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Effect of supplementation of exogenous β-glucans and enzymes on nutrient digestibility, manure odour and ammonia emissions from finisher boars
Livestock Science 134 (2010) 190–193
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
Effect of supplementation of exogenous β-glucans and enzymes on nutrient digestibility, manure odour and ammonia emissions from finisher boars☆ C.J. O'Shea, D.A. Gahan, M.B. Lynch, J.J. Callan, B. Flynn, J.V. O'Doherty ⁎ School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Ireland
a r t i c l e Keywords: β-glucans Odour Ammonia Nitrogen Enzyme
i n f o
a b s t r a c t It was hypothesised that supplementation of an exogenous mixed-linkage (1 → 3), (1 → 4)β-D-glucan to a wheat-based diet may beneficially modulate manure odour and ammonia emissions associated with intensive pig production, without depressing nutrient digestibility as has been observed with intact β-glucans. A complete randomised design experiment was conducted to investigate the addition of β-glucans and enzyme supplementation on nutrient digestibility, manure odour and ammonia emissions from finisher boars. Twenty boars (74.2 kg s.d. 5.6) were assigned to five dietary treatments (n = 4); (1) a basal wheat-based diet, (2) wheat-based diet + exogenous β-glucan, (3) wheat-based diet + exogenous β-glucan + enzyme, (4) barley-based diet and (5) barleybased diet + exogenous enzyme. The wheat-based diets containing β-glucans were formulated to contain comparable concentrations of total β-flucans with barley-based diets. The enzyme mix used contained both β-glucanase and β-xylanase. Inclusion of exogenous β-glucan to a wheat-based diet had no effect on digestibility of dry matter (P N 0.05), ash (P N 0.05), neutral detergent fibre (P N 0.05) or nitrogen (P N 0.05) compared with the basal wheat diet. Pigs offered the barley-based diets decreased manure ammonia emissions from 0 to 240 h (P b 0.05) and increased manure odour emissions (P b 0.05) compared with the basal wheat diet. In conclusion exogenous β-glucans did not effect nutrient digestibility, or beneficially influence manure ammonia emissions. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Intensive pig production generates considerable manure odour and ammonia emissions due to fermentation of undigested dietary protein (Mackie et al., 1998). Previous research from our laboratory indicates that these environmental pollutants may be ameliorated by substituting barley for wheat-based diets through increasing consumption of (1 → 3), (1 → 4)-β-D-glucan (β-glucans) (Garry et al., 2007). However dietary barley is associated with impaired nutrient
☆ This paper is part of the special issue entitled “11th International Symposium on Digestive Physiology of Pigs”. ⁎ Corresponding author. Tel.: +353 1 7167128; fax: +353 1 7161103. E-mail address: [email protected] (J.V. O'Doherty). 1871-1413/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2010.06.138
digestibility (O'Connell et al., 2005). It is therefore desirable to impart the beneficial properties of barley to dietary wheat without the associated implications of diminished nutrient utilisation. The addition of a purified source of cereal βglucans to a wheat-based diet to a similar concentration as found in native barley may stimulate intestinal fermentation to attenuate manure ammonia and odour emissions. Moreover, supplementation with an appropriate enzyme composite containing β-glucanase may indicate whether any beneficial effects are a response to exogenous β-glucan supplementation or an additional fermentable component present in native barley. The hypothesis of the current experiment was that supplementation of a wheat-based diet with an exogenous β-glucan source may repress manure ammonia and odour emissions similar to a barley-based diet.
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
2. Materials and methods 2.1. Experimental diets The experiment was designed as a complete randomised design comprising five dietary treatments as follows: (1) wheatbased diet, (2) wheat-based diet+exogenous β-glucan, (3) wheat-based diet +exogenous β-glucan +enzyme, (4) barleybased diet and (5) barley-based diet+enzyme. Diets were formulated to contain similar concentrations of digestible energy (DE; 13.9 MJ/kg) and apparent ileal digestible lysine (8.6 g/kg) and offered in meal form (Sauvant et al., 2004). The enzyme supplement was derived from Penicillium funiculosum (IMI SD 101) and contained Endo-1, 3 (4)-β-glucanase (EC 3.2.1.6) and Endo-1, 4-β-xylanase (EC 3.2.1.8) only. The exogenous βglucans were derived from oats and sourced from Cambridge Commodities (Ely, Cambridgeshire, UK.). Diets containing exogenous β-glucans were formulated to contain similar concentrations of total β-glucans compared with the barleybased diets. Dietary composition and analysis are presented in Table 1.
