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Potential of rubber seed as protein concentrate supplement for dwarf sheep of Cameroon

R.M. Njwe, M.K. Chifon and R. Ntep
Department of Animal Science
University Centre of Dschang
Dschang, Cameroon


Abstract
Introduction
Material and methods
Results
Discussion
Conclusion
References


Abstract

The performance of West African Dwarf sheep fed concentrates containing graded levels of unextracted rubber seed flour was evaluated in two experiments. In the first experiment carried out in 1984, 15 local sheep were fed concentrates containing 0, 10, 20, 30, 40 and 50 percent unextracted rubber for a period of three months. Results indicated that sheep fed concentrates containing 10 and 20% rubber seed had similar dry matter and crude protein intake as those on the control (0% rubber seed), while those maintained on 30 and 50% rubber seed concentrates consumed significantly (P<0.05) lower levels of dry matter and crude protein. The digestibility of dry matter, organic matter and crude protein was significantly tower in sheep fed 30 and 50% rubber seed concentrates compared to those on the 10 and 20% concentrates. Animals fed concentrates containing 0, 10 and 20% rubber seed gained 9, 10 and 17 g/day whereas those on concentrates containing 30 and 50% rubber seed lost weight at the rate of 26 and 51 g/day respectively. It was concluded that the limit of 20% rubber seed in concentrate rations for sheep should not be exceeded.

In the second experiment, 12 uncastrated male dwarf sheep ranging in age from 8 to 14 months and weighing between 11 and 15 kg were used to investigate performance when fed fresh Elephant grass and concentrate supplements containing 0, 10, 15 and 20% unextracted rubber seed meal as a substitute for cottonseed cake during a period of 56 days.

Dry-matter intake decreased as the level of rubber seed in concentrate supplement was raised. There were no significant differences in dry matter, organic matter and crude protein digestibility between the control and all other treatments containing rubber seed meal. Daily weight gain of sheep fed concentrates containing 0, 10, 15 and 20% rubber seed were 36, 50, 41 and 38 g/day respectively. Twenty percent level of incorporation of rubber seed meal or flour in concentrate rations for sheep is recommended. Application of results on the industrial and smallholder scale is discussed particularly as regards collection, shelling, detoxification and extraction of oil to obtain the cake which is a valuable protein source for livestock.

Introduction

There are large resources of conventional and non-conventional feeds in Cameroon that can be profitably used in stimulating animal production in general and small ruminants in particular. Prominent among the non-conventional agro-industrial feed resources is rubber seed. At the moment the country has the potential of producing 26,000 tons of rubber seed and the quantity will increase considerably when young plantations begin to produce fruits and with the creation of new plantations.

Rubberseed meal and the cake are higher in total digestible nutrients than soya-bean meal and is highly promising as a protein supplement. Rubberseed meal has a high level of lysine and tryptophan, making it a good companion for maize in poultry and pig rations, but poor in lysine (Ensminger and Olentine, 1978). Rubber seeds can be processed into oil and cake by pressing or ether extraction. The seed yields about 44% oil, 50% cake and 6% other wastes. The cake may contain 8 - 15% oil. The oil is comparable to soya-bean oil. The oil can be used for making paint and varnish (IRCA, 1982). Also, seeds when boiled and drained are eaten by Indians in the Amazon Valley of South America (Seibere, 1948).

Despite its potential as a protein feed for animals, fresh rubber seeds contain a toxic factor, cyanogenetic glucocide. The content in fresh seeds is about 200 mg/100 g of seeds (Gick et al, 1967). In the presence of the enzyme limarinase or in a slightly acid medium the cyanogenetic glucocide is converted to hydrocyanic acid which is poisonous. Symptoms of poison include increased pulse rate, no response to stimuli and spasmodic muscular movements (Maner, 1972). The hydrocyanic acid combines with hemoglobin to form a cyanohemoglobin complex which cannot carry oxygen. Small quantities of hydrocyanic acid do not result in death but may adversely affect the health of the animal (Stosic and KayKay, 1981). Detoxification of fresh rubberseed can be carried out by the following methods: Storage of fresh seed for 5-6 months before oil extraction; heat treatment by roasting fresh seeds in a kitchen oven or boiling in hot water, and soaking seeds in ash solution for 12 hours after which they are washed.

Although the cake or rubberseed meal can be used as animal feed (IRCA, 1983; Stosic and KayKay, 1981) little attention has been devoted to exploiting it in Cameroon as feed for livestock.

