1889
Bioassay activity of different tannin sources by gas production technique
Use of agricultural by-products, (such as pistachio hull, Pomegranate hull, Grape pomace, etc.), is often a useful way of overcoming shortage of animal feeds in many countries. These by-products contain tannins, causing reduction of protein utilization in ruminants. Tannin activity is affected by its source so this study was conducted to evaluate the effect of different sources of tannins on tannin biological effect by gas production technique. Each assay was repeated three times (runs). In all assays, 1 g of each sample was incubated in 120 ml serum bottles with or without 1 gr polyethylene glycol, PEG (MW. 4000), in triplicate. Rate and extent of gas production was determined by reading gas volumes at 2, 4, 6, 8, 12 and 24h of incubation time. Results showed that tea green leaves (1.44 in 2h after incubation ) and grape pomace (1.45 in 2h after incubation) had more active tannins than others in all of incubation times (P<0.05). In spite of same TP (180.18 and 182.5 gr/kgDM) and TT (115.35 and 108.38 gr/kgDm) content, pistachio hull and oak fruit tannins had different biological effect. Because there is no significant correlation between TP, TT and biological activity of tannins in all of incubation times. These results prove that independent of tannin content, different sources of tannins have different activities.
Keywords: tannin, bioassay, PEG