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Nutritional studies with West African Dwarf goats in the humid zone of Nigeria

A.A. Ademosun, H.G. Bosman, & P.L. Roessen

Goat Research Project
Department of Animal Science, University of Ife
Ile-Ife, Nigeria


Introduction
Materials and methods
Results
Discussion
Conclusions
Acknowledgements

Summary

Results of two completed and one continuing feeding/growth trials are discussed. When fed Panicum maximum plus concentrates ad lib, West African Dwarf (WAD) bucks attain a growth rate of 60 g.d-1 at a DDMI of 53.3 g kg-0.75.d-1, which is estimated to be approximately 1.8 times the DDMI needed for maintenance. These animals had a heavier dressed carcass (7.15 vs 4.75 kg) and more abdominal fat (0.70 vs 0.11 kg) than WAD bucks receiving P. maximum plus Leucaena leucocephala. Growth rates of WAD goats fed on Gliricidia septum only were similar to those reported for goats at village level. Supplementation with either young fertilized Panicum maximum (A), Manihot esculenta (B) or Leucaena leucocephala (C) improved DDMI (A:40.6, B:45.7, C:42.3 vs 37.9 (Gliricidia only) g.kg-0.75.d-1). Leucaena supplementation also gave significantly higher growth rates (36.0 vs 23.3 g.d-1) than Gliricidia alone. The response to cassava supplementation was confusing and further investigation is required.

Introduction

The Goat Research Project is carried out in collaboration among the National Agricultural University at Wageningen, ILCA and the University of Ife, Nigeria and was started in September 1981.

One of its main objectives is to study the management and economics of production of West African Dwarf (WAD) goats in the humid tropics. This includes not only an evaluation of the present situation but also the development of possible improvements. Since nutrition is seen as one of the most important limiting factors for improved goat production most research has been directed to this area. As the locally available fodder resources are considered as the most promising, investigations have been aimed at the assessment of their nutritive value.

In this paper the results of three experiments are presented. The objectives of experiment 1 were to determine the growth potential of Nigerian WAD goats and to compare concentrate with browse as a supplement to Panicum maximum. Experiment 2 was designed to evaluate the effect of supplementation of a diet consisting of Gliricidia septum only with any of young and fertilized Guinea grass (Panicum maximum), cassava (Manihot esculenta) or Leucaena leucocephala on growth rate and feed intake. The assessment of the effect of substitution of part of a diet consisting only of Gliricidia septum by Leucaena leucocephala on growth rate and feed intake was the main objective of experiment 3.

Materials and methods

EXPERIMENT 1

Six young WAD bucks (3-8 months old) were fed ad lib a ration consisting of Panicum maximum and concentrate (A) while five young bucks were offered ad lib a diet of Panicum maximum and Leucaena leucocephala (B). During an adaptation period of about 44 days, animals in treatment B also received a small and decreasing amount of concentrate to introduce them gradually to Leucaena leucocephala. Concentrate composition was (in per cent): maize 50.0, rice bran 30.0, brewers' dried grains 10.0, groundnut cake 7.5, dicalcium phosphate 1.5, salt 0.5, Vit. mineral mix 0.5. Every fifth to sixth week intake and digestibility were measured over a seven-day period. In total four of these collection periods were effected.

EXPERIMENT 2

Twenty-four WAD goats aged 3-5 months at the beginning of the experiment were divided into four treatment groups of six animals each (four castrates plus two females). The first group (A) received ad lib Gliricidia septum only; the other three received as basic diet Gliricidia (ad lib) supplemented with either young, fertilized Panicum maximum (B), (Manihot esculenta) (C) or Leucaena leucocephala (D) each at a level of 30 g DM kg-0.75. Of the browse, only the leaves and petioles were fed while the cassava supplement consisted of sun dried chopped tubers. Supplements were fed each morning before the rest of the ration. The first 40 days were considered an adaptation period. Every fifth to sixth week digestibility and feed intake were measured. Four of these periods were covered. The experiment was carried out between May and November 1984.

