This paper examines the nutritional and veterinary effects of tannins on ruminants and makes some comparisons with non-ruminants. Tannin chemistry per se is not covered and readers are referred to several excellent reviews instead: (a) Okuda T et al. Heterocycles 30:1195-1218 (1990); (b) Ferreira D and Slade D. Nat Prod Rep 19:517-541 (2002); (c) Yoshida T et al. In Studies in Natural Product Chemistry. Elsevier Science, Amsterdam, pp. 395-453 (2000); (d) Khanbabaee K and van Ree T. Nat Prod Rep 18:641-649 (2001); (e) Okuda et al. Phytochemistvy 55:513-529 (2000). The effects of tannins on rumen micro-organisms are also not reviewed, as these have been addressed by others: (a) McSweeney CS et al. Anim Feed Sci Technol 91:83-93 (2001); (b) Smith AH and Mackie RI. Appl Environ Microbiol 70:1104-1115 (2004). This paper deals first with the nutritional effects of tannins in animal feeds, their qualitative and quantitative diversity, and the implications of tannin-protein complexation. It then summarises the known physiological and harmful effects and discusses the equivocal evidence of the bioavailability of tannins. Issues concerning tannin metabolism and systemic effects are also considered. Opportunities are presented on how to treat feeds with high tannin contents, and some lesser-known but successful feeding strategies are highlighted. Recent research has explored the use of tannins for preventing animal deaths from bloat, for reducing intestinal parasites and for lowering gaseous ammonia and methane emissions. Finally, several tannin assays and a hypothesis are discussed that merit further investigation in order to assess their suitability for predicting animal responses. The aim is to provoke discussion and spur readers into new approaches. An attempt is made to synthesise the emerging information for relating tannin structures with their activities. Although many plants with high levels of tannins produce negative effects and require treatments, others are very useful animal feeds. Our ability to predict whether tannin-containing feeds confer positive or negative effects will depend on interdisciplinary research between animal nutritionists and plant chemists. The elucidation of tannin structure-activity relationships presents exciting opportunities for future feeding strategies that will benefit ruminants and the environment within the contexts of extensive, semi-intensive and some intensive agricultural systems. (c) 2006 Society of Chemical Industry

Unravelling the conundrum of tannins in animal nutrition and health

http://www.anuragaja.staff.ipb.ac.id/files/2011/01/Riaz_2014_LS_Intake-digestibility-ruminant_meta.pdf

Voluntary feed intake and digestibility of four domestic ruminant species as influenced by dietary constituents: A meta-analysis

The in vivo digestibility and the rates of degradation and passage of alfalfa hay (AH) and vetch straw (VS) were compared in three Granadina goats and three Segurena wethers fed at approximately maintenance level, using a change over design. The nylon bag technique was used to estimate the fractional rate of degradation of the feeds in the rumen. The fractional outflow rate of hay and straw particles was determined with chromium as a marker. No significant differences in the digestibility coefficients of nutrients between animal species were found. Nitrogen retention expressed as coefficients of both nitrogen intake and digested nitrogen was lower (P < 0.01) in goats than in sheep when VS was offered. There was no significant difference betwen goats and sheep in the effective degradability (measured at outflow rates in the range of 0.027 to 0.032 h−1) of dry matter (DM) for either forage. However, the effective degradabilities of the neutral detergent fibre (NDF) and crude protein (CP) of VS were lower (P...

A comparative study of nutrient digestibility, kinetics of digestion and passage and rumen fermentation pattern in goats and sheep offered medium quality forages at the maintenance level of feeding.

Complex interactions between livestock, trees and pasture occur in silvopastoral systems. Between trees and pasture, competition for soil resources (nutrients and water) occurs, becoming especially relevant when one of them is in scarce supply. Trees reduce light and water reaching the understorey layers according to tree density and canopy size. However, they may ameliorate extreme climatological features (reducing wind speed and evapotranspiration, and alleviating extreme temperatures), and improve soil properties, for example, deciduous tree litter may contribute to increased pH and soil nutrient concentrations. During tree establishment, there are generally negligible effects on pasture, irrespective of tree type. However, there is a decline in pasture production and nutritive value under shade with increasing tree age and higher stand density. Under the same conditions, deciduous trees affect pasture later (extinction point of pasture occurs at 85% of canopy closure) than evergreen trees (about 67% for Pinus radiata D. Don). This is mainly because deciduous trees have a leafless period that enables pasture recovery, and their litter smothers pasture less intensely because of its relatively fast decomposition. Silvopastoral studies conducted in New Zealand are reviewed to discuss these effects, and differences in the effects of evergreen and deciduous trees are shown using the examples of P. radiata, and Populus and Salix spp. respectively, which exist in many temperate countries. Future research needs are outlined.

