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Effects of processing methods on chemical composition and in vivo digestibility of coffee pulp in Ethiopia - Effets du type de traitement sur la composition chimique et la digestibilite in vivo des pulpes de café en Ethiopie

Getachew Gebru and Beyene Chichaibelu

Department of Animal Science
Alemaya University of Agriculture
P.O. Box 138
Dire Dawa
Ethiopia

and

J.D. Reed

International Livestock Centre for Africa
P.O. Box 5689
Addis Ababa
Ethiopia


Summary
Resume
Introduction
Materials and methods
Results and discussion
Conclusions
References


Summary

Effects of the method of processing of coffee cherries on pulp composition and digestibility in vivo were studied. The effects of wet and dry processing on chemical composition were analysed in Experiment 1. The effects of dry processed pulp (Dcop) and wet processed pulp (Wcop) (0 g/d, 60 g/d, 120 g/d and 150 g/d) on intake, digestibility and nitrogen retention in sheep fed hay were determined in Experiment 2. Processing method affected the contents of neutral-detergent fibre (NDF), acid-detergent fibre (ADF), lignin soluble phenolics and insoluble proanthocyanidins (condensed tannins). Dry processed pulp had higher NDF, ADF, lignin and phenolic compounds. There was no effect of pulp level on feed intake or digestibility but N-balance was significantly depressed at the 120 g and 150 g levels of Dcop, at which both urinary and faecal N losses and total urine excretion increased. No pronounced effects were observed for Wcop. Condensed tannins and caffeine in coffee pulp appear to limit its nutritive value.

Resume

Cet article relate les effets du type de traitement des cerises de café sur la composition et la digestibilité in vivo de la pulpe. Les effets du traitement par voie humide et par voie sèche sur la composition chimique furent étudiés dans l'expérimentation 1. Les effets du traitement par voie sèche (TVS) et par voie humide (TVH) de ces aliments distribués à raison de 0 g/j, 60 g/j, 120 g/j et 150 g/j à des ovins nourris à base de foin furent mesurés par l'évaluation de la quantité ingérée, de la digestibilité et de la retention de matière azotée au cours de l'expérimentation 2. Le traitement affecte les quantités de cellulose évaluée par méthodes NDF et ADF, de lignine, des composés phénoliques solubles et des proanthocyanidins (tanins). La pulpe traitée par vole sèche se caractérise par des teneurs plus élevées en NDF, ADF, lignine et phénoles. Le traitement est sans effet sur la digestibilité et l'ingestion volontaire. Par contra, la balance azotée diminue à partir des niveaux de 120 g et 150 g de TVS, niveaux auxquels les pertes azotées urinaire et faecale ainsi que l'excretion urinaire augmentent. Le TVH ne présente pas d'effet significatif. La présence de tanins condenses et de caféine dans la pulpe limite sa valeur nutritive.

Introduction

Feed availability is a major constraint on animal production in tropical Africa, particularly during the dry season. Rapid development of improved pasture and cultivated forages is not always possible because of limitations imposed by technical, economic and human factors. It is anticipated that mechanization will increase the land area in Ethiopia devoted to food and cash crop production and this will increase the availability of agro-industrial by-products. Livestock production therefore needs to be integrated with and allied to the processing industries. The bulk of available by-products is not effectively used in animal production due to inadequate knowledge of their value in feeding systems and to the requirements for alternative uses.

Coffee is an agricultural crop of significant economic importance in Ethiopia. Pulp is the major by-product from the processing of coffee cherries. The nutritive value of coffee pulp as animal feed may be limited by the presence of secondary plant compounds among which tannins (polyphenolic compounds) are the main agents. High moisture and sugar contents in the wet pulp also mean that more information on developing systems of handling and feeding is required. Method of processing the cherries, origin and agricultural practices may also affect the concentration of various substances in the pulp.

The objectives of this study were to determine the effect of cherry processing methods on pulp composition and on digestibility and nitrogen retention in sheep.

