Livestock Research for Rural Development 34 (10) 2022 LRRD Search LRRD Misssion Guide for preparation of papers LRRD Newsletter

Citation of this paper

Nutritional characterization of eight trees and shrubs used as livestock feeds in the Eastern Democratic Republic of the Congo

Didier K Barwani1,2,3,4, Samy B Bacigale2, Nicolas K Kibitok5, Andrew W Webala1, Mathew G Gicheha1, DieudonnÚ M Katunga4 and Isaac M Osuga1

1 Department of Animal Sciences, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200 Nairobi, Kenya
isaac.osuga@jkuat.ac.ke
2 International Institute of Tropical Agriculture (IITA), Bukavu, DR Congo
3 Department of Animal Production, Faculty of Agriculture and Environmental Sciences, UniversitÚ de Kalemie (UNIKAL), Kalemie, DR Congo
4 Institut National pour l’Etude et la Recherche Agronomique (INERA), DR Congo
5 Department of Animal Sciences, Egerton University, P.O. Box 536-20115 Egerton

Abstract

The poor nutritional quality of natural pastures is one of the main constraints smallholder cattle farmers encounter in the eastern Democratic Republic of the Congo (DRC). Information on the nutritive values of the tree and shrub species most used by farmers is insufficient. This study aimed to assess the chemical composition and in vitro gas production profiles of eight selected trees and shrubs forages from the territories of Kalemie and Kabare in the eastern DRC. The forage samples were analysed for dry matter, ash, crude protein (CP), ether extract (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL) and, condensed tannins (CT). The metabolisable energy, in vitro organic matter digestibility (OMD) and short-chain fatty acids were also estimated. Data obtained were analysed using a one-way analysis of variance in a completely randomised design. The results revealed that the nutrient parameters analysed and calculated differed significantly (p<0.05) between the various species of trees and shrubs and also between the territories within the same species of tree or shrub. The CP ranged from 217 g kg-1 DM in Mangifera indica to 402 g kg-1 DM in Leucaena leucocephala in Kalemie, while from 270 g kg-1 DM in M. indica to 417 g kg-1 DM in Calliandra calothyrsus for samples obtained from Kabare. The forages had moderate NDF ranging from 265 g kg-1 in C. calothyrsus found from Kabare to 690 g kg-1 DM in Erythrina abyssinica found in Kalemie. The condensed tannin content was highest in C. calothyrsus (122 g kg-1 DM) obtained from Kalemie compared to M. indica (68.3 g kg-1 DM) from Kabare. The potential gas production and in vitro OMD were high and comparable between the species such as L. leucocephala, Vernonia amygdalina and E. abyssinica. From this study, it can be concluded that tree and shrub forages had higher CP content and in vitro digestibility, which suggests their suitability for use as protein supplements in livestock diets, particularly during the dry season.

Keywords: animal feeds, condensed tannins, digestibility, nutritive value, tree leaves


Introduction

As in the rest of Sub-Saharan African (SSA) countries, the feed resources of small mixed farms in the Democratic Republic of the Congo (DRC) are mainly rainfed, and smallholders have limited capacity to practice forage conservation technologies for use during the lean periods and appropriate feeding regimes (Bacigale et al 2014). According to Mugumaarhahama et al (2021), the major constraint to livestock production is the scarcity and fluctuation of feed quality and quantity throughout the year. The natural pastures and crop residues are reported to be low in protein and high in fibre and rarely meet the nutritional requirements of livestock, especially during the dry season (Maina et al 2020; Paul et al 2020). The low protein content of feed has been reported to reduce microbial activity in the rumen, therefore, reducing feed intake, low dry matter digestibility and poor animal performance (Abdulrazak et al 2000). The conventional feeds used as alternative supplements in the eastern DRC, such as concentrates and agro-by products, are not readily available and, when available, are costly for the majority of poor smallholder farmers (Maass et al 2012). In addition, increasing population growth and shrinking pastoral land due to agricultural activities and construction development have exacerbated the shortage of animal feed (Mugumaarhahama et al 2021).Consequently, inadequate nutrition of cattle often culminates in substantial economic losses to the farmers due to low rates of weight gain or milk production, poor body condition, reduced productive and reproductive performance and susceptibility to pests and disease infestations (Henry et al 2018). Therefore, there is a need to provide alternative cheap-to-produce and locally available feed resources to supplement the feed produced on smallholder farms.

Forage trees and shrubs are useful sources of cheap and locally available feed resources for ruminants, especially during the dry seasons when natural pastures and crop residues are scarce (Franzel et al 2014). Trees and shrubs are highly valued because of their high volume of biomass production, nutritional value, and adaptation to poor soils and harsh climatic conditions (Pello et al 2021). Incorporating trees and shrubs into animal diets improves palatability, feed intake, digestibility, and animal performance (Derero and Kitaw 2018; Osuga et al 2011).

