The effect of maturity on concentration and biological activity of protein precipitating polyphenolics in ground juniper is dependent upon species

Nutritional characteristics of Juniperus species are now well known and suitability as an abundant, low-cost feedstuff for ruminant animal production is a possibility. Juniperus species produce plant secondary metabolites including condensed tannins (CT) and volatile oils. Maturity of Juniperus species has been shown to affect the concentration of plant secondary metabolites produced. The objectives of this study were to determine the effects of Juniperus species (Juniperus ashei, J. monosperma, J. pinchotii and J. virginiana) and maturity on protein precipitating polyphenolic (PPP) compounds, their biological activity and relatedness of these effects to rumen digestibility characteristics. We found a species by maturity interaction for PPP (P < 0.001) and for the amount of protein bound (PB; P <  0.001) by PPP. Protein precipitable phenolic concentrations were greater (P < 0.001) for all species in the immature stage as compared to the mature stage except for J. virginiana, for which PPP were unaffected by maturity. The PB by J. pinchotii and J. monosperma was greater (P < 0.001) in the immature stage as compared to the mature stage whereas that of J. ashei and J. virginiana remained unchanged by stage of maturity. Linear regression within species and maturity of 48-h IVTDMD and total gas production on PPP suggested a positive correlation exists for immature J. virginiana (R2 = 0.71) and mature J. pinchotii (R2 = 0.68) for IVTDMD, and J. virginiana (R2 = 0.81) for total gas production. There was no relationship for PB within species and maturity of juniper and 48-h IVTDMD or total gas production, suggesting that biological activity of protein binding by PPP is unrelated to overall in vitro digestion of Juniperus species. The effect of maturity on concentration and biological activity of PPP in juniper is dependent upon species.