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The value of Acacia brevispica and Leucaena leucocephala seedpods as a dry season supplement for calves in arid areas of Kenya

E. M. Nyambati1, C.N. Karue2 and N.K.R. Musimba2

1Kenya Agricultural Research Institute, P. O. Box 450 Kitale
2Faculty of Agriculture, University of Nairobi, P.O. Box 30197, Nairobi

Abstract

Two feeding experiments were conducted to evaluate the nutritive value of Acacia brevispica and Leucaena leucocephala seedpods in terms of chemical composition and liveweight performance. In feeding experiment one (FE-1), 18 calves weighing on average 132 kg and aged five to nine months were used. The treatments comprised of A1: control-1, B: Acacia seedpod meal (ASM) and C1: Leucaena seedpod meal (LSM-1). In feeding experiment two (FE-2), 16 calves weighing on average 131 kg and aged five and half to nine months were used. The treatments were A2: control-2 and C2: LSM-2.

Experimental diets were designed to supply isonitrogenous levels of 265 g CP to meet the CP requirement for a predetermined performance goal of 500 g/d. Control calves were given basal hay and wheat bran equivalent to the amount used in formulating ASM and LSM diets. Calves were weighed weekly over five and four weeks in FE-1 and FE-2, respectively. F-test was used to compare experimental groups with the controls.

Chemical analyses of seedpods of A. brevispica and L. leucocephala showed that contents of CP decline and fibre (NDF and ADF) increase with maturity. Seeds of both A. brevispica and L. leucocephala contained higher CP, EE and IVDMD, but lower fibre than empty pods. Dry L. leucocephala seedpods contained appreciably more tannins than A. brevispica. More of the tannins were located in the empty pods.

In FE-1, ADG (g/d) was 486, 250 and 239 for calves on LSM-1, ASM and Control-1, respectively. Calves supplemented with LSM-1 diet had better ADG (P<0.01) than control-1 and ASM supplemented calves. Calves on ASM had superior ADG than control-1, though not significantly (P>0.05). In FE-2, calves on LSM-2 had significantly higher (P<0.01) ADG (559 g/d) than control-2 (276 g/d) confirming the results obtained in FE-1. Intact seedpods of both legume trees had similar digestible energy (DE) contents. However, seedpods of A. brevispica used in FE-1 contained only 65% of their seeds and thus had lower contents of DE. The ADG of calves on ASM diet did not reflect the true nutritive value of intact seedpods.

It was concluded that if most seeds are retained, both seedpods are suitable feeds for ruminants, at least for strategic supplementation by smallholder farmers and agro-pastoralists when other feeds are unavailable in the dry season.

Introduction

Livestock productivity in sub-Saharan Africa remains low. Nutrition is one of the major constraints to cattle production in the tropics, particularly the lack of protein during the dry season (Karue 1974; FAO 1981; Minson 1990). In developing countries, conventional supplements such as oilseed cakes and animal by-product meals are rarely used because they are expensive and not readily available. Under these circumstances, the most practical supplement would be to use feed resources from locally available legume trees. Acacia, a genus of indigenous woody legumes occupy a dominant position in plant communities in semi-arid and arid areas of tropical and subtropical countries (NRC 1979). Studies have indicated that seedpods of some Acacia species such as A. tortilis and A. albida as well as leaves of A. brevispica when offered as supplements to poor-quality roughages, give liveweight gains comparable with those of livestock fed oilseed cakes and lucern (Medicago sativa) (ILCA 1988, 1989; Tanner et al 1990).

Leucaena leucocephala is a versatile drought tolerant tree legume and studies have demonstrated that Leucaena forage when fed as a supplement to roughages, supports liveweight gains comparable to those derived from conventional supplements such as oilseed cakes (Thomas and Addy 1977), animal by-product meals (Siebert et al 1976) and cereal by-product meals (Saucedo et al 1980; Manidool 1983). Chemical analysis of L. leucocephala seedpods in Nigeria (Adeneye 1979) and India (Damothiran and Chandrasekaran 1982) revealed that they are of high nutritive value indicating the possibility of utilising them as a source of cattle feed. Naseeven et al (1989) indicated that cracked L. leucocephala seeds are as good a protein source for fattening cattle as cottonseed cake. Both tree legumes are prolific producers of seedpods which can be harvested and fed to cattle. The current study evaluated the seedpods as a dry season supplement for smallholder farmers and agro-pastoralists when other feeds are unavailable.

