Concentration and composition of condensed tannins in leaves from fodder trees and shrubs in Pakistan

Abstract Background The lack of dependable, high‐quality forage and animal feedstuffs in many areas of the world hampers livestock production. In these regions, farmers often rely on native fodder tree and shrub leaves as a forage source for their animals with little or no information available on nutritional factors of these feedstuffs. In addition, there is a growing need to improve nitrogen use efficiency ( NUE ) in ruminants, especially in agricultural areas where livestock feedstuffs are limited in quantity and of lower quality. Condensed tannins ( CTs ) show capability of protecting protein from degradation during both the ensiling process and rumen digestion, producing greater rumen undegradable protein translating into higher ruminant livestock productivity. Results Determination of the concentration of CTs in the leaves of four fodder tree species ( Salix nigra , Salix alba , Populus nigra , and Elaeagnus angustifolia ), and two shrub species ( Hippophae rhamnoides and Rosa webbiana ) across seasons from three locations in Pakistan is detailed below. The highest levels of CTs were found in S. nigra and S. alba (seasonal averages of 17.9 and 18.5 mg/g, respectively) and were targeted for purification and characterization. 1 H– 13 C heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra of purified CTs indicated the following composition for S. nigra , procyanidin/prodelphinidin ratio = 59/41; cis / trans ratio = 59/41; estimated mean degree of polymerization (mDP) = 8.1. For S. alba , procyanidin/prodelphinidin ratio ≥99/1; cis / trans ratio = 85/15; estimated mDP = 6.9. The CT content of both Salix species trended higher with seasonal growth, with the CT content of S. nigra across seasons statistically significant. The CT content in P. nigra and H. rhamnoides trended lower across all three locations tested but did not reach the level of statistical significance. Insignificant levels of CTs were detected in E. angustifolia and R. webbiana . Conclusion Based on CT literature reports, S. nigra and S. alba likely contain adequate CT levels to bolster NUE in ruminants without exhibiting a detrimental effect on dry matter intake.