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Comparative evaluation of stylo (Stylosanthes guianensis) hay and concentrate as protein supplement for West African Dwarf sheep fed basal diet of elephant grass (Pennisetum purpureum)

R.M. Njwe and B. Kona

Department of Animal Science
University of Dschang, B.P. 222, Dschang, Cameroon

Abstract
Introduction
Materials and methods
Results and discussion
Conclusion
References

Abstract

An investigation was carried out to assess the comparative values of stylo (Stylosanthes guianensis) hay and concentrate as protein supplements for growing West African Dwarf sheep. Three groups of sheep (12-15 months old with an average weight of 13.20 kg) were fed elephant grass (Pennisetum purpureum) alone (EG), or the grass and supplemented with either 200 g stylo hay (SH)/head per day or 140 g concentrate (CC)/head per day (each containing 27.12 g crude protein). The animals were fed in individual metabolism cages for 70 days. It was observed that dry-matter intake increased significantly (P<0.05) when EG (45.06 g/day/kgW0.75) was supplemented with SH (66.16 g/day/kgW0.75) or CC (71.29 g/day/kgW0.75). This same trend was also observed with crude protein intake, dry-matter (DM) and crude-protein (CP) digestibility. The proportion of dietary nitrogen retained by sheep was similar for groups fed SH (61.47%) and CC (61.39%). Sheep fed CC gained 78 g/day compared to 60 and 9 g/day, respectively, for those fed on EG plus SH and EG only. The high cost of concentrates makes them unaffordable by smallholders with limited resources, but SH production in smallholder farms is feasible and can provide a good quality protein supplement that could stimulate high weight gains in growing sheep.

Introduction

The increasing population density in the West and North-West provinces of Cameroon is responsible for the continuous decline in the size of smallholder farm holdings in the region. Mogavero (1986) indicated that in small farm areas of 1.8 ha, intensive agriculture based on Arabica coffee, vegetables, food crops, raffia palm and small livestock such as sheep, goats, pigs and poultry is practiced. Ducret and Grangaret (1986) reported that land is exploited to the maximum and is often cultivated continuously without fallow. Two crop cycles are common during the rainy season; the second cycle is limited to a third of the farmland, involving fewer crops and producing lower yields. Crop associations are complex such that the coefficient of land occupation ranges from 250-400%. The productivity of crop associations is often high (the land equivalent ratio ranging from 140-2305), ensuring on the average adequate feeding for 12 persons/ha, and may provide surplus for sale in some areas. Livestock density is estimated at 0.5-0.6 tropical livestock units/ha cultivated.

With such an intensive system of production, it is necessary to urgently evolve strategies of production that sustain adequate crop yields and at the same time ensure high productivity of livestock. Introduction of forage legumes into the farming system has been suggested as one of the strategies for ensuring the sustainability of livestock and crop yields in this region. Forage legumes do not only contribute to sustaining soil fertility but also provide better quality feed for livestock in the farming system, if available feed resources are judiciously managed. Animals that are confined during the cropping season to avoid crop damage, can be adequately maintained on farm feed resources. Excess forage legume produced during the growing season can be conserved as hay for dry season feeding, when animal feed is scarce. The objective of this study was to compare the performance of West African Dwarf sheep fed stylo hay (SH) and concentrate (CC) as protein supplements to an elephant grass (KG) basal diet.

Materials and methods

Fifteen West African Dwarf male sheep weighing 13.25±1.85 kg on average with ages ranging from 12 to 15 months were used in the trial. They were dewormed and sprayed against external parasites before the trial started. The animals were randomly divided into three groups of five animals each. Each group was allocated to a treatment in a randomised complete block design. After a one-week adaptation period to different diets, the experimental period started. The initial body weight of each animal was determined. Each animal was kept and fed in a separate metabolism cage during the entire experimental period of 70 days.

The three experimental rations were: fresh elephant grass (Pennisetum purpureum) fed alone (KG) as a control, elephant grass plus stylo (Stylosanthes guianensis) hay (EG+SH), and elephant grass plus concentrate (EG+CC). Fresh elephant grass ranging from 1-1.5 months cut on a daily basis was used as the basal diet. The forage was manually cut with a machete and chopped into pieces of about 10 cm before feeding to the animals. Two hundred grams of SH and 140 g of CC (each containing 27.12 g crude protein) were fed to each animal in the treatments already designated, in the morning at 0800 hours. The total daily allocation of fresh elephant grass (2 kg/day) was fed in two equal instalments at 0900 hours and 1600 hours. The compositions of KG, SH and CC are shown in Table 1. The concentrate was made up of 74% maize, 24% unextracted ground soya bean, 0.5% common salt, and 0.5% bicalcium phosphate. Fresh water and salt licks were provided ad libitum. All animals were weighed once a week throughout the experiment. The animals were weighed at 0700 hours before the morning feed was served. The amount of feed and refusals were monitored daily in order to estimate intake. Samples of fresh elephant grass, supplements and refusals were collected daily and their dry matter content determined. They were subsequently bulked on a weekly basis, ground and a sample of 500 g reserved for chemical analysis.