It was reported that information on the nutritional characterization of locally available feed resources in eastern DRC is not adequately addressed, and, where available, values are variably documented (Katunga et al 2014). Furthermore, nutritional analysis conducted in eastern DRC has focused on a few exotic species of trees and shrubs (Katunga et al 2014); most forage resources remain unexplored. The tree and shrub species considered in this study are widely available and used by smallholder farmers. Forage trees and shrubs were prioritized based on information from the surveys conducted in the Kalemie and Kabare territories of the eastern DRC. Preferences for trees and shrubs among smallholder farmers have been reported to be based on animal-related criteria (palatability, ability to satisfy hunger, and contributions to overall animal health) or tree-related criteria (compatibility with cultivated crops, draught resistance, improving soil fertility, and toxicity). Despite the farmer’s knowledge of the importance of trees and shrubs as livestock feeds, studies of the nutritional composition of trees and shrubs used by smallholder farmers in the eastern DRC remain a significant literature gap. Therefore, this study aimed to assess the chemical compositions and in vitro gas production profiles of eight selected trees and shrubs forages from the territories of Kalemie and Kabare in the eastern DRC. The study findings would enable policymakers and smallholder farmers to design appropriate intervention strategies to improve livestock productivity and serve as a basis for future research.


Materials and methods

Description of the study area

Leaf samples from trees and shrubs were collected from the territories of Kalemie and Kabare in the eastern DRC. Kalemie territory is located in the province of Tanganyika between 600║S and 650║S latitude and 2640║E and 2730║E longitude, with an altitude of 880 metres above sea level. The average annual rainfall is 999 mm. The mean annual minimum and maximum temperatures are 18 ░C and 32 ░C, respectively, with an average annual temperature of 27 ░C. The territory of Kabare is located in the province of South-Kivu, between 230║S and 265║S latitude and 2830║E and 2880║E longitude, at the altitude of 2225 meters above sea level. The average annual rainfall is 1897 mm. The mean annual minimum and maximum temperatures are 12.6 ░C and 24.4 ░C, respectively, with an average annual temperature of 18 ░C. The laboratory nutrient analysis and in vitro degradability studies were carried out at the Animal Nutrition Laboratory, Department of Animal Sciences, Egerton University, Nakuru, Kenya.

Sample collection and preparation

Leaf samples from selected eight species of trees and shrubs, including Vernonia amygdalina(Del.), Erythrina abyssinica (Lam), Calliandra calothyrsus (Meisn.), Leucaena leucocephala ((Lam) De Wit), Sesbania sesban (L.), Mangifera indica (L.), Tithonia diversifolia ((Hemsl.) A. Gray) and Ficus glumosa (Delile) were collected during the rainy season (May and June) from at least ten species of trees and shrubs. Representative samples of leaves from trees and shrubs were dried under shade and ground in the mill to pass through a 1 mm sieve and packed in plastic containers for further analysis of chemical compositions.

Chemical compositions and in vitro gas production analysis

Dry matter (DM), ash, nitrogen and ether extract (EE) content of samples of feed were analysed in triplicate according to the procedures of the Association of Official Analytical Chemists (AOAC 2000). Nitrogen (N) content was determined following the Kjeldahl method, and the crude protein (CP) content was estimated by multiplying the N content by 6.25. Neutral detergent fibre (NDF), acid detergent fibre (ADF), and acid detergent lignin (ADL) were analysed in triplicate sequentially according to the procedures of Van Soest et al (1991). Hemicellulose was calculated as the difference between NDF and ADF, whereas cellulose was the difference between ADF and ADL. Phenolics were extracted using 70% aqueous acetone according to the procedures of Makkar (2003). The concentration of TEPH was calculated using the regression equation of the tannic acid standard in duplicate as described by Abdulrazak and Fujihara (1999). Total extractable tannins (TET) and condensed tannins (CT) were measured and computed as leucocyanidin equivalent (Abdulrazak and Fujihara 1999).

