The role of condensed tannins in the nutritional value of mulga (Acacia aneura) for sheep

Abstract

Sheep were fed mulga (Acacia aneura) ad libitum and supplemented with 0, 12 or 24 g/day of polyethylene glycol molecular weight 4000 (PEG), with or without an additional supplement of 1.5 g/day of each of nitrogen (N), phosphorus (P) and sulfur (S) (NPS). Supplementation with either 12 g/day PEG or 24 g/day PEG increased dry matter intake by 56 and 78% respectively and clean wool growth per unit surface area by 166 and 178% respectively. Supplementation with 24 g/day PEG increased wool fibre diameter, linear growth rate and volumetric growth rate by 32, 29 and 143% respectively. Sheep receiving 24 g/day PEG retained more N (1.80 g/day) and S (254 mg/day) and digested more N (218 g/kg) and S (229 g/kg) when compared with non-supplemented animals. These parameters were further enhanced when NPS was supplemented in conjunction with 24 g/day PEG. Maximum precipitation (77%) of mulga condensed tannins (CT) occurred at a PEG to CT ratio of 0.7:l.

Effects of multinutrient blocks and polyethylene glycol 4000 supplies on intake and digestion by sheep fed Acacia cyanophylla Lindl. foliage-based diets

“…The important positive effect of PEG on CP digestibility observed in D2 (+110.8 and 25.19% compared to D0 and D1, respectively) confirmed results of the few earlier studies which dealt with adding PEG to acacia species such as Acacia aneura (Pritchard et al, 1992) and A. cyanophylla (Ben Salem et al, 1996). Tannins in feed can be deactivated by PEG to which they bind more strongly than to protein (Oh et al, 1980).…”

“…This trend is not consistent with several studies where PEG was shown to improve intake of tannin-rich forages (Pritchard et al, 1992;Silanikove et al, 1996). Ben Salem et al (1996) found that adding PEG (two parts of PEG/one part of tannin) to sheep fed 400 g of barley and acacia foliage ad libitum had no effect on acacia intake.…”

“…This exchange reaction may occur due to the stronger hydrophobic property of PEG. It has been suggested that the treatment of tannin-rich leguminous shrubs with PEG offered a viable technique to enhance their nutritive value and animal productivity (Pritchard et al, 1992;Silanikove et al, 1994).…”

Growth and carcass production of young farmed deer grazing sulla (Hedysarum coronarium), chicory (Cichorium intybus), or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture in New Zealand

“…Research, 1999, Vol. 42 10% in Lotus pedunculatus and mulga (Acacia aneura) have been shown to reduce VFI in sheep (Barry & Duncan 1984;Waghorn et al 1990;Pritchard et al 1992). However, the relationship between CT concentration and VFI of deer has not been established.…”

Effect of tannin from blackberry (Syzigium cumini) seed on in vitro rumen fermentation

“…With increasing demand for livestock products as a result of rapid growth of population and also for the supply of balanced nutritional food from livestock and feeding the millions and safeguarding their food security will depend on the better utilization of available unconventional feed resources. Many tree seeds contain anti-nutritional factors like polyphenolics and their presence at high level can significantly restrict intake and utilization (Pritchard et al 1992;Kumar, 1992) and also reduce nutritive value of feed (Reed et al 1990). …”