Chemical Composition, Digestibility and in vitro Fermentation Variables of Mixed Silage from Different Levels of Paulownia Leaves and Forage Corn

Introduction: The dry climate and water scarcity in most areas of Iran caused to serious restriction in planting fodder. Therefore, it is very important to find new fodder sources to feed ruminants in order to reduce the ration costs. One of the new sources of fodder that may have a favorable nutritional value are plants of the Paulowniaceae family in China, East Asia and some parts of Iran. Several types of Paulownia are known in the world. These plants are known for their high growth rate and intense photosynthesis, which are specific to C4 plants, and with wide leaves with a diameter of about 90 cm. The commercial production of Paulownia wood generates a large quantity of leaves, which are typically used as natural fertilizers.At the age of about 6 to 8 years, the production leaf of each Paulownia tree reaches about 100 kg. When the leaves have a favorable nutritional value, they can be used as fodder in feeding ruminants. In Iran, there has been no study on the nutritional value of Paulownia leaves for use in animal feed. Therefore, the aim of this research was to investigate the chemical composition of Paulownia leaves and the chemical composition, gas production parameters, digestion and fermentation characteristics of the silages from the mixture of different levels of Paulownia leaves (Tebjoo hybrid variety) and fodder corn in vitro.Materials and Methods: The corn forage and Paulownia leaves (Tebjoo hybrid variety) were prepared. At first, the chemical composition of corn forage and Paulonia leaf samples was determined based on the conventional methods. Then, both forages were chopped into 2-4 cm sizes using a hand chopper for silage preparation. Experimental treatments included silages containing different ratios of fodder corn and Paulownia leaves (0:100, 75:25, 50:50, 25:75 and 0:100). The materials were compacted in the plastic containers and the silage period lasted 60 days. Determining the chemical composition of fresh fodders and the nutritional value of experimental silages including chemical composition, in vitro gas production and fermentation parameters, digestibility and enzyme activity were carried out based on a completely random design.Results and Discussion: Results indicated that dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), lignin, non-fibrer carbohydrates (NFC) and water soluble carbohydrates content of fresh Paulownia leaves were 266, 911, 173, 402, 201, 35.5, 86.4, 404 and 91.2 g/kg DM, respectively. The mentioned chemical composition in Paulownia silage were 273, 902, 164, 393, 191, 38.8, 74.5, 386 and 25.4 g/kg DM, respectively. With increasing the proportion of Paulownia leaf in silage, DM, CP, lignin, EE, ammonia nitrogen concentration increased linearly (P<0.05). However, OM, NDF and ADF decreased linearly (P<0.05). By increasing the ratio of Paulownia leaf to corn in th silage, in vitro gas production (GP) in 24, 36 and 48 h, GP potential (coefficient b) and short-chain volatile fatty acids concentration decreased linearly (P<0.05), although it linearly increased ammonia nitrogen concentration and microbial protein synthesis (P<0.05). The carboxymethyl cellulase and filter paper degrading activities decreased linearly with increasing the inclusion level of Paulownia leaf in silage (P<0.05). However, ruminal alpha-amylase and protease activity showed a linear increase (P<0.05).Conclusion: The present study showed that the Paulownia leaf of Tebjoo hybrid variety has a favorable nutritional value as a new forage source in animal nutrition. Also, the preparation of silages including different ratio of Paulownia leaves and corn is recommended for animal feeding in the conditions of significant shortage of protein resources in the country. Future research is warranted to investigate how Paulownia leaf affect ruminant performance.