RESEARCH WORK

Effect of the soybean inclusion rate on the in vitro digestibility of the meal from Moringa oleifera pods

I. L. Montejo¹, O. López¹, Tania Sánchez¹, S. Muetzel², K. Becker² y L. Lamela¹

¹Estación Experimental de Pastos y Forrajes "Indio Hatuey". Central España Republicana, CP 44280, Matanzas, Cuba
E-mail: lenin@indio.atenas.inf.cu
²Universidad de Hohenheim, Alemania

ABSTRACT

The objective of this work was to evaluate the effect of the inclusion of soybean meal, in this case in a way of a lab reactive, simulating a conventional protein concentrate, on the in vitro digestibility of the meal from Moringaoleifera pods. Nine treatments of M. oleiferapods:soybean were evaluated (100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 20:80 and 0:100), with a completely randomized design and three replications per treatment. An increase was observed in gas production with the increase of the soybean inclusion percentage; the true digestibility had a similar performance. On the contrary, the production of microbial biomass reached its higher value with the inclusion of 10% soybean. The addition of soybean is concluded to improve the digestibility of the M. oleifera pods, and the optimum utilization efficiency of this diet is reached with the inclusion of 10% soybean.

Key words: digestibility, meals, Moringaoleifera, soybean.

INTRODUCTION

Moringaoleifera, although originated in the southern Himalayas, is widely distributed throughout the planet. It has been planted from sea level to 1800 masl and can be propagated

by seed or cuttings. In addition to its plasticity for adapting to several environment types and climate zones, its importance is due to its good nutritional qualities and high production of fresh biomass.

In the in vitro and in vivo analysis conducted no significant values of secondary compounds with antinutritional effects or trypsin, lectin and amylase inhibitors have been detected (Becker, 1995; Makkar and Becker, 1997; Gidamiset al., 2003). Up to 10% sugars in dry matter and 9,5 MJ of metabolizable energy were found in the leaves per kilogram of DM.

This plant has other uses, such as: natural flocculant, energetic, source of cellulose raw material and of plant growth-regulating hormones.

According to the quantity of seeds per fruit and total seeds of a tree, annually, the pod production of a plant per year was estimated to be between 1 000 and 1 250 (Foidlet al., 2003).

The pods are considered good sources of essential aminoacids. Seemingly, the leaves and pods have also a positive effect on the reduction of cholesterol in blood (Ghasiet al., 2000).

The mixture of the M. oleifera pods as meal- with soybean allows improving the feed quality, and achieving the nutritional utilization of the pods. For such reason, the objective of this work was to determine the most efficient percentage of soybean inclusion, from the nutritional point of view.

MATERIALS AND METHODS

Samples of M. oleifera pods were taken, ground and dried in a forced-air oven. In the elaboration of the treatments, soybean meal was added to simulate the effect of a protein concentrate feed and the rumen liquid of a cannulated rustic cow, 500 kg LW, was used.

Design and samples. The design was completely randomized, with nine treatments (table 1) and three replications.

The equation Yij = µ + Fi + eij was used.

The mathematical model used to describe the evolution of the microbial fermentation, through the cumulative gas production, was the one described by France et al. (1993):

Y = A(1-Exp (-b(t-L) c(Öt - ÖL))

Where: Y is the cumulative gas production (mL/g of incubated DM), A is the fermentation potential under the incubation conditions (asymptote of the curve, mL/g of incubated DM), t is the incubation time (h), b is a constant rate (h1), L is the Lag phase of fermentation (h) and c is another constant rate (h1/2).

The evaluation of the nutritional potential of the meal from M. oleifera pods with different soybean percentages was conducted through the in vitro gas production digestibility technique (Close and Menke, 1986; Blümmel, 2001). The laboratory analyses were made according to the rules of the AOAC (1995), at the Institute for Animal Production in the Tropics and Subtropics of the University of Hohenheim, Germany.

