Effects of pistachio by-products on rumen enzyme activities

According to the Food and Agriculture Organization (FAO) Iran is the largest pistachio (Pistachio vera) producer in the world. Nevertheless, pistachio by-products (PBs) contain a high level of phenolic compounds and tannins, which can affect their utilization by animals. Tannins were primarily considered as anti-nutritional biochemical, however, in recent years, they have been recognized as useful phytochemicals for modulating rumen that they have different effects such as reducing protein degradation in the rumen. The mechanisms by which tannins reduce ruminal degradation of different dietary components are not entirely clear. The present study was conducted to evaluate the effects of PBs tannins on hydrolytic enzyme activities in ruminants.
An experiment was designed in three parts. The first was carried out to examine the effects of PBs tannins on attachment of rumen microorganisms to the substrate. PBs was processed with heat, moisture and poly ethylene glycol to create treatments with different tannin content and similar chemical composition. The treatments were incubated in nylon bags in the rumen for 12 hours and enzyme activities were determined in microbes attached to solid matrix. The second part was carried out to evaluate the effects of PBs tannins on the extracellular enzyme activities (rumen liquor). The PBs aqueous extract containing tannins were added to the culture medium and after 24 hours of incubation at 39 °C, enzyme activities were determined. The aim of the third part was to investigate the effects of PBs tannins on enzyme activities in cell-free extract of rumen liquor (inhibit or enhance the enzyme activities). At this part, after preparation ruminally cell-free extract, the PBs aqueous extract containings tannins were added to the culture medium, and after 24 hours of incubation at 39 °C, enzyme activities were determined.
The highest negative correlations there was between the activity of protease, carboxymethylcellulase (CMCase) and xylanase, with condensed tannins and then total tannins. While there was a positive correlation between amylase activity and various portions of phenolic compounds. In the first part of the experiment, the activities of protease, CMCase and xylanase were increased with decrease the quantity of tannins in treatments, for both micro-organisms that are tightly bound to the washed solid matrix and the fraction containing loosely plus tightly bound micro-organisms, but amylase activity were decreased for two compartments. Moreover the activities of protease, xylanase and amylase were lower in micro-organisms that are tightly bound to the washed solid matrix than the fraction containing loosely plus tightly bound micro-organisms. In the second part of the experiment, the activities of protease, amylase, CMCase and xylanase significantly decreased with increasing the levels of extract, which indicates PBs tannins have negative effects on extracellular enzyme activities (rumen liquor). In the third part by increasing levels of extract the activities of protease, amylase, CMCase and xylanase significantly decreased, which indicates PBs tannins have inhibition effects on hydrolytic enzymes.
Results of this study showed that PBs tannins can restrict proteolytic and fibrolytic enzyme activities in ruminants, which probably do it by reducing the access of microorganisms to substrate, effects on micro-organisms and release enzymes, and effects on the structure of extracellular enzymes and inhibit them.