J. Anim. Sci. 2003. 81:1013-1022
© 2003 American Society of Animal Science
Effects of blood meal pH and irradiation on nursery pig performance1,2
J. M. DeRouchey1,
M. D. Tokach,
J. L. Nelssen,
R. D. Goodband,
S. S. Dritz,
J. C. Woodworth,
M. J. Webster and
B. W. James
Department of Animal Sciences and Industry, Kansas State University, Manhattan, 66506-0201
3 Correspondence:
phone 785-532-5833; fax 785-532-5887; E-mail:
jderouch{at}oznet.ksu.edu.
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Abstract
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A total of 720 nursery pigs in three experiments were used to evaluate the effects of blood meal with different pH (a result of predrying storage time) and irradiation of spray-dried blood meal in nursery pig diets. In Exp. 1, 240 barrows and gilts (17 ± 2 d of age at weaning) were used to determine the effects of blood meal pH (7.4 to 5.9) in diets fed from d 10 to 31 postweaning (7.0 to 16.3 kg of BW). Different lots of dried blood meal were sampled to provide a range in pH. Overall (d 0 to 21), pigs fed diets containing blood meal had greater ADG (P < 0.05) and ADFI (P < 0.05) than pigs fed diets without blood meal. Ammonia concentrations in blood meal rose as pH decreased. However, blood meal pH did not influence (P > 0.16) ADG, ADFI, or gain:feed (G:F). In Exp. 2, 180 barrows (17 ± 2 d of age at weaning) were used to determine the effects of post drying pH (7.6 to 5.9) and irradiation (gamma ray, 9.5 kGy) of blood meal on growth performance of nursery pigs from d 5 to 19 postweaning (6.8 to 10.1 kg of BW). One lot of whole blood was isolated with 25% of the total lot dried on d 0, 3, 8, and 12 after collection to create a range in pH. Overall, pigs fed blood meal had improved G:F (P < 0.01) compared to pigs fed the control diet. Similar to Exp. 1, the ammonia concentration of blood meal increased with decreasing pH. Blood meal pH did not influence ADG, ADFI, or G:F (P > 0.21), but pigs fed irradiated blood meal (pH 5.9) had greater ADG and G:F (P < 0.05) than pigs fed nonirradiated blood meal (pH 5.9). In Exp. 3, 300 barrows (17 ± 6 d of age at weaning) were used to determine the effects of blood meal irradiation source (gamma ray vs. electron beam) and dosage (2.5 to 20.0 kGy) on growth performance of nursery pigs from d 4 to 18 postweaning (8.7 to 13.2 kg of BW). Overall, the mean of all pigs fed blood meal did not differ in ADG, ADFI, or G:F (P > 0.26) compared to pigs fed the control diet without blood meal. Pigs fed irradiated blood meal had a tendency (P < 0.10) for increased G:F compared with pigs fed nonirradiated blood meal. No differences in growth performance were detected between pigs fed blood meal irradiated by either gamma ray or electron beam sources (P > 0.26) or dosage levels (P > 0.11). These studies suggest that pH alone as an indicator of blood meal quality is not effective and irradiation of blood meal improved growth performance in nursery pigs.
Key Words: Blood meal • Irradiation • Nurseries • pH • Pig • Quality Controls
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Introduction
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The use of specialty protein products in nursery diets has become a standard practice to provide the weanling pig with a highly digestible amino acid source immediately after weaning. This practice is based on extensive research that has demonstrated the benefits that specialty protein sources provide to nursery pigs (Hansen et al., 1993; and Kats et al., 1994). However, variation in these ingredients exists; as Steidinger et al. (2000) reported, there were differences in growth performance of pigs fed animal plasma from different sources, and also differences in performance within the same source. Furthermore, the microbial content, specifically of Salmonella, in animal protein products is often higher then plant protein products (McChesney et al., 1995a, b), which may potentially contribute to the variation in growth response seen when feeding these products to nursery pigs.
