The Comparison of Degradability, Digestion and Microbial Fermentation of Siris Leaves or Silk Tree Instead of the Alfalfa in Cow and Buffalo of Khuzestan

Introduction Siris is a tropical legume. It has common names such as silk tree. Compositional studies indicated carbohydrates as major components and potassium was found in the highest amount and copper in the lowest. Siris leaf has high content of N (16 to 23 percent crude protein) and Ca, a low content of tannins and phenolic compounds. Levels of total tannins in the leaf of siris is 4%. The amino acids profile indicated that arginine and lysine are present in large amounts in seeds while glutamic acid and aspartic acid are higher in pods. Siris is an economically important plant for industrial and medicinal uses. This experiment was conducted to investigate the different levels (0, 50 and 100 %) of siris leave or silk tree instead of alfalfa on degradability parameters, fermentative and in vitro digestibility in cows and buffalo Khouzestan.Materials and methods The leave of siris were collected from shushtar and milled. Levels of 0, 50 and 100% leave replaced alfalfa in the diet. Rumen fluid was collected from fistulated cow and buffalo before the morning feeding. About 500 ± 10 mg experimental samples (1.0 mm screen) incubated with 35 ml buffered rumen fluid under continuous CO2 reflux in 100 ml vials for 2, 4, 6, 8, 10, 12, 16, 24, 48, 72 and 96 h, in a water bath maintained at 39°C. Cumulative gas production data were fitted to the exponential equation Y=B (1−e−Ct). Partitioning factor, microbial biomass, actually degradable organic matter was calculated. Digestibility of dry matter and NDF of the samples were determined using an in vitro procedure. Dry matter and crude protein degradability were measured by in situ technique using fistulated animals (fed 60% forage+40% concentrate). Samples put in the polyester bags and incubated in the rumen for 2, 4, 6, 8, 16, 24, 48, 72 and 96 hours. After the specific incubation periods, the bags immediately were hand-rinsed under cold tap water until clear, and dried in a forced-air oven (60 °C, 48 hour). Disappearance of DM and CP of samples from bags with incubation time were calculated using the equation of, P = a + b (1- e -ct), P= fraction degraded in the time t, a= soluble fraction, b= potentially degradable fraction, c= degradation rate and t= incubation time. The effective degradability was calculated using the equation of ED = a + (bc/(c+k). Data were subjected to analysis as a split plot design using the General Linear Model (GLM) procedure of SAS. Results and Discussion Dry matter digestibility of the diet containing 50% siris leave in Buffalo was 85.70 % and in cows, 82/94 %. Regardless of the type of treatment digestibility of dry matter and NDF was not significant between cow and buffalo. Regardless of the type of animal, the potential of gas production in the diets containing 0, 50 and 100 % siris leave was 175.05, 108.44 and 103.14 ml, respectively. The effect of diets containing leave on pf, microbial biomass, microbial biomass efficiency and organic matter digested was not significant. The efficiency of the microbial biomass in Buffalo (0.7281%) was higher than the cow (0.6308%). Slowly degradable fraction (b), constant degradable rate (c), potential of degradability (PD) and effective degradability (ED) of dry matter at 50 % leaf was the highest. Fraction a rapidly degradable (a) and effective degradability (ED) protein at 50 and 100 % the leave was the highest amount in compared to the control diet. In agreement with results, the researchers reported tropical legumes because of high quantity of protein and carbohydrate and lower fiber can be used as a suitable substrate for rumen microbial growth. Also legumes ability to provide required nitrogen, energy and vitamins for microorganisms. But presence of anti-nutritional factors such as tannin, saponin and oxalate in siris might be reduce fibrolytic enzyme activity and consequently fiber digestibility and fermentation. Conclusion: According to the results it ccan be concluded siris leaves or silk tree improved fermentation condition in the rumen, therefore can be used instead of alfalfa in the diet of cow and buffalo in vitro.