In vitro gas production was performed according to the method of Menke and Steingass (1988) using rumen liquor obtained from three mature sheep with a live weight of 27▒20 kg. Donor sheep were fed ad libitum Rhodes grass hay (Chloris Guyana) mixed with molasses and supplemented with 2 kg of dairy meal twice daily. Mineral licks (Maclick mineral brick, COOPER-BRANDS LTD, Kenya) containing 85% Sodium, 5% Calcium, 2.5% Phosphorous, 1% Magnesium, 0.33% Zinc, 0.2% Copper, 0.2% Manganese, 0.015% Iodine and 0.0015% Selenium and freshwater were provided ad libitum to maintain a stable environment before collecting rumen liquor. Rumen liquor was collected at 8:00 a.m. before morning feeding by a vacuum pump through a stomach tube, mixed, strained through four layers of cheesecloth, and kept at 39 ░C under a carbon dioxide (CO2) atmosphere. Approximately 200 mg of sample (milled through a 1 mm sieve) were weighed into 100 ml calibrated glass syringes in triplicate. A 30 mL mixture of rumen liquor and buffer in a 1:2 ratio was added to 100 mL calibrated glass syringes pre-warmed to 39 ░C. Vaseline oil was applied to the pistons to ease movement and prevent gas leakage. Syringes were pre-warmed at 39 ░C before adding 30 mL of rumen liquor and buffer mixture (1:2 ratio) to each syringe. Three blank syringes containing rumen liquor without feed samples were included as controls. All syringes were incubated in a water bath maintained at 39 ░C and periodically agitated. Gas production readings were recorded at 0 and after 3, 6, 12, 24, 48, 72, and 96 hours of incubation. Gas production characteristics were estimated by fitting the average gas volumes to the exponential equation (1) of (ěrskov and Mcdonald 1979) using the Neway-Excel computer program (Macaulay Institute, Aberdeen, UK).

Where is the gas production (mL/200 mg DM) at time, is gas production (mL) from immediately soluble fraction, is gas production (mL) from insoluble fraction ɑ +b is gas production from potential degradable fraction (mL), c is the rate constant of gas production per hour (h), t is the incubation time in hours and e is the exponential constant (2.718).

In vitro gas production parameters were used to estimate organic matter digestibility (OMD) (Menke and Steingass 1988), metabolisable energy (ME) (Makkar and Becker 1996), and short-chain fatty acids (SCFA) (Makkar 2005) using the models shown in the equations below:

OMD(%) = 14.88+0.889 G+0.45 CP+0.0651 CA (2)

ME (MJ/kg)=2.20+0.136 G+0.057 CP (3)

SCFA (mmol/L)=0.0222 G-0.00425 (4)

Where G is gas production after 24 hours (G, mL), CP crude protein content (% DM), and crude ash content (CA, % DM).

Statistical analysis

Data on proximate, fibre, tannins and in vitro gas production of the selected tree and shrubs species were tested using a one-way analysis of variance in a completely randomised design using R software for windows, version 4.1.3 (R Core Team 2022). Differences in the chemical composition of forages between territories were tested using an independent t-test. Tukey’s multiple comparisons test assessed significant differences between means after a significant F-test. These differences were considered significant at p<0.05. The results were presented as means with the corresponding standard error of the means.


Result and discussions

Proximate composition of trees and shrubs species

The proximate composition of the selected eight species of trees and shrubs sampled in the study areas is shown in Table 1. In Kalemie, the highest (p<0.05) DM content was obtained in F. glumosa (960 g kg-1 fresh weight) and the lowest was found in T. diversifolia (925 g kg-1 fresh weight). Whereas from Kabare, the highest (p<0.05) DM contents were recorded in M. indica (951 g kg-1 fresh weight), F. glumosa (948 g kg-1 fresh weight), L. leucocephala (948 g kg-1 fresh weight ) and C. calothyrsus (946 g kg-1 fresh weight), and the lowest were obtained in T. diversifolia (915 g kg-1 fresh weight) and V. amygdalina (912 g kg-1 fresh weight). In terms of location, V. amygdalina, E. abyssinica, S. sesban and T. diversifolia from Kalemie territory had higher (p<0.05) dry matter (DM) content compared to those from Kabare territory. Dry matter indicates the amount of feed nutrients other than water that is available to the animal, and the species with the highest content in this study were found to be F. glumosa found in Kalemie and F. glumosa, L. leucocephala and C. calothyrsus found from Kabare territory.

The ash content of trees and shrubs forages varied from 41.4 g kg-1 DM in S. sesban to 140 g kg-1 DM inT. diversifolia for samples collected from Kalemie, while it was 46.5 g kg-1 DM in L. leucocephala to 163 g kg-1 DM in T. diversifolia for samples obtained from Kabare territory. The highest (p<0.05) ash contents were recorded in T. diversifolia (163 g kg-1 DM) from Kabare and in T. diversifolia (140 g kg-1 DM) and E. abyssinica (134 g kg-1 DM)from Kalemie territory. This finding of T. diversifolia in this study was higher than that of Wambui et al (2006) (124 g kg-1 DM). However, the high ash content found in this study gives an overall representation of the mineral content present in the forage that is essential for improving animal growth (Ravhuhali et al 2022).

