HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schøyen, H. F. Articles by Skrede, A. Search for Related Content PubMed PubMed Citation Articles by Schøyen, H. F. Articles by Skrede, A.

Growth Performance and Ileal and Total Tract Amino Acid Digestibility in Broiler Chickens Fed Diets Containing Bacterial Protein Produced on Natural Gas

H. F. Schøyen^*,1, H. Hetland^*, K. Rouvinen-Watt and A. Skrede^*,

^* Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, N-1432 Ås, Norway; Department of Plant and Animal Sciences, Nova Scotia Agricultural College, Truro, Nova Scotia, Canada B2N 5E3; and Aquaculture Protein Centre, Centre of Excellence, N-1432 Ås, Norway

¹ Corresponding author: hilde.faaland-schoyen{at}umb.no

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
A total of 180 broiler chickens were fed 1 of 3 diets from day-old to slaughter at 35 d: a control diet with 35% soybean meal (SOY) or diets in which either 6% basic bacterial protein meal (BBP) or 6% autolysed bacterial protein meal (AUT) partially replaced soybean meal protein. Ileal and total tract apparent amino acid digestibility were examined in 5 chickens per diet using TiO₂ as an inert marker. Chickens fed the diets with bacterial protein had higher weight gain and feed consumption than control chicks during the first 3 wk, but there were no differences in growth or feed intake during the last 2 wk or during the total experimental period. The birds fed the BBP diet showed more efficient feed conversion compared with chickens fed the SOY and AUT diets. Litter quality at 5 wk was poorer in pens where the chickens were fed the AUT diet compared with the other 2 treatments. There were no differences among diets in the dressing percentage. Ileal amino acid digestibility at 5 wk of age revealed only minor differences between diets. There was a tendency toward lower ileal digestibility (0.12 > P > 0.07) of Arg, Lys, Met, and Phe in the AUT diet compared with the SOY diet, whereas there were no differences between the SOY and BBP diets. Total tract amino acid digestibilities at 5 wk were similar or slightly lower than the ileal digestibilities within diets. Total tract amino acid digestibility at 2 wk was similar to the total tract amino acid digestibility at 5 wk. The diets containing bacterial protein showed lower total tract digestibility of most amino acids compared with the SOY diet. It was concluded that 6% of either basic or autolysed bacterial protein can replace soybean meal in diets for broiler chickens without impairing growth performance, and the basic bacterial protein seemed to be a slightly better substitute than the autolysed bacterial protein.

Key Words: single cell protein • bacterial protein • broiler chicken • growth performance • amino acid digestibility

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Bacterial protein meal (BPM) was produced from natural gas by a mixture of Methylococcus capsulatus (Bath; Bothe et al., 2002), Ralstonia sp., Brevibacillus agri, and Aneurinibacillus sp. living in water suspension. The bacterial biomass was centrifuged, heat-treated to kill the bacteria, and spray-dried to produce a basic BPM containing approximately 70% CP on DM basis. Bacterial protein meal has previously been studied as a feed ingredient for broiler chickens (Skrede et al., 2003), showing similar growth performance with diets containing up to 6% bacterial protein replacing soybean meal and significantly more efficient feed conversion during the last 3 wk of the feeding period with increasing levels of BPM. Higher levels of BPM up to 9% supported slightly reduced gain in 2 experiments, but had no negative effect in a third experiment (Skrede et al., 2003). Another study has shown that overall protein and energy metabolism in broiler chickens was not affected by a dietary content of 6% BPM, corresponding to 20% of dietary N (Hellwing et al., 2006). The amino acid digestibility of BPM has been determined in adult roosters by Skrede et al. (1998), who found a mean total tract digestibility (TD) of 80.5%. The digestibility of the individual amino acids varied considerably in the latter study; Lys and Arg exhibited the highest digestibility and Cys the lowest. Huang et al. (2005) showed varying apparent ileal amino acid digestibility of different feed ingredients at different ages in broiler chickens. Ileal digestibility (ID) is considered to be a more accurate measure of amino acid availability in chickens than the TD (Johnson, 1992; Ravindran et al., 1999; Kadim et al., 2002), mainly due to hindgut microbial activity, although the difference between the ID and the TD may be small for highly digestible feeds (Williams, 1995; Ravindran et al., 1999). Vhile et al. (2005) did not detect any difference in amino acid digestibility of a diet containing 50% basic bacterial protein fed to intact or ileorectally anastomized blue foxes.