2.2. Animals and management—manure odour and ammonia emission study Thirty-five finishing boars (74.2 kg s.d. 5.6) were blocked based on live-weight and allocated a 14-day dietary adaptation period. Twenty boars (n =4) of a uniform weight were selected and transferred to individual metabolism crates. Manure collections and the ammonia emissions study were performed
Table 1 Composition and analysis of experimental diets (as fed basis). Treatment Cereal
2
3
4 Barley
5
Exogenous β-glucans No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
0 705 270 0 7.5
0 659.5 270 0 7.5
0 659.5 270 0 7.5
670 0 275 30 7.5
670 0 275 30 7.5
5 10 2.5
5 10 2.5
5 10 2.5
5 10 2.5
5 10 2.5
0
0
0
50
Ingredients (g/kg) Barley Wheat Soyabean meal Soya oil Dicalcium phosphate Salt Limestone flour Minerals and vitamins Enzyme supplement Exogenous β-glucans (47.5%) Analysed composition Dry matter Ash NDF Xylose Total β-glucans Arabinose:xylose a Arabinoxylans a
1 Wheat
0.05 50
0
0.05
0
0
(g/kg) 886.5 889.2 888.5 893.8 894.8 44.7 48.6 45.0 56.1 55.0 89.9 93.5 104.0 125.0 134.2 25.64 25.78 26.62 26.1 26.1 8.54 27.23 27.23 26.12 26.12 1.082 1.025 0.992 1.003 1.003 53.4 52.2 53.0 52.3 52.3
a Estimated using analysed value for xylose and calculated value for arabinose (Bach Knudsen, 1997).
191
as described by O'Connell et al. (2005). Air samples were collected and analysed to measure the odour threshold concentration of manure as described by Lynch et al. (2008). Manure odour emissions are presented as European odour units (OUE/m3). 2.3. Laboratory analysis of samples Proximate analysis of diets for DM and ash were carried out according to the AOAC (1995). The neutral detergent fibre (NDF) fraction of diets was analysed using a Fibertec extraction unit (van Soest et al., 1991). The nitrogen (N) content of diets was determined using a LECO FP 528 instrument. The β-glucan and xylose content of diets were determined using a Megazyme assay kit (Megazyme International Ireland Ltd., Ireland). 2.4. Statistical analysis Experimental data were analysed as a complete randomised design using the GLM procedure of the SAS Institute (1985). For the nutrient digestibility study, the statistical model investigated the effects of dietary treatments using live-weight as a covariate. A contrast statement was used to compare; (1) T1 (basal wheat diet) vs T2 + T3 (wheat-based diet + exogenous β-glucans), (2) T1 vs T4 + T5 (barley-based diets), (3) T2 + T3 (exogenous β-glucans) vs T4 + T5 (intact β-glucans). All data in the tables are presented as least-square means with standard error of means (LSM ± s.e.m.). 3. Results There was no effect of enzymes on nutrient digestibility (PN 0.05), manure odour (PN 0.05) and ammonia emissions (PN 0.05) compared with unsupplemented diets. There was no significant interaction between enzyme supplementation and cereal type on any variable measured. Inclusion of exogenous β-glucan to a wheat-based diet had no effect on digestibility of dry matter (P N 0.05), ash (PN 0.05), NDF (PN 0.05) or N (PN 0.05) compared with the basal wheatbased diet. Pigs offered the barley-based diets decreased digestibility of dry matter (P b 0.001), organic matter (P b 0.001), NDF (Pb 0.05) and N (Pb 0.001) compared with the basal wheat-based diet. Supplementation of a wheat-based diet with exogenous β-glucans increased digestibility of dry matter (Pb 0.001), organic matter (P b 0.001), NDF (P b 0.001) and N (Pb 0.001) compared with barley-based diets (Table 2). Pigs offered the barley-based diets decreased manure ammonia emissions from 0 to 240 h (Pb 0.05) and increased manure odour emissions (Pb 0.05) compared with the basal wheat-based diet (Table 3). 4. Discussion The hypothesis of the current experiment was that provision of an exogenous source of β-glucans to a wheat-based diet would beneficially impact manure ammonia and odour emissions without depressing nutrient utilisation. In the current study, supplementation with exogenous β-glucans did not negatively influence any measured parameter of digestibility suggesting that dietary β-glucan consumption
