Chemical composition of solar-dried blood meal and
its effect on performance of broiler chickens
A. Donkoh
*, C.C. Atuahene, D.M. Anang, S.K. Ofori
Department of Animal Science, University of Science and Technology, Kumasi, Ghana
Received 20 October 1998; received in revised form 8 February 1999; accepted 28 May 1999
Abstract
The crude protein, fat, fibre, ash and nitrogen-corrected true metabolisable energy contents of solar-dried blood meal (SDBM) were 852.3 g kgÿ1 DM, 14.9 g kgÿ1 DM, 35.1 g kgÿ1 DM,
20.6 g kgÿ1
DM, and 13.08 MJ kgÿ1
DM, respectively. It contained 73.7 g available lysine kgÿ1
DM. In a feeding trial, 480 commercial broiler chicks were randomly allocated to one of four dietary treatments in a completely randomised design. The dietary treatments consisted of the control diet, which contained fishmeal and groundnut cake as the main protein sources, and three other diets which contained varying levels of SDBM (25, 50 and 75 g kgÿ1). The experimental diets
were formulated to be both isoproteic and isoenergetic. Feed and water were provided ad libitum for a period of 5 weeks. Data for the entire 35 days growth assay, indicate the concentration of SDBM in the diet had no impact on feed intake. However, birds fed SDBM at 50 or 75 g kgÿ1
had better weight gains and feed efficiency (p< 0.05) than birds fed 25 g kgÿ1
SDBM and the SDBM-free diet. Carcass yields were similar. Mortality was also unaffected by dietary treatments. In addition, blood parameters (red cell count, haemoglobin, haematocrit and total protein) were unchanged by dietary treatment (p> 0.05). Analysis of productive parameters indicated that dietary SDBM up to 75 g kgÿ1
had a positive effect on growth performance and that partial replacement of other protein sources (fishmeal and groundnut cake) with SDBM was possible.#1999 Elsevier Science B.V. All rights reserved.
Keywords: Solar-dried blood meal; Chemical analysis; Growth performance; Broilers
1. Introduction
Blood meal, an important animal protein by-product, contains over 800 g protein kgÿ1 DM, 90 g total lysine kgÿ1DM and small amounts of ash and lipids. However, a notable
81 (1999) 299±307
*Corresponding author. Tel: +233-5160325.
feature of raw blood is its high moisture content. This makes it particularly sensitive to deterioration by endogenous enzymes and to microbial putrefaction. It must necessarily be processed before incorporation into animal diets.
In some areas, where the adoption of blood meal is almost certain because conventional protein feedingstuffs such as fishmeal are either scarce or expensive, blood from slaughterhouses is discharged into drains, streams and rivers, thus polluting the environment because facilities for drying may not be available. This points to the need for identifying simple procedures for preparing blood meal to be used in poultry feeds. In the tropics, where there is abundance of sunlight, solar drying has been advocated as a simpler and cheaper method of drying than other industrial methods.
Furthermore, the level at which blood meal may be included in broiler diets is not clear. Historically, blood meal was limited to a maximum inclusion level of 30±60 g kgÿ1
diet, because higher levels were considered to be unpalatable or give rise to depressed performance (Kratzer and Green, 1957). More recent research has led to a re-appraisal of optimum inclusion rate, and a recognition that amino acid imbalance may have been the cause of reduced performance in those early studies (King and Campbell, 1978; Ilori et al., 1984; Crawshaw, 1994). Thus, a combination of high quality protein sources might appear to be a sound policy, since one protein source can compensate for the inadequacies or the excesses of another. It is envisaged that the inclusion of blood meal in poultry diets even at relatively low concentrations would help reduce costs and problems associated with the disposal of raw blood from abattoirs, thus reducing the possible pollution of the environment.
This study was therefore undertaken to determine the chemical composition of solar-dried blood meal (SDBM) available in Ghana and further ascertain the concentration at which SDBM could be included in broiler diets, in combination with other protein sources such as fishmeal and groundnut cake, without deleterious effects.