In blood meal manufacturing, liquid blood can be stored for several days post collection before it is dried. During this storage time, microbial populations in the liquid blood may increase and pH decrease. Anecdotal evidence suggests that blood meal with a low pH has an offensive odor, which may result in decreased nutritional value or a negative effect on palatability. Past research, either by chemical laboratory analysis (Dimitrova and Brankova, 1975) or rat growth assays (Downes et al., 1987), has indicated that blood meal can be irradiated to decrease bacteria without jeopardizing protein quality. However, the effects of irradiated blood meal in diets for nursery pigs have not been examined.
Therefore, the objectives of our experiments were to determine if weanling pig performance was affected by pH or irradiation of blood meal. Specifically, we compared the effects of varying pH in two experiments and compared different irradiation sources and dosages in a third experiment to assess the effects of spray-dried blood meal in diets for nursery pigs.
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Materials and Methods
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General
The Kansas State University Institutional Animal Care and Use Committee approved all experimental protocols used in this study.
Pigs (Line 327 sire x C22 dams; PIC, Franklin, KY) were housed in environmentally controlled nurseries. Each pen (Exp. 1, 1.5 m2; Exp. 2 and 3, 1.2 m2) had slatted metal flooring and contained a stainless steel self-feeder and one nipple waterer to allow ad libitum consumption of feed and water.
Each pig in Exp. 1 was provided 0.45 kg of phase I diet (Table 1
) and then a phase II diet until 10 d after weaning. In Exp. 2 and 3, pigs were all fed the phase I diet until 5 and 4 d after weaning, respectively. In all experiments, pigs were weighed and allotted to their respective pens at weaning, then weighed again at the start of the experiment, but were not resorted to different pens. Initial pen weight at the start of the experimental period was used as a covariate for the statistical analysis.
Experimental diets were fed for 21 d in Exp. 1 and 14 d in Exp. 2 and 3. Diets were fed in meal form in all experiments (Table 2) and were formulated to meet or exceed the nutrient requirements of pigs as suggested by the NRC (1998). Ingredient nutrient compositions provided by the NRC (1998) were used in diet formulation. In addition, all diets were formulated to meet or exceed the nutrient requirements set forth by the NRC (1998). Diets in Exp. 2 and 3 were balanced to provide equal Na and Cl concentrations.
Pigs were weighed and feed disappearance measured every 7 d during all three experiments to determine ADG, ADFI, and feed efficiency (G:F). In Exp.1, samples of the blood meal (California Spray-Dry, Stockton, CA) were collected and analyzed (AOAC, 1995) for CP, DM, ash, crude fat, thiobarbituric acid (TBA), and ammonia (NH4). In Exp. 2, blood meal samples were collected and analyzed for individual amino acids, CP, NH4, and bacteria and coliform concentrations (Carter and Cole, 1990). In Exp. 3, blood meal samples were analyzed for individual amino acids, CP, bacteria, coliforms, E. coli, and mold and yeast concentrations (FDA, 1995). All blood meal samples were collected at the time of feed manufacturing.
Experiment 1
Two hundred forty barrows and gilts (17 ± 2 d of age at weaning) were blocked by initial weight and gender and randomly allotted to one of five dietary treatments. Each treatment had six replications (pens) and eight pigs per pen.
Pigs were fed experimental diets from d 10 to 31 postweaning (7.0 to 16.3 kg of BW). Experimental diets included a control diet with no added blood meal and four diets containing 2.5% blood meal. The four blood meals were from the same spray-drying processing facility, but had pH of 7.4, 6.7, 6.4, and 5.9, respectively, after spray drying. The 7.4-, 6.7-, and 6.4-pH blood meals originated from different lots of bovine blood, whereas the blood meal of pH 5.9 was of avian origin.
Experiment 2
One hundred eighty barrows (17 ± 2 d of age at weaning) were blocked by initial weight and randomly allotted to one of five dietary treatments. Each treatment had six replications (pens) and five pigs per pen.
Pigs were fed experimental diets from d 5 to 19 postweaning (6.8 to 10.1 kg of BW). These included a control diet with no added blood meal and four diets containing 5.0% blood meal. A single lot of whole blood from a beef harvesting facility was collected and transported to a spray-drying facility. The whole blood was allowed to clot, and then was sent through a disintegrator and screen before storage (5°C). One fourth of the total lot was dried on d 0, 3, 8, and 12 after collection. This drying schedule resulted in blood meal with pH values of 7.6, 6.4, 6.0, and 5.9, respectively. The blood meal with pH 5.9 was separated into two equal portions, with one of the portions treated with gamma ray irradiation (SteriGenics, Tustin, CA) at an average dosage of 9.5 kGy.
