Developing a Modified in vitro Gas Production Technique to Replace the Nylon Bag Method of Evaluating Protein Degradation of Alfalfa Hay in Ruminants

The present study was conducted to investigate the possibility of using a modified in vitro gas production technique in place of the nylon bag method to estimate protein degradability of alfalfa hay in ruminants. In the in situ experiment dacron bags were filled with 3 g alfalfa hay. This was incubated in the rumen of three ruminally cannulated Ghezel rams for the periods of 0, 2, 4, 8, 12, 16, 24, 36 and 48 h. At the end of the experiment, dry matter, organic matter and crude protein degradability (CPD) were calculated. In the in vitro experiment, buffered rumen fluid was prepared in a solution of 19:1 artificial saliva to rumen fluid, which was pre-incubated by rapidly fermentable carbohydrates for 4 h. After pre-incubation, 30 mL of the buffered rumen fluid were added to 100 mL syringes, containing the alfalfa sample, with 7.5 mg N. The samples were incubated for 2, 4, 6, 8, 12, 16, 24, 36, 48, 60 and 72 hours, after which net gas production was computed. In the third experiment, 25 grams of faeces were mixed with 50 mL of artificial saliva, which was then made up to 1 liter by adding more artificial saliva and filtered. Then, the suspension was pre-incubated for 4 h. After pre-incubation, the same steps used to measure gas production were conducted. Results showed that there were significant differences between gas production with rumen liquor and faeces suspension at 2, 4, 24, 36 and 48 h of incubation, while no significant differences were found at other incubation times. There was a close relationship between crude protein degradation at different times and amount of gas production using rumen liquor [CPD= 58.93 + 0.32 gas (r2=0.76, n=18)] and fecal suspension [CPD= 58.38 + 0.27 gas (r2=0.60, n=18)]. The results indicated that faeces suspension can be used instead of rumen liquor as the medium in the gas production method. Development of the gas production technique could result in reducing the need to use fistulated animals in feed evaluation studies.