Acceptability of selected common shrubs/tree leaves in Nigeria by West African Dwarf goats

I  Ikhimioya

Department of Animal Science, Faculty of Agriculture, Ambrose Alli University, Ekpoma, Nigeria
imounu_ikhimioya@yahoo.com

Abstract

Preference ranking for five leaves from shrubs/trees namely Afzelia africana, Bambusa vulgaris, Chromolaena odorata, Mangifera indica and Newbouldia laevis, was evaluated using 16 indigenous West African Dwarf (WAD) goats.

The average daily intake of the trial leaves by the goats significantly (P < 0.01) varied ranging from 0.95 (Chromolaena odorata) to 4.67 (Bambusa vulgaris) kg/day. Significant differences (P < 0.05) in relative palatability index (RPI) among the leaves were also observed. Preference rankings (i.e. 1st to 5th) for the examined leaves produced the following order: Bambusa vulgaris> Mangifera indica > Afzelia africana> Newbouldia laevis> Chromolaena odorata respectively. Thus, Bambusa vulgaris appeared to be most preferred by the goats compared to the least preference value recorded for Chromolaena odorata. Relative palatability index was positively correlated (P < 0.01) with average daily intake and ash (P < 0.05) content of the leaves while there was a non-significant negative relationship with the fibre components NDF, ADF and lignin.

It is concluded that WAD goats prefer shrub/tree leaves variously and that this type of study could aid in the planning of supplemental feeding programs for ruminant animals.

Keywords: chemical contents, foliages, humid tropic, indigenous goats, preference

Introduction

Indigenous goats and sheep constitute over 95% of the ruminant population in Africa (Rege 1994) as compared to exotic breeds, with rural smallholder farmers being the major owners in Nigeria. The indigenous West African Dwarf (WAD) goat breed adapts to a wide range of environmental conditions and utilizes a variety of plant species for food (Rege 1994). They serve as adjunct to arable and tree-crop production (Upton 1988). Although widely distributed with potential economic role in rural farming systems, the productivity of WAD goats remain low and under-exploited for food and capital in sub-Saharan Africa. According to Sumberg (1985), this is as a result of a combination of complex factors including poor nutrition.

Ruminant diets comprise of plant species and parts which differ in their physical and chemical attributes (Dove 1996). The process of selecting their diets from these plants is mostly influenced by factors such as plant physical structure and chemical composition that is, concentration of anti-nutrient or toxins (Provenza and Cincotta 1994). Quantitative information on the productivity of small ruminants in sub-Saharan Africa concerning the utilization of leaves from shrubs and trees is scanty (Taiwo et al 2004). The potential for improved small ruminant production in Nigeria appears high given the wide distribution of evergreen browse species. There is therefore the need to investigate the abundant forage species of the tropics for their utilization as food for optimum productivity by these small ruminants.

The objective of this study therefore was to determine the preference for some selected shrub/tree leaves including Newbouldia laevis, Afzelia africana, Bambusa vulgaris, Chromolaena odorata and Mangifera indica by WAD goats in Nigeria.

Materials and methods 

This experiment was conducted at the Teaching and Research Farm of Ambrose Alli University, Ekpoma (6.46^º N and 6.04^º E), Nigeria, using leaves from these selected five shrub/trees.

Healthy branches from each of the species were cut daily from natural stands within and around the university premises and defoliated on clean metal sheets. This was done to ensure that the animals received only the leaves of the trial plants.

Sixteen weaned WAD goats weighing on average 7.61kg (SD = 1.31) were used for this study and housed within a single large pen. Following a 6-day adjustment period, consumption data were collected over a 14-day period. The freshly cut leaves were offered to the study animals in a cafeteria system, thus permitting free access to the foliages of their choice. Approximately 4kg (fresh mass) leaves of each species were offered to the animals between 0800h and 1530h daily. After withdrawal of the leaves, the animals were placed on Pennisetum purpureum (Elephant grass) till the following morning. The difference between the initial leaf weight and the leftover weight (on as-fed-basis) following the withdrawals was taken as the daily intake of the individual species.

Relative palatability index (RPI) was calculated daily per plant species by dividing the daily consumption values of individual species by that of the plant with the highest consumption value and multiplied by 100 as described by Larbi et al (1993). These daily RPI values obtained for each of the species were then subjected to analysis of variance (Gomez and Gomez 1984) using the randomized complete block design where the plant leaves served as treatments and the data collection days as the blocks. The species were then ranked based on these calculations with the highest consumption value being the most preferred and vice versa.

Approximately 50g each of the offered leaves was sampled each consumption data collection day. Each day’s samples were oven dried at 60^º C until constant weight was attained to determine their dry matter contents from their residual weights. The dried leaf samples were milled to pass through 1mm sieve mesh, bulked on individual leaf basis and stored in sealed polythene bags for chemical analyses. Proximate composition of the leaves was determined using AOAC (1990) procedures why analyses of NDF, ADF lignin were according to the methods of Goering and Van Soest (1970).

Results and discussion

The chemical composition of the examined leaves is as presented in Table 1.

