Determination of water, blood and rumen fluid absorbencies of some fibrous feedstuffs

O A Makinde and E B Sonaiya

Department of Animal Science, Obafemi Awolowo University, Ile-Ife, Osun State, 220005, Nigeria
olukayodemakinde@oauife.edu.ng

Abstract

The objective of the study was to determine the water absorbency of some fibrous feedstuffs (vegetable carriers) such as wheat offal (WO), maize offal (MO), brewers’ dried grains (BDG), and dewatered rumen content (DRC) as an estimate for their fluid (blood, rumen fluid, and their mixture) absorbencies in the production of novel feeds from abattoir wastes. A simple filtration method involving the use of a burette, funnel, filter paper, and beaker estimated the water absorbencies (g water/g vegetable carrier) of vegetable carriers. Mixing graded levels of salt (0, 10, 15, 16, 17, 18, and 20 g) with 1 kg blood facilitated the determination of the minimum quantity of salt at which clotting will not occur for at least 2 h. Thereafter, blood, rumen fluid, and their mixture were hand-mixed with the vegetable carriers (based on the water absorbency ratios) to determine their fluid absorbencies. 

Wheat offal had the highest (P<0.05) water absorbency followed by MO and BDG (not significantly different from each other), and DRC with the least (P<0.05) absorbency. Eighteen and 20 grams of salt prevented blood from coagulating for at least 6 h. The fluid absorbencies for the vegetable carriers followed the same trend as their water absorbencies, which fairly estimated the fluid absorbencies.

When applicable, the water absorbency method developed provides a fast, simple, and inexpensive way to estimate fluid absorbencies of vegetable carriers, and is therefore well suited for use in the production of novel feed ingredients from abattoir wastes. 

Key words: abattoir waste conversion, blood coagulation test, vegetable carriers

Introduction

Water-holding capacity (WHC) of dietary fiber is usually considered as the amount of water held in association with fiber or non-starch polysaccharides (NSPs) either as trapped water or bound water, and is a function of the source of fiber and method of measurement (Robertson and Eastwood 1981a, b). It can be measured (as g water/g dry feed) by using suction pressure, water flow-rate, and centrifugation and filtration (the most common) techniques (Kyriazakis and Emmans 1995). Water-holding capacity, bulk density, and particle size greatly influence the nutritional value of poultry ingredients (Sundu et al 2005), control feed intake, and thus the productivity of birds (Nir et al 1994). Because WHC varies according to fiber source, the holding capacity of these sources for other liquids or fluids may also vary. Therefore, WHC could be an important indicator of optimum mixing ratios of such liquids to different sources of fiber in the preparation of novel feedstuffs, such as those derived from abattoir wastes. Some of these feedstuffs are vegetable-carried blood meal (Sonaiya 1988), blood and dried rumen content meal (Le Van Lien et al 1995), and blend of blood and maize cob (Donkoh et al 2003). These feedstuffs had been developed by absorbing blood (a high-moisture material) on low-moisture vegetable carriers such as wheat offal, rice bran, palm kernel cake (PKC), brewer’s dried grain (BDG), ground maize cobs, and dried rumen content (Cuperlovic et al 1978; Sonaiya 1988).

Development of feedstuffs from abattoir wastes, which are rich sources of protein, contributes to a reduction in pollution and increase in the potential for the supply of high quality protein ingredients locally and the conservation of foreign exchange used in the importation of expensive protein ingredients such as fishmeal.  However, the variability of processing methods and unclear basis for the use of mixing ratios, and lack of simple preservation methods for blood, limit the development of feedstuffs from abattoir wastes.

The study aimed at developing a simple and rapid filtration method for determining water absorbency of vegetable carriers as a basis in the determination of optimum mixing ratios of fluids such as blood, rumen fluid, and their mixture to vegetable carriers such as from brewery (brewers’ dried grains), milling (maize offal and wheat offal), and abattoir (dewatered rumen content) processes.     

Materials and methods

Water absorbency test

Photo 1 shows the set up for the water absorbency test.