The first experiment was therefore designed to assess the value of rubberseed flour as the major protein source in concentrate supplements for West African Dwarf sheep. The second study was designed to limit the level of rubberseed flour in concentrates to below 20 % such that it substituted cottonseed cake in the diet of Dwarf sheep. The 20 % or less level of rubberseed in sheep concentrate supplements was based on the results of the first experiment.

Material and methods


Experiment I
Experiment II


Experiment I

Fifteen adult West African Dwarf sheep from the University farm, weighing between 15 to 20 kg were used for the study. Prior to the experiment they were dewormed and sprayed against ticks. The animals were randomly assigned to five treatments in a completely randomized design. The basal ration was fresh Guatemala grass (Tripsacum laxum) cut on a daily basis while the treatments were five concentrate supplements containing 0, 10, 20, 30 and 50 % rubberseed flour on weight basis.

Rubberseed flour was obtained from seed that had been stored for 6 months and boiled to detoxify them. The proportions of feedstuff's in each concentrate are shown in Table 1 while the proximate composition is shown in Table 2. Animals were maintained in individual metabolism cages during the entire experimental period of three months (January-April 1984). Concentrate (200 g/day) was served to each animal at 09.00 hours every morning while chopped forage (1.0 kg) was served at 10.00 hours and 16.00 hours. Water was provided to each animal ad libitum. Residues were weighed the following morning in order to estimate intake. The sheep were weighed weekly. During the last week of the experiment faeces were collected for evaluation of digestibility of diets.

Table 1. Experimental rations for local sheep.

Ingredients (%)

Concentrates


A

B

C

D

E

Maize

100

90

80

70

50

Milled rubber seed

-

10

20

30

50

Bicalcium

Phosphate

1

1

1

1

1

Salt

0.5

0.5

0.5

0.5

0.5

Total

100

100

100

100

100

Table 2. Proximate composition of Guatemala grass and concentrates fed to local sheep (%).


DM

OM

ASH

CP

CF

ME

NFE

Forage I

28.84

93.60

6.40

15.95

32.58

1.57

43.50

Forage II

26.16

93.28

6.72

15.67

29.25

2.89

45.47

Concentrate:


A

86.65

97.67

2.33

9.08

2.18

2.23

84.18


B

85.26

96.63

3.37

11.28

2.50

2.63

80.22


C

86.58

97.72

2.37

13.13

2.13

3.18

77.22


D

84.14

97.11

2.89

15.59

3.48

3.73

74.31


E

84.84

96.70

3.30

23.20

7.00

5.47

61.03

I, II represent experimental periods
A = control (no rubberseed in concentrates)
B = 10% rubberseed by weight in concentrate
C = 20% rubberseed by weight in concentrate
D = 30% rubberseed by weight in concentrate
E = 50% rubberseed by weight in concentrate

Experiment II

Twelve uncastrated West African Dwarf rams ranging in age from 8 to 14 months and weighing between 11 and 15 kg from the University farm at Dschang, Cameroon were used for the investigation. The animals were dewormed and sprayed against ectoparasites before the study began. The animals were randomly assigned to four treatments in a completely randomised block design. The basal diet was chopped fresh elephant grass (Pennisetum purpureum), cut on a daily basis while the treatments were for concentrate supplements containing 0, 10, 15 and 20 % rubberseed flour on weight basis. Rubberseed had been stored for 6 months and boiled to detoxify them. The proportions of various feedstuffs in each concentrate are shown in Table 3 while their proximate composition is shown in Table 4.

Animals in each treatment were group-fed for 7 weeks (March-May 1986) and thereafter they were transferred into individual metabolism cages for a period of 2 weeks for evaluation of feed digestibility. The daily ration, 600 g/day of concentrate supplement per group of animals was served at 08.00 hours and 10.00 hours while 6 kg of fresh elephant grass was also served twice a day. Residues of concentrate and forage were weighed after every 24 hours to estimate feed intake. Salt licks and fresh water were provided ad libitum while polyvitamin was provided in drinking water every fortnight. Animals were weighed weekly.

In both experiments proximate analysis of forage, concentrate and faecal samples was carried out according to the methods of A.O.A.C. (1970). Data from the experiments were analysed according to the procedures of Steel and Torrie (1980) for analysis of variance and the Duncan's multiple range test was used to test for significant differences between treatment means.