192
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
Table 2 Effect of cereal type, glucan supplementation and enzyme inclusion on nutrient digestibility parameters (LSM ± sem). Dietary treatments
Significance
Cereal type
Wheat
Exogenous β-glucans
No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
1.9
1.9
1.9
1.9
1.8
Intake parameters Dry matter intake (kg/d) Digestibility coefficients Dry matter Organic matter Neutral detergent fibre Nitrogen Ash Excretory parameters Urine:Faeces Total manure output (kg/d) Faecal dry matter (%)
0.900 0.915 0.533 0.908 0.631 5.9 4.9 29.2
Contrast 1 a
Contrast 2 b
Contrast 3 c
0.05
ns
ns
ns
0.007 0.006 0.032 0.008 0.031
ns ns ns ns ns
*** *** * *** ns
*** *** *** *** ns
0.692 0.571 1.986
ns ns ns
* ns ns
ns ns ns
Barley
0.897 0.914 0.560 0.896 0.615 5.5 4.9 29.2
0.894 0.913 0.598 0.914 0.536 5.4 4.5 34.1
0.845 0.861 0.406 0.841 0.610 3.0 2.4 33.7
0.851 0.867 0.440 0.884 0.615 3.9 4.3 33.2
Sem
Probability of significance: *P b 0.05; **P b 0.01; ***P b 0.001; ns = non significant P N 0.05. There was no interaction between cereal type and enzyme inclusion on nutrient digestibility parameters (P N 0.05). a Contrast 1 (basal wheat diet vs wheat + exogenous β-glucans). b Contrast 2 (basal wheat diet vs barley diets). c Contrast 3 (wheat + exogenous β-glucans vs barley-based diets).
may be enhanced exogenously without adversely impacting nutrient digestibility. Barley-based diets reduced manure ammonia emissions by 31% compared with the basal wheat-based diet as has been previously documented (Garry et al., 2007). In contrast, supplementation of a wheat-based diet with exogenous βglucans induced a negligible effect on manure ammonia emissions. This indicates that exogenous β-glucans did not successfully exert as strong an influence on manure ammonia compared with an intact source of β-glucans as found in native barley. Previous studies have reported that ingested β-glucans are susceptible to considerable depolymerisation during gastrointestinal transit (Johansen et al., 1993). Furthermore, interactions between β-glucans with various other components such as arabinoxylans have been described (Izydorczyk and MacGregor, 2000). It is possible that in an extracted, purified form, without the protection typically afforded through complex-forming with other cell-wall constituents, exogenous β-glucans may be extensively depolymerised by microbial action, thus losing functionality. Furthermore, the extraction methodology employed may have implications for retaining the structural
integrity and characteristics of the exogenous β-glucan supplement similar to an intact source and this point may merit consideration in further investigations. Supplementation with exogenous β-glucans did not beneficially influence manure odour compared with the basal wheat diet. This may further indicate that supplemented β-glucans were degraded extensively in the small intestine and therefore did not influence bacterial populations favourably in the caecum and colon (O'Shea et al., 2009). In the current study, no significant effect was observed of supplementation with exogenous enzymes to diets containing either intact or exogenous β-glucan sources on manure odour. Future strategies to elucidate the action exerted by β-glucans may have to address this problem. 5. Conclusion The addition of β-glucans to a wheat-based diet did not depress nutrient digestibility compared with the basal wheat diet, however there was a negligible benefit in reducing manure ammonia emissions.