In a study with several differently processed bacterial products, including products in which the endogenous enzymes of the bacteria had autolysed the biomass, total tract amino acid digestibility in mink was found to increase with increasing solubility and decreasing protein molecule size (Schøyen et al., 2005). Consistent with the findings of Skrede et al. (1998), Schøyen et al. (2005) found high digestibility of Lys and Arg and low digestibility of Cys in the basic bacterial protein, whereas the autolysed bacterial protein revealed higher digestibility of Ile and Trp compared with basic bacterial protein. The objective of this study was therefore to assess growth performance and ileal and total tract amino acid digestibility of broiler chicken diets in which soybean meal was partially replaced by basic or autolysed BPM.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Birds and Housing
In the growth experiment, 180 one-day-old Ross 208 male broiler chickens (Samvirkekylling, Va °ler, Norway) were used. The chickens were housed in floor pens of 1 m² with wood shavings as bedding. Temperature was kept at about 32°C during the first 3 d and then reduced by 1°C every other day until a temperature of 21°C was reached, subsequently maintaining this temperature. The daily light regimen consisted of 1 h of darkness up to d 7, followed by darkness from 1700 to 2100 h and from 0000 to 0400 h during the remaining experimental period. Feed and water were provided ad libitum. The experimental diets were fed from d 1. The experiment was carried out using 12 pens with 15 chickens in each pen, giving 4 replicate pens per dietary treatment. All pens were in the same room. In the digestibility experiment, excreta and ileal contents from 15 chickens were used, giving 5 replicates per dietary treatment. These birds were kept individually in wire cages, otherwise applying the same conditions as in the growth experiment, albeit the final temperature was 24°C instead of 21°C. Any dead birds were autopsied (Department of Morphology, Genetics and Aquatic Biology, Norwegian School of Veterinary Science, Oslo, Norway).

Experimental Diets
Three pelleted diets were made: a cereal-soybean-based control diet (SOY), and 2 diets reduced in soybean meal (not dehulled, hexane- and 2,3-methylpentane extracted, Denofa AS, Fredrikstad, Norway) and supplied with 6% basic BPM (BBP; Norferm AS, Stavanger, Norway) or 6% autolysed BPM (AUT; Norferm AS, Stavanger, Norway). Endogenous enzymes in the bacterial mass were used to lyse cell structures before spray-drying to yield the autolysed BPM. Amino acid composition of the soybean meal and the BPM is given in Table 1. The diets were calculated to exceed the requirements for protein and indispensable amino acids for the 0- to 3-wk-old broiler (NRC, 1994; Table 2). Titanium dioxide was included in all diets as an indigestible marker. Before mixing, the cereals were ground in a hammer mill with a 3-mm screen and weighed automatically. The rest of the dry ingredients were weighed manually and poured into the mixer. The soybean oil was sprayed into the mixer. The diets were pelleted with a 3-mm die and then cooled and dried (Center for Feed Technology, Norwegian University of Life Sciences).

To determine apparent ID the digesta in the section between Meckel’s diverticulum and the ileocecal junction was collected using gentle digital pressure after CO₂ asphyxiation and dissection of the bird on d 35 of age. The digesta were frozen immediately after collection and subsequently freeze-dried and ground before analyses. Apparent TD was determined from excreta collected daily during 3 d at 2 points (12 to 15 and 31 to 34 d of age). The feed was removed for 6 h before the start of collection, then 3 d later; feed was again removed for 6 h while collection of excreta continued. The collected excreta were frozen, freeze-dried, and ground to obtain representative samples pending analyses.