Materials and methods

Experimental animals

Two feeding experiments were conducted at the University of Nairobi field station, Kabete, Kenya using Boran crossbred calves. In feeding experiment 1 (FE-1) 18 calves aged between five and nine months and weighing an average of 132 kg ( 91 to 150 kg) were used. The calves were assigned to three treatment groups balanced for age, initial liveweight and sex. The treatments were: A 1: control-1; B: Acacia seedpod meal (ASM) diet; and C1: Leucaena seedpod meal (LSM-1) diet. In feeding experiment two (FE-2), 16 calves aged between five to nine months and weighing an average of 131 kg (102 to 162 kg) were used. The calves were assigned to two balanced treatment groups: A2: control-2 and C2: LSM-2 diet.

Experimental feeds

Rhodes grass (Chloris gayana) and Maasai love-grass (Eragrostis superba) hays were used as basal diet in FE-1 and FE-2, respectively. Both hays were chaffed into approximately 510 cm pieces to facilitate handling and feeding. Dry seedpods of A. brevispica and L. leucocephala were collected, sun-dried for two to three days before they were ground into a meal. Approximately 65% of A. brevispica seedpods collected contained seeds. Most of the L. leucocephala seedpods collected contained all the seeds.

Experimental procedures

Calves were confined in individual pens throughout the experimental period. All calves were dewormed using valbazen and sprayed against ectoparasites using stelladone. Fourteen days were allowed as adjustment periods in both feeding experiments. The experimental diets (treatments B and C) were formulated using a legume seedpod meal, wheat bran and a mineral mixture in proportions designed to supply isonitrogenous levels. A daily intake (air dry weight) of 1.5 kg of diet B (ASM) and 1.2 kg of diet C (LSM) and at least 2.5 kg of basal hay would supply 60% (265 g CP) of the total CP requirement for a growth rate of 0.5 kg/d in calves of about 150 kg liveweight (NRC 1976). The control animals were offered 0.6 kg of wheat bran (diet A) equivalent to the amount used in formulating diet B and C. Supplemental diets were offered in the morning (0500 h). All calves were individually offered a basal diet of grass hay ad libitum between 0600 and 1430 h.

Calves were watered once a day (0915 to 1000 h) when ad libitum water was offered. Daily records of hay and supplement offered and orts were kept. Calves were weighed weekly on a weighbridge in the morning when they had been without food and water overnight for approximately 13 hours. FE-1 and FE-2 were conducted for five and four weeks, respectively.

Chemical and statistical analyses

Chemical analyses were carried out on seedpods at four phenological stages to monitor nutrient profiles with maturity and on separated seedpod components to determine the contribution made by seed and the empty pods (carpets) to the nutritive value of the whole seedpod. Chemical analyses were determined following conventional methods (Van Soest 1963; Tilley and Terry 1963; Burns 1963, 1971; AOAC 1980). Weekly liveweights of individual animals were adjusted using covariance analysis based on initial liveweights (SAS 1987). Computed average daily weight gain and grass hay intake data were subjected to one-way analysis of variance and treatment means separated using Duncan's multiple range test (Steel and Torrie 1980).

Results

Chemical analysis

Contents of CP, Ash, NDF and ADF in A. brevispica and L. leucocephala pods at four phenological stages are presented in Table 1. For both seedpods the contents of CP declined while that of fibre (NDF and ADF) increased with maturity. There was no consistent trend in the total ash in both seedpods. However, the levels did not fluctuate much with age. Nutrient composition of separated dry seedpod components of both A. brevispica and L. leucocephala are presented in Table 2. Seeds of both seedpods contained more CP, EE and were more in vitro digestible, but had lower fibre and total ash contents than empty pods (carpels). Seedpods of L. leucocephala had higher tannin contents than A. brevispica, more of which were located in empty pods.

