|Estell, Richard - Rick|
Submitted to: Small Ruminant Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/20/2007
Publication Date: 1/15/2008
Citation: Rogosic, J., Estell, R.E., Ivankovic, S., Kezic, J., Razov, J. 2008. Potential mechanisms to increase shrub intake and performance of small ruminants in Mediterranean shrubby ecosystems. Small Ruminant Research. 74:1-15. Interpretive Summary: Goats and sheep are important consumers of the maquis vegetation that covers much of the Mediterranean grazing region. This vegetation consists mainly of shrubs, many of which contain toxic and/or aversive chemicals that have negative consequences for intake and productivity of the animals consuming them. Negative effects of these types of chemicals on livestock occur on shrub dominated rangelands throughout the world. One strategy that animals can use to increase intake of these shrubs is to diversify their diet, because different chemicals are detoxified by different mechanisms in the body. Spreading out detoxification over more metabolic pathways allows the animal to cope with a greater total intake of toxins through these complementary interactions. Because of the great biological diversity that exists in this region, complementary interactions between forages containing different classes of secondary compounds may occur that allow sheep and goats to utilize shrubby vegetation as a significant component of their diets. Feed additives such as activated charcoal, polyethylene glycol, and calcium hydroxide may also allow for greater shrub intake by decreasing absorption and/or increasing elimination of toxic chemicals. Goats generally have greater shrub intake than sheep, but their response to supplemental charcoal, PEG, and calcium hydroxide is similar. Biological diversity, species complementarity, and dietary additives all help sheep and goats cope with the high consumption of toxins while browsing shrublands.
Technical Abstract: Shrubby vegetation types called “maquis” and “garrigue” are widespread throughout the Mediterranean Basin, including the Adriatic littoral of Croatia. In Croatia and elsewhere, these shrublands represent traditional grazing areas and are a significant source of forage for small ruminants, particularly during the dry summer. Utilization of these Mediterranean shrublands is often limited by secondary compounds that adversely affect forage intake and animal health. Likewise, shrubs containing substantial quantities of secondary compounds dominate arid and semiarid rangelands globally. These secondary compounds reduce livestock productivity, cause significant toxicity and abortion problems, and reduce efficiency of use of rangeland shrubs worldwide. Feed additives (e.g., activated charcoal, polyethylene glycol, and calcium hydroxide) may be useful for enhancing shrub intake through decreased absorption and/or increased elimination of secondary compounds. The biological diversity of Mediterranean maquis vegetation may also positively influence shrub consumption by small ruminants. Consumption of combinations of shrubs containing varied classes of secondary compounds (e.g., tannins and saponins) may lead to complementary chemical interactions within the intestinal tract and/or post-absorption that reduces their toxic effects and/or increase efficiency of detoxification. Although goats consumed more total shrubs than sheep across experiments, both species responded similarly to supplemental charcoal, PEG, and calcium hydroxide.