Citation of this paper

Evaluation of nutritive value of local browses from drylands of Kenya

F Kemboi, J O Ondiek, A M King’ori and P A Onjoro

Egerton University, Department of Animal Science, P O Box 536-20116 Egerton, Kenya
kemboifred15@gmail.com

Abstract

The nutritive value of ten indigenous browses including Terminalia brownii, Grewia bicolor, Balanites aegyptiaca, Acacia brevispica, Berchemia discolor, Codia sinensis, Tamarindus indica, Ziziphus mucronata, Boscia angustifolia and Maerua angolensis from the semi-arid region of Baringo County were assessed for their potential as protein supplements. Rhodes grass ( Chloris gayana) hay was used as the control. Amino acids profile and proximate composition including polyphenols and in-vitro gas production characteristics were determined. The crude protein (CP) content ranged from 51.4 gkg^-1dry matter (DM) in Rhodes grass to 203.7 gkg^-1DM in Maerua angolensis. Total extractable phenolics (TEPH) and condensed tannin (CT ranged from 6.7 to 94.8 gkg^-1DM and 1.7 to 51.5 gkg^-1DM, respectively. Maerua angolensis had the lowest fiber content. The ether extract (EE) content range was from 17.7 gkg^-1DM in Grewia bicolor and 91.5 gkg^-1DM for Tamarindus indica. The organic matter (OM) content ranged from 872.7 gkg^-1DM in Maerua angolensis to 944.7 gkg ^-1DM for Berchemia discolor. The NDF, ADF and ADL contents of Chloris gayana, was higher than in the indigenous browses. The macrominerals P, Ca, K and Mg were in the ranges of 1.3-5.7, 7.9-45.4, 6.1-28.5, and 2.9-12.2 gkg^-1 DM, respectively. Trace elements (mgkg^-1DM) varied in the range of Cu (71.3-141), Mn (0.04-65.1) and Fe (18.1-76.3). The browse species contained significant quantities of aspartic acid, glutamic acid and leucine. The nutritive values fall within the animal requirements as they had a CP of more than 70gkg-1DM which is the minimum required for rumen function according to NRC. It is concluded that these indigenous browses can be utilized in dry season as supplement to improve animal nutrition in arid and semi-arid areas.

Keywords: crude protein, goats, multipurpose trees, Rhodes grass, semi-arid region, supplement

Introduction

The insufficient and poor quality of the available protein and energy feedstuffs, particularly during the dry season, is the most challenging limitation in small ruminant production in the tropics (Njoya et al 2005; Olafadehan et al 2009). In times of scarcity, forage from browses is often obtainable throughout the year particularly when grasses and crop residues are depleted (Aregawi et al, 2008). Browse (shrubs, forbs and tree forage) plays a significant role in providing fodder for ruminants in many parts of the world (Kemboi et al 2017). The nutritional significance of indigenous browses is particularly important for free ranging goats in extensive communal system of production (Njidda 2020).

Legume tree forages have high crude protein, organic matter and mineral content that can be used as supplements to mitigate the effects of the low quality feeds (Ondiek et al 2013). Browses form adequate sources of mineral to supplements the requirements for ruminant livestock (Mangara et al 2017).

The quality and quantity of existing forages decline throughout dry periods and, goats utilize feedstuff from poor natural pastures which is low in protein resulting in low productivity and high body weight loss (Brown et al 2016). This could be overcome by using locally available natural forages such as the different indigenous browse species (Aregawi et al 2008). The browse forages have high Crude Protein content which makes them good protein supplements to poor quality roughages particularly during the dry season (Deng et al 2017). Utilization of browse trees as fodder for ruminant is progressively becoming important in many parts of the tropics (Njidda 2010).