The organic matter (OM) contents of trees and shrubs fodders ranged from 796 g kg-1 DM in T. diversifolia to 903 g kg-1 DM in S. sesban from Kalemie, while it was 766 g kg-1 DM in T. diversifolia to 910 g kg-1 DM in L. leucocephala from Kabare site. The lower OM content of T. diversifolia observed in the study areas of this study is due to its higher ash contents. Forages from Kabare had higher (p<0.05) OM contents compared to those from Kalemie territory. In this study, S. sesban and L. leucocephala had the highest (p<0.05) OM contents in Kalemie and Kabare, respectively. The OM range of S. sesban in this study (868 – 903 g kg-1 DM) was compared to what was reported by Gebreyowhans et al (2018) (948 g kg-1 DM).

The CP content of the forages ranged it ranged between 217 g kg-1 DM in M. indica to 402 g kg-1 DM inL. leucocephala in Kalemie, while it ranged between 270.36 g kg-1 DM in M. indica to 417 g kg-1 DM in C. calothyrsus from Kabare. The samples from Kabare territory had the highest (p<0.05) CP content in all trees and shrubs forages than those from Kalemie, except for L. leucocephala. This result can be explained by the agronomic practices and climate factors such as rainfall. from Kabare territory, land for fodder cropping is scarce, and smallholder farmers rely on planting improved trees and shrubs such as C. calothyrsus, L . leucocephala, S. sesban, F. glumosa to increase biomass production for animal feed, while in Kalemie, the land is available, and farmers often opt for transhumance. In addition, the presence of organizations working in the agricultural sector in the Kabare territory for several decades have created a positive attitude on smallholder farmers to adopt improved tree fodder compared to Kalemie (Katunga et al 2014). These findings agree with Mutwedu et al (2022), who observed similar trends between the provinces of Tanganyika and South-Kivu. In the present study, L. leucocephala (400 g kg-1 DM) and C. calothyrsus (417 g kg-1 DM) obtained from Kabare had higher (p<0.05) content of CP than those reported by Katunga et al (2014) within the same province of South-Kivu. All trees and shrub forage in this study had a CP content above the minimum threshold required for optimal rumen function and feed intake (70 g kg-1 DM of nitrogen). Therefore, they have the potential to be used as sources of protein to supplement poor-quality feeds such as crop residues and natural pastures, especially during the dry season when the quality and quantity of grasses are limited (Bayissa et al 2022; Derero and Kitaw 2018; Osuga et al 2012).

The ether extract (EE) of tree and shrub varied from 15.2 g kg-1 DM in F. glumosa to 50.2 g kg-1 DM in T. diversifolia for samples obtained from Kalemie, while it did so between 10.7 g kg-1 DM in C. calothyrsus to 36.1 g kg-1 DM in T. diversifolia from Kabare territory. The species such as C. calothyrsus, S. sesban and T. diversifolia for samples obtained from Kalemie had higher (p<0.05) EE content than those from Kabare.

Table 1. Proximate composition of tree and shrub leaves (g kg-1 DM)

Species

Dry matter

Ash

Organic matter

Crude protein

Ether extract

Kalemie

Kabare

p value 

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

V. amygdalina

930de

912c

0.00

119b

121c

0.20

806c

802e

0.72

342abc

409a

0.00

16.2cd

17.3cd

0.53

E. abyssinica

934cd

930b

0.01

134a

90.3d

0.00

809c

846d

0.00

306bc

381a

0.02

19.1cd

29.0ab

0.12

C. calothyrsus

946b

946a

1.00

81.9de

62.8f

0.00

869b

887b

0.00

361ab

417a

0.01

20.5cd

10.7d

0.00

L. leucocephala

941bc

948a

0.03

72.6e

46.5g

0.00

873b

910a

0.01

402a

400a

0.81

25.2c

19.5c

0.11

S. sesban

942bc

929b

0.00

41.4f

65.4f

0.00

903a

868c

0.00

285cd

396a

0.01

35.1b

17.7cd

0.00

M. indica

930de

951a

0.01

86.5d

80.1e

0.21

854b

875bc

0.01

217e

270b

0.05

24.2cd

23.8bc

0.88

T. diversifolia

925e

915c

0.01

140a

163a

0.00

796c

766f

0.00

333bc

413a

0.03

50.2a

36.1a

0.00

F. glumosa

960a

948a

0.12

102c

149b

0.00

862b

811e

0.00

230de

301b

0.02

15.2d

34.0a

0.00

SEM

2.22

3.11

6.50

8.30

7.58

9.57

13.0

11.4

2.36

1.80

p-value

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

SEM, standard error of the means; abcdefMeans within columns with different superscripts differ at p<0.05
p-value, independent t-test between Kalemie and Kabare territories
Fibre composition of trees and shrubs species