Analyses
Analyses of the soybean meal, the basic and the autolysed BPM, the diets and the samples of ileal digesta and excreta were carried out according to the official European Union methods. Nitrogen was analyzed according to Commission Directive (CD) 93/28/EEC and DM according to CD 71/393/EEC. All amino acids except Trp were analyzed according to CD 98/64/EC (European Union, 1998). The values for TD of Gly were omitted, because the acid hydrolysis will yield Gly from the uric acid present in the excreta (Kadim et al., 2002). Tryptophan was analyzed according to CD 2000/45/EC (European Union, 2000). Amino acid content is given as free amino acids (i.e., as hydrated amino acids) as g/kg sample as-is. Analysis of the TiO₂ marker was according to Short et al. (1999). The diets were also analyzed for ash (CD 71/250/EEC) and crude fat (CD 98/64/EC).

Digestibility Calculations
Apparent digestibility was calculated using the relative content of the marker in the diet and the ileal digesta (or excreta), as: 1 ÷ marker:nutrient in diet x nutrient:marker in ileal digesta (or excreta). To calculate the mean amino acid digestibility, the value obtained for each amino acid was weighted according to the relative amount of this amino acid in the diet.

Statistics
The model was as follows: Y_ij = µ + _i + _ij, where Y_ij = response; µ = general mean; _i = fixed effect of diet; _ij = random effect (residual error).

Pen was the experimental unit in the production study for the responses feed consumption, weight, and litter quality; whereas for dressing percentage, and in the digestibility experiment, the individual bird was the experimental unit. One-way ANOVA (PROC GLM) was performed using the ANOVA procedure of SAS (SAS Institute, 2001). Results are presented as means for each diet, and variance is expressed as the residual SD (RSD; root MSE in SAS) of the model. Significant (P < 0.05) differences among diets were ranked with the least significant difference test.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The amino acid analyses revealed that the protein in both the basic and the autolysed BPM had a higher content of Met, Trp, and Val but lower content of Arg, Lys, and Phe than the soybean meal (Table 1). The autolysed BPM contained lower levels of Arg and Trp compared with the basic BPM. The diets had similar contents of macronutrients, except for higher N content in the BBP diet than in the SOY and AUT diets. The diets had close to identical contents of total amino acids, and there were only minor differences in the contents of individual amino acids (Table 2).

Growth Performance
The chickens that received the BBP and AUT diets had greater weight gain and higher feed consumption than the birds fed the SOY diet during the first 3 wk (0 to 21 d; Table 3). However, there were no significant differences among treatments in feed consumption or weight gain in the 21 to 36 d period or the total period (0 to 36 d). Feed conversion in the 0 to 21 d period tended (P = 0.082) to be more efficient in the birds fed the BBP diet compared with the SOY diet. For the total period, there was a significantly more efficient feed conversion for the BBP diet compared with the SOY and AUT diets, whereas there was no difference between the SOY and AUT diets.

Digestibility
The total tract amino acid digestibilities determined at 2 wk (TD2) and 5 wk (TD5) did not differ from each other (Table 4). Both diets containing BPM showed lower TD of most amino acids as well as mean amino acid TD compared with the SOY diet, whereas there was no difference between the BBP and AUT diets. Only the digestibility of Ala remained unaffected by dietary treatment. It was found that Cys showed the lowest TD2 and the greatest reduction in TD2 for the BBP and AUT diets compared with the SOY diet.