Materials and methods

Collection and Preparation of Experimental Diets

Leaves and shoots of ten indigenous browses namely Terminalia brownii, Grewia bicolor, Balanites aegyptiaca, Acacia brevispica, Berchemia discolor, Codia sinensis, Tamarindus indica, Ziziphus mucronata, Boscia angustifolia and were harvested by hand stripping from the trees on communal grazing ranges in Marigat Sub-County during the dry season. After harvesting, the forage was spread on a sheet and air dried under shade for 7 days. The dried forages were put in sacks and stored in a well-ventilated shed until time of use. The basal diet consisted of Rhodes grass (Chloris gayana) hay and concentrate that was formulated according to the animal requirements. Forages for compounding the experimental diets were ground to pass through a 4mm sieve. Another 300g sample of each of the forages was ground to pass through 1mm sieve for chemical analysis and in-vitro digestibility.


Balanites aegyptiaca	Acacia brevispica	Berchemia discolor


Maerua angolensis	Grewia bicolor	Codia sinensis


Tamarindus indica	Ziziphus mucronata


Boscia angustifolia	Terminalia brownii

Rumen Fluid Sampling and In-Vitro Digestibility

Five growing Small East African goats weighing 18±2.2 Kg live weight were used as donor animals. They were fed with the experimental diets for 14 days then used to obtain rumen fluid. Rumen fluid was collected before morning feeding from the five goats by vacuum pump through a stomach tube. Each goat provided 220ml of fluid to make a total of one litre of rumen fluid from all the donor goats. This was kept in a thermos flask after being filtered through two layers of cheese-cloth to obtain strained rumen fluid which was continually flushed with carbon dioxide (CO₂) to maintain anaerobic conditions until used. Rumen fluid was used in combination with buffers to simulate the action of saliva. The rumen fluid and buffer medium was mixed in the ratio of 1:2 (v/v). 30 ml of buffer-rumen fluid mixture was passed into syringes holding the browse samples, swirled gently and any air bubbles released. A sample (1mm fine) of browse species weighing 200mgDM was placed into graduated 100 ml glass syringes in triplicate. The syringes were lubricated with petroleum jelly to ease the sliding of the piston and also prevent gas escape, then the silicon rubber tube was closed with a plastic clip. The fermentative activity of the mixed microbial population was determined using the gas production technique (Menke and Steingass 1988). Finally, the syringes were incubated in a thermostatically controlled water bath set at 39 ^oC for 0-96 hours. Both the samples and blank (rumen fluid +buffer) was run in triplicates. The volume of gas produced was determined at 0, 3, 6, 9, 12, 18, 36, 48, 72, and 96 hours by reading the calibration of the syringe. Therefore, gas produced was the total increase in volume minus the mean blank value from the recorded gas production of all samples to give the net gas production. The calculated values of gas production were fitted into the model developed by Ørskov and McDonald (1979) to determine the degradability of the feed:

Y= a + b (1-e^-ct), where:

Y= the volume of gas produced with time (t)

a= initial gas production

b= gas produced during incubation at time t

c= gas production rate constant (fraction /hour)

Then (a+b) represents the potential extent of the gas production.

Proximate, Fibre, Tannin and Mineral Analysis of Samples

The ten indigenous browses namely Terminalia brownii, Grewia bicolor, Balanites aegyptiaca, Acacia brevispica, Berchemia discolor, Codia sinensis, Tamarindus indica, Ziziphus mucronata, Boscia angustifolia and Maerua angolensis was assessed for proximate composition to determine dry matter (DM), crude protein (CP), ether extract (EE), ash and vitamins (A, D, E and K) according to the standard methods of AOAC (2006).

The CP was calculated as (N x 6.25). Essential amino acids profile was determined using amino acid analyzer, high performance liquid chromatography (HPLC), according to the method of AOAC (2006). Neutral detergent fiber (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) was analyzed according to the procedure described by Van Soest et al (1994). Phenolics was extracted using 70% aqueous acetone procedures of Makkar (2003). The total extractable phenolics (TEPH) were determined using Folin Ciocalteu procedures as described by Julkunen- Titto (1985). The condensed tannins(CT) were measured and computed as leucocyanidin equivalent, using the method of Porter et al, (1986). Minerals (macro and trace elements) was determined using atomic absorption spectrophotometry (AAS).

