Chemical Composition, Gas Production Parameters and In Vitro Digestibility of Processed Grass Pea (Lathyrus Sativus) Residues with Some Chemicals

Agriculture residues are of a good potential for use as the energy source in ruminant diets. Lack of nutrient balance and high lignin rate have restricted the usage of these products in ruminant diets. Nutritional value of lignocellulosic compounds can be improved with the help of proper methods of processing. This research was conducted in order to investigate the effect of chemical processing on the nutritional value of grass pea (Lathyrus sativus) residues.

Grass pea residues were treated with sodium hydroxide (NaOH, 50 g/kg DM), calcium oxide (CaO, 160 g/kg DM), hydrobromic acid (Hbr, 60 ml/kg DM) and hydrogen peroxide (H2O2, 57 ml/kg DM). Chemical composition of the samples was determined using the standard methods of AOAC. Ruminal degradability trial was carried out using the nylon bag technique. Gas production test was used to estimate gas production parameters. In vitro digestibility of the samples was determined through the batch culture method.

Chemical processsing was effective on changing the chemical composition of residues (p<0.05). The treatments of CaO, H2O2 and NaOH increased the Ash. Except for Hbr, the other treatments reduced the amount of crude protein (CP). Chemical compounds reduced the amounts of neutral detergent fiber (NDF and acid detergent fiber (ADF). Gas production potential (p=0.0005) and rate, and related estimated parameters were lower in treated samples than control (p<0.0001). Dry matter digestibility (DMD) in HBr and CaO treatments, and organic matter digestibility (OMD) in CaO treatment decreased compared to the control (p<0.0001). The pH of culture medium was increasd by the treatments (p<0.0001), however ammoniacal nitrogen (NH3-N) was the same among the different treatments. The treatments of NaOH, H2O2 and HBr incresed the microbial biomass (MB) and its efficiency (p=0.0001, p=0.0018 respectively).

Overall, although processing decreased the cell wall compounds of grass pea residues, it did not have a positive effect on gas production parameters and in viro digestibility of the samples.