2. Materials and methods
2.1. Source of blood and processing method
The blood used in this study was obtained from the Meat Science Unit of the Department of Animal Science, University of Science and Technology, Kumasi, Ghana. The blood was immediately heated in an open pan for 30 min at a temperature of 60oC to facilitate evaporation of water and coagulation. The coagulated blood, together with the small amount of the liquid fraction which remained, was transferred to a solar dryer for drying at 35±50oC to a moisture content of ca. 100 g kgÿ1 DM, finally ground in a hammer mill to produce the meal and stored in sacks until used in formulations.
2.2. Dietary treatments
Four experimental diets (Table 1) were formulated: a control diet containing no SDBM and others in which SDBM was incorporated at 25, 50 and 75 g kgÿ1
. The experimental diets were formulated to be isoproteic and isoenergetic.
2.3. Chemical analysis
Proximate analyses of SDBM and diets (dry matter, crude protein, ether extract, ash and crude fibre) were carried out using the standard procedures of the Association of Official Analytical Chemists (1990). Amino acids were determined following acid hydrolysis using a Beckman 119 BL-amino acid analyser. Duplicate samples (5±7 mg) were hydrolysed in 500ml of 6 M HCl with 10 g lÿ1added phenol for 24 h at 11018C
in glass tubes sealed under vacuum. Methionine and cystine were determined using the performic acid oxidation method (Moore, 1963). Tryptophan, being destroyed during acid hydrolysis, was determined chemically by the procedure described by Miller (1967). Available lysine content of SDBM was determined by the Ousterhout and Wood (1970) modification of the method of Kakade and Liener (1969).
Eight 6-week-old broiler chicks were used to determine the nitrogen-corrected true metabolisable energy (TMEn) content of SDBM. Birds were fed ad libitum on a broiler finisher diet for 1 week prior to force-feeding (Sibbald, 1986). The birds were housed in individual cages with collection trays, fasted for 24 h and fed 30 g of the test ingredient through crop intubation. Four broilers were kept fasted during the assay to measure endogenous losses. Excreta were collected daily for 48 h after crop
Table 1
Composition of experimental growth dietsa
Level of solar-dried blood meal (g kg-1diet)
Controll
0 25 50 75
Ingredients (g kg-1)
Maize 580 580 580 580
Solar-dried blood meal 0 25 50 75
Fishmeal (630 g CP kg-1DM) 190 165 135 100
Groundnut cake 60 50 35 32
Wheat bran 140 150 170 183
Oyster shell (ground) 20 20 20 20
Vitamin and mineral premix1 5 5 5 5
Salt (NaCl) 5 5 5 5
Chemical analysis (g kgÿ1DM)
Crude protein 217.54 219.80 219.30 219.30
Crude fibre 37.90 38.40 39.30 40.70
Ether extract 40.10 38.90 37.30 35.90
Lysine 12.50 13.40 14.20 15.00
Methionine 5.37 5.24 5.16 5.02
Isoleucine 9.83 9.21 8.98 8.13
Calcium 15.10 14.20 13.30 12.40
Phosphorus 8.20 7.70 7.20 6.70
MEn(MJ kgÿ1) 11.57 11.56 11.53 11.52
aPremix supplied (kg-1diet): vitamin A, 10 000 IU; vitamin D
3, 2000 IU; vitamin E, 10 IU; vitamin K, 3 mg;
riboflavin, 2.5 g; cobalamin, 0.05 mg; pantothenic acid, 5 mg; niacin, 12.5 mg; choline, 175 mg; folic acid, 0.5 mg; Mg, 2.8 mg; Fe, 0.5 mg; Cu, 50 mg; Zn, 25 mg; Co, 62.5 mg.
intubation, oven-dried at 60oC for 48 h, equilibrated to ambient conditions, weighed and ground (Dale and Fuller, 1983). Both SDBM and fecal samples were analysed for gross energy. MEn values for the experimental diets were, however, calculated from values given by the National Research Council (NRC, 1994) and the determined TMEncontent of SDBM.