Results


Experiment I
Experiment II


Experiment I

Dry matter intake, digestibility and liveweight gain by sheep on various treatments are presented in Table 5. Dry matter intake ranged from 30.58 to 54.29 g/day/W0.75 kg. There were no significant differences in dry matter intake between sheep fed concentrate supplements containing 0, 10 and 20 % rubberseed flour with consumption of 53.84, 52.89 and 54.22 g/day/W0.75 kg respectively. When the percentage of rubberseed flour in concentrate was increased to 30 and 50 % there was a significant (P<0.05) decrease in dry matter intake. The trend was similar for crude protein intake. Crude protein intake decreased from 7.20 to 5.61 g/day/W0.75 kg as rubberseed flour in concentrate was raised from 0 to 50 %.

Table 3. Composition of rations fed to local sheep.

Ingredients (Percentage)

A

B

C

D

Maize

76.1

69.9

66.8

63.7

Rubberseed cake

0

10.0

15.0

20.0

Cottonseed cake

22.4

18.6

16.7

14.8

Salt

0.5

0.5

0.5

0.5

Bicalcium phosphate

1.0

1.0

1.0

1.0

Total

100

100

100

100

Table 4. Proximate composition of concentrate rubberseed and forage.

Components (percentage)

A

B

C

D

Rubber seed

Forage

Dry matter

89.8

90.4

90.3

90.3

92.7

15.35

Ash

3.5

5.1

3.2

3.8

2.6

13.90

Crude protein

20.5

19.3

19.3

19.6

21.0

8.48

Crude fibre

3.1

3.7

3.6

6.3

4.0

16.96

Ether extracts

5.7

8.1

10.9

12.3

39.7

3.78

Nitrogen free

67.2

64.2

53.0

58.0

32.7

56.88

A = Control (only cottonseed cake)
B = 10% rubberseed
C = 15% rubberseed
D = 20% rubberseed

Dry matter digestibility decreased as the level of rubberseed flour in rations was raised. Whereas for the control treatment dry matter digestibility was 77.91% for rations containing rubberseed it declined from 73.22% (10% rubberseed flour) to 57.42% (50% rubberseed flour). The same trend was observed for organic matter digestibility. Crude protein digestibility was quite high with values ranging from 74.96% to 79.99% for treatments with rubberseed flour in the concentrate. There were no significant differences between treatments.

While animals on the control treatment and those containing 10 and 20% rubberseed flour registered increase in weight or maintained their weight, those on concentrate containing 30 and 50 percent rubberseed flour lost weight continuously up to the 7th week after which they began to register gains but the initial weight was not attained when the experiment ended. Sheep on. diets containing 30 and 50 percent rubberseed flour had an average daily weight loss of 21 and 51g respectively, while those having 10% and 20% rubberseed flour registered daily weight gains of 17 and 10 g respectively. The average daily gain for the control ration was 9 g.

Experiment II

Feed intake, digestibility and live weight gain by dwarf sheep maintained on fresh elephant grass and concentrate supplements containing various levels of rubberseed flour as substitute for cottonseed cake are presented in Table 6.

There were no significant differences in dry-matter intake between treatments. Values ranged from 59.82 to 63.18 g/day/W0.75 kg. Crude protein intake decreased as the level of rubberseed flour substituted for cottonseed cake in the concentrate was raised. Differences between treatments were not significant. For the control treatment, crude protein was 9.25 g/day/W0.75 kg while for sheep on concentrates with 10, 15 and 20 % rubberseed daily crude protein intake was 9.25, 8.66 and 7.68 g/day/W0.75 kg respectively. Dry-matter digestibility ranged from 67.22 to 70.66 % for sheep having concentrates with rubberseed flour while for those on concentrates containing only cottons seed as protein supplement it was 69.62 %. There were no significant differences between treatments. Organic matter and crude protein digestibilities were high with ranges of 69.29 to 72.36 and 73.21 to 76.45 % respectively. There were no significant differences between treatments. There were significant differences between treatments in daily weight gain. Whereas sheep on the control ration gained 36 g/day those on concentrates containing 10, 15 and 20 % rubberseed flour had weight gains of 50, 41 and 38 g/day respectively. Sheep on concentrate with 10% rubberseed flour had significantly (P<0.05) higher weight gain than other treatments.

Table 5: Feed intake digestibility and live weight gain by West African dwarf sheep fed fresh Guatemala grass and concentrate supplements containing various levels of rubberseed flour.


