Horticultural residues as ruminant feed in peri-urban area of The Gambia

 

F S Nouala, O O Akinbamijo, O B Smith* and V S Pandey**

 

International Trypanotolerance Centre PMB 14 Banjul, The Gambia,
*International Development Research Centre, Ottawa, Canada,
**Institute of Tropical Medicine Nationalestraat 155 Antwerp, Belgium
s.nouala@itc.gm

Abstract

 

Chemical analysis, in sacco rumen degradability and in vitro true digestibility (IVTD) procedures were employed to elucidate the potential contribution of horticultural residues to ruminant nutrition in the Greater Banjul Area of The Gambia.

 

Bean and pea vines had higher crude protein contents (140 g/kg and 183 g/kg, respectively) compared to 106 g/kg for the conventional feed of groundnut hay. Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were lower (437 and 427 g/kg and 352 and 345 g/kg, for bean and pea vines, respectively) compared with 510 and 471 g/kg for groundnut hay. The baby corn stover had a crude protein content of 50 g/kg, and NDF and ADF of 631 and 398 g/kg respectively. The IVTD (on dry matter basis) ranged between 65.2% and 76.4%, while the potential degradability (PD) ranged between 67.6% and 79.2% with rate constants ranging between 0.014 and 0.065 per hour.

 

The chemical properties support the view that horticultural residues have enormous but under-exploited potential as emerging ruminant feed sources in the Greater Banjul area of The Gambia.

 

Key words: chemical composition, horticultural residues, in vitro, in sacco, nutritive value

Introduction

 

Tropical countries face a perennial problem of inadequate quality and quantity of ruminant feeds, especially during the long dry season. Consequently, alternative feed resources such as crop residues and agro-industrial by-products have become an increasingly important way of feeding ruminants (Kayouli 1997). The evaluation of the nutritive value of crops residues has been the subject of several reviews including those of Kevelenge et al (1983), Powell (1984) and Pozy et al (1995). The available evidence suggests that while proximate analysis may be interesting, only biological measurements (in sacco, in vitro, in vivo digestibility) can provide sufficient information about the nutritive value of fibrous feeds or residues (Ørskov 1987).

 

Groundnut hay, the most important crop residue in The Gambia, is as important to the farmer as the primary produce (groundnut) and, therefore, not always available and affordable to small-holder farmers who are the potential owners of crossbred animals living in peri-urban areas.

 

On the other hand, there has been a remarkable growth within the horticultural sector and most of the farms are located around the city fringes. In general, these farms are small-holdings or communal market-oriented gardens producing short-cycle crops. They generate considerable residues round the year. In the nutrient cycling context these residues are of enormous advantage to ruminant nutrition. However, optimum modalities of incorporating these fodder resources in the ruminant nutrition system are lacking. Generally, alternative feed resources are being identified and characterised within the available natural resource base before they can be meaningfully incorporated into the feed resource base.

 

The aim of this study was to determine the nutritive value of the major horticultural residues available in the Greater Banjul Area compared to groundnut hay. To achieve this goal, these residues were evaluated for nutritive values using proximate analyses, in sacco rumen degradability,and in vitro dry matter degradability.

Materials and Methods

 

All feed samples investigated were collected from peri-urban horticultural farms in Banjul. They were chosen on the basis of availability, spatial distribution and indigenous knowledge of farmers. Target crop residues were:

 

Sixty-day old Baby corn stover; (Zea mays L.) variety Pacific 421.
Fifty-day old Bean vines (Phaseolus vulgaris L.) variety Amy and Pea vines (Pisum sativum L.) Variety Cascadia.
Groundnut hay (Arachis hypogaea L.)

 

The vines and stover consisting of all above-ground plant parts were collected from the garden, chopped manually to a size of about 5 cm. Sub-samples were dried at 65°C in forced draught ovens (Flinn and Heazlewood 2000). This dry matter is known as partial dry matter. The partially dried samples were milled in a Christy Hunt hammer - Christy Hunt engineering LTD England - (2.5 - 3 mm mesh sizes). A final sample of about 500 g for each was stored in airtight plastic bottles.