A 220 cm³ (100 mm internal diameter) Pyrex glass funnel, in which Whatman #1 (12.5 mm) filter paper was folded to line the internal surface, was filled to the brim with vegetable carrier, and after leveling with a ruler without compaction, emptied and weighed on an electronic scale to determine bulk density (g/cm³). The vegetable carrier was returned into the glass funnel and a smaller filter paper (Whatman #1, 9 mm) was placed on top of the vegetable carrier in such a way that it  did not touch the edges of the funnel. The funnel set up was held over a beaker by a retort stand. A water-filled burette, held by another retort stand, pointed at the center of the filter paper on top of the vegetable carrier. The room and water temperature (^oC), and moisture content (%) of the vegetable carriers were measured at the start of experiment. Water from the burette was released drop-wise (about 70 drops per minute) until after the first drop of water fell into the beaker from the funnel spout, and the total volume of water absorbed by the vegetable carrier read off the burette as the change in volume. Weight of water to the weight of the vegetable carrier gave the water absorbency (g water/g vegetable carrier). This test was replicated thrice per vegetable carrier and the mean value used as a basis for the starting quantity of blood, rumen fluid or blood and rumen fluid mixture hand-mixed with vegetable carriers in the estimation of the optimum mixing ratios. 

Blood coagulation test

The blood hand-mixed with the vegetable carriers was obtained from cattle as they were slaughtered at a commercial slaughter slab. To prevent blood from clotting, a simple preservation method was established using common salt. Graded levels of salt (0, 10, 15, 16, 17, 18, and 20 g) were mixed with 1 kg blood in order to determine the minimum quantity of salt at which clotting will not occur for 2 h.  There were two replicates for each quantity of salt used. The mixture was kept for 6 h while watching for signs of clotting at 15-minute intervals, and the time interval before the onset of clotting recorded. The minimum concentration of salt (g salt/kg blood) at which clotting did not occur for at least 2 h was adjudged desirable. Rumen content (collected from slaughter slab) processed by dewatering (to obtain rumen fluid and dewatered rumen content) for 30 minutes with an experimentally fabricated 10-ton hydraulic press, and the resulting cake pulverized by rubbing through a

2 mm sand sieve.

Estimation of optimum mixing ratios of fluids to vegetable carriers

In order to evaluate the suitability of the water absorbency method in estimating fluid absorbency, the vegetable carriers and each of blood, rumen fluid or blood and rumen fluid were mixed thoroughly with hand (until fluid was not superfluous) using the predetermined mixing ratios from water absorbency as starting ratios. Only blood was mixed twice to obtain two types of vegetable-carried blood meals, vegetable-carried blood meal 1 and 2, respectively. Rumen fluid or blood and rumen fluid mixture were not mixed with dewatered rumen content.

Statistical analysis

The differences between vegetable carriers for water absorbency, bulk density, moisture content, and weight of water absorbed were analyzed statistically using the General Linear Models (GLM) procedure of SAS^® (SAS institute, 2000) for analysis of variance for a completely randomized block design. The three replicates per vegetable carrier were analyzed as blocks. Significant differences between the treatment means were separated by Duncan’s multiple range test (Steel and Torrie, 1980).
 

Results and discussion

Table 1 shows some physical characteristics of vegetable carriers and differences in their water absorbance capacities.

The vegetable carrier with the highest (P<0.05) bulk density was maize offal (MO) followed by brewers’ dried grains (BDG), wheat offal (WO), and dewatered rumen content (DRC).  Similarly, Longe and Fagbenro-Byron (1990) reported that MO had a higher bulk density than either palm kernel meal (PKM) or BDG. The weight of water absorbed by the carriers was highest for MO (P<0.05), followed by BDG, WO, and DRC. However, water absorbency for WO was more (P<0.05) than MO or BDG, which were not were not statistically different from each other. Dewatered rumen content had the lowest water absorbency (P<0.05). The differences in water absorbency between the vegetable carriers conforms with the general observation that low bulk density feedstuffs have high water holding capacity (Sundu et al, 2005). However, water absorbency for DRC did not follow this trend. DRC had the highest (P<0.05) moisture content before the water absorbency test, because it was just partially dry after pressing, and as expected it had the least water absorbency. Moreover, DRC is partially digested vegetation mainly made up of cellulose, reported to contain insoluble NSP with low water-holding capacity (Hetland et al, 2004), therefore, the water absorbency was not expected to be significant.