Statistical Analysis

Data collected on proximate, fiber and tannins was subjected to the analysis of variance(ANOVA) in a completely randomized design (CRD) using the General linear model procedure of statistical analysis system (SAS 2002) version 9.0. Significant means was separated using Tukey’s HSD (Tukey’s Honestly Significant Difference Test) at 5% significance.

Results and discussion

Chemical composition

The CP content ranged from 51.4 gkg^-1DM in Chloris gayana and 203.7 gkg^-1DM to Maerua angolensis. The comparatively high CP content range (77.3 to 203.7 gkg^-1DM) of ten selected indigenous browses show the likely contribution of indigenous browse as protein source important for the utilization of the growing goats in the arid and semi-arid regions. The relatively high crude protein content of the browses (150-249g/kg ^-1 DM) provide enough nutrients for the utilization of the browse leaves to supplement low quality natural pastures and crop residues (Osuga et al, 2006). The OM content ranged from 872.7 gkg ^-1DM in Maerua angolensis and 944.7 gkg^-1DM to Berchemia discolor. The TEPH and CT contents ranged from 6.7 to 94.8 gkg^-1DM and 1.9 to 51.5gkg^-1DM, respectively (Table 1 and Fig.1).

Table 1. Chemical composition (gkg^-1DM) of ten browse species and Rhodes grass as control
Browse species	OM	CP	EE	NDF	ADF	ADL	TEPH	CT

Acacia brevispica	936.7^b	172.3^c	53.4^c	294.6^h	215.5^g	153.9^d	37.6^d	32.1^b
Balanites aegyptiaca	872.3^h	168.4^d	48.8^e	278.5ⁱ	217.5^f	242.9^b	16.4^f	6.1^e
Berchemia discolor	944.7^a	188.0^b	21.3ⁱ	170.7^j	154.6^j	143.8^f	49.2^c	4.8^f
Boscia angustifolia	917.4^e	168.8^d	19.7^j	461.5^c	311^d	92.2ⁱ	11.1^g	4.5^f
Codia sinensis	881.0^g	77.3ⁱ	82.5^b	401.7^e	356.1^b	182^c	6.5i	3.1ⁱ
Grewia bicolor	913.0^f	160.3^e	17.7^k	518^b	331^c	139^g	11.4^g	3.8^ih
Maerua angolensis	872.2^h	203.7^a	43.0^f	103.1^k	80.2^k	88.8^j	27.3^e	10.8^c
Tamarindus indica	923.0^d	87.9^h	91.5^a	326.2^g	201.2ⁱ	151.4^e	71.3^b	51.5^a
Terminalia brownii	910.4^f	95.5^g	32.7^g	411.6^d	283.3^e	58.7^k	94.8^a	6.7^d
Ziziphus mucronata	930.0^c	155.6^f	51.6^d	383^f	211^h	98.1^h	8.2^h	4.1^gf
Chloris gayana	920.0^ed	51.4^j	22.7^h	691.3^a	475.3^a	461.4^a	6.18ⁱ	1.7^j
SEM	0.668	0.305	0.186	0.198	0.161	0.132	0.101	0.141
P	<.0001	<.0001	<.0001	<.0001	<.0001	<.0001	<.0001	<.0001
ADF, acid detergent fiber; ADL, acid detergent lignin; CP, crude protein; EE, ether extracts; NDF, neutral detergent fiber; OM, organic matter; TEPH, total extractable phenolics; CT, condensed tannins. ^abcmeans values without common superscript differ at P<0.05

Figure 1. Total extractable phenolics (TEPH) and condensed tannins (CT) contents of forages

High concentrations of condensed tannins and phenolic which tend to lower feed digestibility and nutrient utilization have also been reported by Kemboi et al (2017), Ondiek et al (2010) and Osuga et al (2006) in earlier studies. The NDF, ADF and ADL contents of Chloris gayana, was higher than indigenous browses. Crude protein, NDF and ADF value was similar to those reported reported by (Deng et al 2017, Kemboi et al 2017 and Mangara et al 2017) especially for Tamarindus indica, Codia sinensis and Balanites aegyptiaca.

