6.2 Apparent digestibility coefficient
6.3.2 Litter condition
Litter was on a good condition in all pens (the score mean was 1 for all diets). Faeces dry matter content in the different groups ranged between 19.8 % and 21.2 % for the diets Y10% and X30% respectively, but did not differ significantly (Table 15).
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Table 13. Body weight and feed intake before starting the experiment
Parameter (g) Standard feed Mean value SE
BW at day 7 147.8 7.14
BW at day 14 408.2 25.45
BW at day 21 867.8 42.72
BW at day 28 1546.5 66.07
Feed Intake day 1-10 238.2 12.34 Feed Intake day 10-28 1670.9 68.28
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Table 14. Some production parameters during the experiment period for the different diets
Parameter Experimental diet
SE P-value
Control X10% X20% X30% Y10% Y20% Y30%
BW at Day 35 (g) 2410.48 2341.06 2321.46 2377.40 2346.09 2300.71 2242.89 83.92 0.86 FCR (28-35) 1.47 bcd 1.52 d 1.49 cd 1.36 ab 1.44 abcd 1.40 ab 1.33 a 0.0396 0.0212 Feed intake 28-35 (g) 1191.5 a 1165.6 a 1120.7 a 1127.1 a 1175.8 a 1098.5 a 986.9 b 26.96 0.0002 Growth rate 28-35 (g) 116.4 109.6 107.7 118.8 116.7 112.3 106.2 3.85 0.1828
*Values within rows with different superscripts are significantly different (P < 0.05).
Table 15. Dry matter content (%) in the faeces from different groups
Experimental diet
SE P-value
Control X10% X20% X30% Y10% Y20% Y30%
DM % 20.1 20.5 20.6 21.2 19.8 20.5 20.8 0.402 0.3307
*Values within rows with different superscripts are significantly different (P < 0.05).
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7 Discussion
This study was done to evaluate the apparent digestibility of fungi based biomass as a source of protein in broiler chicken diets. This biomass was produced from wheat-DDGS using filamentous fungus, namely Neurospora intermedia which has the ability to secrete a wide range of enzymes that can degrade the complex structure of wheat-DDGS converting it to a protein-rich biomass with high nutritional value (Bátori et al., 2015; Lennartsson et al., 2014).
The chemical composition of the two fungal biomasses X and Y shows a high content of CP (34% and 47.4% respectively) and good amino acid profile (Table 3). Furthermore, X and Y have relatively low levels of crude fibre (2.8% and 8.9% respectively). These chemical characteristics make these biomasses of interest as a protein source in chicken diets. Adebiyi and Olukosi, (2015c) reported the content of ADF and NDF in wheat DDGS to be 39.9% and 22.3% respectively. In our study, ADF and NDF content in Y was 29.1% and 23% respectively.
This means that producing fungal biomass using wheat-DDGS reduced the level of ADF in the latter for more than 10%.
The findings of this study suggest that both X and Y can be a potential source of protein. The AIDCs of CP and most AA in wheat-DDGS is relatively low and differ between publications (Adebiyi and Olukosi, 2015b; Bandegan et al., 2009). Differences were found in CP and AA contents in wheat-DDGS among 19 samples of wheat-DDGS from 7 ethanol plants in Europe (Cozannet et al., 2011). These differences can be attributed to the different procedures between different plants such as adding of nitrogenous non-protein substances (enxymes), temperature and yeast (Kim et al., 2008). When comparing with the AIDCs in the test ingredients with results from a study on wheat-DDGS done by Adebiyi and Olukosi, (2015b), we find that these values are still not comparable even after adding proteases. The AIDC of CP and AA was higher especially for lysine which was in wheat-DDGS with enzymes equal to 0.02 while in X and Y this value was 0.61 and 0.72 respectively. On the other hand, when comparing AIDCs with results from Bandegan et al. (2009), we found that value of CP was equivalent to the values in X and Y (0.74, 0.74 and 0.72 respectively) and AIDC of cystine was comparable the value in Y (0.62 and 0.60 respectively). However, comparing with other studies would be bias since as mentioned there are differences in CP and AA between different ethanol plants. Thus, to conclude digestibility improvement, wheat-DDGS from the same plant should have been used in the same trial.
Results from this study suggest that inclusion of both X and Y had a negative effect on AIDC values of CP and AA compared to the control diet. However, this adverse effect did not increase with increasing inclusion level. Generally, the adverse effect was more pronounced in diet Y30 for all values in comparison to other diets. As the fungal biomass Y had a high content of CP (47.7 %), the diet Y30 had not only a very high content of CP (28.7%) but also a high AME in comparison to other experimental diets (Table 7). These high levels of energy and protein in Y30 could have affected feed intake and consequently FCR and resulted in this significant decrease (Cheng et al., 1997; Holsheimer and Veerkamp, 1992). In addition, the fungal biomass Y had a higher content of fibre (crude fiber, total dietary and insoluble fibres) than X (Table 3). The fibre content in Y is also higher than in soyabean meal the most common protein
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feedstuff in poultry diets. In our study, NDF content in Y was equal to 29.1%, while in soyabean meal the corresponding value was reported to be highest 12.8% (Ravindran et al., 2014). This high fibre content could be attributed to the fungal cell walls that consist mainly of glucan and chitin (Bowman and Free, 2006). Chitinase (the enzyme which hydrolyse chitin) exists in the digestive tracts of adult chicken (Gallus gallus) but the prevailing amount is not enough to catalyze chitin hydrolysis (Jeuniaux and Cornelius, 1978). Though, the inclusion of chitin at level up to 2.8% in broiler diet has a positive effect on performance and chitin degradation may have some positive physiological effects like including antimicrobial activity, immune-enhancing activity, and the stimulation of proteoglycan biosynthesis (Chen et al., 2002; Khempaka et al., 2011, 2006). Even though the existence of these fungal cell walls would limit the inclusion of X and Y (especially Y) at high levels, the inclusion at low levels would possibly be beneficial (when chitin levels do not exceed 2.8%).