The differences in water absorbency between WO, MO, and BDG may be due to differences in the soluble non-starch polysaccharide (NSP) contents. Cereal grains are broadly categorized into viscous and non-viscous cereals depending on their content of soluble NSP (Choct, 2006), and this affects water-holding capacity. Generally, water-holding capacity and viscosity increases with increasing content of soluble NSP (Choct, 2006); and viscosity varies among cereals in the following increasing order: sorghum, maize, wheat, triticale, barley and rye (Carre, 2004). Since WO, MO, and BDG are by-products of wheat, maize, and maize and sorghum processing respectively, it may be deduced that they will possess similar water-holding characteristics as their corresponding substrates. The results of this study conform to the trend described by Carre (2004) because WO (obtained from wheat) had significantly higher water absorbency than MO or BDG (obtained from maize or maize and sorghum respectively).

Figure 1 shows the effect of increasing concentration of salt on time taken for blood to coagulate.

Increasing salt concentrations caused a gradual increase in the time it took blood to clot from 20 seconds (0.3 min) to 30 min for 0-17 g of salt, and rose very steeply thereafter between 18-20g of salt. Eighteen and 20 grams of salt prevented blood from coagulating for at least 360 min. It appears that, under the conditions of this study, the critical point for the significant effect of salt concentration on preventing blood coagulation was between 17 g and 18 g. Gentry and Downie (1992) affirmed that one of the ways that blood anti-coagulants work is by chelating calcium ions that are obligatory cofactors in the conversion of prothrombin to thrombin. Thrombin in the presence of calcium ions effects conversion of fibrinogen insoluble fibrin, an irreversible reaction that eventually causes blood coagulation (Guyton and Hall, 2004); thus if calcium ions could be removed from plasma, coagulation will be prevented.  Sonaiya (1995) suggested a concentration of 1 g of salt (sodium chloride) per kg of blood as effective for preventing coagulation. However, this concentration was only effective in preventing coagulation for 10 minutes. It would appear that chloride ions from salt (at 18 g/kg of blood) reached the critical concentration to form complexes with calcium ions in the blood thereby preventing coagulation.

Table 2 shows the optimum mixing ratios of vegetable carriers with bovine blood, rumen fluid, and their mixture.

The optimum mixing ratios obtained for the vegetable carriers with bovine blood, rumen fluid, and their mixture followed the same trend as the water absorbency for the vegetable carriers. Wheat offal absorbed the highest quantity of blood (1 WO: 1.5 blood) than either BDG (1 BDG: 1.25 blood) or MO (1 MO: 1 blood) or DRC (1 DRC: 0.75 blood). However, the amount of blood absorbed by WO, BDG, and DRC increased by 26, 29, and 120%, respectively, more than the amount of water absorbed by each vegetable carrier. Nevertheless, the amount of blood absorbed by MO decreased by about 6% than the amount of water absorbed. The greater quantities of fluid absorbed was probably as a result of the more active mixing of fluid to vegetable carrier due to hand mixing compared with the passive drain of water through the carriers in the water absorbency test. The decrease in fluid absorbed by MO is unclear. Nevertheless, the similarity between the water absorbency and optimum mixing ratios for fluids by the vegetable carriers indicate that the simple water absorbency test developed in this study may be suitable in approximating the quantities of fluids required in the determination of optimum mixing ratios.

Conclusion

• The simple and rapid filtration method developed in this study for determining the water absorbency of vegetable carriers provides an approximate way of estimating the optimum mixing ratios of fluids such as blood and rumen fluid to vegetable carriers such as wheat offal (WO), maize offal (MO), brewers’ dried grains (BDG), and rumen content (RC). This will minimize inefficient usage of materials (blood, rumen fluid, and vegetable carriers) due to uneconomical combinations. However, development of a more efficient mixing method other than hand mixing may improve mixing ratios and increase efficiency of materials usage.

  
  

• The method also provided new information on optimum mixing ratios for blood and rumen fluid to various vegetable carriers in the processing of abattoir wastes into useful products as livestock feed.

Acknowledgement

Sincere appreciation goes to Raw Materials Research and Development Council (RMRDC), Abuja, Nigeria for the financial support for the research reported in this article

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Received 19 June 2007; Accepted 14 August 2007; Published 5 October 2007

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