The effect of different additives (nutrients, moisture absorption) on chemical composition, gas production and digestibility of pea pod silage

Nowadays, agricultural wastes that have high value and are also available are used by livestock farmers who are aware of their nutritional value. These wastes are sometimes used as the main part of animal feed without any changes and sometimes in a processed form. In the production and processing of livestock and agricultural products, there are a large amount of plant residues, crop residues and by-products with acceptable nutritional value for animal feed, which is mostly due to the lack of a proper structure and insufficient information from the farmers. These wastes are traditionally used by livestock farmers without changing the method, which is needed according to the conditions, new ideas for using agricultural wastes in preparing a nutritional program (Shakhesi, 2008). Pea plant is cultivated in Golestan province to produce green seeds for human nutrition and for canning and fresh consumption. Post-harvest by-products include the green seedless stalk, leaves, and pods. Harvesting is usually done 5-7 days after flowering, and since pod development is rapid, the operation can be done every day (Richard Ebesu, 2004). Seif Duati et al (2017) reported the chemical composition of green pea pods as 10.03% for raw cultivation, 40.31% for neutral detergent insoluble fiber, and 8.05% for ash. The aim of this study was to investigate the effect of using different nutrients on the chemical composition, fermentation properties, gas production parameters and in vitro digestibility of pea pod silage.
Pea pods were prepared after deseeding and chopped into pieces of about 3-4 cm by a chopper and manually compressed and ensiled in plastic bags in a completely randomized design (four treatments and three replications). Representative of pea pods sample was packed manually, in triplicate into plastic bags. The filled silos were stored at ambient temperature and allowed to ensile for 45 days. The experimental treatments included: 1) pea pod silage + wheat straw, 2) pea pod silage + wheat straw + molasses, 3) pea pod silage + barley flour, 4) pea pod silage + Dried Citrus Pulp. After the specified ensiling time, the silos were opened and the samples were mixed together and dried in an oven at 60 °C for 48 hours. After designated ensiling times, silos were opened and the ensiled forage was mixed thoroughly and then were dried at a 60°C in oven for 48 h and then ground to pass through a 2 mm screen for later analysis. The chemical composition of the samples was determined using standard methods. In order to estimate the gas production parameters, the gas production test and in vitro digestibility were used using the batch culture method.
Results showed that there were significant differences among treatments on NDF, CP and pH (P>0.05). Enzyme treated silages had lowest NDF content (46.50%) compared with other treatments (P<0.05). The lowest pH was related to treatment containing molasses. Silage treated with organic acid improved aerobic stability, significantly. There were significant differences among treatments on gas production parameters (P<0.05) and molasses and enzyme treated pea silage had highest and lowest gas production potential than others (199.1 and 183.3 ml/g DM, respectively). Results showed that there were no significant differences among treatments on DMD and partitioning factor (P>0.05). Organic acid treated silages had lowest effect on DMD and OMD compared with other treatments (P<0.05).
Conclusion :Overall, results showed that using molasses and molasses + enzyme as additive can be improwed nutritive value of pea silage better than others. Anyway, green pea forage according to the appropriate level of crude protein similar to corn forage and its silage characteristics, has the potential of silage and can be used in livestock feeding.