Livestock Research for Rural Development 8 (3) 1996

Citation of this paper

Replacing concentrates with molasses blocks and protein-rich tree leaves for reproduction and growth of rabbits

Le Thu Ha, Nguyen Quang Suc, Dinh Van Binh, Le Thi Bien and T R Preston(1)

(1) Finca Ecolológica, University Agriculture and Forestry, Ho Chi Minh City, Vietnam - e-mail: thomas%preston%sarec%ifs.plants@ox.ac.uk

Goat and Rabbit Research Centre, SonTay, Vietnam

Abstract

Conventional feeds for commercial rabbit production in Vietnam are concentrates and grass. Increasingly, concentrates are becoming more expensive and they compete with human needs as they are based on cereals and protein meals such as soya bean and fish meal. A problem also with local production of concentrates is the absence of facilities to make "pellets" and rabbits do not like to eat feeds in the form of meal or powder because the fine particles cause respiratory and digestive problems.

This study is part of a research programme that aims to develop feeding systems that use locally available feeds accessible to poor farmers.

This study aimed to evaluate multi-purpose trees such as Mulberry (Morus indica) and Trichantera gigantea (introduced from the coffee-growing region of Colombia) as sources of protein; and molasses, cassava root meal and rice bran as sources of energy produced in the form of a "block" to avoid the "dust" problem.

Two experiments were carried out. Experiment 1 was in the reproduction/lactation phase with 20 New Zealand White does in individual cages. Experiment 2 was during growth and fattening (weaning to 2 kg body weight) with 60 weaned rabbits housed 5 per cage. The two treatments were the same in both experiments and were: concentrates and grasses (control) ; a molasses block and mixture of leaves from mulberry and trichantera (70%) and grasses (30%) (experimental).

The diet of molasses block and leaves from mulberry and Trichanthera gigantea resulted in better performance than the diet of concentrates and grass. During gestation and lactation the molasses/leaves diet supported higher body weight of does, heavier litters at birth and weaning, higher milk yield, better feed conversion and lower feed costs; and during growth and fattening, faster growth (by 30%), better feed conversion and lower feed costs. It was concluded that the new system was well suited to family scale production.

Key words: Rabbits, local feed resources, tree leaves, molasses blocks, growth, gestation, lactation, mulberry, Morus indica, Trichantera gigantea

Introduction

Rabbits are important in the rural economy as poor farmers can obtain income with little capital investment. The opportunity to consume animal protein is also a means of improving the diet of women and children.

Conventional feeds for commercial rabbit production in Vietnam are concentrates and grass. Increasingly, concentrates are becoming more expensive and they compete with human needs as they are based on cereals and protein meals such as soya bean and fish meal. A problem also with local production of concentrates is the absence of facilities to make "pellets" and rabbits do not like to eat feeds in the form of meal or powder because the fine particles cause respiratory and digestive problems.

In Vietnam molasses, rice bran, cassava root meal are cheap agricultural by-products which can be used instead of cereal grains for rabbits. New sources of protein are the leaves of trees such as Trichantera gigantea (introduced from the coffee-growing region of Colombia) and Mulberry which have been shown to have a high protein content and also are eaten readily by rabbits (Olsson and Sandberg 1995).

This study aimed to evaluate the leaves from multi-purpose trees such as Mulberry (Morus indica) and Trichantera gigantea as sources of protein; and molasses, cassava root meal and rice bran as sources of energy produced in the form of a "block" to avoid the "dust" problem.

Materials and methods

Two experiments were carried out. Experiment 1 was in the reproduction/lactation phase with 20 New Zealand White does in individual cages. Experiment 2 was during growth and fattening (from 30 days of age to 2 kg body weight) with 60 weaned rabbits housed 5 per cage. The two treatments were the same in both experiments and were: concentrates and grasses (control) ; a molasses block and mixture of leaves from mulberry and trichantera (70%) and grasses (30%) (experimental).