2.4. Experimental animals and management
Four hundred and eighty unsexed 14-day-old commercial broiler chickens (AF Bosbek strain) were individually weighed and allotted randomly to the four dietary treatments. Each treatment was replicated three times. The birds were placed and reared in deep litter pens each measuring3.2 m3.0 m, a floor space of 0.24 m2per bird. The study was conducted for 35 days (2±7 weeks of age). Birds had free access to feed and water throughout the experimental period. Chickens were vaccinated against Gumboro and Newcastle diseases. They were protectively medicated for Coccidiosis at 3 days of age and again during the third week using Sulfadimidine Sodium 33% (Bremer Pharma GMBH, Germany) via the drinking water.
2.5. Parameters measured
Birds were individually weighed and feed consumption per pen were recorded weekly. Feed : gain ratio was determined weekly for individual replicates of each dietary treatment. Records of mortality were also kept. All sick and dead chickens were sent to the Veterinary Laboratory for post-mortem examination. At 49 days of age, four broilers from each of the 12 replicates were selected at random, starved of feed for ca. 18 h to empty their crops, killed by cutting the jugular vein, exsanguinated, defeathered and eviscerated. Carcass yield was calculated from eviscerated weight and liveweight.
2.6. Blood collection and assays
To avoid a macrocytic hypochromic anaemia (Christie, 1978) caused by repeated bleeding, the birds were bled only at 4 and 6 weeks of age between 09.00 and 11.00 h. The birds were fasted for 12 h prior to the collection of blood specimens to avoid post-prandial lipemia (Kirk et al., 1990). Various blood parameters studied included: red blood cell count (RBC), haemoglobin, haematocrit (packed cell volume, PCV) and blood protein. The series of blood tests were performed on blood drawn from the brachial vein. Blood samples for the haematological tests were mixed with the dipotassium salt of EDTA (1.5 mg mlÿ1
blood) as anticoagulant. Erythrocyte (RBC) counting method was similar to that described by Maxwell (1981). Two separate counts were made for each blood sample and the mean of the two counts calculated. The quantity of haemoglobin and the haematocrit (PCV) values were respectively determined by the cyanmet± haemoglobin and microhematocrit methods (Dacie and Lewis, 1975) using the average of duplicate samples. Total plasma protein was determined in duplicate by the Biuret method outlined by Oser (1965).
2.7. Histological studies
At 49 days of age, the possible deleterious effects of SDBM on liver were also assessed. Four chickens from each treatment were randomly selected, killed by cervical dislocation, the liver excised and examined to determine whether the diets had resulted in any gross pathological changes. Liver sections were cut before staining with haematoxylin and eosin (Humason, 1979) and examined microscopically for any abnormalities in the cells.
2.8. Statistical analysis
The dietary treatment effects for all the variables measured were analysed using the general linear models procedure of SAS (1987). The data were subjected to regression analysis to show the effect of including SDBM on performance.
3. Results and discussion
The chemical composition of SDBM (Table 2) showed that it contained, on g kgÿ1DM basis, 852.3 crude protein, 14.9 fat, 35.1 crude fibre and 20.6 ash. The values presented here for the proximate composition are close to the values reported by NRC (1994). The results indicate a very high concentration of protein in SDBM. NRC (1994) reported high protein contents of 881 g kgÿ1
DM for vat-dried blood meal and 889 g kgÿ1
DM for spray- or ring-dried blood meal. Comparison of the amino acid composition of SDBM with the amino acid requirements of chicks as given by NRC (1994) are also shown in Table 2. SDBM had a good essential amino acid profile relative to non-ruminant (chick) requirements. It contained substantial amounts of essential (indispensable) amino acids, including lysine, methionine, arginine, cystine, leucine and threonine but was very poor in isoleucine. Amino acid digestibility and availability are complex phenomena affected by many interacting factors (Moughan, 1991). Processing may, if not carried out with careful control, reduce digestibility and availability of the product. Overheating during drying of blood meal can seriously lower digestibility and the availability of specific amino acids, particularly lysine (Hamm and Searcy, 1976; Moughan and Donkoh, 1991; Crawshaw, 1994; NRC, 1994). The fact that SDBM used in the present study contained high amounts of total (81.4 g kgÿ1) and available lysine (73.7 g kgÿ1) indicates that the processing conditions used in the present study were not severe enough to adversely affect the nutritional quality of SDBM.
