Background
Condensed tannins (CT) are, prevalent in many plants and, may reduce ruminal protein degradation, which can increase intestinal protein flow when provided at moderate doses of 2 to 4 % CT in the dry matter (DM) [1]. However, Barry and Manley [2] reported that digestibility of all nutrients was reduced when sheep were fed high-CT (>5 % CT DM) containing Lotus pedunculatus. Commercial Quebracho CT added to a CT-free diet similarly reduced protein digestibility in a dose-dependent manner in ruminants [3]. However, goats are predominantly browsers and able to consume larger amounts of tannin-rich browse than sheep under similar conditions [4] without any signs of toxicity [5]. Recently, Min et al. [6, 7] have described the improvement of animal performance and average daily gain (ADG) in meat goats fed CT-containing ground pine bark (PB; 0, 15, and 30 % PB/kg of DMI) without any detrimental effects. Therefore, the source of CT, as well as its concentration, needs to be considered in studies involving protein degradation and plasma blood metabolisms. The objective of this study was to assess the effects of different levels of CT-containing PB on ruminal digestibility, nitrogen balance, and mineral retention in goats.