The CP content of the leaves was high with moderately high levels of NDF, ADF and lignin. Moreover, with all the leaves having CP contents generally higher than 8%, below which, Norton (2003) observed that feeds will not provide the required levels of ammonia for optimum rumen microbial activity is suggestive of the fact that these leaves could be of high nutritional quality. The CP range in the leaves of this study were however observed to be higher than the range of 137.5-212.5 g/kg reported for browses of West Africa by Rittner and Reed (1992). As well, these values were observed to be higher than the 130-140 g/CPkg required for high producing animals (Meissner 1997). Besides, the moderately high NDF level in this study was lower than the safe upper limit of 60% (Meissner et al 1991) for guaranteed forage intake by sheep. The variation in the NDF levels in the tested leaves did not vary widely in contrast with the report by Hove et al (2001) in browses. This could have been due to the non inclusion of the petioles of the leaves as observed by Mokoboki et al (2005) with leaves from Acacia.

Table 2 presents values for average daily intakes and RPI and the rankings of the studied leaves fed to the goats.

There were significant differences between the leaves with regards to average daily leave intake (P < 0.01) and RPI (P < 0.05) with both parameters having similar patterns in statistical differences among the leaves. This probably indicates that daily intakes of the leaves dictated to a large extent the RPI of the goats. Relating to this observation, Gherardi and Black (1991) had reported earlier that acceptability of forages by sheep was associated with differences in intake of roughages. Average daily intake of the leaves by goats ranged from 0.95kg for Chromolaena odorata to 4.67kg for Bambusa vulgaris.

Several factors influence preference by goats (Morand-Fehr 2003). The highest ranking (1st) reported for Bambusa vulgaris could be supported by its being the most coarse of the leaves in terms of texture since according to Ouédrago et al (1996) goats prefer coarse feeds. As well, Holst and Simmonds (2000) reported Bambusa spp to be highly palatable to goats.

Goats more readily accept diets with which they have had previous experience. Prior to the commencement of this study cut mango leaves was provided as feed to the goats. Thus, the preference for mango leaves (ranked 2nd) in this study supports the observation of Provenza and Cincotta (1994) that conditioning influences preference of small ruminants for forages. On the other hand, lack of prior experience with Newbouldia leaves in this investigation appears to be the primary reason for its low RPI ranking (4th). The utilization of this shrub for livestock feeding although readily available is presently very limited. The observed least preference for Chromolaena odorata leaves going by its least ranking may best be explained by its strong smell as observed by Apori et al (2000) thus resulting in aversion for it by goats.

The relationship between RPI and the intake and chemical traits of the leaves is shown on Table 3.

Intake of the leaves had a very strong relationship with RPI as well as with the ash content of the leaves. The positive relationship of ash with RPI could be a confirmation of the fact that mineral concentration is a plant linked factor that affects the acceptability of plants (Walker 1980; Hadjigeorgiou et al 2003) an observation likened to that of Hadjigeorgiou et al (2003). On the contrary the fibre contents (NDF, ADF, Lignin) of the leaves although relatively high, related negatively with RPI. Dry matter content revealed a high non-significant relationship with RPI compared to the negatively weak and virtually with no relationship that was found between CP and RPI of the examined leaves. This is in contrast with the report of Lambert et al (1989) that preferences for sheep and goats correlate positively with N content of forages. The high and positive relationship between RPI and DM as well as its lack of relationship with CP is similar to the findings of Hadjigeorgiou et al (2003. The assertions of Minson (1990) and Thompson and Poppi (1990) that a strong correlation exists between many of the chemical constituents of plants were not fully supported by the findings of this study.

Conclusions 

• The results from this study indicate that preference for shrub/tree leaves by WAD goats varied widely and may probably have been influenced by variations in the concentration of minerals in the leaves together with differences in their intakes.

  
  

• It is thought that studies of this nature could be used in the identification of preferred tropical forages thus aiding the planning of supplemental feeding programs for tropical ruminant livestock.

References 

AOAC 1990 Official Methods of Analysis, 15th edition. Association of Official Analytical Chemists. Washington, DC.

Apori S O, Long R J, Castro F B and Ørskov E R 2000 Chemical composition and nutritive value of leaves and stems of tropical weed Chromolaena odorata. Grass and Forage Science 55:77-81

Dove H 1996 Constraints to the modeling of diet selection and intake in grazing ruminants. Australian Journal of Agricultural Research 47:257-275

Gherardi S G and Black J L 1991 Effect of palatability on voluntary feed intake by sheep. 1. Identification of chemicals that alter the palatability of forage. Australian Journal of Agricultural Research 42:571-584

Goering H K and van Soest P J 1970 Forage fibre analysis (apparatus, reagents, proceedings and some applications). Agricultural Handbook 379, ARS, USDA, Washington, D.C.

Gomez K A and Gomez A A 1984 Statistical Procedures for Agricultural Research. 2nd edition. John Wiley and Sons, New York, USA. 680pp.