Experiment 3
Three hundred barrows (17 ± 6 d of age at weaning) were blocked by weight and allotted to one of 10 dietary treatments. Each treatment had six replications (pens) per treatment with five pigs per pen.
Pigs were fed experimental diets from d 4 to 18 postweaning (8.7 to 13.2 kg of BW), which included a control diet with no added spray-dried blood meal, a diet with 5% regular spray-dried blood meal, or 5% spray-dried blood meal with irradiation treatment. Irradiated treatments included blood meal treated with either gamma ray (cobalt-60 source; SteriGenics) or electron beam (Steris-Isomedix Services, Libertyville, IL) irradiation at increasing dosage (2.5, 5.0 10.0, and 20.0 kGy). All blood meal used in this experiment was from the same original lot, was of bovine origin, and had an initial pH of 7.4.
Statistical Analyses
Data from all experiments were analyzed as a randomized complete block design with pen as the experimental unit. Pigs were blocked based on weaning weight, and analysis of variance was performed using the GLM procedure of SAS (SAS Inst., Inc., Cary, NC). Contrasts were used to determine the effect of blood meal in diets compared to the control (no blood meal). Linear and quadratic polynomial contrasts for unequally spaced treatments were used to determine the effects of blood meal pH (Exp. 1 and 2) and irradiation dosage (Exp. 3). In addition, contrasts were used to determine the effect of blood meal irradiation (Exp. 2 and 3) and irradiation source (Exp. 3). Initial pen weight at the start of the experimental period (Exp. 1, d 10; Exp. 2, d 5; and Exp. 3, d 4) was used as a covariate for statistical analyses. Statistically significant differences are reported as P < 0.05, whereas statistical tendencies are reported as P < 0.10.
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Results
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Experiment 1
Blood meal pH did not change the CP, DM, ash, or crude fat content of blood meal (Table 3). In addition, TBA increased with decreasing pH to 6.7, but no further increases in rancidity were seen thereafter. The concentration of ammonia increased with decreasing blood meal pH.
During d 0 to 10 after weaning (common diet fed), pigs had ADG, ADFI, and (G:F) of 190 g, 200 g, and 1.05, respectively (Table 4). Average daily feed intake increased (P < 0.05) from d 7 to 14, d 14 to 21, and overall (d 0 to 21) for pigs fed diets containing blood meal compared to pigs fed the control diet. In addition, overall ADG was greater (P < 0.05) for pigs fed blood meal compared to those fed the control diet. Blood meal pH did not affect ADG, ADFI, or G:F.
Experiment 2
Chemical analyses of blood meal for CP and individual amino acids revealed similar values to those published by the NRC (1998), which were used in diet formulation (Table 5). The concentration of bacteria (Table 6) rose as storage time increased until d 8 (pH of 6.0), and then declined slightly at d 12 of spray drying (pH of 5.9). The greatest reduction in blood meal pH was seen when blood was stored for 8 d and there were minimal changes with further storage. Irradiation of the blood meal with a pH of 5.9 reduced the bacteria concentration from 6.6 x 106 to 9.0 x 101 cfu/g. No coliforms were detected in any blood meal lots.
During d 0 to 5 after weaning (common diet fed), pigs had ADG, ADFI, and G:F of 109 g, 104 g, and 1.05, respectively (Table 7). From d 0 to 7, pigs fed irradiated blood meal had increased ADG and ADFI (P < 0.05) compared to pigs fed nonirradiated blood meal (pH 5.9). From d 7 to 14, both ADG and G:F tended (P < 0.10) to increase in pigs fed irradiated blood meal vs. those fed nonirradiated spray-dried blood meal. Feed efficiency was improved from d 7 to 14 (P < 0.05) and overall (P < 0.01) for pigs fed blood meal compared to those fed the control diet. Overall, pigs fed irradiated blood meal had increased (P < 0.05) ADG and G:F compared to pigs fed nonirradiated blood meal. Pigs fed blood meal did not have different ADG or ADFI compared to pigs fed the control diet. Furthermore, blood meal pH did not influence pig ADG, ADFI, or G:F.
