Nutritive value and palatability rating of fifteen selected indigenous Kenyan browse species fed to Small East African goats

J O Ondiek, S A Abdulrazak and E N Njoka¹

Egerton University, PO Box 536-20115 Egerton, Kenya
ondiekjo2002@yahoo.com
¹ Chuka University, PO Box 109-60400 Chuka, Kenya

Abstract

A palatability study was conducted using fifteen indigenous multipurpose tree leaf forages offered to twenty intact male Small East African Goats, 7 to 8 months and 18kg ± 2.1kg. The CP (gkg^-1DM) of the best five species were: M. angolensis (321), A. senegal, (249),Z. mucronata, (200), G. bicolor, (196) and A. brevispica, (187). The NDF and ADF contents ranged from 218-601 for A. hockii and A. amara, and 160-462 for A. hockii and A. abyssinica, respectively. The palatability ranking of the forages was in the order: A. tortilis> M. angolensis> B. aegyptiaca> Z. mucronata> A. coriaria> A. Senegal> A. abyssinica> A. mellifera> A. brevispica> A. elatior> A. amara> G. bicolor> A. nilotica> B. micrantha> A. hockii. M. angolensis and Z. mucronata had OMD of 68.0 and 73.8%, respectively. M. angolensis, Z. mucronata ranked highly on the parameters studied. It is concluded that Maerua angolensis and Zizyphus mucronata being high in nutritive value and palatability, are potential protein supplements to low quality basal diets.

Key words: Acacia tortilis, B. aegyptiaca, Maerua angolensis, organic matter digestibility, potential supplements, Zizyphus mucronata

Introduction

Livestock productivity in the tropical rangelands is low due to poor nutrition caused by inadequate quantities and poor quality of the feeds consumed. Animals on the large part of the year depend on natural pastures that are low in digestible nutrients and, therefore, inadequate to meet the animals requirements. Supplementing poor basal diets containing less than 7% crude protein with multipurpose trees and shrubs (MPTS) browse improves both feed intake and animal performance (Abdulrazak et al 1997; Ondiek et al 1999. Ondiek et al 2000), hence there is need to exploit locally available legume forage resource.

Various MPTS have been documented as useful livestock fodders (Topps, 1992; World Agroforestry Centre, 2005). As the species show a wide variation in nutritive value, it is imperative to screen them to evaluate their nutritional contribution to animals using simple techniques like the proximate and palatability methods. The objective of this study was to assess the potential nutritive value and relative palatability of fifteen Kenyan indigenous browse species.

Materials and methods

Leaf browse from Acacia abyssinica, Acacia brevispica, Acacia elatior, Acacia hockii, Acacia mellifera, Acacia nilotica, Acacia senegal, Acacia tortilis, Albizia amara, Albizia coriaria, Balanites aegyptiaca, Bridelia micrantha, Grewia bicolor, Maerua angolensis and Zizyphus mucronata were collected from Baringo and East and West Pokot Districts of Kenya. The leaf browse were dried and milled through a 4 mm screen for proximate composition estimation (AOAC 1990). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) were determined by the method of Van Soest et al (1991). Total extractable phenolics (TEPH) were determined using Folin Ciocalteu procedures as described by Makkar (2000). Another larger set of samples were collected in gunny bags and used for palatability trial.

Palatability was determined using twenty indigenous Small East African intact male goats aged 7-8 months and weighing approximately 18±2kg. Each goat was provided with an individual feed trough subdivided into fifteen separate compartments to contain each of the test browses in addition to a separate trough for the basal diet of chopped C. gayana hay. Clean drinking water was provided in a water trough twice daily at 0830 and 1400 hr and mineral blocks were available ad libitum.

Each goat was offered 150g of respective browse species as well as 300g of basal diet between 0800 and 1200 hr after which the respective refusals were removed and weighed separately. Data was collected according to the method described by Kaitho et al (1996) and measurements considered were as described by Ben Salem et al (1994). The relative palatability index (R) was calculated following the method of Kaitho et al (1996). The 15 day period was described into five periods, thus:

Period 1= day 1; Period 2= days 2 to 5; Period 3= days 6 to 12; Period 4= days 13 to 15 and Period 5= days 1 to 15. The following variables were determined according to procedures of Ben Salem et al(1994):

H1, H2,............H5: hay intake in periods 1-5

M1, M2,..........M5: MPTS intake in periods 1-5

HO1, HO2,....HO5: hay quantity offered in periods 1-5

MO1, MO2....MO5: MPTS quantity offered in period 1-5

The relative palatability indices (R) describing the palatability of individual MPTS in relation to Rhodes grass hay were calculated as:

R1 = (M1/HO1)/(H1/HO1)

R2 = (M2/HO2)/(H2/HO2)

R3 = (M3/HO3)/(H3/HO3)

R4 = (M4/HO4)/(H4/HO4)

R5 = (M5/HO5)/(H5/HO5)

The MPTS were ranked using these indices as animal prefence.

Chemical analysis

The sundried forages were kept in paper bags. Random samples were picked from each bag to make a composite sample of about 400 g. Samples of the forages were ground to pass through a 1mm sieve and used for analysis. The proximate composition including DM, OM and N were determined following standard methods (AOAC, 1990). Crude protein was calculated as Nx6.25. The NDF, ADF and ADL were determined according to Van Soest et al (1991). Phenolics were extracted using 70% aqueous acetone. Total extractable phenolics (TEPH) were determined using Folin Ciocalteu procedures described by Makkar (2000). The concentration of TEPH was calculated using the regression equation of tannic acid standard. The total extractable tannins (TET) were estimated indirectly after absorption to insoluble polyvinylpyrridone (PVP) and the TET concentration calculated by subtracting the TET remaining after PVP treatment from the initial TEPH.