Table 3 Effect of cereal type, β-glucan supplementation and enzyme inclusion on manure odour and ammonia emissions (LSM ± sem). Dietary treatments
Significance
Cereal type
Wheat
Exogenous β-glucans
No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
40.17 61.07 101.24
26.95 60.50 87.45
29.10 58.12 87.22
19.87 50.26 70.13
38.15 51.90 90.05
2034.6
5212.0
3461.4
5543.2
4426.1
Ammonia (mg/g N intake) 0–96 h 96–240 h 0–240 h Odour (72 h) Concentration (OuE/m3)
Contrast 1 a
Contrast 2 b
Contrast 3 c
4.378 5.120 6.063
ns ns ns
ns ns *
ns ns ns
709.0
ns
*
ns
Barley Sem
Probability of significance: *P b 0.05; **P b 0.01; ***P b 0.001; ns = non significant P N 0.05. There was no interaction between cereal type and enzyme inclusion on manure odour and ammonia emissions (P N 0.05). a Contrast 1 (basal wheat diet vs wheat + β-glucans). b Contrast 2 (basal wheat diet vs barley diets). c Contrast 3 (wheat + exogenous β-glucans vs barley-based diets).
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
Conflict of interest None of the authors had any conflict of interest in this work. Acknowledgements Funding for this research was provided under the National Development Plan, through the Research Stimulus Fund, administered by the Irish Department of Agriculture, Fisheries & Food. References Association of Official Analytical Chemists, 1995. Official Methods of Analysis. AOAC, Washington DC, USA. Bach Knudsen, K.E., 1997. Carbohydrate and lignin contents of plant materials used in animal feeding. Anim. Feed Sci. Technol. 67, 319–338. Garry, B.P., Fogarty, M., Curran, T.P., O'Doherty, J.V., 2007. Effect of cereal type and exogenous enzyme supplementation in pig diets on odour and ammonia emissions. Livest. Sci. 109, 212–215. Izydorczyk, M.S., MacGregor, A.W., 2000. Evidence of intermolecular interactions of β-glucans and arabinoxylans. Carbohydr. Polym. 41, 417–420.
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Johansen, H.N., Wood, P.J., Knudsen, K.E.B., 1993. Molecular weight changes in the (1 →3)(1→4)-beta-D-glucan of oats incurred by the digestive processes in the upper gastrointestinal tract of pigs. J. Agric. Food Chem. 41, 2347–2352. Lynch, M.B., O'Shea, C.J., Sweeney, T., Callan, J.J., O'Doherty, J.V., 2008. Effect of crude protein concentration and sugar-beet pulp on nutrient digestibility, nitrogen excretion, intestinal fermentation and manure ammonia and odour emissions from finisher pigs. Animal 2, 425–434. Mackie, R.I., Stroot, P.G., Varel, V.H., 1998. Biochemical identification and biological origin of key odor components in livestock waste. J. Anim. Sci. 76, 1331–1342. O'Connell, J.M., Callan, J.J., Byrne, C., Sweeney, T., O'Doherty, J.V., 2005. The effect of cereal type and exogenous enzyme supplementation in pig diets on nutrient digestibility, intestinal microflora, volatile fatty acid concentration and manure ammonia emissions. Anim. Sci. 81, 357–364. O'Shea, C.J., Lynch, M.B., Callan, J.J., O'Doherty, J.V., 2009. Dietary supplementation with chitosan at high and low crude protein concentrations promotes Enterobacteria spp in the caecum and colon and increases manure odour emissions from finisher boars. XI International Symposium on Digestive Physiology of Pigs. Livestock Science, Montbrio del Camp, Costa Daurauda, Spain, p. 149. Sauvant, D., Perez, J.-M., Tran, G., 2004. Tables of Composition and Nutritional Value of Feed Materials. Pigs, Poultry, Cattle, Sheep, Goats, Rabbits, Horses, Fish. Wageningen Academic Publishers, The Netherlands. Statistical Analysis Systems Institute, 1985. Statistical Analysis Systems. SAS Institute Inc., Cary, NC, USA. van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fibre, neutral detergent fiber and non starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597.