 

The laboratory dry matter was determined using the method described by Galyean (1997). The total dry matter (DM) was then computed as: DM= Partial dry matter x laboratory dry matter. The organic matter (OM) was determined according to Galyean (1997).  The crude protein (CP) content was determined by the Kjeldahl method, as describe by Galyean (1997).  The neutral detergent fibre (NDF) and the acid detergent fibre (ADF) were determined using the Ankom fibre Analyser (Ankom Technology 1998a), with the method described by the manufacturer. Four ml of alpha amylase was added in the vessel of the fibre analyser during NDF determination.

 

For the in sacco rumen degradability study, two four-year old N'Dama X Jersey crossbred bulls, weighing about 300 kg and fitted with rumen canulae, were used. They were offered a daily ration consisting of maize stover (pacific 421) ad libitum during the incubation of horticultural residues, and groundnut hay for the incubation of groundnut hay. Both bulls were supplemented with 1.5 kg DM/day of concentrate supplement. The supplement consisted of 50% rice bran and 50% groundnut cake and was offered in two equal meals in the morning and in the afternoon. Minerals lick and water were available ad libitum.

 

Nylon bags made from polyester filter cloth (Blutex No 150- Tripette et Renaud, France) measuring about 140 x 90 mm when laid flat with a pore size of 46 µm were used.  The nylon bags were oven dried at 60-65° C for 30 min and their empty weight measured after allowing to cool at room temperature in a desiccator. About 3.0 g of feed sample was weighed accurately directly into each bag and the bags heat-sealed. The bags were then moistened for about one minute, anchored by a 500 mm nylon string to the cap of the rumen canulae of each bull. The zero hour bags were left for five minutes in water at 39° C (Deville et al 1980).

 

The samples were incubated for 0, 2, 6, 12, 24, 48, 72 and 96 hours in a " Sequential removal" method (Osuji et al 1993). Three bags were incubated for each sample in each bull for each incubation time. After the incubation, the bags were washed for about three minutes in slow-running cold tap water, by rubbing between the fingers and the thumb for five minutes and oven-dried at 70°C for 48 hours and weighed after cooling at room temperature in a desiccator. A zero hour residue was obtained by soaking the bags in a water-bath at 39°C for five minutes followed by oven drying. DM disappearance was expressed as a proportion of amount incubated, and the data was fitted to the exponential model proposed by Ørskov and McDonald (1979):

P = A + B (1- ℮^-Ct)

Where:
            P = the DM disappearance at time t,
            A = the zero time intercept,
            B= the slowly degradable fraction and
            C = the rate of degradation.
 

The potential degradability (PD) was estimated as (A + B). The in vitro true digestibility was performed with the 'Daisy' Incubator, using the method described by the manufacturer (Ankom Technology 1998b). The in vitro trials were conducted in parallel with the in sacco studies described above. The rumen inoculum was collected from bulls fitted with rumen cannulae.

 

The significance of differences in the chemical composition and degradability characteristics between the feedstuffs was assessed by analysis of variance. A Duncan test was then performed to separate the feedstuffs into groups of equal composition or characteristics. Level of statistical significance was taken at P<0.05.

Results

 

In comparison with the conventional feedstuffs apart from the understandably high moisture content of the fresh horticultural residues, they presented a very attractive composition in terms of organic matter, fibre and crude protein (Table 1).  The horticultural legumes had higher (P<0.05) CP and lower fibre constituents compared to groundnut hay.

The potential degradability of bean and pea vines was not different (P>0.05) even though the rate constant of degradation of pea vines was more than twice that of bean vines (Table 2). Baby corn stover had a low rate constant of degradation (0.014) and groundnut hay had a high rate (0.065).  The peas vines had the highest IVTD and Baby corn stover the lowest.