Results and discussion

The result of proximate composition is shown in Table 1. The DM ranged between 859 to 903gkg^-1DM for Z. mucrunata and .B micrantha, respectively. The OM was high for A. mellifera and for A. amara while the levels of CP ranged from 112 to 321gkg^-1DM for B. micrantha and M. angolensis, respectively. The CP for M. angolensis is similar to that reported by Osuga et al (2006). Only five species, namely,A. hockii, A. nilotica, A. tortilis, B. aegyptiaca and B. micrantha had CP levels below 160 gkg^-1DM which is recommended by the Kenya Bureau of standards for commercial animal feeds, especially ruminant diets. The NDF varied between 290 and 601 gkg^-1DM; the ADF fraction was in the range of 160 to 462 gkg ^-1DM. The tannins (TEPH and TET and organic matter digestibility (OMD) are shown in figure 1a, 1b and 1c, respectively. The TEPH and TET were low to moderate, being 1.4-26.7 and 0.3-24.3 for M. angolensis and A. hockii/A. nilotica; and the TET was lowest for M. angolensis, B. aegyptiaca and A. coriaria. This indicates that M. angolensis was lowest in the TEPH and TET composition and may be a good indication of its acceptability to goats. In a previous study (Ondiek et al 2010), M. angolensis was highly degraded in vivo, (88.6%) with potential degradation of 79.0 at K=0.05 compared to Z. mucronata (90.7% and only 62.9 at K=0.05, respectively). M. angolensis also had the highest gas production (52.2ml) and an OMD of 59.3% compared to Z. mucronata the next best that produced 45.7ml of gas with a digestibility of 73.9% among the other forages. In the current study, A. brevispica, A. mellifera, A. nilotica, A. Senegal, G. bicolor, M. angolensis and Z. mucronata had comparable or higher values of CP and consequently are suggested to be adequate supplemental protein sources for goats that are offered low quality basal roughage diets with a CP <7% such as the test hay that had a CP of 5.2%.

The current results present values for indigenous tree browses that are found in the Kenyan rangelands. An earlier study by Ondiek et al (1999) with cultivated tree fodders of Leucaena leucocephala andGliricidia sepium reported a CP level of 192 and 234 gkg ^-1DM, respectively, which agreed with those reported by Smith and van Houtert (1987) and Topps (1992). Ondiek et al (2000) reported that G. sepium, with a CP content of 208 gkg^-1DM, was a suitable supplements for growing goats that attained an ADG of 43 gd ^-1. At those CP levels, the authors showed that the species were suitable sources of protein and had the potential to substitute commercial protein sources. In the current study, Acacia mellifera, Acacia nilotica, Acacia senegal, Acacia brevispica, Grewia bicolor, Maerua angolensis and Zizyphus mucronata had comparable or higher values of CP and consequently are suggested to be adequate supplemental protein sources for goats that are offered low quality basal diets with a CP <7% as the test hay had a CP of 5.20%.

Variations of proximate components have been reported (Dzolewa et al 1995; Larbi et al 1998). This may be within and between seasons with most forages declining in nutritive value in the dry season. The ratio of the leaves to other plant parts in the diet considerable affect the nutritive value in that the higher the former, the better the nutrient composition. Goats in natural browsing would pick the most nutritious plant parts and this would be the leaves and less of the other parts.

Figures 1a-1c. Total extractable phenolic (TEPH), total extractable tannins (TET) and organic matter digestibility of 15 selected indigenous Kenyan browse forages.

Figure 1a. presents the % total extractable phenolic (TEPH) of forage browse.

Figure 1b. The % total extractable tannins (TET) of forage browse.

Figures 1c. Organic matter digestibility (%) of selected forages.

Figure 2a, 2b, 2c and 2d show the results of ranked palatability indices of 15 selected indigenous Kenyan browse forages used in the current study. The period 5 results, Figure 2d, representing days 1 to 15 inclusive showed the best results as earlier reported by Kaitho et al (1996). The results indicated A. tortilis had the highest palatability, while A. hockii was the lowest. Animals may consume feedstuff selectively and this does not necessarily conform with the nutritive value of the particular species as was observed in the current study.A. tortilis that was highly palatable contained 117 gkg ^-1DM of CP against B. micrantha that despite having a similar CP level (112 gkg^-1DM) had a very low palatability of 0.28. Again, M. angolensis in spite of the highest (321 gkg ^-1DM) CP was second to A. tortilis. The best five highly palatable species in the 15 day period index were in decreasing order: A. tortilis> M. angolensis> B. aegyptiaca> Z. mucronata> A. coriaria. Some ranking was done including the proximate analysis, palatability and the degradability of organic matter.

Figure 2a. Palatability index of forages in day 1.

Figure 2b. Palatability index of forages in days 2-5.

Figure 2c. Palatability index of forages in days 6-12	Figure 2d. Palatability index of forages in days 13-15

Figure 2e. Palatability index of forages for the whole period of days 1-15.

Conclusion

• It is concluded that these local MPTS are potentially nutritious and palatable and particularly M. Angolensis, Z. Mucronata, A. Hockii, G. Bicolor and A. Senegal warrant further studies as protein supplements to evaluate animal feeding potential and performance.

Acknowledgement

The authors appreciate financial support from the African Academy of Sciences and Egerton University and Tatton Demonstration Unit for animals and facilities.

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Received 14 January 2017; Accepted 12 April 2017; Published 1 June 2017

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