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
Effect of supplementation of exogenous β-glucans and enzymes on nutrient digestibility, manure odour and ammonia emissions from finisher boars☆ C.J. O'Shea, D.A. Gahan, M.B. Lynch, J.J. Callan, B. Flynn, J.V. O'Doherty ⁎ School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Ireland
a r t i c l e Keywords: β-glucans Odour Ammonia Nitrogen Enzyme
i n f o
a b s t r a c t It was hypothesised that supplementation of an exogenous mixed-linkage (1 → 3), (1 → 4)β-D-glucan to a wheat-based diet may beneficially modulate manure odour and ammonia emissions associated with intensive pig production, without depressing nutrient digestibility as has been observed with intact β-glucans. A complete randomised design experiment was conducted to investigate the addition of β-glucans and enzyme supplementation on nutrient digestibility, manure odour and ammonia emissions from finisher boars. Twenty boars (74.2 kg s.d. 5.6) were assigned to five dietary treatments (n = 4); (1) a basal wheat-based diet, (2) wheat-based diet + exogenous β-glucan, (3) wheat-based diet + exogenous β-glucan + enzyme, (4) barley-based diet and (5) barleybased diet + exogenous enzyme. The wheat-based diets containing β-glucans were formulated to contain comparable concentrations of total β-flucans with barley-based diets. The enzyme mix used contained both β-glucanase and β-xylanase. Inclusion of exogenous β-glucan to a wheat-based diet had no effect on digestibility of dry matter (P N 0.05), ash (P N 0.05), neutral detergent fibre (P N 0.05) or nitrogen (P N 0.05) compared with the basal wheat diet. Pigs offered the barley-based diets decreased manure ammonia emissions from 0 to 240 h (P b 0.05) and increased manure odour emissions (P b 0.05) compared with the basal wheat diet. In conclusion exogenous β-glucans did not effect nutrient digestibility, or beneficially influence manure ammonia emissions. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Intensive pig production generates considerable manure odour and ammonia emissions due to fermentation of undigested dietary protein (Mackie et al., 1998). Previous research from our laboratory indicates that these environmental pollutants may be ameliorated by substituting barley for wheat-based diets through increasing consumption of (1 → 3), (1 → 4)-β-D-glucan (β-glucans) (Garry et al., 2007). However dietary barley is associated with impaired nutrient
☆ This paper is part of the special issue entitled “11th International Symposium on Digestive Physiology of Pigs”. ⁎ Corresponding author. Tel.: +353 1 7167128; fax: +353 1 7161103. E-mail address: [email protected] (J.V. O'Doherty). 1871-1413/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2010.06.138
digestibility (O'Connell et al., 2005). It is therefore desirable to impart the beneficial properties of barley to dietary wheat without the associated implications of diminished nutrient utilisation. The addition of a purified source of cereal βglucans to a wheat-based diet to a similar concentration as found in native barley may stimulate intestinal fermentation to attenuate manure ammonia and odour emissions. Moreover, supplementation with an appropriate enzyme composite containing β-glucanase may indicate whether any beneficial effects are a response to exogenous β-glucan supplementation or an additional fermentable component present in native barley. The hypothesis of the current experiment was that supplementation of a wheat-based diet with an exogenous β-glucan source may repress manure ammonia and odour emissions similar to a barley-based diet.
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
2. Materials and methods 2.1. Experimental diets The experiment was designed as a complete randomised design comprising five dietary treatments as follows: (1) wheatbased diet, (2) wheat-based diet+exogenous β-glucan, (3) wheat-based diet +exogenous β-glucan +enzyme, (4) barleybased diet and (5) barley-based diet+enzyme. Diets were formulated to contain similar concentrations of digestible energy (DE; 13.9 MJ/kg) and apparent ileal digestible lysine (8.6 g/kg) and offered in meal form (Sauvant et al., 2004). The enzyme supplement was derived from Penicillium funiculosum (IMI SD 101) and contained Endo-1, 3 (4)-β-glucanase (EC 3.2.1.6) and Endo-1, 4-β-xylanase (EC 3.2.1.8) only. The exogenous βglucans were derived from oats and sourced from Cambridge Commodities (Ely, Cambridgeshire, UK.). Diets containing exogenous β-glucans were formulated to contain similar concentrations of total β-glucans compared with the barleybased diets. Dietary composition and analysis are presented in Table 1.
