L.A. Mtenga1, D. M. Komwihangilo2 and G. C. Kifaro1
1Department of Animal Science and Production Sokoine University of Agriculture, P.O. Box 3004, Chuo Kikuu, Morogoro, Tanzania2Livestock Production Research Institute P. O. Box 202, Mpwapwa, Tanzania
Abstract
Introduction
Materials and methods
Results and discussion
Behavioural and intake studies
Conclusion
References
Selectivity of Blackhead Persian sheep and Small East African goats fed Albizia lebbek, Gliricidia septum, Leucaena leucocephala and Tamarindus indica was determined through behavioural and intake studies conducted at the Sokoine University of Agriculture, Tanzania between May and July 1991. The four sheep used were 1-2 years old. The four goats were 4-5 years old. The weight of the animals was between 20 and 29 kg. During the behavioural study, animals were confined into pens of 170 x 160 cm. Time spent by each animal on feeding, ruminating and idling activities was monitored from 0900 hours to 1700 hours for four consecutive days. The amount of dry matter (DM) of tree species eaten by animals was recorded for two consecutive days.
The behavioural and intake studies showed that leucaena was the most preferred tree species. Sheep and goats spent 155 and 160 min per eight hours respectively eating leucaena and consumed 40.2 ± 15 and 46.50 ± 11.32 g DM/kgW0.75 per day. Gliricidia septum was the tree least preferred by both animal species and time spent on it and amount consumed was negligible. There was no difference (P<0.05) between sheep and goats in utilising these tree species during the behavioural study, but there was a difference (P<0.05) between animal species during the intake study. Albizia lebbek was more favoured by sheep (P<0.05) than by goats. Sheep and goats did not differ (P>0.05) in utilising Tamarindus indica. The need for further investigation is highlighted in this study.
Choix alimentaires d'ovins et de caprins du fourrage d'Albizia, Gliricidia, Leucaena et Tamarindus, espèces à usages multiples
Résumé
De mai à juillet 1991, des études de comportement et de consommation ont été effectuées à l'Université agricole de Sokoine en Tanzanie, pour déterminer les choix alimentaires de moutons Blarkhead Persian et de petites chèvres d'Afrique de l'Est recevant du fourrage d'Albizia lebbek, Gliricidia sepium, Leucaena leucocephala et Tamarindus indica Les 4 moutons utilisés étaient âgés de 1 à 2 ans, et les 4 chèvres, de 4 à 5 ans. Le poids des animaux variait de 20 à 29 kg. Pour l'étude de comportement, les animaux étaient enfermés dans des box de 170x 160 cm. Le temps consacré par chaque animal à l'alimentation, à la rumination et au repos a été observé entre 9 et 17 heures pendant quatre journées consécutives; la quantité de matière sèche des espèces ligneuses consommée par chaque animal a été relevée sur deux journées consécutives.
Leucaena s'est révélé l'espèce ligneuse la plus appréciée. Sur une période de huit heures, les ovins et les caprins consacraient respectivement 155 et 160 min au broutage de cette espèce, dont ils consommaient respectivement 40,2 ± 15 et 46,50 ± 11,32 g de MS/kg de P0,75 par jour. L'espèce la moins recherchée tant par les ovins que les caprins était Gliricidia sepium; le temps consacré à son broutage et les quantités consommées étaient négligeables.
L'étude de comportement n'a pas fait apparaître de différence (P<0,05) entre les caprins et les ovins pour ce qui est de l'utilisation de ces espèces ligneuses, mais une différence (P<0,05) entre espèces animales a été observée dans l'étude de consommation. Albizia lebbek était plus apprécié par les moutons (P<0,05) que par les chèvres. Aucune différence (P>0,05) n'a été observée entre les moutons et les chèvres pour ce qui est de l'utilisation de Tamarindus indica L'article souligne la nécessité de poursuivre cette étude.
The use of multipurpose trees (MPTs) has been advocated in the tropics for several reasons. These include: supply of fodder to livestock; wind breaks; providing protection and supplying nutrients to the soil and therefore to plants; supplying fuel for cooking and heating; acting as live fences; and providing shade to both man and livestock. In Tanzania, the cut-and-carry system of using MPTs is common in many areas, particularly Kilimanjaro, Arusha, Mbeya and Tanga. The MPTs play a special role in supplying the animals, particularly sheep and goats, with protein and energy during the dry season.