Experiment 3
As in Exp. 2, chemical analyses of blood meal for CP and individual amino acids revealed values similar to those published by the NRC (1998), which were used in diet formulation (Table 5
). Blood meal treated with gamma ray irradiation had no detectable levels of aerobic bacteria when treated with a dosage above 5 kGy (Table 8). However, a low level of aerobic bacteria was cultured at similar dosage levels (5 to 20 kGy) treated with electron beam irradiation. E. coli, mold, and yeast were detected in nonirradiated blood meal, but after irradiation, regardless of source and dosage, all were eliminated. When comparing the bacteria levels of the whole diets, irradiation of blood meal had very little impact on the overall bacteria concentration.
During d 0 to 4 after weaning (common diet fed), pigs had ADG, ADFI, and G:F of 293 g, 220 g, and 1.33, respectively (Table 9). For the overall experimental period (d 0 to 14), pigs fed diets containing blood meal had similar ADG, ADFI, and G:F compared to pigs fed the control diet.
From d 0 to 7, as well as overall (d 0 to 14), the inclusion of irradiated blood meal tended (P < 0.10) to increase G:F with no effects on ADG or ADFI. No differences in ADG, ADFI, and G:F were detected between pigs fed blood meal irradiated from different sources and dosages.
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Discussion
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The correlation of increasing bacterial concentrations and decreased pH with extended storage time of whole blood prior to spray drying was confirmed by our findings. However, pH as a quality control parameter for blood meal was not an effective indicator and should not be used as the only criteria.
In the present experiments, feeding diets containing blood meal with different pH did not affect growth performance. Anecdotal reports of an increase in the odor offensiveness of blood meal as pH decreases reported by feed manufacturers were confirmed by the authors olfactory sensing of the blood meal lots. Palatability may be of concern when a higher level of blood meal with a pH of 5.9 is included into the diet since Exp. 1 contained 2.5% blood meal, whereas Exp. 2 contained 5.0%. Additionally, the blood meal lot with pH 5.9 was of avian origin in Exp. 1, but in the other blood meal lots it was of bovine origin. However, research has indicated that pigs performed similarly when fed blood meal from either bovine or avian origin (Kats et al., 1994), and therefore would not be considered a confounding factor in regards to pH in our experiment. In Exp. 2, the blood meal with pH 5.9 was stored for a longer time prior to spray drying. An increase in NH4 concentration is associated with bacterial activity on nitrogen products (Mayes, 2000). Upon laboratory analyses, the NH4 level from the blood meal lots increased with an increase in storage time prior to spray drying. Even though an increase in NH4 and odor was observed, the nutritional value seemed to remain unchanged due to similar ADG and G:F compared to the other blood meal lots within Exp. 2. However, palatability may be a concern for blood stored for 12 d prior to spray drying.
The second area of ingredient quality addressed by these experiments focused on the possible interaction of bacterial concentrations of blood meal and its subsequent effect on pig performance. Irradiation has proven an effective means to reduce the bacteria level in dried blood products (Brankova and Dimitrova, 1975; Downes et al., 1987; and Turubatovic et al., 1993). In Exp. 2, we irradiated a portion of the blood meal generated from the last spray-drying day because we believed that the bacterial concentration of this lot would be the highest after the longest storage period. However, upon analyses, all blood meal that was dried in Exp. 2 had high levels of bacteria, and relatively little change in concentrations occurred with the storage times used in our study. Similar bacterial concentrations were observed between the nonirradiated blood meal samples from Exp. 2 and 3.