The general performance of the experimental population is shown in Table 3. Feed intake by birds was not significantly (p> 0.05) influenced by the level of SDBM in the diets suggesting that broilers will consume diets up to 75 g SDBM kgÿ1
.
There was little difference in average chick weight, after selection at 2 weeks of age, for birds fed diets containing 0, 25, 50 and 75 g SDBM kgÿ1
diet. In general, inclusion of graded levels of SDBM in broiler diets had significant (p< 0.05) impact on mean body weight gain during the period of 2±7 weeks of age. Birds fed SDBM at 50 or 75 g kgÿ1 had better weight gains than those fed 25 g kgÿ1SDBM and the SDBM-free diet. The
following correlation between the level of SDBM in the diet and weight gain of broiler chickens was found: Y (weight gain) = 1.79 (0.087) + 0.001(0.0003)x (r= 0.70;
p: < 0.05), wherexis the level of SDBM in the diet.
Efficiency of feed utilisation progressively improved (p< 0.05) when the levels of dietary SDBM were progressively elevated. Birds receiving SDBM had a better feed : gain ratio than those receiving no SDBM. Regression of feed conversion ratio against level of SDBM yielded the linear equation: Y (feed : gain) = 2.10 (0.15)ÿ0.009(0.0004)x(r=ÿ0.88;p< 0.05).
The increase in weight gain and the improved ability to utilise the SDBM-based diets efficiently particularly, for birds fed on diets which contained 50 and 75 g SDBM kgÿ1 might have been caused by the positive effect of SDBM as indicated by the high indices of correlation for weight gain and feed conversion (r= 0.70 and ÿ0.88, respectively). This could further be explained on the basis of a greater efficiency in the conversion of feed into tissue which in turn was the result of adequate amounts of the various nutrients required for proper growth, particularly amino acids, such as lysine, which is the
first-Table 2
Chemical composition of solar-dried blood meala
Component NRC requirement (g kg-1) Dry matter (g kg-1)
Proximate analysis
Dry matter 903.5
Crude protein 852.3
Ether extract 14.9
Crude fibre 35.1
Ash 20.6
Amino acid
Arginine 14.4 39.1
Lysine 12.0 81.4
Histidine 3.5 53.3
Phenylalanine 7.2 61.3
Tyrosine 6.2 28.8
Methionine 5.0 12.8
Leucine 13.5 116.0
Isoleucine 8.0 8.50
Valine 8.2 79.0
Threonine 8.0 45.9
Cystine 4.3 11.7
Tryptophan 2.3 14.6
Alanine ± 68.5
Aspartic acid ± 88.0
Glutamic acid ± 82.8
Proline ± 63.3
Serine ± 45.6
Glycine ± 37.1
Other chemical parameters
Available lysine 73.7
TME (SE) (MJ kg-1) 3.08 (0.45)
aThe values are the means of three samples.
most limiting amino acid. The data in Table 1 indicated that as the concentration of SDBM in the diets increased, the lysine contents of the diets increased. The broiler diets containing the highest levels of SDBM (50 and 75 g kgÿ1) for example, were calculated to contain 14.2 and 15 g lysine kgÿ1, respectively, which were above the value of 12 g kgÿ1 reported to be adequate for broiler chickens by NRC (1994). The dietary requirement for protein is actually a requirement for amino acids. Thus, the higher growth rates observed for birds fed on diets containing higher concentrations of SDBM might be caused by the increased amount of lysine available for growth when true growth is considered as deposition of amino acids (of which lysine is the most critical under practical conditions of feed formulation). This ultimately affected the efficiency of feed conversion into tissue.
