental week (week 3) than in the first (week 2), but the intake of sesbania was only slightly higher in the 0.6 group offered about 12.5 kg/d than in the 0.3 group offered only 6.3 kg/d. Intake of the corresponding leucaena-fed cows increased to over 11kg/d when additional feed was offered, compared to the 12-14 kg/d reported by Plucknett (1970).
Table 1: Intake of cows offered sesbania and leucaena to replace 0.3 and 0.6 of their concentrate allowance*
|
|
Mean intake of concentrate* and fresh browse (kg/d) | |||
|
|
Week 2 (12-18/12) |
Week 3 (19-25/12) | ||
|
Group |
Concentrate |
browse |
Concentrate |
browse |
|
Control |
5.7 |
- |
6.7 |
- |
|
0.3 Sesbania |
3.7 |
4.8 * 0.5 |
3.6 |
4.9 * 0.5 |
|
0.6 Sesbania |
2.2 |
5.6 * 1.7 |
2.2 |
6.1 * 1.3 |
|
0.3 Leucaena |
3.5 |
4.7 * 0.7 |
3.5 |
5.1 * 0.6 |
|
0.6 Leucaena |
2.0 |
10.4 * 1.1 |
2.0 |
11.3 * 0.4 |
* Lower concentrate intake of leucaena groups indicates that groups randomly assigned to leucaena had lower initial milk yields.
Dry matter (DM) intakes (Table 2) show that browse intake adequately replaced the planned 0.3 and 0.6 of the concentrate, except in the 0.6 sesbania group. Concentrate intake in that group was reduced by 3 kg DM but sesbania intake replaced only 2 kg of this amount.
Table 2. DM intake of cows fed browse to replace 0.3 and 0.6 of their concentrate ration.
|
|
Mean intake of concentrates and browse (kg/DM/d) | ||||||
|
|
Concentrate |
Week 2 |
(12-18/12) |
Week 3 (19-25/12) | |||
|
|
entitlement |
conc. |
Browse |
total |
Conc. |
Browse |
total |
|
Control |
5.27 |
5.27 |
- |
5.27 |
5.27 |
- |
5.27 |
|
0.3 sesbania |
4.85 |
3.44 |
1.69 |
5.13 |
3.44 |
1.73 |
5.17 |
|
0.6 sesbania |
5.12 |
2.05 |
1.92 |
3.97 |
2.05 |
2.09 |
4.14 |
|
0.3 leucaena |
4.65 |
3.26 |
1.41 |
4.67 |
3.26 |
1.58 |
4.84 |
|
0.6 leucaena |
4.71 |
1.86 |
3.11 |
4.97 |
1.86 |
3.47 |
5.33 |
Leucaena DM intake averaged about 47% of the supplement, not including the additional intake of grazed pasture and straw offered overnight. There was no problem from the mimosine content of leucaena even though leucaena formed more than 40% of the total diet (Donaldson et al, 1970, Dharmaraj et al, 1984, Jones and Jones 1984). The mimosine content of mature leucaena foliage in the dry season is likely to be quite low.
Response of individual cows: Comparison showed that the mean yield in the 2 experimental periods in all groups exceeded the mean of the initial sod final control periods. Calculation for each cow showed that mean milk yield was higher in the experimental than in the control periods by 0.45 kg/d in the controls, by 0.85 and 0.30 kg/d in the 0.3 and 0.6 sesbania groups and by 0.76 and 1.18 kg/d in the 0.3 and 0.6 leucaena groups respectively. The increase in yield of the control cows was because the experimental concentrate allowance was higher than the Centre's routine concentrate feeding level.
Comparison with controls: Milk yields in the 2 experimental and final control periods showed a significant correlation (r = 0.82) with yield in the initial week. Milk yields adjusted by covariance on initial yields are shown in Table 3, with results of the analysis of variance indicated by superscripts.
