Use of a new instrument for the in vitro evaluation of ruminants feeds through gas production: preliminary study

The gas production technique has been applied, until now, only for scientific purposes and had relatively limited diffusion, since it was based mainly on the use of syringes and data collection was generally non-automated. The present study was conducted to evaluate a new instrument to be used in the “in vitro” measurement of gas production as an alternative to the method by Menke and Steingass (1988) to evaluate dairy cattle feed nutritive value. Starting from a patent of the University of Uppsala (Sweden), and with the Start up “Bioprocess Control”, a new instrument called “Gas Endeavour” was enveloped and adapted to ruminal fermentation studies. This instruments allow to: a) operate with 500 ml batches b) simulate the physiological rumen movements by continuous or discontinuous stirring; c) operate using from 2 to 8 g of dry sample or about 20 grams of fresh forage, depending on the substrate; d) measure and register continuously the amount of gas produced on 15 batches. Cumulative gas production profile of 24 hours interval were generated using the GAS ENDEAVOURVR at a temperature of 39 C under discontinuous stirring (20 sec on and 40 sec off). Van Soest buffer, macro-mineral and micro-mineral solution were used to obtain the fermentation medium while the Van Soest method was the reference for the amount of rumen fluid inoculum, medium and sample substrate, that were proportioned to batches of 400 ml. The fermentation trials were made on four corn silage samples having different composition (starch content: 32.00, CSA; 18.31, CSB; 21.57, CSC and 27.74%, CSD) and on a sample of alfalfa hay on three different fermenters with of 5 g of pre-dried sample. In particular, CSA has been tested 11 times while measurements on CSB, CSC and CSD were repeated four times to assess the reproducibility of the fermentation process and the repeatability of the resulting amount of gas (CH4 þ CO2) produced. The average amount of gas produced (ml/g DM), the relative standard deviation and the coefficient of variation (CV %) amounted to 199.94 ± 4.03 ml (CV 2.02%), 158.86 ± 4.69 ml (CV 2.95%), 176.09 ± 6.48 ml (CV 3.68%), 192.71 ± 5.88 ml (CV 3.05%). The alfalfa hay sample was repeated 5 times with a gas production (ml/g DM) equal to 141.09 ± 4.93 ml (CV 3.50%). Compared to bibliographic data, obtained with the use of syringes and other systems without automation, the GAS ENDEAVOUR equipment proved to be very reliable and performed highly repeatable measurement over time.