Other researchers have shown positive effects of irradiation of blood meal. Brankova and Dimitrova (1975) examined the microbiology of animal plasma that was irradiated by gamma rays at doses of 0, 5, 10, 15, and 20 kGy. A dosage of 15 kGy resulted in marked reductions of bacteria and a dosage of 20 kGy resulted in sterility in their study. Uchman et al. (1986) evaluated the efficacy of increased dosage of gamma ray irradiation on liquid animal plasma (0.3, 0.5, 1.0, 3.0, 4.0, and 8.0 kGy) and on spray-dried animal plasma (0.1, 1.0, 2.0, 4.0, and 6.0 kGy). Initially, the liquid plasma had bacterial concentrations ranging from 1.5 x 106 to 3.2 x 106 cfu/cm3. Post irradiation bacterial counts linearly decreased from 8.5 x 101 to 0 cfu/cm3 as the dosage was increased. The initial bacterial concentrations of the spray-dried plasma ranged from 2.2 x103 to 4.3 x103 cfu/g. with post irradiation bacterial counts linearly decreasing from 2.0 x 103 to 0 cfu/g with increased dosage. This study demonstrates that liquids are much more sensitive to lower levels of irradiation, but at higher levels (6.0 kGy), all bacteria were eliminated, regardless of the physical form of the raw material. However, after storage of liquid plasma for 48 h post irradiation at 4.0 kGy, bacterial levels rose to levels similar to those before irradiation (Uchman et al., 1986). After irradiation of dried animal plasma, bacteria levels rose slightly, but after 6 wk of storage, the level of contamination was stable and lower in comparison with untreated samples. The authors also determined that no yeast and mold existed when dried plasma was irradiated at a dosage of 2.0 kGy or above, which would be consistent with data from Exp. 3 showing no yeast and mold when irradiation of 2.5 kGy was applied.
De Souza Biagio (1987) reported that gamma ray irradiation was slightly more effective than electron beam irradiation in reducing microbial concentrations at similar dosages. The author estimated that the 10D value kGy, or the dosage amount to achieve a 1 log reduction in bacteria, was 0.82 and 1.06 kGy for gamma ray and electron beam irradiation, respectively. This equates to an irradiation dosage of approximately 3.3 kGy for gamma ray and 4.2 kGy for electron beam to achieve sterilization of blood meal with an initial bacterial concentration of 9.6 x103 cfu/g. Downes et al. (1987) evaluated gamma ray irradiation at increasing dosages (0, 10, 20, 45, and 50 kGy) on spray-dried blood powder to determine the influence on bacterial concentrations and its effect on the relative nutritive value (multislope ratio assay with body protein as the response criteria) in rats. They reported an increase in the feeding value of blood meal that was irradiated (10 kGy) compared to blood meal that was not. Also, analyses for bacteria concentrations revealed no detectable levels present for total aerobes, aerobic spores, anaerobic spores, fecal streptococci, coliforms, Salmonella sp., and B. subtilis (heat resistant) at all irradiation dosages used. In addition, the liquid whole blood was contaminated with Bluetongue and Banzi viruses prior to spray drying, but both were inactivated during the spray-drying process (80°C for 2 to 3 s).
The benefits of irradiation, however, must be weighed against possible alterations in feed value. Most research shows little, if any, negative effect on blood meal properties and some show slight benefits. Dimitrova and Brankova (1975) reported that irradiation (from 0 to 20 kGy) of blood meal did not influence pH or protein solubility. In addition, Hayashi et al. (1991) reported that irradiation dosages of 5, 10, and 15 kGy from both electron beam and gamma ray sources on freeze-dried porcine plasma reduced bacterial concentrations to less then 10 cfu/g from an initial microbial load of 2.2 x 104 cfu/g. Upon testing the irradiated samples, they observed no significant changes in the functional properties of protein solubility and emulsifying capacity from either gamma ray- or electron beam-treated blood meal. However, solubility declined linearly as the dosage increased for blood meal treated with either type of irradiation. Uchman et al. (1987) evaluated the solubility, emulsifying capacity, and viscosity of spray-dried blood meal treated at gamma ray irradiation doses of 0, 1.0, 2.0, 3.0, 4.0, 5.0, 10,0, 16.7, 20.0, and 50.0 kGy. They reported that all functional properties of blood meal were unaffected by irradiation doses up to 5 kGy. However, a significant worsening of solubility and viscosity, but an improvement in emulsifying capacity occurred at dosages above 5 kGy.
The limited research available shows little effect on amino acid content and protein quality of feed ingredients or whole diets after irradiation. Metta and Johnson (1951) reported no differences in digestibility or biological value of irradiated (28 kGy) wheat gluten and corn protein. They also reported no loss of available lysine in a guinea pig diet made from natural ingredients when irradiated at 25 kGy. Ford (1976) reported that the total amino acid, true digestibility, biological value, and net protein utilization of a complete rat diet were not significantly affected when irradiated at 25 and 100 kGy. However, Ford (1976) did observe a slight reduction in lysine availability at both dosage levels of irradiation. Furthermore, Hansen (1966) reported no loss in available lysine of blood meal when irradiated at 50 kGy.
