Goats fed tannin-containing leaves do not exhibit toxic syndromes

The blood metabolic profile was examined in 2-3 year old non-lactating and non-pregnant Mamber goats consuming Quercus calliprinos (oak), Pistacia lentiscus (pistacia) and Ceratonia siliqua (carob) leaves to determine whether intake of tannin-rich fodder induces subclinical systemic toxicity. Total phenolic and condensed tannin content ranked in the order pistacia > oak > carob. Goats did not exhibit toxic effects following consumption of 10-23 g kg(-1) day(-1) of tannin-rich leaves. Metabolite blood concentrations did not differ from goats fed wheat straw, and were within the normal range. Certain serum metabolic indices that are known to be sensitive indicators of damage to the liver (gamma glutamyltranspeptidase, alkaline phosphatase, cholesterol) and kidneys (urea, uric acid, minerals) were within the normal range for goats. Thus, it appears that goats used in this study were well adapted to the nutritional environment and may consume large amounts of tannins (1.1-2.7 g per kg BW per day condensed tannins and 0.4-0.9 g kg(-1) BW day(-1) soluble phenolics) without suffering any ill effects.