2.2. Animals and management—manure odour and ammonia emission study Thirty-five finishing boars (74.2 kg s.d. 5.6) were blocked based on live-weight and allocated a 14-day dietary adaptation period. Twenty boars (n =4) of a uniform weight were selected and transferred to individual metabolism crates. Manure collections and the ammonia emissions study were performed
Table 1 Composition and analysis of experimental diets (as fed basis). Treatment Cereal
2
3
4 Barley
5
Exogenous β-glucans No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
0 705 270 0 7.5
0 659.5 270 0 7.5
0 659.5 270 0 7.5
670 0 275 30 7.5
670 0 275 30 7.5
5 10 2.5
5 10 2.5
5 10 2.5
5 10 2.5
5 10 2.5
0
0
0
50
Ingredients (g/kg) Barley Wheat Soyabean meal Soya oil Dicalcium phosphate Salt Limestone flour Minerals and vitamins Enzyme supplement Exogenous β-glucans (47.5%) Analysed composition Dry matter Ash NDF Xylose Total β-glucans Arabinose:xylose a Arabinoxylans a
1 Wheat
0.05 50
0
0.05
0
0
(g/kg) 886.5 889.2 888.5 893.8 894.8 44.7 48.6 45.0 56.1 55.0 89.9 93.5 104.0 125.0 134.2 25.64 25.78 26.62 26.1 26.1 8.54 27.23 27.23 26.12 26.12 1.082 1.025 0.992 1.003 1.003 53.4 52.2 53.0 52.3 52.3
a Estimated using analysed value for xylose and calculated value for arabinose (Bach Knudsen, 1997).
191
as described by O'Connell et al. (2005). Air samples were collected and analysed to measure the odour threshold concentration of manure as described by Lynch et al. (2008). Manure odour emissions are presented as European odour units (OUE/m3). 2.3. Laboratory analysis of samples Proximate analysis of diets for DM and ash were carried out according to the AOAC (1995). The neutral detergent fibre (NDF) fraction of diets was analysed using a Fibertec extraction unit (van Soest et al., 1991). The nitrogen (N) content of diets was determined using a LECO FP 528 instrument. The β-glucan and xylose content of diets were determined using a Megazyme assay kit (Megazyme International Ireland Ltd., Ireland). 2.4. Statistical analysis Experimental data were analysed as a complete randomised design using the GLM procedure of the SAS Institute (1985). For the nutrient digestibility study, the statistical model investigated the effects of dietary treatments using live-weight as a covariate. A contrast statement was used to compare; (1) T1 (basal wheat diet) vs T2 + T3 (wheat-based diet + exogenous β-glucans), (2) T1 vs T4 + T5 (barley-based diets), (3) T2 + T3 (exogenous β-glucans) vs T4 + T5 (intact β-glucans). All data in the tables are presented as least-square means with standard error of means (LSM ± s.e.m.). 3. Results There was no effect of enzymes on nutrient digestibility (PN 0.05), manure odour (PN 0.05) and ammonia emissions (PN 0.05) compared with unsupplemented diets. There was no significant interaction between enzyme supplementation and cereal type on any variable measured. Inclusion of exogenous β-glucan to a wheat-based diet had no effect on digestibility of dry matter (P N 0.05), ash (PN 0.05), NDF (PN 0.05) or N (PN 0.05) compared with the basal wheatbased diet. Pigs offered the barley-based diets decreased digestibility of dry matter (P b 0.001), organic matter (P b 0.001), NDF (Pb 0.05) and N (Pb 0.001) compared with the basal wheat-based diet. Supplementation of a wheat-based diet with exogenous β-glucans increased digestibility of dry matter (Pb 0.001), organic matter (P b 0.001), NDF (P b 0.001) and N (Pb 0.001) compared with barley-based diets (Table 2). Pigs offered the barley-based diets decreased manure ammonia emissions from 0 to 240 h (Pb 0.05) and increased manure odour emissions (Pb 0.05) compared with the basal wheat-based diet (Table 3). 4. Discussion The hypothesis of the current experiment was that provision of an exogenous source of β-glucans to a wheat-based diet would beneficially impact manure ammonia and odour emissions without depressing nutrient utilisation. In the current study, supplementation with exogenous β-glucans did not negatively influence any measured parameter of digestibility suggesting that dietary β-glucan consumption
192
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
Table 2 Effect of cereal type, glucan supplementation and enzyme inclusion on nutrient digestibility parameters (LSM ± sem). Dietary treatments
Significance
Cereal type
Wheat
Exogenous β-glucans
No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
1.9
1.9
1.9
1.9
1.8
Intake parameters Dry matter intake (kg/d) Digestibility coefficients Dry matter Organic matter Neutral detergent fibre Nitrogen Ash Excretory parameters Urine:Faeces Total manure output (kg/d) Faecal dry matter (%)
0.900 0.915 0.533 0.908 0.631 5.9 4.9 29.2
Contrast 1 a
Contrast 2 b
Contrast 3 c
0.05
ns
ns
ns
0.007 0.006 0.032 0.008 0.031
ns ns ns ns ns
*** *** * *** ns
*** *** *** *** ns
0.692 0.571 1.986
ns ns ns
* ns ns
ns ns ns
Barley
0.897 0.914 0.560 0.896 0.615 5.5 4.9 29.2
0.894 0.913 0.598 0.914 0.536 5.4 4.5 34.1
0.845 0.861 0.406 0.841 0.610 3.0 2.4 33.7
0.851 0.867 0.440 0.884 0.615 3.9 4.3 33.2
Sem
Probability of significance: *P b 0.05; **P b 0.01; ***P b 0.001; ns = non significant P N 0.05. There was no interaction between cereal type and enzyme inclusion on nutrient digestibility parameters (P N 0.05). a Contrast 1 (basal wheat diet vs wheat + exogenous β-glucans). b Contrast 2 (basal wheat diet vs barley diets). c Contrast 3 (wheat + exogenous β-glucans vs barley-based diets).