During the last two weeks of the experiment, a digestibility and N-balance trial was carried out. Faecal collections were carried out in order to estimate the digestibility of the rations. At 0800 hours total faecal output was collected, weighed, mixed thoroughly and 10% of each day's collection was used for dry matter determination. Subsequently, the samples collected over the seven-day period were combined, ground to pass through a 1 mm sieve and stored in a plastic bag for chemical analysis. The total urine output in 24 hours was collected in plastic jars containing 5 ml concentrated hydrochloric acid. It was mixed thoroughly, and 10% of the day's collection stored in sample bottles in a deep freezer. The urine samples collected over a seven-day period were bulked before analysis for urinary nitrogen.

Table 1. Chemical composition of feeds.

Proximate components

Elephant grass

Stylo hay

Concentrate

Dry matter %

21.46

88.04

88.01

Organic matter (% DM)

88.10

92.09

96.44

Crude protein (% DM)

11.56

13.56

19.69

Crude fibre (% DM)

31.00

29.50

3.50

Ether extracts (% DM)

1.44

4.03

6.45

NFE (% DM)

44.10

45.00

66.80

Ash (% DM)

11.90

7.91

3.56

Analysis of feeds, refusals, faeces and urine were carried out according to the methods of AOAC (1980). Data were analysed using the general linear model of the Statistical Analysis System (SAS 1985) software. Differences between treatments means were detected with the Duncan's multiple range test.

Results and discussion

Feed intake, digestibility and liveweight gain values are indicated in Table 2. There were significant (P<0.05) differences in DMI based on metabolic weight by animals fed unsupplemented diets and those provided the basal diet supplemented with either SH or CC. Mafwere and Mtenga (1992) made similar observations that protein supplements of lablab meal in diets containing 11.36, 13.22, 15 and 16.73% crude protein resulted in dry matter intakes of 58.7,64.8,69.5 and 72.0 g/day/kgW0.75, respectively. Van Soest (1982) indicated that protein supplementation tends to improve intake by increasing N supply to the rumen microbes. This has a positive effect in increasing microbial population and also improves the rate of breakdown of digesta. When the rate of breakdown and passage of digesta increase, there is a corresponding increase in feed intake.

The trend of organic-matter (OM) intake was similar to that of dry-matter intake (DMI). Organic-matter intake by sheep fed EG only was 39.70 g/day/kgW0.75 and supplementation with SH and CC resulted in a significant (P<0.05) increase in intake to 58.97 and 64.12 g/day/kgW0.75, respectively.

Table 2. Feed intake and digestibility by West African Dwarf sheep fed elephant grass and protein supplements.


Parameters

Treatments

EG

EG+SH

EG+CC

Feed intake (g/day)


Dry matter

640.76±28.63

799.40±13.53

698.33±23.49


Organic matter

278.09±18.80

470.06±7.81

495.04±23.02


Crude protein

36.49±2.47

63.73±0.94

73.55±3.03

Feed intake (g/day/kgW0.75)


Dry matter

45.06±3.86c

66.15±4.50b

71.27±2.79a


Organic matter

39.70±3.40c

58.97±4.02b

64.12±2.54a


Crude protein

5.21±0.44c

7.99±0.55b

53±0.40a

Digestibility (%)


Dry matter

56.61±4.97b

69.32±2.07a

72.49±1.59a


Organic matter

59.89±4.58b

71.51±1.90a

75.05±1.63a


Crude protein

62.02±4.17a

77.79±1.45b

82.30±1.24a

EG = elephant grass;
SH = Stylosanthes hay;
CC = Concentrate.
Row means with different superscripts are significantly different (P<0.05).

Table 3. Nitrogen utilisation by West African Dwarf sheep fed elephant grass (KG) and protein supplements of stylo hay (SH) and concentrate (CC).

Parameters

EG

EG+SH

EG+CC

N-intake (g/day)

5.83-00.40b

10.20-0.15b

11.76-0.48a

Faecal-N (g/day)

2.20-0.15a

2.28-0.10a

2.09-0.23a

Urine-N (g/day)

0.73-0.09c

1.65-0.17b

2.46-0.09a

Absorbed-N (g/day)

3.63-0.47c

7.92-0.24b

0.68-0.28a

Retained-N (g/day)

29.0-0.40c

6.27-0.12b

7.22-0.20a

% absorbed-N

62.26

77.65

82.31

% retained-N

49.74

49.74

61.39

Means in a row with the same letter superscript are not significantly different (P>0.05).

Crude-protein intake (CPI) was significantly (P<0.05) different between various experimental treatments. Animals on the control treatment consumed 5.21 g crude protein/day/kgW0.75 whereas those fed SH and CC had an intake of 7.99 and 9.53 g/day/kgW0.75, respectively.

