Influence of phytase enzyme on ruminal biogas production and fermentative digestion towards reducing environmental contamination

Abstract

Environmental impact of livestock production has received a considerable public scrutiny because of the adverse effects of nutrient run-offs, primarily N and P, from agricultural land harboring intensive energy livestock operations. Hence, this study was designed to determine the efficacy of dietary phytase supplementation on fermentation of a sorghum grain–based total mixed ration (TMR) using a ruminal in vitro digestion approach. Phytase was supplemented at three doses: 0 (control), 540 (P540), and 720 (P720) g/t dry matter, equivalent to 0, 2.7 × 10⁶, and 3.6 × 10⁶ CFU/t DM, respectively. Compared to P720 and the control, gas production was higher for P540 after 12 h (P = 0.02) and 24 h (P = 0.03) of fermentation suggesting a higher microbial activity in response to phytase supplementation at lower phytase levels. Correspondingly, dry matter degradability was found to have improved in P540 and P720 compared to the control by 13 and 11% after 24 h of incubation (P = 0.05). For ammonia nitrogen (NH₃-N), a tendency towards lower values was only observed for P540 at 24 h of fermentation (P = 0.07), while minimal treatment effects were observed at other fermentation times. The concentrations of total volatile fatty acids (VFA) were higher (P < 0.05) after 48 h of fermentation for P540 and P720 compared to the control (P = 0.03) by 10% and 14%, respectively. Ruminal acetate tended towards higher values in the presence of phytase after 12 h of fermentation (P = 0.10), but towards lower values after 24 h of fermentation (P = 0.02), irrespective of the phytase dose applied. A trend towards lower ruminal propionate levels was observed in the presence of phytase after 6 h (P = 0.10) and 12 h (P = 0.06) of fermentation, while no effects were found at other fermentation times. In conclusion, phytase supplementation has the potential to improve metabolic energy activity of rumen microorganisms and the use of feed constituents. Thus, phytase supplementation could help to reduce environmental contamination in areas of ruminant production.

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