There has been little study however of the physical and chemical composition of the MPTs commonly used by farmers. There is also limited information on the behavioural aspect of sheep and goats when fed several cut MPTs simultaneously. The aim of this preliminary study was to determine the physical and chemical composition of the cut MPTs and to assess the eating preferences and selectivity of sheep and goats.
Location, animals and feed
The experiments were conducted at the Department of Animal Science and Production, Sokoine University of Agriculture, Tanzania between May and July, 1991.
Four female mature Blackhead Persian (BHP) sheep and four female mature Small East African goats were used. The sheep were 1-2 years old and weighed between 20-25 kg. The goats were 4-5 years old and weighed between 21-29 kg.
The tree species used in the study were Albizia lebbek, Gliricidia septum, Leucaena leucocephala and Tamarindus indica Chloris gayana hay was provided as a basal ration to the animals.
Experiment I: behavioural study
Two sheep and two goats were confined in separate groups in pens of size 170 x 165 cm inside the main sheep/goat house. Branches of the tree species were tied separately and placed at different heights for maximum exploitation of the grazing/browsing behaviour and for ease of observation during the experiment. Chloris gayana hay and drinking water were also available ad libitum. The pens were cleaned and the previous day's residues removed before the feed or water was replaced.
There was a preliminary adjustment period of seven days followed by the trial period of four consecutive days. The animals were observed from 0900 hours to 1700 hours every day. The animals' behaviour actions towards fodder were observed as described by Lehner (1987). The way an animal utilised the four randomly placed tree species and Chloris gayana hay was monitored. Records kept included: time in minutes spent on each tree species; time spent eating hay; time spent drinking water; time spent walking; time spent lying and ruminating; time spent standing and ruminating; and time spent idling. The plant parts browsed/grazed by the animals were also noted. At the end of every observation day animals were transferred to other pens where they were housed at night without any feed.
Chemical analysis
Dried samples of favoured plant parts i.e. leaves, pods and bark were taken for chemical analysis. Materials were ground to pass through a 1.25 mm screen in a Christy and Norris 20 cm laboratory hammer mill. Chemical components such as dry matter (DM), Ash, ether extract (EE), crude fibre (CF), calcium (Ca) and phosphorus (P) were determined by standard methods (AOAC, 1990). Nitrogen-free extract (NFE) was calculated by using the formula:
NFE = 100-(Moisture + CP% + CF% + EE% + Ash%)
Statistical analysis
Data on time spent by both sheep and goats on different tree species were subjected to analysis of variance as outlined by Snedecor and Cochran (1989). Parameters considered during the analysis included means, standard deviations and standard errors or the difference between means. These were calculated according to the following model:
Yijk = m + Ti + Aj + Ek + (TA)ij + (TE)ik + AEjk + (TAE)ijk + Rijkl
where:
m = general mean
Ti = effect of tree species
Aj = effect of animals species
Ek = effect of the day of test
(TA)ij = interaction between animal and tree species
(TE)ik = interaction between tree species and day of test
(AE)jk = interaction between animal species and day of test
(TAE)ijkl = interaction between tree species, animal species and day of test
Rijkl = residual
Experiment 2: intake study
The eight animals used in Experiment 1 were put in individual pens and provided with the four tree species, hay and water for a preliminary period of seven days. Samples of the branches of trees fed to animals were taken before feeding and fractionated separately into leaves (including tender branches), pods, bark and wood. The samples were weighed when fresh, dried in an oven at 60-62°C for 24 hours, then weighed again.
The measurement period was two consecutive days for each of the tree species provided per animal. To ensure that every animal had a continuous access to the feeds, every fodder tree was provided to allow for 20% refusals. Clean water was available all the time.
Refusals were collected, fractionated and dried in an oven at 60-65° C for 24 hours for dry matter (DM) determination. The quantity of leaf materials eaten by an individual animal was calculated by the difference between weight of leaves given (gDM) and the weight of leaves refused (gDM).
Chemical analysis
Chemical analysis of Albizia lebbek, Gliricidia septum, Leucaena leucocephala, Tamarindus indica, and Chloris gayana hay was as described in Experiment 1.