EXPERIMENT 3

Eighteen WAD goats (3-5 months old) were divided into three groups (two females plus four castrates per treatment). Group A was offered a ration of Gliricidia septum only (ad lib), which in groups B and C was partly substituted by Leucaena leucocephala (25 and 50 per cent respectively). Stems were offered separately from the leaves plus petioles by hanging them inside the cage. All animals within the same treatment received equal amounts of stem according to the proportion of Gliricidia and Leucaena in their ration. The first 40 days were considered an adaptation period. Every fifth to sixth week, feed intake and digestibility were measured over a seven-day period. The trial started in May 1985 and is still in progress.

In all three experiments animals were housed in individual metabolism cages after treatment against endo- and ecto-parasites. They had free access to clean drinking water and a salt lick throughout. The animals were weighed weekly (except during collection periods) and their rations adjusted accordingly.

Results

EXPERIMENT 1

Preliminary results have been presented elsewhere (Ademosun et al, 1985). Mean weights increased linearly after the adjustment period until day 156 of the experiment (Figure 1). The growth depression observed between days 156 and 200 was probably due, as appeared during the carcass evaluation, to a subclinical pneumonia outbreak. Growth performance and feed intake were therefore evaluated on the basis of the data recorded between days 44 and 156.

Data on feed intake and growth rate are summarized in Table 1. Dry matter intake and digestibility were higher in the concentrate treatment (A) resulting in a higher DDM intake in this group (55.1 vs 35.0 g.kg-0.75.d-1). Animals in the Leucaena treatment (B) ate absolutely and relatively (as percentage of DMI) more P. maximum. (B: 23.5 g.kg0.75.d-1 and 36 per cent vs A: 16.3 g.kg-0.75.d-1 and 25 per cent). Goats in group A grew faster (60.0 vs 34.8 g d-1) although the variation in the concentrate group was higher (s.d. 12.8 vs 5.3).

Figure 1. Weight gains of young WAD bucks on two different rations

Table 1. Feed intake and growth rates of WAD bucks fed ad lib Panicum maximum plus concentrates (n=6) or ad lib Panicum maximum plus Leucaena leucocephala (n=5)

Parameter



Treatment

Panicum + concentrate

Panicum + Leucaena

± std.

± std.

DM intake (g.kg-0.75.d-1)


Panicum

16.3a

2.6

23.5b

4.6


Leucaena

-

-

40.8

2.7


Concentrate

61.7

6.8

-

-

Digestibility (%)

69.3a

2.8

51.1b

3.2

DDMI (g.kg-0.75.d-1)

55.1a

4.2

35.0b

2.6

Growth rate days 44-156 (g.d-1)

60.0a

12.8

34.8b

5.3

Means in the same row without a common superscript differ significantly (P < 0.01)

The results of the carcass evaluation are given in Table 2. All components of the empty carcass were heavier in group A, except the empty gut. Animals in the Leucaena group put on relatively less fat but had a more developed gut system.

EXPERIMENT 2

Table 3 shows feed intake and weight gains for experiment 2. Two animals on each of treatments B and C had to be removed from the experiment because of illness (not due to treatment). Supplementation resulted in a higher DDM intake in all treatments, with the highest value for the cassava group (37.9 (A) vs 40.6 (B) and 42.3 (D) vs 45.7 g.kg-0.75.d-1 (C)). At the same time the mean intake of Gliricidia decreased in the grass and especially the Leucaena and cassava groups (66.7 (A) vs 56.8 (B) vs 42.5 (C) and 45.3 g.kg-0.75.d-1 (D)). However, as the standard deviation indicates, the response in group C was inconsistent (maximum/minimum: 67.2/15.4 g.kg-0.75.d-1)

Table 2. Carcass composition of WAD bucks (four animals per treatment) fed ad lib on P. maximum + concentrates (A) or P. maximum + L. leucocephala (B)

Body components


Weight (kg)

As % empty body weight

A

B

sign.