 

Discussion

 

The results on the chemical composition were consistent with the usual ranges of tropical feeds (Kearl 1982; Richard et al 1989; Pond et al 1995). With their high moisture content (Table 1), horticultural residues will need adequate conservation methods to avoid moulding that can adversely affects their nutritive value. The ADF analysis was introduced in the study to evaluate the fibre quality as suggested by Van Soest and Moore (1965). Early maturing horticultural crops tended to have less fibre (ADF) components compared with the late maturing groundnut. However, due to its low protein content (Table 1), which is lower than the minimum dietary crude protein concentration required for milk production from dairy cows (Muia et al 1999), the baby corn stover will need to be supplemented before meaningful production level can be attained.

 

The feedstuffs used in this experiment had different degradability characteristics. Ørskov et al (1988) observed that when feeds of similar potential degradability were fed to two groups of animals, those receiving feed with the higher rate constant ate more and grew better. The higher rate constant of legumes (groundnut hay, peas and beans vines) as compared to baby corn has also being reported by Van Soest (1988) and Bruno-Soares et al (2000). Mertens (1993) reported that some factors of physical nature, crystallinity and degree of polymerisation of the polysaccharides of the cell wall might have a greater effect on the digestion rate than the cell wall itself. The potential degradability and the rate constant of maize (baby corn stover) were similar to that found by Shem et al (1995). The rate constant of pea vines was similar to that reported by Bruno-Soares et al (2000), but that of bean vines as well as its potential degradability were different from that reported by Ramirez et al (1999). This may be due to the difference in the variety of beans used, harvesting period and methods of conservation. These factors are known to affect the chemical composition and thus the degradability characteristics (Kevelenge et al 1983; Fall et al 1998). Ørskov et al (1988), Blummel and Ørskov (1993) demonstrated a positive relationship between the in vitro, in sacco degradability characteristics and voluntary feed intake. The IVTD of horticultural residues was high which suggests that the horticultural residues used in this study have good potential in reducing dry season nutritional stress.

 

Conclusions

 

The chemical composition and the degradability characteristics of the horticultural residues in this study confirmed their high potential as feed for ruminants in the greater Banjul area, especially as peri-urban dairying is being developed. The horticultural legume vines with their high crude protein and low fibre contents can serve as valuable supplements to baby corn stover based rations.

 

Acknowledgement

 

The authors wish to express their gratitude to the International Development Research Centre, Canada for providing financial support to conduct this study. The permission to publish this paper by the Director General of the International Trypanotolerance Centre, Banjul is also gratefully acknowledged.

 

References

 

Ankom Technology Corporation 1998a Method for determining Acid Detergent Fibre, Neutral Detergent Fibre and Crude Fibre, using the Ankom Fibre Analyser. Ankom Technology Corporation, 14 Turk Hill Park, Fairport New York 14450, USA

 

Ankom Technology Corporation 1998b In vitro true digestibility using Daisy incubator. Ankom Technology Corporation, 14 Turk Hill Park, Fairport New York 14450, USA

 

Blummel M and Ørskov E R 1993 Comparison of in vitro gas production and nylon bag degradability of roughage in predicting feed intake in cattle. Animal Feed Science and Technology 40: 109-119.

 

Bruno-Soares A M, Abreu J M F, Guedes C V M and Dias-da-Silva A A 2000 Chemical composition, DM and NDF degradation kinetics in rumen of seven legume straws. Animal Feed Science and Technology 83: 75-80.

 

Deville J, Figon C and Emmanuel S 1980 A Comparison of the rumen degradability of some feeds by the artificial fibre bag technique. Tropical Animal Production 5: 50-52 http://www.fao.org/ag/aga/agap/frg/tap51/5_1_9.pdf

 

Fall S T, Cissè M, Ditaroh D, Richard D, Ndiaye N S and Diaw B 1998 In vivo nutrient digestibility in sheep, and rumen dry matter degradability in cattle fed crop by-product based diets. Journal of Animal Feed Science 7: 171-185.

 

Flinn P C and Heazlewood P G 2000 A uniform objective system for quality description of Australian fodder. Rural Industries Research and Development Corporation (RIRDC), publication No 00/134. Kington, Australia.