Data processing and statistical analysis
Data on leaf bark and wood fractions eaten or refused of each tree species were expressed simply as percentages of total amount of each tree plant material offered.
Data on the amount of leaf materials eaten were subjected to the same ANOVA (Snedecor and Cochran, 1989) model used for experiment 1.
The physical and proximate composition of MTPs and hay fed to the sheep and goats are presented in Tables 1 and 2, respectively.
Table 1. Physical composition of samples of multipurpose trees fed to sheep and goats (%).
|
Trees species |
Parts |
|||
|
Leaves |
Bark |
Pod |
Wood |
|
|
Albizia lebbek |
38 |
16 |
13 |
33 |
|
Gliricidia septum |
40 |
16 |
- |
44 |
|
Leucaena leucocephala |
39 |
16 |
- |
45 |
|
Tamarindus indica |
22 |
14 |
36 |
28 |
Table 2. Proximate composition of leaves of the multipurpose trees and hay fed to sheep and goats (%).
|
Tree species |
DM |
CP |
CF |
Ash |
|
Albizia lebbek1 |
38.7 |
21.9 |
28.3 |
7.3 |
|
Gliricidia septum |
23.7 |
25.2 |
17.9 |
11.1 |
|
Leucaena leucocephala3 |
33.0 |
24.0 |
22.2 |
6.7 |
|
Tamarindus indica2 |
46.5 |
11.5 |
20.8 |
9.1 |
|
Chloris gayana hay |
90.8 |
6.6 |
44.4 |
8.2 |
1 Pods of A. lebbek had 20.3% CP.
2 Pods of T. indica had 8.7% CP.
3 Barks of L. leucocephala had 11.8% CP.
The chemical composition of Albizia lebbek leaves (Table 2) compared well with values reported by NAS (1971) and FAO (1981) in terms of CP but slightly higher values of CF were obtained in this study (28.3% vs 26.5%). The variations in the chemical composition between different parts are due to the physiological fractions of the parts such as photosynthesis in the leaves and storage in the pods. Variations are also caused by the stage of growth of the plant parts (Brewbarker and Hulton, 1979).
The chemical composition of Gliricidia leaves and Leucaena leaves was similar to values reported by Atta-Krah and Reynolds (1989). For Gliricidia leaves, however, slightly higher values of protein were obtained when compared to the value obtained by Semenye et al (1986). The crude protein and crude fibre contents of Leucaena leaves were within the ranges reported by Atta-Krah and Reynolds (1989). The ash value is similar to that of 6.95% obtained by Hulman et al (1978). Le Houérou (1980) reported average crude protein and crude fibre contents of tamarind leaves to be 10.9% and 14.8%, respectively. Results from Tamarindus indica for crude protein were similar to those reported by Le Houérou, but in this study the crude fibre content was higher.
The stage of regrowth of different forages were reported to cause differences in nutritive values (Brewbaker and Hulton, 1979). This could account for variations in the chemical composition reported by different workers. The plant materials in this study were collected from different locations and were at different stages of growth. Variation in chemical composition of different parts of the same plant species could also be due to the functional role of the plant part and its stage of growth in relation to the other parts.
In the behavioural study (Tables 3, 4 and 5), sheep and goats showed no difference (P<0.05) in utilising Gliricidia septum and Leucaena leucocephala. However, these animals differ (P<0.05) in the way they utilise Albizia lebbek and Tamarindus indica. The behavioural study showed that sheep find Albizia lebbek more palatable than do goats. Similarly, the intake study showed that there was a difference (P<0.05) in the amounts of Albizia lebbek consumed by the goats and sheep. Goats consumed an average of 112 g DM/day of Albizia leaves, compared to sheep whose daily consumption was 289 g DM/day.
The study showed also that pods of Albizia lebbek were not eaten by either sheep or goats. This is contrary to what was reported by Singh et al (1989). Palatability and selectivity are determined partly by the animal's prevailing nutritional and physiological status and partly by the environmental circumstances. Environmental circumstances include the relative availability of various parts from which the choice is made (French, 1970). These factors may contribute to the differences observed in this study.