Table 1. Contents of CP, Ash, NDF and ADF in L. leucocephala and A. Brevispica seedpods at four phenological stages.

Stage of growth

%DM

ADF

CP

Ash

NDF

A. brevispica

Immature (5)a

18.6

4.4

42.3

36.1

Dough (9)

18.4

5.0

49.0

36.6

Mature (13)

17.8

4.5

5.09

34.2

Dry (15)

14.3

4.1

55.0

33.5

L. leucocephala

Immature (5)

27.2

5.4

29.2

20.0

Dough (9)

2.08

5.5

46.8

34.4

Mature (13)

2.03

5.09

53.3

42.2

Dry (15)

18.6

5.7

56.1

42.1

a Number in parentheses denotes age in weeks after pod formation.

Table 2. Contents of CP, Ash, EE, NDF, ADF, IVDMD, DE and Tannin content of separated dry seedpod components of Leucaena leucocephala and Acacia brevispica.

 

Whole pods

Empty pods

Seeds

 

Leucaena

Acacia

Leucaena

Acacia

Leucaena

Acacia

CP

18.6

14.3

5.7

8.5

28.2

18.6

Ash

5.7

4.1

7.8

5.1

4.2

3.3

EE

4.4

3.8

2.3

2.2

9.1

4.2

NDF

56.1

55.0

73.7

78.5

41.3

30.7

ADF

42.1

33.5

62.0

58.1

19.3

16.0

IVDMD %

53

54.7

21.2

21.5

72.6

80.9

DEa (Kcal/g DM)

2.409

2.504

0.628

0.645

3.507

3.971

Tanning content (%)bc

1.76

0.09

2.03

0.18

1.55

005

a Estimated using regression equation, Y = –0.559 + 0.056X ; r = 0.966 and SE = 0.083 (Heaney and Pigden 1963) where X = digestible organic matter in g/100 g DM.

b Expressed as catechin equivalent.

c Standard curve given in Appendix 2.

Nutrient composition of feed ingredients, experimental diets and hay used in FE-l and FE-2 is given in Table 3. LSM and the formulated LSM diet had higher total ash, lower fibre, higher in vitro digestible and more estimated digestible energy (DE) than ASM and the formulated ASM diet, respectively. LSM-2 used in FE-2 had lower CP, higher fibre and lower in vitro dry matter digestibility than LSM-1. Both hays used in FE-1 and FE-2 contained similar contents of CP, ash, and fibre except for in vitro dry matter digestibility which in FE-2 hay was higher.

Table 3. Nutrition composition of feed ingredients, experimental diets and hay used in FE-I and FE-2.

 

%DM

DE (Kcal/g DM)

DM

CP

Ash

NDF

ADF

IVDMD

FE-1

Acacia seedpod meal

89.1

12.1

4.9

63.7

49.0

40.0

1.681

Leucaena seedpod meal-1

89.9

17.7

5.5

52.7

38.6

54.8

2.510

Wheat bran-1

88.9

16.0

6.9

53.5

16.4

72.5

3.501

Diet A1 (control-1)

92.3

15.6

8.3

50.5

15.6

75.4

3.663

Diet B (ASM)

91.8

14.0

6.5

59.0

32.6

56.0

2.577

Diet C1 (LSM-1)

92.1

16.6

7.3

52.8

25.1

66.9

3.187

Hay-1

94.2

4.1

8.7

79.2

49.3

41.8

1.782

FE-2

Leucaena seedpod meal-2

90.6

15.3

5.9

59.7

47.7

48.6

2.163

Wheat bran-2

89.2

19.0

6.8

43.9

13.8

75.3

3.658

Diet A2 (control-2)

88.9

18.3

8.7

43.4

13.2

78.2

3.820

Diet C2 (LSM-2)

88.7

17.2

7.2

50.7

29.4

64.6

3.059

Hay-2

91.4

3.6

6.3

78.0

53.0

53.4

2.431

Intake and liveweight performance

Intake of feeds and nutrients and ADG of calves in FE-1 and FE-2 are presented in Table 4a and 4b, respectively. Supplementation of legume seedpod meal diets increased the intake of protein and energy. The daily DM intake of hay expressed per unit metabolic weight (g DM/kg 0.75) was not different (P>0.05) among treatments but that of treatment B was lower (50.8) than that of treatment C (53.3) (Table 4a).