Table 2. Major and trace elements in ten Kenyan indigenous browse and Cloris gayana
Browse species	Major elements, (gkg^-1DM)				Trace elements, (mgkg^-1DM)
Browse species	P	K	Ca	Mg	Cu	Mn	Fe

Acacia brevispica	2.6	13.9	19.6	4.1	123	32.7	46.1
Balanites aegyptiaca	2.3	22.9	28.5	5.3	81.3	65.1	20.2
Berchemia discolor	5.7	23.9	16.9	5.2	71.3	55.4	18.3
Boscia angustifolia	2.1	7.9	16.0	3.5	114	21.7	51.1
Codia sinensis	3.7	45.4	19.8	3.7	114	21.7	51.1
Grewia bicolor	5.6	23.4	17.1	3.4	123	32.7	46.1
Maerua angolensis	1.5	22.8	26.4	12.2	86.0	1.41	76.3
Tamarindus indica	1.9	23.5	6.1	2.9	138	0.04	40.0
Terminalia brownii	3.7	18.9	15.4	3.6	141	0.04	40.0
Ziziphus mucronata	2.2	24.8	17.7	3.5	86.0	1.4	86.9
Cloris gayana	1.3	21.1	7.1	5.4	14.3	0.1	36.2

The major minerals P, Ca, K and Mg were in the ranges of 1.3-5.7, 7.9-45.4, 6.1-28.5, and 2.9-12.2 gkg^-1DM, respectively (table 2). Trace elements (mgkg^-1DM) varied in the range of Cu (71.3-141), Mn (0.04-65.1) and Fe (18.1-76.3). The current study reported the highest levels for macro elements P, K, Ca and Mg at 5.7, 28.5, 45.4and 12.2gkg^-1DM and lowest level at 1.5, 6.1, 7.1, 2.9gkg ^-1DM respectively. This is similar to results of Mangara et al (2017) and Kemboi et al (2017) especially on major minerals in Balanites aegyptiaca. Similar results were reported by Ondiek et al (2010) on the mineral content especially on Maerua angolensis, Acacia brevispica, Ziziphus mucronata and Grewia bicolor.

The amino acid profiles of 10 indigenous browses are presented in Tables 3. Amino acids are the building blocks of proteins required for optimal growth, maintenance and reproduction with methionine and lysine usually the first limiting amino acids in ruminants (Kung et al 1996).

The sample contains significant quantities of aspartic acid, glutamic acid and leucine. These amounts were lower than the values reported by Ndamitso et al (2017) on Acacia nilotica seeds. Although the ten indigenous browses contained all the essential amino acids, histidine, cysteine and methionine were in low quantities. The amino acid profile from indigenous browses is indicative of high nutritive value and can be exploited by the pastoralists as well as feeds industries for feed formulations (Ndamitso et al 2017). The nutritive values are within the animal requirements as they had a CP of more than 70gkg-1DM which is the minimum required for rumen function according to NRC (2007).

Table 3. Amino acid concentration (g/100g protein) of ten selected indigenous browse species
	Z. mucronata	A. brevispica	C. sinensis	T. brownii	B. aegyptiaca	M. angolensis	G. bicolor	B. angustifolia	T. indica	B. discolor