Materials and methods

Origin and processing of the pulp

Pulp was obtained from the plantation projects of the Ministry of Coffee and Tea Development in Kaffa Administrative Region. Both wet and dry processing of cherries is practiced in this region. Wet pulp was transferred to plastic barrels (120 litre capacity) with lids and transported to ILCA, Debre Zeit and ensiled for 120 d.

Animals and management

Eight intact male highland Ethiopian sheep were eartagged, sprayed and drenched against external and internal parasites. They were divided into 4 groups of 2 animals each with live weights uniformly distributed across treatments and housed in wooden crates with slatted floors. Animals were fed individually on 4 levels of pulp (0 g/d, 60 g/d, 120 g/d and 150 g/d). Hay was fed ad libitum and mineral bricks and water were permanently available.

Rubber urine funnels connected to collection bottles were attached to each animal. Faeces were collected from beneath the pens. Animals were acclimatised to the crates and given their respective rations for a period of 30 d.

Experimental design

A cross-over design arranged as a 4 x 4 latin square was used. Each experiment lasted 120 d in 4 periods of 30 d, each comprising a 20 d adaptation and a 10 d collection period. Feed intake, faeces and urine output were measured at the same time each day. Feed, which was offered at 08:00 and 16:00, was weighed and sampled daily during the collection period and samples were bulked over the period. Subsamples were taken at the end of the period for analysis. Feed refusals were weighed during the collection days and bulked on an individual basis over the period. Subsamples were taken at the end of the period for analysis.

Faeces and urine were collected daily before feeding. Total urine output of each sheep was recorded, 15 ml of 2N HCl was added as a preservative and 5% (w/w) of the daily output was saved and frozen. The entire daily faeces output of each sheep was collected and 20% (w/w) was saved and frozen.

Sample processing and chemical analysis

At the end of the experimental period the total faeces saved was thawed, dried in a draught oven for 24 hr at 60°C, ground to pass a 1 mm sieve and bottled for chemical analysis.

Dry matter (DM) and ash were determined according to AOAC (1980). In vivo digestibility, neutral-detergent fibre (NDF), acid-detergent fibre and acid-detergent lignin were determined by standard methods (Goering and van Soest, 1970): N and N in NDF were determined by Macro procedures. Phenolics and tannins soluble in aqueous acetone were analysed by gravimetric procedure based on precipitation by ytterbium acetate (Reed et al, 1985). Proanthocyanidins insoluble in neutral detergent were determined by the methods of Reed et al (1982).

Results and discussion

Effect of processing method on chemical composition

There was considerable variation in the contents of ADF, NDF, lignin, soluble phenolics and insoluble proanthocyanidins between the 2 treatments (Table 1). The high NDF and lignin levels in DCop suggest that the material has low nutritive value.

The presence of the hulls or the parchment might contribute to the high content of NDF as it has been reported that coffee hulls have high concentrations of lignin, pentoses and hexoses (Murillo et al, 1970). The phenolic compounds also have nutritional implications as soluble phenolics form indigestible protein and carbohydrate complexes in the digestive tract that increase apparent fibre and lignin excretion in faeces (Osbourn et al, 1971).

Table 1. Crude protein, neutral-detergent fibre, acid-detergent fibre, lignin and phenolics contents (% of DM) of Ethiopian dry and wet processed coffee pulp.

Component

Processing method

Dry

Wet

Crude protein

11.1

10.6

Neutral-detergent fibre

57.1

29.5

Acid-detergent fibre

52.1

25.7

Lignin

16.4

5.6

Soluble phenolics

32.5

24.6

Insoluble proanthocyanidins (A550/g NDF)

20.0

11.5

Effect of processing method and pulp level in the ration

Effect on intake and digestibility. There was no effect of pulp level on intake and digestibility of wet processed pulp (Table 2). For dry processed pulp there was no effect on DM intake of the level of pulp in the ration but there was a decrease (P < 0.01) in DM digestibility and also a decrease (P < 0.05) in N digestibility. The low apparent digestibility can be attributed to the capacity of tannins to form insoluble complexes with proteins and reduce OM and N digestibility as observed in this experiment.