Silvopastoralism in New Zealand: review of effects of evergreen and deciduous trees on pasture dynamics

We examined the effects of wild ungulates (deer and elk) and domestic sheep browsing on the growth, structure, and reproductive effort of two common willow species, Salix boothii and S. geyeriana, in a montane northeast Oregon riparian zone. With the use of exclosures, large herbivore effects on willows were studied in an area browsed by native mammals only and an adjacent area in which domestic sheep also lightly grazed during summer months. Growth variables were repeatedly measured on individual plants over a 5-year period to understand physiognomic and flowering responses of native willows to different levels of browsing pressure. At the beginning of the study, all willows were intensely browsed but were significantly taller in the area browsed only by native mammals than in the area also grazed by sheep (69 versus 51 cm, respectively). Willows inside exclosures responded with pronounced increases in height, crown area, and basal stem diameters while the stature of browsed plants outside exclosures stayed constant or declined. In the area browsed by both sheep and wild herbivores, the size of browsed plants remained at pre-treatment levels (<60 cm in height) for the duration of the study. There was no significant difference in growth rates of enclosed willows, indicating that current herbivory was the primary cause of growth retardation in the study area. Foliar area was strongly correlated with basal stem numbers for enclosed plants but much less so for browsed plants. Willows inside exclosures had more than twice as much foliar area per stem. Stem diameters were a positive function of crown area: stem-number ratios, suggesting lower photosynthetic potential was correlated with diminished radial growth among browsed plants. No flowering was observed until 2 years after exclusion when plants inside all exclosures and browsed willows in the wild ungulate area responded with a large pulse in flowering. Browsed plants in the sheep + wild ungulate area did not flower. The number of catkins produced per plant was significantly associated with willow height and plants <70 cm in height did not flower, thus suggesting a size threshold for reproduction in these species. Our results suggest that even relatively light levels of domestic livestock grazing, when coupled with intense wild ungulate browsing, can strongly affect plant structure and limit reproduction of riparian willows.

Cumulative effects of wild ungulate and livestock herbivory on riparian willows

Voluntary intake and apparent digestibility of tree willow (Salix matsudana Χ alba) and of osier willow (Salix viminalis) were measured with male sheep and goats and voluntary intake only with male deer. Both willow species had been selected for extremely rapid growth, and were grown in coppices on high fertility soil. In a first experiment spring primary growth of both willows was fed to sheep, goats and deer in early summer, whilst in a second experiment summer regrowth (i.e. secondary growth) of osier willow was fed to sheep and goats in autumn.Although the ratio of readily fermentable to structural carbohydrate (0·51–0·70) and total N concentration (18–24 g/kg D.M.) in primary growth of the willows was less than normally found in high quality fresh temperate forages, the values were similar to those of many dried forages normally used as supplements. Averaged over sheep and goats, voluntary intake of digestible D.M. was 22% less for osier than for tree willow, this being associated with higher concentrations of lignin (197 ν 182 g/kg D.M.) and of condensed tannin (66 ν 29 g/kg D.M.) in the osier willow. The lower digestible dry-matter intake was attributable to both lower voluntary intakes and lower digestibility of the D.M. (0·57 ν 0·64). Both voluntary intake and apparent digestibility of secondary growth willow were lower than that of primary growth.When expressed as functions of the amount required for maintenance, voluntary metabolizable energy intake of goats was approximately double that of sheep, both for primary growth (2·2 ν 1·1) and for secondary growth (1·8 ν. 0·7) willow. This was attributable to consistently higher voluntary D.M. intakes/kg W0'6 by goats, and to a trend for higher digestibility than sheep, which attained significance in Expt 2but not in Expt 1. The ratios of dry-matter intake/kg W075 per day for sheep: deer: goats fed primary growth willow were 1·0:1·5:1·9, with deer thus being intermediate between the other two species. There were no differences in voluntary intake (g/kg W0·75 per day) of sheep, goats and deer fed a high quality lucerne hay.It was concluded that willows grown during spring and summer could adequately be used as supplementary feed during summer droughts and that willow could be used most effectively if fed to goats, followed by deer, with sheep being the least efficient. Tree willow is a preferred choice to the osier willow used here, and it was further concluded that like Lotus pedunculatus, high concentrations of lignin and condensed tannin, both of which are produced by the same biochemical pathway, are likely to be limiting nutritive value of the more leafy osier willow.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0021859600082745

Sharon M. McCabe

Papers

Nutritive value of willow (Salix sp.) for sheep, goats and deer