Ala	1.353	1.053	0.204	0.273	0.390	0.459	0.331	0.344	0.221	0.424
Arg	1.188	0.929	0.181	0.246	0.433	0.416	0.311	0.368	0.209	0.386
Asp	2.082	1.609	0.309	0.421	0.666	0.796	0.502	0.538	0.363	0.660
Cys	0.104	0.075	0.017	0.026	0.050	0.052	0.036	0.040	0.013	0.063
Glu	2.475	1.958	0.383	0.508	0.820	0.861	0.626	0.638	0.440	1.006
Gly	1.255	0.943	0.189	0.269	0.469	0.427	0.305	0.328	0.212	0.395
His	0.476	0.406	0.069	0.121	0.153	0.145	0.120	0.119	0.099	0.153
Ile	1.078	0.826	0.154	0.204	0.331	0.336	0.236	0.254	0.191	0.328
Leu	2.000	1.533	0.281	0.388	0.611	0.629	0.486	0.493	0.344	0.655
Lys	1.459	1.362	0.227	0.326	0.519	0.500	0.378	0.400	0.304	0.514
Met	0.205	0.156	0.028	0.041	0.025	0.052	0.019	0.032	0.011	0.054
NH3	0.323	0.235	0.060	0.085	0.207	0.175	0.099	0.155	0.099	0.143
Phe	1.395	1.063	0.182	0.282	0.430	0.435	0.338	0.361	0.245	0.507
Ser	0.970	0.791	0.157	0.191	0.329	0.343	0.230	0.277	0.175	0.327
Thr	1.009	0.761	0.187	0.197	0.335	0.339	0.247	0.267	0.173	0.335
Tyr	0.857	0.681	0.130	0.182	0.303	0.322	0.239	0.265	0.159	0.353
Val	1.271	1.019	0.204	0.269	0.385	0.442	0.313	0.346	0.222	0.414

Gas production and fermentation parameters are presented in Table 3 and Figure 1. Cordia sinesis, Tamarindus indica, Maerua angolensis, Acacia brevispica and Berchemia discolor were highly degraded at the 24 hours compared to the 48hours.The gas is normally produced by the fermentation and degradation of organic matter by microbes in the feed (Blümmel and Fernandez-Rivera 2002).

Table 4. In-vitro gas production (ml/200mg DM) of indigenous browses and Chloris gayana as control
Species	24hr	48hr	A	B	C	A+B	RSD

Acacia brevispica	9.2	5.3	1.5	2.7	0.1	4.2	3.0
Balanites aeyptiaca	6.2	13.7	0.4	66.8	0.0	67.2	0.2
Berchemia discolor	15.7	10.1	0.9	7.4	0.2	8.3	4.3
Boscia angostifolia	7.8	10.2	0.7	6.3	0.1	7.0	2.4
Cordia sinesis	9.8	9.0	0.3	4.3	13.1	4.5	3.5
Grewia bicolor	3.1	5.6	0.2	5.8	0.0	6.0	0.9
Maerua angolensis	13.4	9.8	0.8	6.6	28.3	7.3	3.9
Tamarindus indica	6.3	5.5	0.3	4.3	0.2	4.6	1.6
Terminalia browni	4.0	4.8	0.2	8.9	0.1	9.0	0.7
Ziziphus mucronata	9.2	11.1	1.2	4.5	6.9	5.6	3.6
Chloris gayana	9.0	13.0	0.2	7.3	8.1	7.5	4.2
A, B, C are constants (Ørskov and McDonald, 1979)

The in-vitro fermentation characteristics of the browse species DM varied widely among the ten selected indigenous species. The total gas production (ml/200mg DM) at 24hr and 48hr shown in table 3 and Figure 2 show variations in the digestibility potential withBal anites aegyptiaca (13.7) being the highest and Terminalia browni (4.8) being the lowest at 48hrs.

Berchemia discolor

Ranked the lowest in gas production potential, this could be due to high level of tannins and other anti-nutritive factors which affects nutrient utilization by the microbes. The differences in gas production between the indigenous browse species could be due to the quantity of substrate fermented (Osuga et al 2006 and Kemboi et al 2017).

Figure 2. Patterns of in vitro cumulative gas production on Rhodes grass hay and 10 indigenous browses species

Conclusions

Indigenous browse species provide a substantial part of animal requirement for protein and minerals to overcome the adverse impact of the dry season as depicted in the current findings.
The highest values obtained in in vitro gas production for the rate of gas production and parameters in Berchemia discolor show better feed degradability by rumen microbes.

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