Ileal amino acid digestibilities ranged from 75.7 (Cys in AUT) to 94.1% (Met in SOY), and total tract values ranged from 73.5 (Cys in AUT) to 93.1% (Met in SOY). There was little or no difference in the amino acid digestibility between collection sites (total tract vs. ileum) within diets. In the SOY diet, all amino acids but Met and Ala displayed similar digestibility in the ileum and the total tract (Table 4), and Met and Ala showed lower TD5 than ID. In the BBP diet, Lys, Met, Val, Ala, and Tyr had lower TD5 than ID. However, there were no significant differences between ID and TD for any amino acid in the AUT diet. The mean ileal amino acid digestibility was significantly higher than the corresponding TD5 values for the SOY and BBP diets, but not for the AUT diet.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The similarity among diets in total amino acid content allowed comparison of amino acid digestibility and effects on growth, even though there was a divergence in N content among diets, probably partly due to nonprotein N, because BPM contains roughly 10% nucleic acids (Skrede et al., 1998). The reason why the birds ate more and grew better when fed the BPM diets compared with the control diet and also exhibited a significantly more efficient feed conversion remains unclear. The diets were formulated to present similar amounts of nutrients to the birds, and there were negligible differences in amino acid digestibility. Hence, differences in amino acid digestibility are unlikely to be the cause of the more efficient feed conversion in birds fed the basic BPM. Skrede et al. (2003) suggested that the high Trp content of BPM may affect the birds’ energy requirement and have an influence on feed conversion. In the present study, the content of ileally digestible Trp was found to be 2.5 g/ kg in the SOY diet and 2.7 g/kg in the BBP diet. Although all diets exceeded the NRC (1994) requirement for Trp, the higher feed consumption of the chickens fed the BBP diet than the SOY diet and, subsequently, a higher Trp supply, may contribute to explain the better bird performance. In addition, the more efficient feed conversion in the BBP than SOY-fed chicks can partly be explained by higher weight gain during 0 to 21 d leading to a lower cost of maintenance. Calculation of the ME (MJ/kg of feed) content of the diets using table values for the feed ingredients (UMB, 2006) indicated that the BPM diets had a slightly higher ME content (12.4) than the SOY diet (12.1), which also may have affected feed conversion efficiency. However, the soybean meal content was reduced from 35 to 25% as-fed from the SOY diet to the BPM diets, and the positive effects of the BPM diets could be partly related to a reduced content of the nonde-hulled soybean meal, containing high levels of indigestible fibrous components.

The high digestibility of Lys, Arg, and Met and the low digestibility of Cys in diets containing BPM is in agreement with Skrede et al. (1998) and Schøyen et al. (2005). Fernández-Fígares et al. (2002) found high endogenous output of Cys relative to the feed content, which can partly explain the low apparent digestibility. The apparent TD of Trp in mink has previously shown to be higher in the autolysed than in the basic bacterial protein (Schøyen et al., 2005). In this experiment, no such statistically significant relationship in ID or TD5 was found, but the TD2 showed significantly higher values for Trp in the diet containing the autolysed compared with the basic bacterial protein.

The tendency toward lower amino acid digestibility of the bacterial protein-containing diets compared with the soybean-based control diet is probably associated with the high content of cell walls and membranes (D’Mello, 1973; Berge et al., 2005; Schøyen et al., 2005). The linkages between the 2 alternating sugar derivatives in the peptidoglycan layer in the bacterial cell wall are ß (1,4) glycosidic bonds, and the birds’ own digestive enzymes are not capable of hydrolyzing these bonds. Thus, as the bacterial ß-glycans pass through the intestine, they may make the digesta more viscous, and hence hamper nutrient digestion and absorption.

Increased digesta viscosity often leads to litter moisture problems (Leeson and Summers, 2001). The poorer litter quality (i.e., the more wet and caking litter) in the pens where the AUT-fed chicks were kept compared with the SOY-fed chicks, may have been caused by more viscous digesta. Hellwing et al. (2005) observed that increasing levels of bacterial protein in mink diets increased fecal excretion of water and suggested that this was caused by the water-binding properties of the undigested components. However, analysis of the diets showed that the AUT diet had higher Na content than the SOY and BBP diets. This could lead to higher water excretion in the AUT-fed birds, although the content of Na in the AUT diet was within normal ranges (NRC, 1994). Earlier research by Skrede et al. (2003) showed better litter quality with increasing basic BPM inclusion in broiler diets in 1 experiment, and the present study indicated that AUT may have a negative effect on litter quality. A better understanding of the modes of action of BPM components during digestion are desirable to fully exploit the potential offered by this new feed ingredient.