The neutral detergent fibre (NDF) content of tree and shrub species ranged from 365 g kg-1 DM in C. calothyrsus to 690 g kg-1 DM in E. abyssinicafor samples obtained from Kalemie territory. Whereas from Kabare, the lowest NDF content was recorded in C. calothyrsus (265 g kg-1 DM) and the highest in E. abyssinica (580 g kg-1 DM) and L. leucocephala (578 g kg-1 DM). The highest (p<0.05) NDF content was recorded in Kalemie territory (Table 2). This could be due to the intensity of solar radiation, and the lesser amount of rainfall resulted in faster maturation during the dry season, which could result in higher cell wall contents than from Kabare, where the rainy season is longer. The range of NDF content (265-690 g kg -1 DM) in this study was within the critical level of 55-60 g kg-1 DM, of which above the critical value, the voluntary feed intake and feed conversion efficiency had been reportedly decreased due to longer rumination time (Bayissa et al., 2022). The range of NDF in this study was slightly lower than that reported by Katunga et al (2014) (319-726 g kg-1 DM).The acid detergent fibre (ADF) content of tree and shrub samples ranged from 248 g kg-1 DM in S. sesban to 519 g kg-1 DM in E. abyssinica in Kalemie, and from 167 g kg-1 DM in T. diversifolia to 424 g kg-1 DM in M. indica from Kabare territory. The ADF results of this study were similar to the ranges of 317 g kg-1 DM to 472 g kg -1 DM reported by Bayissa et al (2022). The lower ADF value in this study could be a sign of better digestibility than in other browse forages.

The acid detergent lignin (ADL) content of trees and shrubs species ranged from 74.6 kg-1 DM in S. sesban to 428 g kg-1 DM in M. indica for samples obtained from Kalemie, while it was between 21.0 kg-1 DM in C. calothyrsus to 462 kg-1 DM in M. indica for samples obtained from Kabare. Lignin is a compound, which attributes strength and resistance to plant tissue, thereby limiting the ability of the rumen micro-organisms to digest the cell wall polysaccharides and these become more digestible once the lignin is removed (Osuga et al 2012). Therefore, trees and shrubs with higher lignin content could have a low digestibility than those with low lignin content. The hemicellulose content of tree and shrub species ranged from 50.3 g kg -1 DM in V. amygdalina to 229 g kg-1 DM in S. sesban for samples obtained from Kalemie. While for samples collected from Kabare, the range varied from 67.7 g kg-1 DM in C. calothyrsus to 278 g kg -1 DM in T. diversifolia. The average cellulose content of tree and shrub species ranged from 21.3 g kg-1 DM in M. indica to 402 g kg-1 DM in S. sesban for samples collected from Kalemie, while it was 45.6 g kg-1 DM in M. indica to 417 g kg-1 DM in L. leucocephala.

Table 2. Fibre composition of tree and shrub leaves (g kg-1 DM)

Species

Neutral detergent fibre

Acid detergent fibre

Acid detergent lignin

Hemicellulose

Cellulose

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

V. amygdalina

495c

491b

0.46

455b

415a

0.02

139c

46.6de

0.02

50.3d

76.0d

0.06

356ab

444ab

0.03

E. abyssinica

690a

580a

0.00

519a

408ab

0.00

381ab

184b

0.17

172ab

172c

0.97

309ab

396abc

0.51

C. calothyrsus

365f

265d

0.00

256e

197d

0.04

184bc

21.0e

0.00

109cd

67.7d

0.15

181bc

244d

0.00

L. leucocephala

487cd

578a

0.00

270de

269c

0.86

106c

107cd

0.90

217a

309a

0.00

381ab

471a

0.01

S. sesban

477cde

507b

0.00

248e

269c

0.00

74.6c

74.6de

1.00

229a

238b

0.14

402a

433abc

0.12

M. indica

449de

508b

0.01

296cd

424a

0.00

428a

462a

0.20

153bc

83.8d

0.01

21.3c

45.6e

0.10

T. diversifolia

437e

454c

0.39

330c

167d

0.00

220abc

82.7cde

0.00

106cd

287a

0.00

217abc

371bc

0.00

F. glumosa

586b

510b

0.00

513a

371b

0.00

384ab

154bc

0.00

73.7d

139c

0.05

203abc

356c

0.01

SEM

19.6

19.4

22.5

20.1

29.9

27.7

13.2

19.0

28.1

27.7

p value

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

SEM, standard error of the means; abcdeMeans within columns with different superscripts differ at p<0.05; p value, independent t-test for Kalemie and Kabare territories
Tannin compounds of trees and shrubs species