Table 3. Adjusted milk yields of control and browse-fed groups
|
|
Mean yield (kg/cow/d) |
|
|
|
Initial and final control periods |
2 expt. per |
|
Control group |
7.22 |
7.62a* |
|
0.3 sesbania |
7.40 |
8.25b |
|
0.6 sesbania |
7.31 |
7.70a |
|
0.3 leucaena |
7.40 |
8.25b |
|
0.6 leucaena |
7.51 |
8.65b |
* Values with different superscripts differ significantly (P<0.01)
Whereas the 0.6 sesbania group milk yield was no higher than the controls, the other browse-fed cows all gave significantly higher yields; 0.3 sesbania and 0.3 leucaena gave similar yields and the 0.6 leucaena group, although highest, was not significantly higher than the 0.3 browse groups. This confirms the result of the individual comparison of unadjusted milk yields, above.
The original intention to feed browse to replace up to 75% of the concentrate had to be modified. It would have been possible with leucaena but not with sesbania. Except in the case of the high level of sesbania, milk yield increased under browse supplementation.
Whether response to browse supplementation is beneficial in economic terms clearly depends on the cost of growing the forage. 1kg browse DM can be viewed as nutritionally equivalent to 1 kg concentrate, but even with leucaena, there is likely to be some wastage in feeding.
The mandate of the Institute of Agricultural Research in Ethiopia is to conduct research and the extension activity is being carried out by the Ministry of Agriculture. Within the Ministry of Agriculture, the Fourth Livestock Development Project is responsible for the extension activity of the pasture and forage results (programme). The research-extension linkage of the country was limited until 1985. Since then research-extension linkage committees have been organised in various parts of the country. It is hoped that in future, research results could be easily disseminated to the farmers.
With regard to leucaena and sesbania utilisation the rate of acceptance of these browse plants by farmers is encouraging.
It was reported that leucaena has been used in Hararge region by farmers for fattening and in Gojan region farmers use sesbania for alley cropping. This indicates that leucaena and sesbania have been successfully adopted by farmers. Since more seeds could be produced from both species, farmers can easily get the seeds and in future it is likely that these browse species could be easily multiplied and used by farmer in most parts of the country.
The total cost of establishing 1 hectare of browse was about 30 cents per kg of forage harvested in the first year. In later years the cost could be reduced to maintenance and harvesting, and the yields from 3 to 4 harvests could be 9 to 10 tonnes/ha/yr. Hence the cost of forage should be not more than about 5 cents/kg and the cost of concentrate is over 30 cents/kg. This shows that sesbania and leucaena can replace the expensive and often unavailable concentrate.
The economic benefit of sesbania and leucaena in terms of milk and meat has shown considerable success both under research and in farmers, condition. In the long run this innovation has to be tested by farming system research unit which is now in its foundation stage.
The authors wish to thank Assefa Haile Selassie and Simon Abay for their valuable technical assistance with all the browse-feeding operations and Hailu Gebremariam, Centre Manager, for accepting so cheerfully any interruptions to routine herd management that the experimental operations caused.
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Donaldson L.E. Hamilton, R.I. Lambourne, L.J. and Little, D.A., 1970. Assessing Leucaena leucocephala for deleterious effects in cattle and sheep proc. XI th Int. Grassl. Congr. University of Queensland Press. p. 780.
Jones, R.J. 1979. The value of Leucaena leucocephala as a feed for ruminants in the tropics. Wld, Anim. Rev. 31:31.
Jones R.M. and Jones R.J. 1984. The effect of leucaena leucocephala on liveweight gain, throid size end throxine levels of steers in South-eastern Oueensland. Aust. J. Exp. Agric. Anim. Husb. 24:4.
Plucknett, D.L. 1970. Productivity of tropical Pastures in Hawaii. Proc. XIth Int. Grassl. Congr. P. A38. University of Queensland Press, Brisbane.
Skerman, P.J. 1977. Tropical forage legumes. FAO, Rome.
