chemical composition, in vitro digestibility and fermentative gas production of kochia scoparia irrigated by water containing different level of salinity

introduction shortage of feedstuff is one of the important problems of animal nutrition in iran. salinity is a global problem worldwide in particular in arid and semi-arid zones such as iran. salinity is an important factor in the growth of plants. its initial effect to plants is through its effect in the availability of water to plants. halophytes have good ability to draw water from soils of low water potential due to their ability to maintain a salt balance comparable to the salt in the soil they are growing. lands in high irrigation districts are susceptible to soil salinization. soil salinization is the primary cause of productivity decline in highly developed and irrigated land schemes while the increase in soil and water salinity in many agricultural areas of the world has created major challenges in the production of food crops, it has also presented some new prospects for livestock agriculture. there are plants that grow under saline conditions, and historically, they have been opportunistically used as fodder for grazing livestock or as components of mixed rations to replace roughage. using of seawater for irrigation of this plant because of shortage of sweet water and for higher production of these plants was necessary for feedstuff. the aim of this study was evaluation of chemical composition, in vitro digestibility and gas production of kochia scoparia under six level of salinity including 10, 20, 30, 40, 50, 60 ds/m. materials and methods the kochia scoparia was irrigated by normal tap water (the control) and water containing 6 levels of salinity including 10, 20, 30, 40, 50, 60 deci siemens per meter (ds/m). the salinity was applied gradually in accordance with the plant growth advancement (2 ds/m increment per each irrigation period. oven dried (65◦c for 48 h) chopped samples were ground to pass through a 1-mm screen. the samples were analyzed according to the standard procedures for chemical composition (aoac 2000, van-soest et al. 1991). procedure of in vitro gas production was performed according to menke and steingass (1988). rumen fluid was obtained from three fistulated baluchi male lamb before morning feeding. the dm degradation data were fitted to the exponential equation p = a + b (1 - e-ct). the in vitro dry matter, ndf and organic matter digestibility were determined according to the arroquy et al (2005) procedure. test samples were incubated for different hrs and then filtered through the nylon cloth with the pore size of 44microns. the remaining materials were dried at 60 °c for 72 hrs and utilized for the subsequent analysis according to the procedure. in vitro gas production was completed according to the procedure described by menke and steingass (1988). each sample, both original forages and insoluble residues, weighing about 200mg, were put into 100ml calibrated glass syringes (fortuna®, häberle labortechnik, germany) together with 30ml rumen liquid media solution on a 1:2 ratio. syringes were incubated in a water bath at 39°c, where a transparent plastic lid with holes held the syringes upright. two blanks and a standard hay sample of known gas production were included in each run. results and discussion ndf content of kochia scoparia without salinity (irrigate with tap water) was higher than that for kochia samples irrigated with various levels of salinity. crude protein (cp) content of the control kochia sample (11%) was significantly (p<0.05) lower than the cp content of kochia samples irrigated with different levels of salinity. ash content of the samples from kochia under various levels of salinity were significantly (p<0.05) higher than that for the control sample. the results of in vitro gas production demonstrated the highest rate of gas production for the control sample. these results demonstrated that irrigation of kochia scoparia with saline water caused to decrease in rate of gas production was indicated 6 hrs after incubation in compared with control treatment (without salinity). although rate and level of gas production decreased with enhancement of salinity levels in irrigation. in vitro batch culture digestibility indicated that digestibility was increased with increasing the salinity levels. conclusion it was concluded that feeding quality of kochia scoparia increased following increasing the level of salinity therefore, it can be recommended as a suitable forage for many parts of iran with low rainfall and feed scarcity mainly in arid or semi-arid conditions.