The results of tannin composition of trees and shrubs leaves of samples collected from the Kalemie and Kabare territories are presented in Table 3. The condensed tannins (CT) content of trees and shrubs fodders ranged from 25.5 g kg-1 DM in V. amygdalina and S. sesban to122 g kg-1 DM in C. calothyrsus for samples collected from Kalemie, while it was 34.8 g kg-1 DM in V. amygdalina to 68.3 g kg-1 in M. indica for samples collected from Kabare. The CT contents of C. calothyrsus, L. leucocephala and M. indica from Kalemie were higher (p<0.05) than those from Kabare, except for S. sesban. Trees and shrubs have been reported to contain high phenolic compounds and tannins (Osuga et al 2006). These compounds tend to limit their use, particularly as protein supplements because tannins decrease feed intake, impair feed digestibility, and are toxic to rumen microbes. A moderate concentration of CT can exert beneficial effects on protein and increase protein outflow from the rumen, thereby increasing the absorption of amino acids in the small intestine, thus improving animal performance (Osuga et al 2011). Species such as V. amygdalina, S. sesban, F. glumosa, T. diversifolia and E. abyssinica found in Kalemie, and all trees and shrubs forage found Kabare can exert these benefits as they contain a low and moderate levels of CT. In contrast, high concentrations of CT in the diet reduce voluntary feed intake, digestive efficiency, and animal productivity. The results of this study revealed that C. calothyrsus, M. indica and L. leucocephala from samples collected in Kalemie territory contained high (p<0.05) levels of CT than those from Kabare. The CT content of C. calothyrsus in the present study was in the range 82.1-131 g kg-1 DM reported by Rakhmani et al (2005) and is lower than that of Rira et al (2021) (361 g kg-1 DM). C. calothyrsus is widely used as a supplemental source of protein by smallholder farmers in animal production in many Sub-Saharan African countries. The digestibility of C. calothyrsus may be affected by CT level due to its ability to bind proteins, which reduces the digestibility of the feed. Thus, C. calothyrsus can be used in animal nutrition in a mixture with other feeds, especially those rich in nitrogen, to dilute the anti-nutritive activity of tannins or by treatments such as drying the fodder. Moreover, the condensed tannin content of C. calothyrsus can vary within the species, and its composition depends on the region and growing season (Premaratne and Perera, 1999). However, in eastern DRC, the type of C. calothyrsus accession introduced and used by smallholder farmers and its tannin levels are less documented. It is recommendable that research be carried out to determine the tannins levels. Total extractable tannins (TET) ranged from 5.28 g kg-1 DM in V. amygdalina to 29.3 g kg-1 DM in F. glumosa, and from 2.43 g kg -1 DM in E. abyssinica to 18.3 g kg-1 DM in C. calothyrsus in samples collected from Kabare territory. The total extractable phenolics (TEPH) varied from 20.0 g kg-1 DM in T. diversifolia to 42.5 g kg-1 DM in M. indica in samples obtained from Kalemie, while it was between 20.6 g kg-1 DM in F. glumosa to 34.8 g kg-1 DM in E. abyssinica samples obtained from Kabare. The results of TET were within the range of 0.6 to 38.5 g kg-1 DM reported by Osuga et al (2006) and the range of 11.8 g- 52.3 g kg-1 DM to -1 DM of TEPH reported by the same author was comparable to the result of this study.

Table 3. Tannin compound of trees and shrubs leaves (g kg-1 DM)

Species

Condensed tannins

Total extractable Tannins

Total extractable phenolics

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

V. amygdalina

25.5f

34.8d

0.07

5.28c

9.13abc

0.30

32.7ab

32.0

0.89

E. abyssinica

61.8cd

62.7ab

0.93

6.46c

2.43c

0.22

37.1ab

34.8

0.82

C. calothyrsus

121.8a

66.2ab

0.02

22.3ab

18.3a

0.47

37.5ab

34.1

0.28

L. leucocephala

80.6bc

41.7cd

0.01

8.80c

15.5ab

0.11

30.8ab

34.4

0.72

S. sesban

25.5f

53.0bc

0.01

9.12c

8.14bc

0.61

31.3ab

33.5

0.55

M. indica

86.3b

68.3a

0.01

8.44c

10.4abc

0.37

42.5a

24.1

0.03

T. diversifolia

48.1de

37.9d

0.08

13.8bc

7.35bc

0.07

20.0b

21.8

0.37

F. glumosa

33.8ef

37.1d

0.09

29.3a

2.58c

0.00

20.3b

20.6

0.91

SEM

8.30

3.46

2.12

1.42

2.12

1.76

P-value

0.00

0.00

0.00

0.00

0.01

0.09

SEM, standard error of the means; abcdefMeans within columns with different superscripts differ at p<0.05
p-value, independent t-test for Kalemie and Kabare territories
In vitro gas production profile of the trees and shrubs forages