TREATMENTS


A

B

C

D

E

Feed intake

Dry matter g/day

448.08

370.67

369.61

326.11

298.17

g/day/W0.75 kg

53.84a

52.59a

54.22a

37.56b

30.58b

Crude protein g/day

66.63

50.69

54.08

51.43

48.99

g/day/W0.75 kg

7.20

7.19

7.94

5.92

5.61

Dry matter

77.91

73.22ab

72.50b

60.95c

57.42d

Organic matter

79.28a

74.15b

73.52b

69.90c

60.52c

Crude protein

80.22a

79.10a

78.37a

74.96a

79.99a

Live weight changes

Mean initial weight (kg)

18.86

12.36

12.53

20.30

22.36

Mean final weight (kg)

19.80

13.76

13.40

18.10

18.06

Average live weight gain (g/day)

9

17

10

26

56

NB: Figures in the same row with the sane letter script are not significantly different (P>0.05)

Table 6. Feed intake, digestibility and live weight gain by castrated dwarf sheep fed elephant grass and concentrate supplements containing graded levels of rubberseed flour as substitute of cottonseed cake.


Treatments


A

B

C

D

Feed intake

Dry matter






g/day

464.24

430.53

535.81

365.83


g/day/W0.75kg

63.14

63.88

59.82

55.22

Crude Protein






g/day

67.62

67.22

61.95

51.29


g/day/W0.75kg

9.25

9.25

8.66

7.68

Digestibility (%)


Dry matter g/day

69.62

67.22

67.22

70.66


Organic matter

71.77

69.44

69.29

72.36


Crude protein

75.18

76.21

73.21

76.45

Weight changes


Mean initial weight kg

13.58

11.33

13.33

12.00


Mean final weight kg

15.60

14.13

15.60

14.13


Average live weight gain (g/day)

36

50

41

38

A = 0% rubberseed
B = 10% rubberseed
C = 15% rubberseed
D = 20% rubberseed

Discussion

In both experiments, there is generally the tendency for dry matter intake to decrease as the level of rubberseed flour in rations is raised, but this decrease is not significant until the 20% level of incorporation is exceeded. Bo Gohl (1982) pointed out that rubberseed cake can constitute upto 25% of rations for poulets so long as it is supplemented with sulphur containing amino acids. Buvanendran and Siriwardene (1970) reported that rubberseed meal could be used upto the level of 20% for broiler rations while Maffeja (1984) found 20% level of incorporation appropriate for pig rations. Rubber seed may be incorporated in rations at higher levels after detoxification and defattening (Stosic and KayKay, 1981). The seed used for the experiments being reported here were not defatted. Riviere (1978) recommended 0.5 - 1.0 kg/day of rubberseed cake for young cattle while Bo Gohl (1982) suggested 2 - 3 kg per day for adult cattle, but indicated that the product was not quite appetising to sheep.

A decrease in crude protein intake with increase in the level of rubberseed flour in concentrate supplements for sheep was also evident in both experiments. This may be associated with diminishing amounts of concentrate that are consumed as rubberseed proportion in the concentrate is increased which is particularly significant when the proportion exceeds 20 %.

Dry matter digestibility was generally high in both studies, indicating that the rumen microbial population was adequately supplied with dietary nitrogen. The high digestibility of crude protein was also an indication of efficient use of dietary protein.

Meanwhile weight gains were poor in Experiment I when compared to the same levels of incorporation of rubberseed flour in Experiment II (i.e. 10 and 20%). This may be attributed partially to the use of adult sheep in Experiment I whereas growing sheep were used in Experiment II. Also, rubberseed was the major source of dietary protein in Experiment I whereas cottonseed cake and rubberseed were used in experiment II. This could have introduced differences in efficiency of feed intake and utilisation between the two groups of animals. However, the consistent loss in weight by sheep fed concentrate rations with 30 and 50 % level of rubberseed flour in experiment I may be attributed to the possibility of accumulation of hydrocyanic acid in the product which may not have been adequately detoxified before the seeds were milled into flour. Weight loss could also result from the low dry-matter intake that was observed.

At the moment, rubberseed is not used as animal feed despite abundant production in various rubber plantations in the rainy forest region of Cameroon. The cost of production involves collection from the plantations, shelling of fruits to obtain the seeds, detoxification either by treatment with ash solution or heat or long storage for at least 6 months, milling of seed into flour, and separation of oil to obtain the cake using a press or ether extraction.