The composition of the molasses blocks and the concentrate is shown in Table 1. Clay was used in the blocks to improve the "hardness" and texture. Molasses and cassava root meal were the main sources of energy in the blocks. In the concentrate the energy was from broken rice, maize meal and cassava root meal. The protein content of the concentrate was 14.7% (DM basis) and 9.723% in the block , half of which came from soya bean meal . The protein content (DM basis) was 11% for elephant grass and 13% for guinea grass, in the leaves of mulberry (only leaves) it was 25% and in Trichantera gigantea (leaves and petioles) 16%.

Table 1: Composition of the molasses blocks and the concentrates

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Concent.

----% air dry ----

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Molasses

37

Cassava root meal

23

26

Rice bran

20

Clay

10

Soya bean meal

10

8

Broken rice

25

Maize meal

26.5

Fish meal

3

Groundnut cake

5

Mineral mixture

3

Bone meal

3

Salt

0.5

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For Experiment 1 the does were started on the test diets immediately after mating and continued until weaning for one complete cycle of pregnancy and lactation. The experiment 2 on growing-fattening began with weaned rabbits at 30 days of age and continued for 60 days until 90 days of age.

Records were kept daily of feed offered and refused. The does were weighed at the beginning and at weaning. Litters were weighed at birth, at 21 days and at 30 days (weaning). Milk production was calculated as [(weight of litter at 21 days - litter weight at birth) x 1.18] g (Lebas et al 1986). Growing rabbits were weighed at the beginning, at 10 day intervals, and after 60 days (90 days of age).

Results

Reproduction and lactation

The results for liveweight change and (calculated) milk production in Table 2 show significant benefits for the diet of molasses blocks and tree leaves compared with the conventional system of concentrates and grass. On the former the does gained 34 g during the production cycle while on the "conventional" system they lost 32 g (P=0.12). The litters from does fed the blocks were heavier at birth and at weaning (P=0.01) and this advantage was reflected in the 10% higher milk yield (P=0.01). Litter size was not affected by treatment. Conversion of feed dry matter and protein (N x 6.25) were significantly better on the molasses block and leaves than on the concentrate-fed control. Feed costs per unit weight of weaned rabbit were only one half that recorded for the control group.

Table 2: Effect on reproduction performance of rabbits of replacing concentrates and grass with molasses block and tree foliages

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Control

SE/P

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Liveweight, g

Initial

2,780

2,755

±84/NS

Final

2,802

2,736

±30/0.12

Weight change

33.8

-31.8

±30/0.12

Litter size

Birth

5.2

5.1

±0.15/0.65

Weaning

5.2

5.1

±0.15/0.65

Litter weight, g

Birth

298

278

±8.7/0.01

21d

1303

1188

±13/0.01

30d

2718

2547

±73/0.11

Milk yield, g

1808

1638

±44/0.01

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Table 3: Mean values for feed intake of rabbits during pregnancy and lactation fed a molasses block and protein-rich leaves as replacement for concentrate and grasses

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M B

Con/grass

SE/ Prob

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Feed intake (g/d)

Molasses block

186

0

Concentrate

0

163

Mulberry

347

0

T. gigantea

1262

0

Guinea grass

619

2205

Elephant grass

214

750

Total DM

203

244

±1.23/ 0.85

N x 6.25

23.4

34.6

±0.16/ 0.63

Conversion (kg/kg)

DM

4.92

6.23

±0.18/0.001

N x 6.25

0.57

0.88

±0.002/0.001

VND feed/kg weaned

4,974

10,804

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Growing rabbits

The rabbits grew 33% faster (P=0.001) on the molasses block and leaves than when fed concentrates and grass (Table 4). Feed DM conversion was 24% better on the experimental diet (P=0.08) and there was more economical use of the protein (P=0.005). Feed costs on the molasses block and leaves were only half of those for the concentrate and grass diet.

Table 4: Mean values for growth and feed intake of fattening rabbits fed a molasses block and tree leaves or concentrates and grass

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Concen.

