Effects of Application Rate of Poultry Litter on Chemical Composition and in vitro Gas Production of Rumen Content in Vermicomposting

Introduction Vermicomposting is the process of composting using various worms to decomposing vegetable, food waste, bedding materials and many organic waste materials. Many wastes and residues have been used to produce vermicompost. Using variety of left over products such as vegetable cuttings, food wastes and manure from cattle and chickens for vermicomposting can inhibit environmental pollution while producing valuable vermicompost. However, worms require specific conditions for activity and composting. Vermicast (worm manure) is the end product of the breakdown of organic matter by earthworms which usually applies as an organic and natural fertilizer. Due to appropriate protein and organic matter of vermicast or vermicompost, it is maybe possible to use vermicompost as a feedstuff in ruminant animals such as low producing cattle, sheep and goats. Then, the aim of the current research was to investigate the possibility of using rumen content which has been enriched with poultry litter as a decomposing material for worms and nutritive value of the produced vermicast for ruminants.
Materials and Methods Rumen content was treated with 0 (T1), 3 (T2), 5 (T3) or 7% (T4) of poultry litter in triplicate samples. Three boxes (65×35×30 cm) were made for each treatment and 8 kg of materials and 80 grams of worms (200 worms) were added to one of them. The boxes were kept for 75 days in a room with 25oC temperature and 65-70% of relative humidity. After 75 d, a sample of each replicated was chosen for pH and dry matter analysis. Another sample from each replicated was grounded and analyzed for chemical composition (crude protein, ash, crude fiber, neutral detergent fiber, acid detergent fiber) and gas production measurement. Gas volume was recorded at 2, 4, 6, 8, 12, 16, 24, 36, 48, 72 and 96 h of incubation. The kinetics of gas production was estimated using model: Y = A (1 – e−ct). Cumulative gas production at 24 h was used for estimation of metabolizable energy, net energy for lactation, short chain fatty acids and digestible organic matter.
Results and Discussion Vermicomposting efficiency was lower in T4 and higher in T2 and T3 treatments when compared with T1. The highest and lowest vermicomposting efficiency was in T3 and T4 treatments, respectively. Moreover, T3 treatment showed the highest crude protein and crude fat concentrations among the treatments. T3 treatment also had the lowest ash, crude fiber, neutral detergent fiber and acid detergent fiber concentrations among the treatments. The values of pH after 75 days were 6.76, 6.73, 7.10 and 6.57, respectively. The concentrations of crude protein for T1 to T4 were 16.50, 17.32, 18.84 and 15.45%, respectively. Also, the concentrations of neutral detergent fiber for T1 to T4 were 41.5, 42.5, 39.6 and 43.9%, respectively. Moreover, the concentrations of acid detergent fiber for T1 to T4 were 27.33, 28.50, 26.40 and 30.33%, respectively. Gas production was higher in T3 treatments compared with other treatments in all incubation hours. The cumulative gas productions for 24 h were 110.96, 116.24, 156.40 and 101.74 ml/g DM for treatments 1 to 4, respectively. Also, the cumulative gas productions for 96 h were 176.80, 210.58, 237.08 and 150.08 ml/g DM for treatments 1 to 4, respectively. T3 and T4 had the highest and the lowest potential of gas production among the treatments. The potential of gas production were 184.44, 225.65, 241.56 and 156.31 ml/g DM for treatments 1 to 4, respectively. The greatest and lowest metabolizable energy, net energy for lactation and organic matter digestibility were in T3 and T4 treatments, respectively. The calculated metabolisable energy values for T1 to T4 were 4.70, 4.87, 6.16 and 4.39 MJ/kg DM, respectively. The calculated net energy for lactation values for T1 to T4 were 2.26, 2.39, 3.33 and 2.04 MJ/kg DM, respectively. Organic matter digestibility values for T1 to T4 were 32.29, 33.33, 41.45 and 30.31%, respectively.
Conclusion The results of this study show that using up to 5% poultry litter in vermicomposting rumen content can produce vermicompost with great nutritive value (higher protein and lower fiber concentration) and high digestibility and energy content, which can be used in ruminants nutrition.