Utilisation of rubberseed meal or cake has a lot of applications at the level of the smallholders in the southern parts of Cameroon where rubber plantations employing e large labour force are common. Associated with these plantations are smallholder schemes which also sell latex to the large agricultural corporations.

The abundant family labour available in rubber plantations can supplement family income considerably from collection of seed which can be marketed and subsequently processed into the oil and cake on an industrial basis. The oil can be transformed into soap, paint and varnish.

The smallholders can provide better quality feed for poultry, pigs, sheep and goats just by collecting and processing rubber seeds that are presently allowed to rot in plantations. Locally undefatted meal or cake can be used as animal feed. The only constraints against the exploitation of the product are the cost of collection; the bulky nature of the fruits containing the seeds and the tendency for the seed to become mouldy as they are not stored under proper conditions. Also, rubberseed production is seasonal. A large crop is obtained between August and September while a minor one occurs in December and January. Interrupted supply will therefore demand adequate storage to cover other seasons of the year. These constraints can be surmountable at the smallholder level. Any press used for palm, soybean or groundnut oil extraction can also be used for rubberseed oil extraction. Since there is competition for consumption or export of palm, soybean or groundnut oil, rubberseed oil at the smallholder scale may form a basis for small-scale soap production at the family and village level.

Small-scale farmers in the south of Cameroon are not aware of the potential of using rubberseed as animal feed and production of soap from its oil. There is a need to develop a cheap press for extraction of rubberseed meal and a fruit cracker to reduce the time factor associated with these operations so that the processing of rubberseed is more appealing to small-scale farmers. Pilot studies in a rural setting to demonstrate the processing of rubberseed and possibilities for utilisation are needed for smallholders in order to captivate their interest.

Conclusion

Utilisation of undefatted rubberseed meal in rations of sheep should not exceed the 20% level of incorporation. Higher levels may be used if extraction of oil is carried out to obtain the cake. A mixture with other protein sources like cottonseed cake is an advantage. Detoxification is a prerequisite for utilisation of rubberseed. Processing and use of rubberseed meal or cake as animal feed especially for small ruminants has a lot of potential at the smallholder scale. Soap production is a small-scale industry that can develop from the processing of rubberseed.

References

A.O.A.C. Association of official Analytical Chemists. 1970. Official methods of analysis. Washington D.C. USA.

Bo Gohl, 1982. Les aliments du be'tail sous les tropiques: Donnees sommaires et valeur nutritive. Division de Production et Sante' Animale, FAO, Rome, Italy.

Bufanendran, V. and Siriwardene, J.A. 1970. Rubber seed meal in poultry diets. Cevlon Vet. J. 18:33-38.

Ensminger, M.E. and Olentine, C.G.J. 1978. Feeds and nutrition. Clinton Press, Clovis, California, USA.

Gick, L.T. Samsudin, M.D., Husaini, B.S. and Tarwotjo, I.T. 1967. Amer. J. Clin. Nutr. 20:1300-1303.

IRCA (Institut de Recherche sur le caoutchouc en Afrique) 1981. L'Hevea cultures en France: les station I.R.C.A. (Institut de Recherche sur le caoutchouc en Afrique) des Caraibes. Caoutchouc et Plastiques 630:69-70.

IRCA (Institut de Recherche sur le caoutchouc en Afrique). 1983. Utilisation des graines d'hevea. Caoutchouc et Plastiques 629:83-84.

Maner, J.H. 1972- Cassava in swine feeding. In: First Latin American Swine Seminar, CIAT, Cali, Colombia, September 18-21, 1972. Centrol International de Agricultura Tropical, Cali, Colombia.

Meffeja, F. 1984. Utilisation of agro-industrial by-products in animal feeding: Replacement of cottonseed cake with 0, 20, 30 and 40% rubberseed meal supplemented with blood meal in pig rations. Final year Memoire, ENSA Dschang University Centre, Yaound Cameroon.

Riviere, R. 1978. Manual d'alimentation des ruminants domestiques en milieu tropical Ministere de la Cooperation, Paris, France.

Stosic, D.D. and KayKay, J.M. 1981. Rubber seed as animal feed in Liberia. World Animal Review 39:29-39.

Steel, R.G.D. and Torrie, J.H. 1980. Principles and procedures of statistics - a biometrical approach. 2nd ed. McGraw Hill Book Company Inc., New York, USA.


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