Dry-matter digestibility of sheep on EG only was 56.61 %. Supplementation of the forage with SH and CC as protein sources significantly (P<0.05) improved dry-matter digestibility to 69.32 and 72.49%, respectively. However, there was no significant difference in dry-matter digestibility between treatments receiving protein supplements. Butterworth (1985) also reported that dry-matter digestibility was improved when roughage was supplemented with legume or concentrate.

The trend of organic-matter digestibility was similar to that of dry matter. Crude-protein digestibility was significantly (P<0.05) different between all the experimental treatments, with the highest digestibility coefficient recorded for sheep fed the CC supplement (82.30%) followed closely by those fed SH (77.59%) and then those fed EG (62.02%).

Nitrogen intake by sheep fed EG only (5.53 g/day/kgW0.75) was significantly (P<0.05) lower than grass supplemented with SH or CC with intakes of 10.20 and 11.76 g/day/kgW0.75, respectively (Table 3). Faecal-N was statistically similar for all treatments. Significant (P<0.05) differences were also observed for urinary-N, absorbed-N and retained-N with sheep fed SH and CC supplement, and these treatments were also significantly (P<0.05) higher than the control. When absorbed-N was expressed as a percentage of N-intake, the efficiency of N absorption was 62.26, 77.65 and 82.31 %, respectively, for sheep on the control ration, SH and CC supplemented diets. However, when retained-N was also expressed as a proportion of N-intake, there was no significant difference between the efficiency of N-retention by sheep on SH (61.47%) and CC (61.39%) supplemented diets, but these diets were significantly (P<0.05) superior in efficiency of N-retention than grass alone fed to sheep.

Average weight gains of sheep maintained on EG only were low (9 g/day) whereas those fed grass plus SH gained 60 g/day, and those on CC supplement gained 78 g/day (Table 4). The differences between these treatments were significant (P<0.05). The significant difference in liveweight gain between the control and supplemented treatments may be attributed to increased crude protein intake. Kay and MacDearmid (1973) indicated that a dietary crude-protein content of 11% was ideal for normal weight gain by sheep and goats. From this study, it is evident that higher levels of dietary crude protein are required for higher weight gains by sheep. These results agree with reports by Mafwere and Mtenga (1992) who observed that as dietary crude-protein level was increased from 11.36 to 13.22, 15 and 16.73%, corresponding growth rates of 34.14, 65.65,68.01 and 70.5 g/day, respectively, were obtained for weaned lambs fattened on Chloris gayana hay and lablab meal as protein supplement.

Table 4. Liveweight changes in West African Dwarf sheep fed elephant grass (KG) and protein supplements of stylo hay (SH) and concentrate (CC).

Parameters

EG

EG+SH

EG+CC

Initial weight (kg)

13.20±1.86

13.96±1.73

12.60±1.56

Final weight (kg)

13.86±1.73

18.10±1.64

18.04±1.25

Weight change (kg)

0.66±0.21

4.18±0.73

5.44±0.36

Average daily gain (g/day)

9±3c

60±10b

78+5a

Average body weight (kg)

13.53±1.79

16.03±1.65

15.32±1.40

Metabolic weight (kgW0.75)

7.04±0.70

8.00±0.61

7.73±0.54

Means in the same row with the same letter superscript are not significantly different (P>0.05).

Conclusion

It may be concluded from this study that in the absence of concentrate, smallholder farmers can provide 200 g/day of stylo hay supplement to yearling lambs to obtain significant increases in feed intake, utilisation and weight gain.

References

AOAC (Association of Official Analytical Chemists). 1980. Official Methods of Analysis. 12th edition. AOAC, Washington, DC, USA. 1018 pp.

Butterworth M.H. 1985. Beef Cattle Nutrition and Tropical Pastures. Longman Group Ltd., London, UK. 500 pp.

Ducret G. and Grangaret I. 1986. Quelques Aspects des Systèmes de Culture en pays Bamileke. Centre Universitaire de Dschang, Cameroun. 33 pp.

Kay M. and MacDearmid E. 1973. A note on the effects of changing the concentration of protein in the diet to fattening beef cattle. Animal Production 10:205-207.

Mafwere W.D. and Mtenga L.A. 1992. Lablab (Dolichos lablab) meal as protein supplement for weaned fattening lambs. In: Rey B., Lebbie S.H.B. and Reynolds L. (eds), Small Ruminant Research and Development in Africa. Proceedings of the First Biennial Conference of the African Small Ruminant Research Network, ILRAD, Nairobi, Kenya, 10-14 December 1990. ILCA (International Livestock Centre for Africa), Addis Ababa, Ethiopia. pp. 375-386.

Magavero J.P. 1986. Typologie de Structure des Exploitations Agricole de Bafou (Ouest-Cameroun). Centre Universitaire de Dschang, Cameroun. 20 pp.

SAS (Statistical Analysis System). 1985. SAS User's Guide. 5th edition. Statistics Institute Inc., Cary, North Carolina, USA.

Van Soest P.J. 1982. Nutritional Ecology of the Ruminant. O and B Books Inc., Corvallis, Oregon, USA. 374 pp.


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