The results of this study indicated net synthesis of amino acids in the hindgut when feeding the BBP diet but no net change when feeding the SOY and AUT diets. Incomplete digestion in the ileum results in more undigested residues in the hindgut, increasing the potential for differences between measurements of digestibility in the ileum and the total tract due to hindgut microbial fermentation (Johnson, 1992; Williams, 1995; Ravindran et al., 1999; Kadim et al., 2002). The hindgut flora depends on both energy and N building blocks, and our diets most likely provided sufficient fermentable carbohydrates for the microbes to synthesize microbial protein from available N compounds. However, because only the BBP diet resulted in net microbial protein synthesis, this may indicate a higher supply of fermentable N compounds from the BBP diet than from the SOY and AUT diets. Also, the autolysed BPM may have increased viscosity more than the basic BPM, as inferred from the decreased litter quality, thus impeding hindgut activity.

Although the numeric differences in amino acid digestibility among diets were smaller when determined in the total tract than in the ileum, there were several significant differences in TD but none in ID. This is most likely due to the larger variation in ID than TD measurements. The difference in variability may be explained by the fact that the excreta samples were much more representative than the ileal grab samples ("snapshots"). Lemme et al. (2004) suggested that at least 4 replicates per treatment should be run, but that digesta from several birds may be pooled to obtain sufficient quantity for analysis. Previously, it has been shown that TD determinations in broilers are more variable than ID (Ravindran et al., 1999).

It is concluded that 6% of either basic BPM or autolysed BPM can replace soybean meal in diets for broiler chickens without impairing growth performance. The basic BPM may be preferable to the autolysed BPM due to more efficient feed conversion and better litter quality. Digestibility determination based on excreta collection slightly underestimated the disappearance of amino acids from the BBP diet compared with ileal sampling. Further research is warranted to examine the mechanisms by which BPM improves appetite, growth rate, and efficiency of feed conversion in broiler chickens.

	ACKNOWLEDGMENTS

 
The study was supported by grant 143196/140, "Protein produced from natural gas—a new feed resource for fish and other domestic animals," from the Research Council of Norway.

Received for publication June 13, 2006. Accepted for publication September 4, 2006.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Berge, G. M., G. Baeverfjord, A. Skrede, and T. Storebakken. 2005. Bacterial protein grown on natural gas as protein source in diets for Atlantic salmon, Salmo salar, in saltwater. Aquaculture 244:233–240.

Bothe, H., K. Møller Jensen, A. Mergel, J. Larsen, C. Jørgensen, H. Bothe, and L. Jørgensen. 2002. Heterotrophic bacteria growing in association with Methylococcus capsulatus (Bath) in a single cell protein production process. Appl. Microbiol. Biotechnol. 59:33–39.[ISI][Medline]

D’Mello J. P. F. 1973. The use of methane-utilising bacteria as a source of protein for young chicks. Br. Poult. Sci. 14:291–301.[ISI][Medline]

European Union. 1998. Commission Directive 98/64/EC establishing community methods of analysis for the determination of amino acids, crude oils and fats, and olaquindox in feedingstuffs and amending directive 71/393/EEC. Off. J. Eur. Commun. L 257:14–28.

European Union. 2000. Commission Directive 2000/45/EC establishing community methods of analysis for the determination of vitamin A, vitamin E and tryptophan in feed-ingstuffs. Off. J. Eur. Commun. L 174:32–50.

