Abstract
This research was performed to evaluate the effects of increasing doses of exogenous fibrolytic enzymes (EFE), namely at 0 (control), 1 (low), 2 (medium) and 4 (high) μL/g dry matter (DM), on the ruminal fermentation of low-quality agro-industrial by-products, grape pomace, almond hull and pomegranate peel. For pomegranate peel, the addition of EFE increased gas production linearly from the immediately soluble fraction, and from the insoluble fraction, the potential of gas production (significant linear effect), organic matter digestibility and metabolizable energy. The highest doses were the most effective. As the doses increased, the effectiveness increased accordingly. Unlike pomegranate peel, EFE had a quadratic effect on the indices of almond hull, namely a significant response on gas production from the immediately soluble fraction, the insoluble fraction, potential of gas production, organic matter digestibility and metabolizable energy. The lowest dose was the most effective while the highest dose had inhibitory effects for gas indices, organic matter digestibility and metabolizable energy. On the other hand, this supplementation had no effect on the ruminal fermentation of grape pomace. This study indicates that the response to this feed additive was influenced by the dose, the structure of the substrate, and the interaction between dose and the substrate. Exogenous fibrolytic enzymes could enhance the use of almond hull and pomegranate peel in ruminant nutrition, and reduce their negative environmental impact. Keywords: almond hull, feed additive, grape pomace, pomegranate peel
Highlights
In recent years, the dramatic increases in the prices of roughage and concentrates have necessitated the use of alternative feeds in animal nutrition, such as agro-industrial by-products
The chemical compositions of the by-product feedstuffs that were used in this study (Table 1) were consistent with those found by Basalan et al (2011) for grape pomace, by Jafari et al (2011) for almond hull, and by Shabtay et al (2008) for pomegranate peel
Unlike with almond hull or pomegranate peel, the addition of exogenous fibrolytic enzymes (EFE) to grape pomace did not affect dry matter (DM) solubilize and ruminal fermentation. This result may be because of the high lignin contents of grape pomace, which protect cellulose and hemicelluloses from hydrolytic enzymes (Hatfield et al, 1999). These results showed that the response to EFE addition was influenced by the by-products’ substrate
Summary
The dramatic increases in the prices of roughage and concentrates have necessitated the use of alternative feeds in animal nutrition, such as agro-industrial by-products. The use of agro-industrial by-products in animal nutrition reduces the negative environmental impact of the food industry (Elferink et al, 2008) Because of their poor quality, many agro-industrial by-products, such as almond hull, grape pomace and pomegranate peel, are rarely used in ruminant nutrition (Shabtay et al, 2008; Basalan et al, 2011; Jafari et al, 2011; Delavar et al, 2014). In recent years, the use of exogenous fibrolytic enzymes (EFEs) as feed additives for ruminants to increase the nutritive values of poorquality roughage has been the object of several studies. The aim of this study was to evaluate the effects of commercial EFES on these agro-industrial by-products
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