SE/Prob

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Liveweight, g

Initial

501

502

±13/NS

Final

1738

1429

±40/0.001

Daily gain

20.6

15.5

±0.67/0.001

Feed intake, g/day

Molasses block

65.5

0

Concentrate

0

60.2

Mulberry

123

0

T. gigantea

638

0

Guinea grass

206

605

Eleph grass

113

291

Total DM

72.1

71.3

±3.11/0.85

N x 6.25

10.4

11.0

±0.86/0.63

Conversion (kg/kg)

DM

3.51

4.61

±0.22/0.08

Protein

0.53

0.66

±0.04/0.005

Feed cost/kg gain

(VND)

3,920

8,055

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The calculated daily intakes of protein and the proportions for the main diet constituents are summarized in Table 5. Does fed concentrates ate more total protein and a much higher proportion (59%) in the form of "protein meals" compared with those fed the blocks and leaves. In the latter case, "meals" accounted for 43% of the protein while the leaves supplied 42%. For growing rabbits, protein intakes were similar for both treatments but the proportion as "protein meal" was 27% for the concentrate diet compared with 15% for the molasses blocks. On the latter diet the leaves supplied 65% of the protein.

Table 5: Amounts of protein from different diet constituents

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Concent.

g/d

%

g/d

%

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Does:

Meals

11.5

43

20

59

Leaves

11.2

42

0

0

Grass

4.0

15

13.7

41

Total

26.7

100

33.7

100

Growing:

Meals

5.1

15

7.7

27

Leaves

22.6

65

0

0

Grass

7.2

20

20.9

73

Total

34.9

100

28.6

100

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Discussion

In the first experiment with molasses blocks at this centre (Dinh Van Binh et al 1991) the blocks were based on a formula developed for cattle and contained 50% molasses, 20-30% bagasse pith and only 13% rice bran. The supplementary forage was elephant grass. Growth rates were between 9 and 15 g/day and less than on the control (17.5 g/day. The results from the present trial were much better with growth rates of 20.6 g/day for the blocks compared with 15.5 for the control. The differences were in the composition of the blocks (less molasses, no bagasse and inclusion of a small amount [10%] of soya bean meal) and the use of tree leaves (mulberry and Trichantera gigantea) replacing 70% of the forage. Probably both the more nutritional block and the protein-rich leaves contributed to the better performance in the experiments reported here. This finding is in agreement with the report of Olsson and Sandberg (1995) that weight gains on a nutrient-rich block (40% molasses, 35% rice bran, 15% cassava root meal, 10% clay) with 70% leaves and 30% grass were significantly higher (12.3 g/d) than when the forage contained 70% grass and 30% leaves (9.1 g/day).

The lower feed cost for the diet of molasses blocks and leaves was partly because of better feed conversion and also due to cheaper ingredients.

The actual proportions of leaves consumed were 82% of the total forage for the does and 66% for the growing rabbits. Thus for does there appeared to be more selection for the leaves and slightly less in the case of the growing rabbits (offer level was 70% in both cases).

The fact that leaves supplied most of the protein on the molasses block diets, and that the rabbits performed better on this treatment, provides support for our hypothesis that leaves from multi-purpose trees such as mulberry and Trichantera gigantea, which can be grown by the farmer, can replace the greater part of the dietary protein normally supplied by purchased concentrates.

Conclusion

Acknowledgements

This research was supported by the International Foundation for Science through a grant to the senior author (B/1251-1).

References

Dinh v. Binh, Bui-v-Chinh and T R Preston 1991 Molasses-urea blocks as supplements for rabbits. Livestock Research for Rural Development Volume 3, Number 2, pp:13-18

Lebas F, Coudert P, Rouvier R and Rochambeau H de 1986 The rabbit; husbandry, health and production.FAO Animal Production and Health Series, No 21

Olsson Anna and Sandberg Veronica 1995 Small-scale animal husbandry in North Vietnam. A literature review and result from a case study in North Vietnam. Swedish University of Agricultural Sciences and International Rural Development Centre. Working paper 299, pp57.

 

(Received 31 August 1996)