A

B

sign.

Blood

0.55

0.41

**

4.3

4.7

n.s.

Skin + feet + head

2.99

2.12

***

23.1

24.4

n.s.

Empty gut

0.74

0.72

n.s.

5.7

8.3

**

Organs

0.79

0.59

**

6.1

6.8

n.s.

Abdominal fat

0.70

0.11

**

5.4

1.3

***

Dressed carcass

7.15

4.75

***

55.3

54.6

n.s.

Empty weight

12.95

8.70

***

100.0

100.0


*** P < 0.001
** P < 0.01
n.s. not significant

Only Leucaena supplementation resulted in an improved growth rate and cassava tended to have a negative effect (23.3 (A) and 14.3 (C) vs 36.0 g.d-1 (D)). Growth rates of individual animals showed a considerable variation in the Leucaena (cv = 19 per cent, minimum/maximum 23.3/52.0 g.d-1) and cassava groups (cv = 76 per cent, minimum/maximum 0/30 g.d-1). It appeared that the poor performers in (C) had a lower DDM and a relatively higher cassava intake than the good performers (and as a consequence they had a diet with a rather low protein content).

EXPERIMENT 3

Table 4 gives some preliminary results on feed intake and weight gain up to and including the first collection period.

Total DMI was highest in the 75 per cent Gliricidia/25 per cent Leucaena (B) group (73.1 g.kg-0.75.d-1) whereas these values for 100 per cent Gliricidia (A) and 50 per cent Gliricidia/50 per cent Leucaena treatment (C) did not differ (65.2 and 66.9 g.kg-0.75.d-1 respectively). The same pattern was observed for the DDMl (45.3 (B) vs 38.0 (A) and 41.7 g.kg-0.75.d-1 (C)). Bark DMI accounted for about 16 per cent of total DMI and did not differ among treatments.

Table 3. Feed intake and weight gain of WAD goats fed on Gliricidia only (A) or supplemented with P. maximum (B), cassava (C) or L. leucocephala (D)

Treatment


n



DM offered

DM intake

Total DMI


DDMI


Growth rate days 40-168


Gliricidia

Supplement

Gliricidia

Supplement

A

6


94.0

-

66.7a

-

66.7

37.9c

23.3bc

± std.

5.9

-

6.2

-

6.2

3.2

3.7

B

5


93.7

32.4

56.8b

13.8b

70.6

40.6b

28.7ab

± std.

5.8

2.2

6.6

5.1

4.5

3.2

4.9

C

5


94.2

30.1

42.5c

23.0a

65.5

45.7a

14.3c

± std.

6.2

0.4

22.9

7.0

19.3

10.1

11.3

D

6


93.0

32.4

45.3c

25.6a

70.9

42.3b

36.0a

± std.

5.5

1.5

9.4

4.4

7.5

3.5

10.6

All values are g.kg-0.75.d-1 except for growth rate which is g.d-1.
Means in the same column without a common superscript differ significantly (P < 0.05).

Table 4. Preliminary results on feed intake and growth rate of WAD goats (six animals per treatment) fed diets containing 100 per cent Gliricidia septum (A), 75 per cent Gliricidia septum plus 25 per cent Leucaena leucocephala (B) or 50 per cent Gliricidia plus 50 per cent Leucaena leucocephala (C)

Parameter




A

B

C

+ std.

+ std.

+ std.

