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The effect of supplements of crop residues and agro-industrial by-products on the growth performance of Swazi goats

B.H. Ogwang and S.K. Karua

University of Swaziland, P.O. Luyengo, Swaziland

Abstract
Introduction
Methodology
Results and discussion
Conclusions
Reference

Abstract

Goat production in Swaziland is characterised by low offtake resulting from lack of management of rangelands and seasonal fluctuations in feed resources. Periodic droughts and extensive dry spells in winter which cause nutritional stress result in low productivity of the goats. The aim of the study reported here was to assess the growth response in young male Swazi goats grazed on natural pastures to supplementation with maize stover, sugar-cane tops and dry pineapple pulp. The major findings from the study were that (a) the growth rates in goats under natural grazing can be improved by protein supplementation (b) dried pineapple pulp has considerable potential as an energy feed for goats (c) higher growth rates can be achieved by supplementing the pineapple pulp with protein (d) maize stover and sugar-cane tops, in their present form, have limited possibility for improving weight gains in goats.

Introduction

Goats play a very important role in Swazi custom and culture as well as in the economy (Ogwang et al 1994). However, goat production is characterised by low offtake resulting from poor management of the rangelands and seasonal fluctuations in feed resources. Periodic droughts and extensive dry spells in winter cause severe feed shortages resulting in undernourishment and low productivity among the animals. Any effort to improve their nutrition could therefore enhance productivity and utility.

The study reported here is the second phase of a research project being conducted under the African Small Ruminant Research Network on the use of crop residues and agro-industrial by-products by smallholder farmers in Swaziland. The main objective of the study was to measure the growth response of goats to supplementation with maize stover, sugarcane tops and dried pineapple pulp.

Methodology

Animals and treatment

At the start of the study, 63 indigenous male goats were bought from local farmers and assembled for acclimatisation at the University farm. Eleven goats died of heartwater and worm infestations within a three-week period. The remaining goats were subsequently treated on a monthly basis with Deadline to control the heartwater and Panacur to control worms and diarrhoea. No deaths occurred thereafter.

Out of the remaining 52 goats, 48 were selected for the experiment based on age and weight. The age range, based on dentition, was from 14 to 23 months. Individual goat weights varied from 12 to 29 kg at the start of the feeding period. The goats were grouped according to age and weight from which they were randomly assigned to the treatments indicated in Table 1.

Table 1. Assignment of goats (in groups of 4) to the different dietary treatments.

Dietary treatment

Levels of protein supplement

0 g

80 g

160 g

Grazing only

(4)

(4)

(4)

Grazing + maize stover

(4)

(4)

(4)

Grazing + sugar-cane tops

(4)

(4)

(4)

Grazing + pineapple pulp

(4)

(4)

(4)

The goats were grazed on natural pastures from 1100 to 1600 hours after which they were given the crop by-products and water ad libitum overnight. The protein supplement was given at 0800 hours.

The goats were weighed at two-week intervals and intakes of the crop residues and supplement were monitored on a regular basis.

Feed composition

The dominant grass species grazed were Hyparrhenia filipendula, H. dissoluta, Heteropogon contortus, Eragrostis racemosa, Bothriochloa insculpa and Brachiaria brizantha while the shrub species included Acacia nilotica, A. caffra, Terminalia phanerophlebia, Melia azedarach, Combretum apiculatum and Dichrostachys nyassana. The chemical composition of the grass and shrub species during the study period is presented in Table 2 together with those of maize stover (MS), sugar-cane tops (SCT) and dried pineapple pulp (DPP). The protein supplement was prepared by mixing a commercial concentrate with yellow maize to give a high protein concentrate (HPC) mixture with an average protein content of 26%.

Table 2. The chemical composition of natural grazing and crop by-products.

Feeds

DM (%)

CP (% DM)

CF (% DM)

EE (% DM)

Ash (% DM)

NFE (% DM)

Grass

95

3.5

31.3

0.7

4.7

59.8

Browse

93

10.7

13.9

-

5.7

-

Maize stover

92

4.2

34.4

2.1

4.4

54.9

Sugar-cane tops

92

4.2

34.3

2.2

6.9

52.4

Pineapple pulp

92

3.4

16.1

1.6

4.2

74.7

DM = dry matter;
CP = crude protein;
CF = crude fibre;
EE = ether extract;
NFE = nitrogen-free extract.

Results and discussion

Daily intakes of MS, SCT and DPP without protein supplementation and monitored weekly from mid-September to November 1994 are presented in Figure 1.

The daily intakes of MS and SCT were similar averaging about 80 g over the eight-week period. However, intake of DPP was much higher reaching a peak of 750 g per day in the sixth week. MS and SCT are known to be low quality roughages which contribute little to animal production unless subjected to some physical or chemical treatments. Dried pineapple pulp appears to be a good source of energy for the goats.

There was no evidence of any dramatic improvement in intake of MS and SCT and DPP through protein supplementation (Figures 2, 3 and 4). At a low level of protein supplementation, the intakes of MS and DPP were slightly depressed.

Changes in live weights of the Swazi goats over a 75-day period under different dietary treatments are presented in Table 3.

High level protein supplementation improved growth rate in goats grazed on natural pastures only as well as those fed crop-resides in addition to grazing. Growth response to protein supplementation was more remarkable under grazing only and when grazing was combined with the feeding of DPP. The better improved growth rates observed in goats grazed on natural pastures only and those given DPP in addition to grazing suggest that protein was more limiting in those circumstances than was the case in animals fed SCT and MS in addition to grazing (Table 1). The DPP could also have been better utilised because of its low crude fibre content and high energy potential compared to SCT and MS.

Figure 1. Changes in daily intake of crop residues with time.

Figure 2. Change in daily intake of maize stover with time.

Figure 3. Daily intake in sugar-cane tops with time.

Figure 4. Changes in daily intake of dried pineapple pulp with time.

Conclusions

Growth rates in goats under natural grazing can be improved if supplemented with adequate protein. It seems then that under the grazing conditions studied, protein could be a more limiting factor for goat production than energy. There is therefore a need to explore cheap and easily available protein sources. When protein is available, the energy requirement can be further supplemented with DPP. Maize and sugar-cane tops have limited possibilities for improving weight gains in goats unless subjected to some physical or chemical treatments.

Table 3. Changes in live weight of goats under different dietary treatments.




Level of protein supplement*

0 g

80 g

160 g

AWC (kg)

ADG (g)

AWC (g)

ADG (g)

AWC (kg)

ADG (g)

Grazing only

4.9

65.3

4.7

62.7

6.1

81.3

Grazing + maize stover

2.4

32.0

2.7

36.0

3.5

47.7

Grazing + sugar-cane tops

2.5

33.3

3.1

41.3

3.6

48.0

Grazing + pineapple pulp

4.5

60.0

6.1

81.3

6.3

84.0

* AWC = average weight change;
ADG = average dietary gain.

Reference

Ogwang B.H., Mavimbela D., Vilakati R. and Khumalo G.Z. 1994. Socio-economic aspects of goat nutrition in Swaziland. In: Lebbie S.H.B., Rey B. and Irungu E.K. (eds), Small Ruminant Research and Development in Africa. Proceedings of the Second Biennial Conference of the African Small Ruminant Research Network, AICC, Arusha, Tanzania, 7-11 December 1992. ILCA (International Livestock Centre for Africa)/CTA (Technical Centre for Agricultural and Rural Cooperation). ILCA, Addis Ababa, Ethiopia. pp. 15-18.


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