may be enhanced exogenously without adversely impacting nutrient digestibility. Barley-based diets reduced manure ammonia emissions by 31% compared with the basal wheat-based diet as has been previously documented (Garry et al., 2007). In contrast, supplementation of a wheat-based diet with exogenous βglucans induced a negligible effect on manure ammonia emissions. This indicates that exogenous β-glucans did not successfully exert as strong an influence on manure ammonia compared with an intact source of β-glucans as found in native barley. Previous studies have reported that ingested β-glucans are susceptible to considerable depolymerisation during gastrointestinal transit (Johansen et al., 1993). Furthermore, interactions between β-glucans with various other components such as arabinoxylans have been described (Izydorczyk and MacGregor, 2000). It is possible that in an extracted, purified form, without the protection typically afforded through complex-forming with other cell-wall constituents, exogenous β-glucans may be extensively depolymerised by microbial action, thus losing functionality. Furthermore, the extraction methodology employed may have implications for retaining the structural
integrity and characteristics of the exogenous β-glucan supplement similar to an intact source and this point may merit consideration in further investigations. Supplementation with exogenous β-glucans did not beneficially influence manure odour compared with the basal wheat diet. This may further indicate that supplemented β-glucans were degraded extensively in the small intestine and therefore did not influence bacterial populations favourably in the caecum and colon (O'Shea et al., 2009). In the current study, no significant effect was observed of supplementation with exogenous enzymes to diets containing either intact or exogenous β-glucan sources on manure odour. Future strategies to elucidate the action exerted by β-glucans may have to address this problem. 5. Conclusion The addition of β-glucans to a wheat-based diet did not depress nutrient digestibility compared with the basal wheat diet, however there was a negligible benefit in reducing manure ammonia emissions.
Table 3 Effect of cereal type, β-glucan supplementation and enzyme inclusion on manure odour and ammonia emissions (LSM ± sem). Dietary treatments
Significance
Cereal type
Wheat
Exogenous β-glucans
No
Yes
Yes
No
No
Enzyme supplement
No
No
Yes
No
Yes
40.17 61.07 101.24
26.95 60.50 87.45
29.10 58.12 87.22
19.87 50.26 70.13
38.15 51.90 90.05
2034.6
5212.0
3461.4
5543.2
4426.1
Ammonia (mg/g N intake) 0–96 h 96–240 h 0–240 h Odour (72 h) Concentration (OuE/m3)
Contrast 1 a
Contrast 2 b
Contrast 3 c
4.378 5.120 6.063
ns ns ns
ns ns *
ns ns ns
709.0
ns
*
ns
Barley Sem
Probability of significance: *P b 0.05; **P b 0.01; ***P b 0.001; ns = non significant P N 0.05. There was no interaction between cereal type and enzyme inclusion on manure odour and ammonia emissions (P N 0.05). a Contrast 1 (basal wheat diet vs wheat + β-glucans). b Contrast 2 (basal wheat diet vs barley diets). c Contrast 3 (wheat + exogenous β-glucans vs barley-based diets).
C.J. O'Shea et al. / Livestock Science 134 (2010) 190–193
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