RESULTS AND DISCUSSION

A M. oleifera tree can produce more than 1 000 pods per year (Foidlet al., 2001; Fuglie, 2001), with a productivity higher than 7 kg of pods/plant, for which its industrial use when harvesting the seeds for oil extractioncan generate a contamination problem instead of being an environment-friendly technology, if it is not utilized to enhance animal production.

The chemical composition of the M. oleifera pod and of soybean is shown in table 2. The crude protein content of the former was 30,32 g/kg DM and coincides with the report by Mendieta-Araica (2011), which could have occurred due to the drying methods used, such as sunlight and shade (Murroet al., 2003; Kakengiet al., 2007; Olugbemiet al., 2010). The dry matter values coincide with the ones reported by Foidlet al. (2001).

In literature it is reported that with drying the crudest fraction is removed and a highly digestible product is obtained, with a high nutrient content (Nouala, 2004; Sarwattet al., 2004; Douala et al., 2006). In addition, the cell wall content is significantly increased (Ategaet al., 2003), which was observed in the values found in this study.

Figure 1 shows the gas production of the evaluated treatments; as the soybean inclusion percentage increased, the in vitro gas production also increased, which is in correspondence with the characteristics of the incubated feedstuffs. This is due to the fact that, when incubating a higher amount of dry matter, there is more raw material for the development of microbial activity, and this brings about an increase of feed degradation, which is perceived in an increase of gas production.

The inclusion of soybean, in spite of increasing the gas production, does not indicate that the evaluated feedstuff is utilized, because the degradation of the incubated diet has two outputs: 1) that which is utilized by microorganisms to be nourished and form cell structures, which are eventually used by the animal by increasing postruminal protein (Foidlet al., 2001), and 2) the nutrients which do not become biomolecule structures, are turned into gas, which is not really a utilization of the evaluated feed.

For such reason, it is necessary to calculate or estimate the true digestibility of the M. oleifera pods. Figure 2 shows an increase of the true digestibility, proportional to the inclusion of up to 100% soybean, which is digested in more than 98%. This is in correspondence with the statement by Blümmel (2000), who proved that digestibility increases due to the high protein content of the evaluated material.

However, this does not mean that those are the most adequate proportions for ruminants to make an optimum utilization of the nutrients contained in the diet; this is due to the imbalance between energy and the protein evaluated, because as there is not a balance between these indicators the rumen does not function well (Agabrielet al., 2007).

In order to have a more accurate evaluation regarding what animals utilize of the diet and the evaluated nutrients, the calculation of the microbial protein which can be obtained with each treatment under study was made. When analyzing the production of microbial protein (fig. 3), the values decreased as the soybean inclusion percentage increased.

McLoughlin (2010) stated that depending on the rumen pH, the dry matter intake level and the ration digestibility, for a correct balance of degradable protein in rumen (DPR/energy in rumen) between 70 and 130 g of DPR per kilogram of the total digestible nutrients (TDN) ingested are necessary.

The dry matter and protein percentages contributed by each feedstuff to the treatment were calculated.

Taking into consideration that the buffer used for setting the technique guarantees the maintenance of the rumen pH, that the incubated feed to be evaluated is equivalent to the dry matter intake and that 100% of M. oleifera pods and 100% of soybean have 46 and 99% digestibility, respectively, the calculated parameters were related; the only value found in the range of 70-130 g of DPR/kg of TDN (Mac Loughlin, 2010) was obtained with the proportion that included 10% soybean meal (approximately 124 g/kg of incubated DM), which coincided with the proportion with higher production of microbial protein (fig. 3). This corroborated that it is necessary to do an energy balance in diets, coinciding with the statement by Posada and Noguera (2005).

The results had direct repercussion on the nutritional utilization made by the ruminants when consuming this mixture, and on the utilization of the harvest residue of M. oleifera seeds.

CONCLUSIONS

The inclusion of 10% soybean was the most efficient from the nutritional point of view, because it improved the digestibility of the meal of M. oleifera pods and increased the microbial biomass.