Ionophores and nutrient digestion and absorption in ruminants.
This paper reviews the effects of feeding ionophores on nutrient digestion and absorption. In cattle, monensin and lasalocid increase apparent digestible energy by an average of 2.0 percentage units. In sheep, responses in digestible energy to ionophore feeding have been more variable, and neither monensin nor lasalocid have, on average, affected digestible energy. The effect of ionophores on fiber digestibility appears to depend on diet composition and source of fiber because both increases and decreases in fiber digestibility have been associated with ionophore feeding. Lasalocid and monensin reduce the percentage of starch digested in the rumen and increase the quantity of starch digested in the intestine. However, total gastrointestinal tract digestion of starch has generally not been affected by ionophores. Apparent nitrogen digestibility has been increased by ionophore feeding in a number of animal species. Apparent absorption of magnesium, phosphorus, zinc and selenium has been increased by ionophore supplementation. Absorption of calcium, potassium and sodium has been inconsistently affected by ionophores. Possible mechanisms whereby ionophores may affect nutrient digestion and absorption are discussed.
Spears
J W
JW
Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
D000818:Animals; D004063:Digestion / Q000187:drug effects*; D007408:Intestinal Absorption / Q000187:drug effects*; D007476:Ionophores / Q000494:pharmacology*; D008903:Minerals / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D012418:Ruminants / Q000378:metabolism*
D007476:Ionophores; D008903:Minerals; D009584:Nitrogen