In general, digestible CP and AA in feedstuffs is used when formulating diets (NRC, 1994).
Using that method is advantageous and may result in decreasing feed cost and reduce excretion of nitrogen to the environment (Kim, 2010). Therefore, when formulating broiler diets, ingredients are chosen depending on their availability (digestible CP and AA) rather than only meeting total levels of energy and amino acids (Beski et al., 2015).
When comparing digestible CP and AA (g/kg as fed basis) in X with other common protein-rich feedstuffs shown in Table 18, we can observe that digestible CP in X was 251 which is comparable to the corresponding values in sunflower meal (262). Digestible CP in Y was relatively high and higher than the corresponding values in many protein-rich feedstuffs in Table 18, but lower than this in soyabean meal (342 and 390, respectively). Digestible cystine in both X and Y was comparable to these values in soyabean meal, (4.90, 4.81 and 5.5, respectively). Digestible lysine in X was lower than most of the corresponding values in other protein-rich feedstuffs (Table 18). However, digestible lysine in Y was higher or comparable to most protein-rich feedstuffs but lower than this value in soyabean meal (11.97 and 25.5 respectively). Digestible methionine in X was 4.07 which is comparable to the corresponding value in soyabean (5.3), and in Y this value was 6.39 which is and higher than the corresponding value in soyabean meal, rapeseed meal, cottonseed meal (5.3, 5.8 and 4.7 respectively). The value of digestible threonine in the fungal biomass X was 7.33 which is lower than values in all protein-rich feedstuffs mentioned in Table 18 but chickpeas and faba beans (5.7 and 6.3 respectively). Furthermore, digestible threonine in the fungal biomass Y was 11.69 which is lower than the value in soyabean meal which is equal to15. In practice, methionine and cystine are the first limiting amino acids for growth and production in poultry and then comes lysine (Ravindran and Bryden, 1999). Based on this fact, Y would be a conceivable source of these limiting AA in addition to the higher digestible CP. However, since the calculated approximate production capacity of X is about 15 times more than Y, X is more likely to become a potential source of these AA than Y. Still, using Y as a protein source in the start feed for broilers where CP is included at high level (higher than growing and finisher feed) would perhaps be suitable.
34
When describing the available energy in a feedstuff to poultry, AME is mostly used (NRC, 1994). The calculated AME in the fungal biomasses X and Y was 15.6 and 17.3 MJ/kg DM respectively and this difference can be attributed to the crude fat content in X and Y (Table 3).
Adebiyi and Olukosi, (2015c) reported that AME in wheat-DDGS with or without enzymes was 15.0 and 15.5 MJ/kg DM. Even though the relatively high AME, the inclusion of wheat-DDGS is still limited due to the SP high content (Thacker and Widyaratne, 2007; Wang et al., 2007 a,b,c, 2008) making X and Y superior sources of energy in broiler chicken diets.
The main hindering factor for inclusion DDGS at high levels in poultry diets are the high level of NSP and low digestibility of the CP and AA due to Maillard reaction in the drying process (especially lysine) (Adebiyi and Olukosi, 2015b; Cozannet et al., 2011; Thacker and Widyaratne, 2007; Wang et al., 2007a,b,c, 2008). Using wheat-DDGS as a substrate for producing a fungal based biomass will enhance their nutritional value and provide the market with new competitive protein-rich feedstuffs regardless of the relatively high fibre content in Y (Table 3). As stated before, the high proteins content allows lower inclusion levels of Y to meet the requirements especially in case of starter diets.
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8 Conclusion
Both fungal biomasses X and Y can be potential sources of protein in broiler chicken diets with relatively high digestible and AA and high apparent metabolizable energy.
36
9 Future outlook
Additional analyses of these fungal biomasses, especially the NSP such as arabinoxylans, glucans, cellulose and chitin, are needed in order to optimize the use of these products in broiler nutrition and to include them at levels that do not have adverse effects on the animals and their productive parameters. Furthermore, studying methods for disrupting fungal cell walls or use exogenous enzymes to improve the digestibility and reduce the fibre content could be a way to allow higher inclusion levels.
Since biomass product X would be produced in a great deal higher amount than Y, finding a way to enhance the nutritional quality of X with maintained high production level is worth to be further studied.
The effects of these fungal biomasses on properties of the final product, i.e. meat quality are unknown. Thus, studying the sensory quality of the final product is of importance and this should be furtherly examined before using X or Y on large scale.
Correlation between intestinal microbiota and performance in broiler production has been studied. It was suggested that cecal microbiota profile reflects efficiency of feed digestion and nutrient utilization in the proximal intestine (duodenal loop to proximal ileum) (Dumonceaux et al., 2006; Rinttilä and Apajalahti, 2013). Therefore, studying the effect of fungal biomass on the intestinal microbiota would be beneficial toexplore.
Furthermore, investigating the possibility to include these fungal biomasses in laying hen and broiler breeder nutrition is of interest. Adult birds differ physiologically from growing poultry such as broiler chickens and can tolerate higher levels of fibre in their diets.
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