DM offered:

Gliricidia

106.7

0.6

78.8

0.4

53.0

0.5

Leucaena

17.6

3.4

24.9

0.3

50.4

1.5

Bark

17.6

3.4

14.9

2.1

13.7

1.5

DM intake:

Gliricidia

54.3a

4.3

39.2b

4.4

28.5c

9.8

Leucaena

-

-

22.1

0.5

28.8

10.2

Bark

10.9

4.4

11.7

1.8

9.6

2.7

Total

65.2b

3.7

73.1a

3.7

66.9b

3.4

DDMI


38.0b

1.8

45.3a

3.9

41.7b

4.9

Growth rate day 40-84


16.4

4.5

33.5

11.8

25.9

5.8

All values are g.kg-0.75.d-1 except growth rate which is g.d-1
Means in the same row without a common superscript differ significantly (P < 0.05)

Animals on the low Leucaena level ate almost all the Leucaena on offer (89 per cent) whereas on the high level, mean Leucaena intake equalled mean Gliricidia intake. However, as can be seen from the relevant standard deviations, variation among individual animals was considerable. It appeared that three goats did not consume more Leucaena as in treatment B ( = 20.9 g.kg-0.75.d-1)while two goats showed a pronounced preference for it ( = 38.5 g.kg-0.75.d-1).

The first weight records showed that most animals were gaining weight constantly after the adaptation period. Since growth rates have been calculated over a short period these should be regarded as a first indication, especially in view of the possible harmful effect of Leucaena when fed for an extended time.

Discussion

Growth rates and feed intake data found when offering ad lib P. maximum and concentrates are comparable to those obtained by Zemmelink, Tolkamp & Meinderts, (1985) feeding ad lib good hay plus 60 g.kg-0.75.d-1 concentrates (58.5 g.d-1) and by Adebowale & Ademosun (1981) including 15 per cent brewers' dried grains in a Stylosanthes based diet (56.1 g.d-1).

Zemmelink, Tolkamp & Meinderts, (1984) estimated the energy requirements for maintenance and growth respectively at 26.0 g DOM (kg-0.75) and 2.41 g DOM per gram of liveweight gain. Assuming an ash content of 10 per cent, this means that 28.9 g DDMI is needed for maintenance only. Animals on the concentrate treatment consumed 1.8 times this requirement which is about 11 per cent lower than the ratio found in the Netherlands where dwarf goats were fed high quality hay and concentrates ad lib.

It is not clear whether this difference is due to genetic or other effects such as climate or feed. Nevertheless, the value obtained in this experiment is a useful guide for the evaluation of the nutritive value of locally available feed resources.

Animals fed only on Gliricidia ate only 30 per cent more than needed to meet their estimated maintenance requirements. Growth rates at this level of intake were similar to the estimated daily gain of 20 g.d-1 between 90 and 150 days of age at village level (Mack, 1983).

Inclusion of more components in the diet tends to increase DDMI and hence, except in the case of cassava supplementation, animal performance. The combination of Leucaena and Gliricidia seems, in this respect, the most promising with a daily DDMI up to 57 per cent above estimated maintenance requirements, allowing a growth rate of about 35 g.d-1, which is 75 per cent higher than the weight gain at village level.

The continuing evaluation of different levels of Leucaena and Gliricidia might provide interesting information about the optimum levels in rations of both browse species, although it is still too early to draw clear conclusions.

The fact that the poor performers on the cassava treatment had a relatively as well as an absolutely higher cassava intake and relatively low DDMI might suggest a possible negative effect of cassava on total DMI. In this respect it is perhaps useful to recall that the supplements were offered before the rest of the ration. More research is needed to determine the exact effect of level and method of offering cassava on both feed intake and animal performance.

The carcass evaluation data show that young bucks fed intensively are able to put on considerably more meat (and not only fat) than bucks fed roughage only.

Conclusions

The following main conclusions can be drawn:

- West African Dwarf bucks in Nigeria can attain a growth rate of 60 g per day when fed intensively;

- diets containing Leucaena leucocephala and Gliricidia septum are quite promising as basic rations for fattening WAD goats, giving considerably higher growth rates than those achieved at village level;

- more research is needed to assess the effect of cassava supplementation on feed intake and animal performance.

Acknowledgements

The authors acknowledge the contributions of the whole project team especially H.J. Jansen, M. van Houtert, J. Ikpea and O.B. Smith. They are also grateful to students who participated in the project, in particular A.A. Egbe, Idowu and M. Boon.


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