Table 4a. Liveweight gain and intake of grass hay, supplement, total CP and estimated digestible energy (DE) in FE-1.

Variables

Treatment

SE

CV

A1 (control)

B (ASM)

C1 (LSM)

Liveweight gain (g/d)

239a

250ab

486c

42

32

Intake

Grass hay (g DM/d)

1935a

2058a

2247a

135

 

(gDM/kg 0.75 bwt/day)

50.8a

50.3a

53.3a

 

11

Supplement (g/d)

554

1339

11.5

   

Total CP (g/d)

165

271

275

   

Estimated DE (Mcal/d)

5.477

7.118

7.525

   

abc Treatment means followed by the same letter superscript do not differ significantly (P<0.01).

Table 4b. Liveweight gain and intake of grass hay, supplement, total CP and estimated digestible energy (DE) in FE-2.

Variables

Treatment

SE

CV

A1 (control)

C2 (LSM)

Liveweight gain (g/d)

276a

559b

51

34

Intake

Grass hay (g DM/d)

3214a

3126a

104

 

(gDM/kg 0.75bwt/d)

79.8a

77.4a

 

7

Supplement (g/d)

553

1064

   

Total CP (g/d)

212

296

   

Estimated DE (Mcal/d)

9.926

10.854

   

ab Treatment means followed by the same letter superscript do not differ significantly (P<0.01).

Calves on LSM-1 diet had significantly (P<0.01) higher ADG (486 g/d) than those on ASM diet (250 g/d) and control-1 (239 g/d) (Table 4a). ADG of calves on ASM diet was higher (P>0.05) than control-1. Calves on LSM-2 had (P<0.01) better (P<O.OI) ADG (559 g/d) than control-2 (276 g/d).

Discussion

The amount of ASM diet consumed accounted for 39% of the total diet consumed, while the amount of LSM diet consumed accounted for 33% and 25% of the total diet consumed in FE-1 and FE-2, respectively. The intake of less than the amount of ASM diet offered and the lower intake of grass hay by calves on the ASM diet, could be attributed to the lower digestibility (Table 3) and the higher substitution effect resulting from the higher amount of ASM diet offered. The watering regime of once per day (Weeth et al 1968) and the CP content of less than 7% (Minson and Milford 1967) of grass hay could in part explain the lower DM intake than that recommended by NRC (1976).

The difference between calves on ASM and LSM-1 diets in daily intake of total CP was insignificant and yet differences (P<0.01) were observed in ADG. The superior ADG of calves on LSM diet could in part be attributed to the higher intake of DE and mineral contents of this diet.

Intact seedpods of both A. brevispica and L. leucocephala have similar in vitro DM digestibility and contents of estimated DE, more of which is located in the seeds (Table 2). A. brevispica seedpods used lost 35% of their seeds due to dehiscence (Lamprey 1967) and damage caused by a bruchid beetle (Southgate 1983) explaining why the ASM had low content of estimated DE. L. leucocephala used in FE-2 contained 80% of their seeds, but the higher CP and IVDMD of wheat bran used in FE-2 elevated the CP and IVDMD of LSM-2 used in FE-2 to a level comparable to that of LSM-1 which contained most of their seeds.

Conclusions

In arid and semi-arid tropical regions where seasonal changes (rainfall etc.) are extreme, both quantity and quality of pasture fluctuate rapidly with consequent periods of critical nutrient deficiencies. On communal African rangelands, which are often chronically overstocked, undernutrition and malnutrition lead to overall reduced growth rates and poor reproductive performance.