Table 3. Time in minutes spent by sheep and goats on eating the multipurpose trees and hay on free choice basis for eight hours.
|
Feed |
Sheep |
Goat |
|
A. lebbek |
20.5a |
5.1b |
|
|
(5.67) |
(1.47) |
|
G. septum |
0.3 |
1.3 |
|
|
(0.63) |
(0.18) |
|
L. leucocephala |
155.1 |
160.1 |
|
|
(42.15) |
(45.90) |
|
T. indica |
53.7b |
100.3a |
|
|
(14.59) |
(28.78) |
|
C. gayana hay |
138.5a |
81.8b |
|
|
(36.91) |
(23.7) |
Figures in brackets represent percentage time.
ab = Values within rows bearing different superscripts are significantly different (P<0.05).
Table 4. Time in minutes spent by sheep and goats on different activities during the eight hour study period.
|
Activity |
Sheep |
Goats |
|
MPTs |
229.4 |
267.1 |
|
Eating hay |
138.5 |
82.0 |
|
Ruminating |
68.3 |
33.8 |
|
Drinking water |
31.2 |
85.2 |
|
Walking |
1.3 |
1.4 |
|
Idling |
11.1 |
9.7 |
This study shows that the animals did not like Gliricidia septum. Both species spent very little time eating this plant. Studies in India also showed that cattle did not like this tree species. The intake study showed that goats ate only 45 g DM/day (4.6 g DM/W0.75). However, Onwuka (1986) reported an intake of 176.83 g/day and Mba et al (1982) reported an intake of between 233.80 to 294 g/day by goats. Onwuka (1986) used dry Gliricidia leaves to feed his goats while Mba et al (1982) used fresh materials. In both studies periods of up to six months were used. It is probable that longer periods of exposure are required before the animals can accept Gliricidia. Chadhokar and Kantharaju (1980), however, reported that Gliricidia maculata was found palatable by both cattle and sheep even when fed in very large quantities over a long period.
Although the difference in intake by sheep and goats of wilted and fresh Gliricidia has not been well documented, wilting is believed to increase the acceptability of the forage leaves.
The ranking of tree species eaten is shown in Table 5. Semenye et al (1986) ranked Gliricidia last and Leucaena leucocephala as number one among the six protein feed resources studied in their experiment. Meulen et al (1979) reported the presence of secondary plant metabolites such as beta-carotene and xanthophyll in Leucaena. These may make Leucaena leucocephala the most preferred of the four tree species.
The results of this study are contrary to the report by Wilson (1957) that goats are not very selective regarding plant species. Selectivity by goats and sheep was shown to be related to the species of the plant materials offered, especially in the cut-and-carry system (Semenye, 1991). Knowledge of the palatability of plants fed to sheep or goats may be used as a tool to increase dry matter intake (DMI) of animals by offering the least palatable first and the most palatable last (Semenye, 1991). Palatability ranking could have been clearer if more forage tree species had been included.
The higher crude protein and lower crude fibre contents in leaves and pods of MPTs suggests that they may be used as supplements to low crude protein feeds such as Chloris gayana hay particularly during the dry season. However, acceptability of the different fractions of MPTs differ between sheep and goats. The chemical composition of a plant or plant part may not determine its acceptability to the animal. Techniques of sampling and measuring yield and nutritive value of edible parts (leaves, bark, pods) of MPTs also need to be developed.
Table 5. Palatability ranking and dry matter intake (g DM/day) by sheep and goats.
|
Feed |
Sheep |
Goats |
||
|
Intake |
Rank |
Intake |
Rank |
|
|
L. leucocephala |
432+16 |
1 |
453 ± 25 |
1 |
|
|
(40.2 ± 15.6) |
|
(46.5 ± 1 1.3) |
|
|
T. indica |
229 ± 75 |
3 |
251 ± 87 |
2 |
|
|
(21.3 ± 6.9) |
|
(25.8 ± 14.1) |
|
|
A. lebbek |
289 ± 99 |
2 |
112 ± 60 |
3 |
|
|
(26.9 ± 90) |
|
(11.4 ± 6.2) |
|
|
G. septum |
18 ± 4.0 |
4 |
45 ± 22 |
4 |
|
|
(1.7 ± 1.0) |
|
(4.6 ± 2.2) |
|
1Figures in brackets show intake in g/kgW0.75
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