Abstract
An in vitro gas production technique was used to study the effect of different levels of dicalcium phosphate (0, 0.037, 0.074, and 0.111 of 1 g DM) on gas production, rumen fermentation, dry and organic matter digestibility, and the activity of amylase and carboxymethyl cellulase (CMCase). A gas production technique was performed using rumen fluid collected from three fistulated Santa Ines sheep. Cumulative gas production was recorded at 3, 6, 9, 12, 16, 24, 30, 36, 48 and 72 h of incubation. Kinetics of gas production was fitted to an exponential model. Volatile fatty acids (VFA), Ammonia-N (NH3-N) concentrations, dry and organic matter digestibility and enzyme activity (CMCase and amylase) were determined at 24 h of incubation. The cumulative volume of gas production increased with increasing the level of phosphorus. Total gas produced at 72 h of incubation was higher for concentrate and hay (H) +concentrate (C). The highest value of individual VFA for H+C was at level 2 of treatment and for concentrate at level 4, while the addition of different levels of P was decreased the value of individual VFA for hay. No significant effects were observed on pH, NH3-N levels or truly dry and organic matter digestibilities with P addition. The specific activity of amylase and CMCase of sonicated the bottles contents after incubation time were significantly increased at level 2 for H, C or C+H.
Key words: Phosphorus, gas production, rumen fermentation and in vitro