Fernández-Fígares, I., R. Nieto, C. Prieto, and J. F. Aguilera. 2002. Estimation of endogenous amino acid losses in growing chickens given soya-bean meal supplemented or not with DL-methionine. Anim. Sci. 75:415–426.

Hellwing, A. L. F., A.-H. Tauson, Ø. Ahlstrøm, and A. Skrede. 2005. Nitrogen and energy balance in growing mink (Mustela vison) fed different levels of bacterial protein meal produced with natural gas. Arch. Anim. Nutr. 59:335–352.[ISI][Medline]

Hellwing, A. L. F., A.-H. Tauson, and A. Skrede. 2006. Effect of bacterial protein meal on protein and energy metabolism in growing chickens. Arch. Anim. Nutr. 60:365–381.[ISI][Medline]

Huang, K. H., V. Ravindran, X. Li, and W. L. Bryden. 2005. Influence of age on the apparent ileal amino acid digestibility of feed ingredients for broiler chickens. Br. Poult. Sci. 46:236–245.[ISI][Medline]

Johnson R. J. 1992. Principles, problems and application of amino acid digestibility in poultry. World’s Poult. Sci. J. 48:232–246.

Kadim, I. T., P. J. Moughan, and V. Ravindran. 2002. Ileal amino acid digestibility assay for the growing meat chicken—comparison of ileal and excreta amino acid digestibility in the chicken. Br. Poult. Sci. 43:588–597.[ISI][Medline]

Leeson, S., and J. D. Summers. 2001. Nutrition of the Chicken. 4th ed. M. L. Scott and Associates, Ithaca, NY.

Lemme, A., V. Ravindran, and W. L. Bryden. 2004. Ileal digestibility of amino acids in feed ingredients for broilers. World’s Poult. Sci. J. 60:423–437.

National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC.

Ravindran, V., L. I. Hew, G. Ravindran, and W. L. Bryden. 1999. A comparison of ileal digesta and excreta analysis for the determination of amino acid digestibility in food ingredients for poultry. Br. Poult. Sci. 40:266–274.[ISI][Medline]

SAS Institute. 2001. Version 8.2. SAS Inst. Inc., Cary, NC.

Schøyen, H. F., J. R. K. Frøyland, S. Sahlström, S. H. Knutsen, and A. Skrede. 2005. Effects of autolysis and hydrolysis of bacterial protein meal grown on natural gas on chemical characterization and amino acid digestibility. Aquaculture 248:27–33.

Short, F. J., J. Wiseman, and K. N. Boorman. 1999. Application of a method to determine ileal digestibility in broilers of amino acids in wheat. Anim. Feed Sci. Technol. 79:195–209.

Skrede, A., G. M. Berge, T. Storebakken, O. Herstad, K. G. Aarstad, and F. Sundstøl. 1998. Digestibility of bacterial protein grown on natural gas in mink, pigs, chicken and Atlantic salmon. Anim. Feed Sci. Technol. 76:103–116.

Skrede, A., H. F. Schøyen, B. Svihus, and T. Storebakken. 2003. The effect of bacterial protein grown on natural gas on growth performance and sensory quality of broiler chickens. Can. J. Anim. Sci. 83:229–237.

UMB. 2006. Subject: Feed ingredient database. http://www.umb.no/iha/fortabell/index.php Accessed July 2006.

Vhile, S. G., A. Skrede, Ø. Ahlstrøm, R. Szymeczko, and K. Hove. 2005. Ileal and total tract nutrient digestibility in blue foxes (Alopex lagopus) fed extruded diets containing different protein sources. Arch. Anim. Nutr. 59:61–72.[ISI][Medline]

Williams P. E. V. 1995. Digestible amino acids for non-ruminant animals: Theory and recent challenges. Anim. Feed Sci. Technol. 53:173–187.

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schøyen, H. F. Articles by Skrede, A. Search for Related Content PubMed PubMed Citation Articles by Schøyen, H. F. Articles by Skrede, A.