engleski

Role of species diversity and secondary compounds complementarity on diet selection on Mediterranean shrubs by goats

Goats foraging on Mediterranean shrubs containing secondary compounds (toxins) may consume a variety of shrubs that contain different phytotoxins to increase shrub intake and avoid toxicosis. We conducted eight experiments to examine whether goats offered different mixtures of shrubs containing different phytotoxins (tannins and saponins) would consume more shrub biomass than goats offered one shrub with a single phytotoxin (tannin or saponin). In the first three experiments, goats fed a mixture of three tannin-rich shrubs (Quercus ilex, Arbutus unedo, and Pistacia lentiscus) ate more foliage (P < 0.01) than goats offered only one shrub (23.2 vs.10.7 g/kg BW ; 25.2 vs.13.4 g/kg BW, and 27.9 vs. 7.9 g/kg BW), regardless of tannin concentration in individual shrub species. Goats also consumed more foliage (P < 0.01) when offered the same three tannin-rich shrubs than when offered the saponin-rich shrub Hedera helix in Exp. 4 (25.4 vs. 8.0 g/kg BW). However, goats offered a mixture of the same three tannin-rich shrubs consumed less foliage (P < 0.01) than goats offered a mixture of two shrubs containing tannins and saponins (Exp. 5-7): Quercus and Hedera (21.6 vs. 27.1 g/kg BW), Arbutus and Hedera (21.8 vs. 27.1 g/kg BW), and Pistacia and Hedera (19.7 vs. 22.0 g/kg BW). Comparison of intake of shrubs containing only tannins (Exp. 1, 2, and 3) or saponins (Exp. 4) to intake of shrubs containing both tannins and saponins (Exp. 5, 6, and 7) indicated goats consumed more total biomass (P < 0.01) when fed shrubs with both classes of compounds than with either tannins or saponins alone. Our results suggest goats can increase intake of Mediterranean shrubs high in secondary compounds by selecting those with different classes of phytotoxins. Simultaneous ingestion of shrubs containing tannins and saponins may promote chemical interactions that inhibit toxic effects of these phytotoxins in the intestinal tract. In addition to complementary interactions between tannins and saponins, biological diversity within Mediterranean maquis vegetation also plays a positive role in increasing shrub intake by goats.

Mediterranean shrubs; maquis; biodiversity; secondary compounds; tannins; saponin; goats

USDA, financiran od MZOŠ, Hrvatsko-Američki projekt.