Effect on nitrogen balance. Nitrogen in the faeces increased (P < 0.05) with increasing levels of dry processed pulp in the ration while nitrogen balance became more negative (P < 0.05) (Table 3). Urine-nitrogen showed a non-significant increase at the 120 g and 150 g levels. Similar results have been reported elsewhere (Daqui, 1974; Cabezas et al, 1977), and are related to the diuretic effect of caffeine (Sollman, 1957). The non-significant increase in NDF-N in the faeces is associated with proanthocyanidins which form tannin protein complexes.

Table 2. Effect of Ethiopian dry and wet processed coffee pulp intake, organic matter digestibility and nitrogen digestibility in sheep.

Item

Processing method

Pulp level (g/d)

0

60

120

150

DM intake (g/kg0 75/d)


Wet

59.05

61.13

61.12

62.69

Dry

41.98

41.87

40.97

40.41

DM digestibility (%)


Wet

38.1

41.0

39.8

35.1

Dry

56.6

55.8

53.8

53.0**

N digestibility (%)


Wet

47.1

35.2

40.6

42.4

Dry

51.2

50.4

49.5

47.2*

** P < 0.01 * P < 0.05

Conclusions

The method of processing coffee pulp can affect its chemical composition and its utilization by sheep. The most negative effects of feeding dry processed pulp were on N-utilization. The presence of caffeine and other phenolic compounds in coffee pulp appear to limit its utilization. The availability of certain by-products like coffee pulp does not warrant their immediate inclusion in livestock feeding. Additional characterization of the material is required to understand the nature of the complexing of nitrogen with polyphenols and simple and cheap methods of breaking down these complexes need to be developed to enable better utilization of coffee pulp.

Table 3. Effects of Ethiopian dry processed coffee pulp on N-balance of sheep.

Item

Pulp level (g/d)

0

60

120

150

Urine output (ml/d)

319.1

426.1

510.8

522.6

N-urine (g/d)

2.9

2.6

3.7

3.7

N-faeces (g/d)

5.1

5.2

5.4

5.4*

NDF-N faeces (g/d)

1.2

1.3

1.4

1.4

N-balance (g/d)

2.5

2.6

1.3

1.3*

* P < 0.05

References

AOAC 1980. Official methods of analysis (13th edition). Association of Official Analytical Chemists, Washington DC, USA.

Cabezas M T. Vargas E, Murillo B and Bressani R. 1977. Utilization of coffee fruit without seeds (coffee pulp) in ruminant feeding. First international symposium on feed composition, animal nutrient requirements and computerization of diets. Utah State University, Logan, USA.

Daqui L E. 1974. Characteristicas quimicas y nutricionales de la pulpa de cafe ensilada con pasto napier y planta de maiz. Tesis Magister Scientificas. Universidad de San Carlos de Guatemala, San Carlos, Guatemala.

Goering H K and van Soest P J. 1970. Forage fiber analysis. Agricultural Handbook No. 379. Department of Agriculture, Washington DC, USA.

Murillo B T. Cabezas R. Jarquin R and Bressani R. 1977. Effect of bisulfite addition on the chemical composition and cellular content fractions of dehydrated coffee pulp digestibility. Journal of Agricultural and Food Chemistry 25: 1090-1092.

Osbourn D F. Terry R A, Cammel S E and Outen G E. 1971. The effect of leuco-anthocyanins in sainfoin (Onobrychis vicifolia) on the availability of protein to sheep and upon the determination of the acid detergent fiber and lignin fractions. Proceedings of the Nutrition Society 30A: 13-14.

Reed J D, McDowell R E, van Soest P J and Horvath P J. 1982. Condensed tannins: a factor limiting the use of cassava forage. Journal of the Science of Food and Agriculture 33: 213-220.

Reed J D, Horvath P J. Allen M S and van Soest P J. 1985. Gravimetric determination of souble phenolics including tannins from leaves by precipitation with trivalent ytterbium. Journal of the Science of Food and Agriculture 36: 255-261.

Sollman T. 1957. A manual of pharmacology. W B Saunders and Co, Philadelphia, USA.


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