The effect of different additives (organic acid, mollasses and enzyme) on chemical composition, aerobic stability, fermentation parameters, digestibility and gas production of pea (Pisum sativum) silage

Sources of protein are the most expensive part of animal feed, and every year a large amount of these sources are imported from abroad for use in animal husbandry industry. One of the important steps in reducing the cost of feed is the optimal use of available resources and the recognition of new foods and their use in animal rations. On the other hand, every year, a huge amount of agricultural product residues are obtained, which can be used in animal nutrition. Optimum use of agricultural by-products and processing industries in feeding ruminants is important from economic and environmental aspects. Pea (Pisum sativum L.) is a cool-season crop and one of the most important legumes, in the temperate climatic regions and it has been widely consumed as a legume or vegetable throughout the world for the purpose of both human nutrition and animal nutrition. Peas are cultivated with the aim of producing green seeds, but after harvesting the pods containing seeds, its waste can be used by ruminants as high-quality bulk feed. The by-product after the harvesting of chickpeas (green chickpeas) which can be extracted and separated manually is the parts of the stem, leaves and pods that are free of green seeds. This research was conducted in order to investigate the effect using organic acid (acetic acid) and fibrinolytic enzyme and molasses on chemical composition, fermentation characteristic, gas production and digestibility parameters of pea silage.

Whole crop pea silage was harvested and chopped with a conventional forage harvester under farm condition to length of 2-3 cm. Representative of pea forage 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 following treatments were applied to the forage samples: 1) pea forage without any additives (control), 2) control + fibrinolytic enzyme(2 grams per kg of dry matter), 3) control + organic acid(2%), 4) control + molasses(8%) and 5) control + (fibrinolytic enzyme+ molasses). Additives diluted in deionized water and applied with a hand held sprayer while forage samples were stirred manually. A similar quantity of deionized water was sprayed on the control forage. 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.

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).

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.