In the only swine feeding trial to evaluate irradiated blood meal, Hansen et al. (1966) compared spray-dried blood meal from one lot that was divided equally and subsequently irradiated (25 kGy) or heat treated (145°C for 45 min). Pigs fed diets containing irradiated blood meal from 20 to 50 kg had reduced ADFI per kilogram of gain compared to the heat-treated blood meal. No differences were found from 50 to 90 kg of BW. Their trial design, pig size and age, and lack of a control diet (containing nonirradiated spray-dried blood meal) created difficultly in comparing their results to the present experiments. However, the increase in efficiency of gain during the initial feeding period would agree with our results.
In the present experiments, pigs fed diets containing irradiated blood meal had improved growth performance compared to blood meal that was not irradiated. In Exp. 2, overall ADG and G:F were improved by approximately 24 and 8%, respectively, whereas in Exp. 3, G:F increased by 7% when comparing the average of all pigs fed irradiated blood meal compared to pigs fed nonirradiated blood meal. Pigs in Exp. 3 were heavier at the initiation of the study and had a much wider variation in age than those in Exp. 2. This may explain why no blood meal response was observed in Exp. 3 when compared to the control diet and why significant responses to irradiation of blood meal were not seen.
Research evaluating the microbial characteristics of irradiated blood meal clearly indicates that both electron beam and gamma ray sources of irradiation are effective in reducing bacterial concentrations. Although irradiation of blood meal reduces or eliminates bacteria, the low inclusion level of blood meal used in our experimental diets would not alter the total diet microbiology dramatically. However, higher levels of bacteria then expected were cultured in blood meal that was treated with electron beam irradiation in Exp. 3. The reason for this is unknown since the processor certified irradiation application.
Results are mixed when comparing the functional properties of irradiated blood products in previous research. However, in Exp. 3, irradiation dosage up to 20 kGy did not adversely affect performance. Data from previous trials conflict slightly in regard to amino acid and protein quality at the irradiation dosage that we used in our experiments. Some of the experiments demonstrated either a slight improvement or slight decrease in quality, with the majority indicating no changes. No experiments, however, reported detrimental effects to amino acids or overall protein quality. This data, along with the current experiments, would indicate that irradiation at the doses used in our experiments would, at the very least, have no damaging effects on the protein portion of blood meal and may be beneficial.
Further investigation into the irradiation of other dried blood products or specialty protein sources for nursery pigs is needed and the mode of action for the improved growth performance of nursery pigs fed irradiated spray-dried blood needs to be determined.
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Implications
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The current experiments demonstrate that storage time of whole blood before spray drying affects the pH and ammonia concentration of blood meal. However, feed manufacturers should not base blood meal quality solely on pH or use pH as a quality-control indicator. Because nursery pig performance was improved when pigs were fed irradiated blood meal compared with blood meal in regular form, manufacturers need to evaluate processes that can reduce bacterial levels of dried blood meal. Although the exact mechanism for this increase in nursery pig performance when fed irradiated blood meal is not known, further research to determine whether this response results from a reduction in the bacterial concentration, deactivation of an unknown antinutritional factor associated with spray-dried blood meal, or other unknown factors.
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Footnotes
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1 Contribution no. 02-218-1 of the Kansas Agric. Exp. Stn., Manhattan 66506-0210. 
2 Appreciation is expressed to California Spray-Dry Co., Stockton, CA, for providing the spray-dried blood meal used in these experiments.
Received for publication January 26, 2002.
Accepted for publication November 27, 2002.
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J. M. DeRouchey, M. D. Tokach, J. L. Nelssen, R. D. Goodband, S. S. Dritz, J. C. Woodworth, B. W. James, M. J. Webster, and C. W. Hastad
Evaluation of methods to reduce bacteria concentrations in spray-dried animal plasma and its effects on nursery pig performance
J Anim Sci,
January 1, 2004;
82(1):
250 - 261.
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Abstract
Introduction