Furthermore, blood meal contains a very high level of leucine but both its isoleucine content and digestibility are relatively low and there is evidence that a high level of leucine may elevate the isoleucine requirement of animals such as the rat (Harper et al., 1955; Spolter and Harper, 1961; Rook, 1983; McDonald et al., 1996), the chick (D'Mello and Lewis, 1970; NRC, 1994), turkey poult (D'Mello, 1975) and the pig (Oestemer et al., 1973; Taylor et al., 1984; NRC, 1988). Fisher (1968), working with chickens, and diets containing 110±130 g blood meal kgÿ1, concluded that not only was isoleucine limiting, but also methionine and arginine. These results suggest that careful attention to a complex web of interacting amino acids is necessary (Crawshaw, 1994). The benefit of such a measure, as evidenced by the results of the present study, suggest isoleucine or any other essential amino acid deficiency should not have existed in the SDBM-based diets. This is also corroborated by the studies of Dafwang et al. (1986) who noted the complementary effects for laying hens of using both fish and blood meals. Ranjhan (1993) also reported on a feeding trial in which supplementation of a poultry diet with 30, 60 and 90 g of
Table 3
Effect of solar-dried blood meal on performance and blood componentsaof broiler chickens over the period from
14 to 49 days of age
Response criteria Level of solar-dried blood meal (g kgÿ1) SEMb rc
0 25 50 75
Feed intake (kg) 3.76 3.72 3.76 3.74 0.02 ÿ0.14
Protein intake (kg) 0.81 0.82 0.83 0.82 0.004 0.63
ME intake (MJ) 43.50 43.08 43.35 43.09 0.10 ÿ0.60
Weight gain (kg) 1.79 1.78 1.84 1.82 0.01 0.70d
Feed conversion ratio 2.10 2.09 2.04 2.05 0.02 ÿ0.88d
Mortality (%) 0.83 0.83 1.67 0.83 0.42 0.26
Carcass yield 0.797 0.807 0.790 0.795 0.0035 ÿ0.44
Red blood cell count (millions mÿ3) 2.47 2.40 2.44 2.46 0.02 0.04
Haemoglobin (g 100 mlÿ1) 13.80 13.40 13.70 13.80 0.10 0.20
Haematocrit (%) 33.90 33.80 33.90 33.90 0.03 0.26
Total plasma protein (g 100 mlÿ1) 4.62 4.68 4.60 4.64 0.02
ÿ0.08
aEstimated at 4 and 6 weeks of age and the mean calculated. bStandard error of means.
cCorrelation coefficient. dp< 0.05.
blood meal kgÿ1
gave the same performance as the control diet which contained maize, groundnut cake and fishmeal. Wahlstrom and Libal (1977), working with pigs, concluded that blood meal could constitute 600 g of the supplemental protein kgÿ1
diet, in combination with either soybean meal or meat meal to support similar feed intake and pig performance.
The level of SDBM in the diet gave a correlation coefficient ofÿ0.44 when linearly regressed against carcass yield indicating SDBM exerted no influence on this parameter. A total of five mortality cases were recorded during the experimental period (Table 3). Of this number, two (1.67%) occurred among birds fed on the 50 g SDBM kgÿ1and one (0.83%) each from the other remaining treatments. The mortality values were rather variable and show no trends that can be attributed to SDBM. Post-mortem autopsies indicated no specific causes for deaths.
The levels of SDBM in the diet did not affect red blood cell count, haemoglobin, haematocrit and total plasma protein values.
The findings, under the conditions of this study, showed no toxic effects in terms of gross tissue changes in the liver. The histological characteristics of the liver from birds on the control diet were similar to those from birds on SDBM-based diets.
It is concluded that SDBM is a suitable alternative protein source to be investigated in greater detail.
Acknowledgements
The authors thank Gyedu±Baah Apanin and F.A. Kwarteng for technical assistance, T. Edusei and P. Wallace of Animal Research Institute of Ghana for chemical analysis and Ms. Gladys Ndziba for her secretarial assistance.
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