The results of in vitro gas production of trees and shrubs species are presented in Table 4. Gas production at 24 hours of incubation in the rumen liquor ranged from 1.06 mL/200 mg DM in L. leucocephala to 17.4 mL/200 mg DM in M. indica in samples collected from Kalemie territory, whereas it ranged between 0.70 mL/200 mg DM in C. calothyrsus to 17.0 mL/200 mg DM in V. amygdalina in samples collected from from Kabare. The result of this study revealed that M. indica in Kalemie and V. amygdalina in samples collected from Kabare produced high (p<0.05) amount of gas at 24 hours than other species. Gas production from the immediate soluble fraction (a) of tree and shrub species ranged from -0.45 mL/200 mg DM in S. sesban to 1.88 mL/200 mg DM in F. glumosa in Kalemie. While from Kabare, gas production from the immediate soluble fraction (a) was the highest (p<0.05) in M. indica. Gas production from an insoluble fraction (b) of trees and shrubs fodder was the highest (p<0.05) in L. leuceocephala (21.0 mL/200 mg DM) for samples collected from Kalemie and T. diversifolia (30.9 mL/200 mg DM) for samples collected from Kabare. The potential gas production (a+b) was the highest (p<0.05) (20.8 mL/200 mg DM) in L. leucocephala in samples collected from Kalemie and T. diversifolia (31.0 mL/200 mg DM) in samples collected from Kabare. The rate of gas production (c) in this study ranged from 0.01 mL h-1 in L. leucocephala to 2.74 mL h-1 in M. indica in Kalemie, whereas samples obtained from Kabare, it was ranged between 0.01 mL h-1 in C. calothyrsus to 0.17 mL h-1 in S. sesban.

Table 4. Gas production profile of trees and shrubs leaves (mL/ 200 mg DM)

Species

24

a

b

c

a+b

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

V. amygdalina

9.34b

17.0a

0.01

0.24ab

0.98ab

0.38

5.13b

5.60b

0.66

0.12

0.13ab

0.81

5.37b

6.58b

0.07

E. abyssinica

2.13c

2.14d

0.18

0.33ab

0.37ab

0.94

4.00b

5.95b

0.04

0.03

0.22ab

0.70

4.33bc

6.32b

0.02

C. calothyrsus

11.6b

0.70d

0.01

0.79ab

0.05b

0.05

3.18bc

16.4ab

0.34

0.12

0.01b

0.00

3.98bcd

4.43bc

0.42

L. leucocephala

1.06c

1.40d

0.73

-0.23b

-0.19b

0.89

21.0a

6.37b

0.00

0.01

0.02ab

0.24

20.8a

6.19b

0.00

S. sesban

1.41c

3.51cd

0.18

-0.45b

0.01b

0.27

4.96b

3.13b

0.12

0.06

0.17a

0.27

4.51bc

3.15c

0.26

M. indica

17.4a

5.94c

0.00

1.32ab

1.93a

0.38

2.90bcd

2.00b

0.41

2.74

0.10ab

0.37

4.22bcd

3.93bc

0.47

T. diversifolia

9.00b

1.81d

0.00

1.83a

0.03b

0.02

0.64d

30.9a

0.00

2.43

0.02b

0.36

2.47d

31.0a

0.00

F. glumosa

8.31b

10.8b

0.08

1.88a

0.76ab

0.18

1.01cd

3.06b

0.03

0.05

0.12ab

0.31

2.89cd

3.81bc

0.03

SEM

1.16

1.14

0.21

0.17

1.28

2.31

0.43

0.02

1.18

1.82

p-value

0.00

0.00

0.00

0.01

0.00

0.00

0.53

0.01

0.00

0.00

SEM, standard error of the means; abcdMeans within columns with different superscripts differ at p<0.05; p-value, independent t-test for Kalemie and Kabare territories

The metabolisable energy, organic matter digestibility, and short-chain fatty acids were estimated at 24 hours of incubation in the rumen liquor (Table 5). The metabolizable energy (ME) of trees and shrubs species ranged from 1.82 MJ kg-1 DM in S. sesban to 3.63 MJ kg-1 DM in C. calothyrsus for samples obtained for samples obtained from Kalemie. The highest ME for samples obtained from Kabare was reported in V. amygdaline (4.04 MJ kg -1 DM). The organic matter digestibility (OMD) of tree and shrub species varied from 31.3 % kg-1DM in E. abyssinica to 41.9 % kg-1 DM inC. calothyrsus for samples obtained from Kalemie, whereas it ranged between 32.82 % kg-1 DM in M. indica to 44.6 % kg-1 DM in V. amygdalina for samples obtained from Kabare. The short-chain fatty acids (SCFA) of the tree and shrub species ranged from 0.02 mmol/200mg DM in L. leucocephala to 0.38 mmol/200mg DM in M. indica for samples obtained from Kalemie, while from 0.02 mmol/200mg DM in C. calothyrsus to 0.38 mmol/200mg DM in V. amygdalina for samples collected from Kabare. The results of this study revealed that the highest (p<0.05) OMD, ME, and SCFA content were found in the leaves of M. indica samples obtained from and V. amygdalina samples collected from Kabare. This can be attributed to the moderate content of NDF, ADF, and high CP content, as well as the low CT content that M. indica and V. amygdalina contained. These findings are consistent with Kedir and Feki (2021) and Mengistu et al (2020), who mentioned that increasing the condensed tannin contents decreased the ME and OMD content of the leaves of trees and shrubs.