It is concluded that seedpods of L. leucocephala and A. brevispica can be used by smallholder crop–livestock farmers and agropastoralists in arid and semiarid areas to provide feed that is cheap and locally available at least for strategic supplementation to critical classes of cattle, particularly calves in the dry season when other feeds are unavailable. This may lift the major feed constraints to the development of livestock sector in arid and semi-arid areas of developing countries, thus increasing the livestock productivity of smallholder farmers.

Acknowledgements

The senior author thanks the University of Nairobi and the Kenya Agricultural Research Institute (KARI) for supporting his studies at the University of Nairobi.

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Valeur des gousses d'Acacia brevispica et de Leucaena leucocephala comme compléments alimentaires de saison sèche pour les veaux en zones arides au Kenya

Résumé

Deux essais d'alimentation ont été effectués afin d'évaluer la valeur nutritive des gousses d'Acacia brevispica et de Leucaena leucocephala sur la base de leur composition chimique et des performances pondérales des animaux. Dans le premier essai (E1), 18 veaux pesant en moyenne 132 kg et âges de 5 à 9 mois ont reçu les rations A1 (ration témoin n° 1); B (complémentation de farine de gousses d'Acacia(FGA)) et C1 (complémentation de farine de gousses de Leucaena (FGL1)). Dans le second essai (E2), 16 veaux pesant en moyenne 131 kg et âgés de 5 mois et demi à neuf mois ont requ les rations A2 (ration témoin n° 2) et C2 (complémentation de farine de gousses de Leucaena (FGL2).

Les rations expérimentales étaient conçues de façon à fournir uniformément 265 g de protéines brutes en vue de couvrir les besoins en protéines brutes nécessaires pour atteindre l'objectifde croissance de 500 g/j. Les veaux des lots témoins ont reçu une ration de base composée de foin et de son de blé dont la valeur protéique était équivalente à celle utilisée pour formuler les rations FGA et FGL. Les animaux ont été pesés une fois par semaine pendant 5 et 4 semaines, respectivement pour les essais E1 et E2. Le test F a été utilisé pour comparer les groupes expérimentaux avec les groupes temoins.

Les analyses chimiques des gousses d'A. brevispica et de L. leucocephala ont montré que leur teneur en protéines brutes baissait et que leur taux de cellulose (fibres NDF et ADF) augmentait avec la maturité des gousses. Leurs semences avaient des taux de protéines brutes, d'extractif éthére (EE) et de digestibilité in vitro de la matière sèche (DIVMS) plus élevés, mais un taux de cellulose plus faible que ceux des gousses vides. Les gousses sèches de L. leucocephala avaient une concentration en tanins beaucoup plus élevée que celle d'A. brevispica. Ces tanins étaient surtout concentrés daps les gousses vides.

Pour l'essai E1, les GMQ étaient de 486, 250 et 239 g/j respectivement pour les veaux recevant les rations C1, B et la ration A1. Les veaux recevant la ration C1 avaient un GMQ supérieur (P<0,01) à celui des animaux recevant la ration A1 ou la ration B. Les veaux recevant la ration B avaient un GMQ supérieur (P>0,05) à celui des animaux recevant la ration A1 mais cette différence n'était pas significative. Pour l'essai E2, les veaux recevant la ration C2 avaient un GMQ (559 g/j) significativement supérieur (P<0,01) à celui des animaux recevant la ration A2 (276 g/j), ce qui confnme les résultats du premier essai. Les gousses intactes de ces deux légumineuses arbustives avaient des teneurs en énergie digestible analogues. Toutefois, les gousses d'A. brevispica utilisés dans le premier essai ne renfermaient que 65% de leurs graines et avaient donc une teneur en énergie plus faible. Enfin, le GMQ des veaux recevant la ration FGA ne reflétait pas la véritable valeur nutritive des gousses intactes.

Il ressort de cette étude que les gousses des deux espèces peuvent, ensemble avec leurs semences, servir à la complémentation stratégique de l'alimentation des ruminants au niveau des petits agriculteurs et agro-pasteurs au cours de la saison sèche, c'est-à-dire en période de pénurie d'aliments du bétail.

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