Hadjigeorgiou I E Gordon I J and Milne J A 2003 Comparative preference by sheep and goats for Gramineae forages varying in chemical composition. Small Ruminant Research 49 (2):147-156

Holst P J and Simmonds H E 2000 Palatability of weeds to goats in Australia. In: Proceedings of the 7th International conference on goats. France, 15-21 May, pp 111-113

Hove L, Topps J H, Sibanda S and Ndlovu L R 2001 Nutrient intake and utilization by goats fed dried leaves of the same legumes Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala as supplements to native pasture hay. Animal Feed Science and Technology 91:95-106

Lambert MG, Jung G A, Fletcher R H, Budding P J and Costall DA 1989 Forage shrubs in North Island  hill country. 2. Sheep and goat preferences. New Zealand Journal of Agricultural Research 32:485-490

Larbi A, Lazier J and Ochang J 1993 Fodder production and nutritive value of six shrubs on acid soil in Southern Ethiopia. Tropical Agriculture (Trinidad) 70:13-15

Meissner H H 1997 Recent research on forage utilization by ruminant livestock in South Africa. Animal Feed Science and Technology 69:103-119

Meissner H H, Viljoen M O and van Niekerk W A 1991 Intake and digestibility by sheep of Antherphora, Panicum, Rhodes and Smooth finger grass In: Proceedings of the IVth International Rangeland Congress, September 1991, Montpellier, France pp 648-649

Minson D J 1990 Forage in ruminant nutrition. Academic Press Incorporated, New York, USA.

Mokoboki H K, Ndlovu L R, Ng’ambi J W, Malatje M M and Nikolova R V 2005 Nutritive value of Acacia tree foliages growing in Limpopo province of South Africa. South Africa Journal of Animal Science 35(4):221-228

Morand-Fehr P 2003 Dietary choice of goats at the trough. Small Ruminant Research 49 (3):231-239

Norton B W 2003 The nutritive value of tree legumes In: Forage Tree Legumes in Tropical Agriculture. Gutteridge R G and Shelton H M (Editors), http://www.fao.org/ag/AGP/AGPC/doc/Publicat/Gutt-shel/x5556e0j.htm#4.1

Ouédrago Y, Morand-Fehr P, Hervieu J and Sauvant D 1996 Effect of humidity and particle size on barley and beet pulp palatability in dairy goats In: Proceedings of the 6th International Conference on Goats. Beijing, China, 6-11 May 1996, pp 554-557

Provenza F D and Cincotta R P 1994 Foraging as a self-organisational learning process: Accepting adaptability at the expense of predictability In: Hughes R N (editor.) Diet selection. Blackwell Scientific Publications, Oxford, UK pp 79-101

Rege J E O 1994 Indigenous small ruminants: A Case for characterization and improvement In: Lebbie S H B, Rey B and Irungu E K (editors) Small ruminants research and development in Africa. Proceedings of the second biennial conference of the African Small Ruminants Research Network, AICC, Arusha, Tanzania 7-11 December 1992. ILCA/CTA, ILCA, Addis Ababa, Ethiopia pp 205-211  http://www.fao.org/Wairdocs/ILRI/x5472B/x5472b14.htm#indigenous%20african%20small%20ruminants:%20a%20case%20for%20characterisation%20and%20improvement

Rittner U and Reed J D 1992 Phenolics and in-vitro degradability of protein and fibre in West African browse. Journal of the Science of Food and Agriculture 58:21-28

Sumberg J E 1985 Small ruminant feed production in a farming system context In: Sumberg J E and Cassaday K (editors) Sheep and Goats in humid West Africa. Proceedings of the workshop on Small ruminant production systems in the humid zone of West Africa, Ibadan, Nigeria, January 23-26, 1984. ILCA, Addis Ababa, Ethiopia pp 3-5

Taiwo B B A, Adu I F and Taiwo  TO 2004 Feed sources and variation in weight of small ruminants in Obafemi Owode Local Government Area of Ogun State, Nigeria In: Proceedings of the 29th Annual Conference of the Nigerian Society for Animal Production, 21st-25th March 2004, Usmanu Danfodiyo University, Sokoto pp 333-335

Thompson K F and Poppi D P 1990 Livestock production from the pasture In: Pastures - Their ecology and management. Langer R H M (editor) Oxford University Press, Oxford, UK pp 263-283

Upton M 1988 Goat Production in the humid tropics – actual and potential contribution to agricultural development In: Smith O B and Bosman H G (editors) Goat production in the humid tropics. Proceedings of a workshop at the University of Ife, Ile-Ife, Nigeria, 20-24 July 1987: 11-20

Walker B H 1980 A review of browse and its role in livestock production in southern Africa In: Le Houérou H N (editor) Browse in Africa - The current state of knowledge. International Livestock Center for Africa, Addis Ababa, Ethiopia: 7-24  http://www.ilri.org/InfoServ/Webpub/Fulldocs/Browse_in_Africa/Chapter2.htm#TopOfPage

Received 15 February 2008; Accepted 27 March 2008; Published 10 June 2008

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