Table 5. Metabolisable energy (MJ kg1), organic matter digestibility (%), and short-chain fatty acids (mmol kg1) of tree and shrub leaves

Species

Metabolisable energy

Organic matter digestibility

Short-chain fatty acids

Kalemie

Kabare

p value

Kalemie

Kabare

p value

Kalemie

Kabare

p value

V. amygdalina

2.58bc

4.04a

0.01

34.2bc

44.6a

0.01

0.20b

0.38a

0.01

E. abyssinica

2.03c

2.46c

0.02

31.3c

34.5bc

0.02

0.04c

0.04d

1.00

C. calothyrsus

3.63a

2.47c

0.02

41.9a

34.7bc

0.02

0.25b

0.02d

0.01

L. leucocephala

2.44bc

2.47c

0.83

34.4bc

34.4bc

0.96

0.02c

0.03d

0.71

S. sesban

1.82c

2.53bc

0.04

34.7bc

34.7bc

1.00

0.03c

0.07cd

0.19

M. indica

3.61a

2.35c

0.01

40.7a

32.8c

0.01

0.38a

0.13c

0.00

T. diversifolia

3.12ab

2.60bc

0.01

38.8ab

36.0bc

0.03

0.20b

0.04d

0.00

F. glumosa

2.44bc

3.19b

0.02

33.3bc

39.0b

0.01

0.18b

0.24b

0.08

SEM

0.14

0.12

0.82

0.79

0.03

0.03

P-value

0.00

0.00

0.00

0.00

0.00

0.00

SEM, standard error of the means; abcdMeans within columns with different superscripts differ (p<0.05);
p value1, independent t-test for Kalemie and Kabare
Associations among nutritive components of the tree and shrub species

Dry matter content was positively (p<0.05) correlated with organic matter and acid detergent fibre, while negative correlations were found in crude protein, cellulose, metabolisable energy and organic matter digestibility (Table 6). The results showed that CP was positively correlated with ME and OMD and negatively correlated with NDF, ADF and ADL. These findings were consistent with Derero and Kitaw (2018). NDF content was negatively correlated with ME, OMD and SCFA. These results were similar to those of Osuga et al (2005), who showed that NDF, ADF and ADL were negatively correlated with gas production parameters.

Table 6. Pearson’s correlation coefficient among nutritional components across all species, N=48

DM

Ash

OM

CP

EE

NDF

ADF

ADL

Hemicellulose

Cellulose

ME

OMD

SCFA

DM

1

Ash

-0.45a

1

OM

0.65a

-0.95a

1

CP

-0.40a

-0.04

-0.08

1

EE

-0.27

0.36b

-0.36b

-0.09

1

NDF

0.04

0.17

-0.13

-0.26

-0.01

1

ADF

0.15

0.31b

-0.25

-0.46a

-0.21

0.68a

1

ADL

0.30b

0.14

-0.02

-0.75a

-0.03

0.38a

0.55a

1

Hemicellulose

-0.15

-0.21

0.17

0.31b

0.27

0.28

-0.51a

-0.28

1

Cellulose

-0.29b

-0.03

-0.06

0.61a

0.03

0.27

-0.12

-0.79a

0.48a

1

ME

-0.33b

0.29b

-0.33b

0.08

0.04

-0.33b

0.05

-0.03

-0.32b

-0.19

1

OMD

-0.37b

0.21

-0.27b

0.131

0.17

-0.40a

-0.20

-0.18

-0.20

-0.08

0.95a

1

SCFA

-0.20

0.31b

-0.32b

-0.36b

-0.02

-0.15

0.26

0.27

-0.52a

-0.38a

0.86a

0.79a

1

a Correlation is significant at the 0.01 level; b Correlation is significant at the 0.05 level; DM, dry matter; OM, organic matter; CP, crude protein; EE, ether extract; NDF, neutral detergent fibre; ADF, acid detergent fibre; ADL, acid detergent; ME, metabolisable energy; OMD, organic matter digestibility; SCFA, Short chain fatty acids


Conclusion


Acknowledgements

This study was conducted under the Integrated Project for Agricultural Growth in the Great Lake regions (PICAGL), funded by the World Bank Group through the government of the Democratic Republic of the Congo and implemented by the International Institute of Tropical Agriculture (IITA) in South-Kivu and Tanganyika provinces. We also thank the government authorities in Tanganyika and South-Kivu provinces, farmers, and interviewers for their support during data collection.


Disclosure statement

The authors reported no potential conflict of interest


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