 

Galyean M L 1997 Laboratory procedures in animal nutrition research (12^th edition). West Texas A and M University, Division of Agriculture and Texas A and M Research and Extension Center, Amarillo

 

Kayouli C 1997 The role of feeding system based on cereal residues in integrated farming systems in sub-Saharan Africa. Livestock feed resources within integrated farming system. Second FAO electronic conference on tropical feeds (9 September- 28 February 1997) http://www.fao.org/ag/AGA/AGAP/FRG/TFCONF2.HTM

 

Kearl L C 1982 Nutrient requirements of ruminants in the developing countries. International Feedstuff Institute, Publication of  Utah Agriculture Experiment Station. Utah State University. Logan, Utah 381 pp.

 

Kevelenge J E E, Said A N and Kiflewahid B 1983 The nutritive value of four arable farm by-products commonly fed to dairy cattle by small-scale farmers in Kenya. 1 Organic structural components and in vitro digestibility. Tropical Animal Production 8: 162-170 http://www.fao.org/ag/aga/agap/frg/TAP83/83-162.pdf

 

Mertens D R 1993 Kinetics of cell wall digestion and passage in ruminants. In: Forage cell wall structure and digestibility. Editors: Jung H G, Buxton D R, Hatfield  R D and Ralph J, Madison, WI, USA.

 

Muia J M K, Tamminga S, Mbugua P N and Kariuki J N 1999 Optimal stage of maturity for feeding Napier grass (Pennisetum purpureum) to dairy cows in Kenya. Tropical Grassland 33,182-190.

 

Ørskov E R 1987 A method of estimating nutritive value of fibrous residues. In: Utilization of agricultural by-products as livestock feeds in Africa. Editors: Little D A and Said A N ILCA, Addis Ababa, Ethiopia, Pp1-4.

 

Ørskov E R and McDonald I 1979 The estimation of protein degradability in the rumen from incubation measurements weighed according to the rate of passage. Journal of Agricultural Science Cambridge 92: 499-503.

 

Ørskov E R, Reid G W and Kay M 1988 Prediction of intake by cattle from degradation characteristics of roughage. Animal Production 46: part 1 pp 29-34.

 

Osuji P O, Nsahlai I V and Khalili H 1993 Feed evaluation. ILCA manual 5. ILCA, Addis Ababa, Ethiopia. 40 pp.

 

Pond W G, Church D C and Pond K R 1995 Basic Animal Nutrition and Feeding. (4^th edition) John Wiley and Sons, New York. 615 pp.

 

Powell J M 1984 Sorghum and millet yields and stover consumption by livestock in the sub-humid zone of Nigeria. Tropical Agriculture 62: 77-81.

 

Pozy P, Dehareng D and Deswysen A G 1995 Chemical composition and calculated nutritive value of commonly available feedstuffs for ruminants in Burundi. Communication au IVe symposium International sur la nutrition des herbivores. 1-15 Septembre 1995, Clermont-Ferrand, France. Annales de Zootechnie, 44 suppl. 1, 50.

 

Ramirez R G, Ledezma-Torres R A and Martinez R 1999 Nutrient utilisation of bean straw, alfalfa hay and leaves of shrub Cercidium macrun by goats and sheep. Journal of Applied Animal Research 15: 137-148.

 

Richard D, Guèrin H and Fall S T 1989 Feed in the dry tropics. In: Ruminant Nutrition: Recommended allowance and feed tables. Editor: Jarrige. INRA, France. pp. 345-357.

 

Shem M N, Ørskov E R and Kimambot A E 1995 Prediction of voluntary dry-matter intake, digestible dry-matter intake and growth rate of cattle from degradation characteristics of tropical foods. Animal Science 60: 65-74.

 

 

Van Soest P J and Moore L A 1965 New chemical methods for analysis of forage for the purpose of predicting nutritive value. Proceedings of the 10^th international grassland congress, Sao Paulo Brazil paper 424 1: 783-789.