Production and physiological effects of perennial ryegrass alkaloids under thermoneutral conditions in Merinos

A confined feeding study was conducted to compare the production and physiological effects of feeding three doses of wild-type perennial ryegrass alkaloids via whole seed to Merino sheep housed under thermoneutral conditions (21°C, 50% relative humidity). Eighteen Merino ewe weaners (16 months; initial bodyweight 47 ± 1.94 kg) were offered Nil, Low (50 μg/kg liveweight ergovaline, 22 μg/kg liveweight lolitrem B) or High (100 μg/kg liveweight ergovaline, 44 μg/kg liveweight lolitrem B) doses of alkaloids for 21 days. Dry matter intake tended (P ≤ 0.072) to decrease in a linear manner with increasing dietary alkaloid concentration. Rectal temperature and respiration rate increased (P ≤ 0.002 for both) in a linear manner with increasing dietary alkaloid concentration. Oxygen consumption increased linearly (P ≤ 0.064) and quadratically (P ≤ 0.015) with increasing alkaloid concentration, being highest in the Low dose and intermediate in the High dose group. Plasma prolactin decreased linearly (P ≤ 0.002) with increasing dietary alkaloids. These data clearly show that animal production and efficiency are compromised when sheep consume perennial ryegrass alkaloids, even over a short period of time. This study indicates that a pyrogenic response can occur when alkaloids are consumed, even under thermoneutral conditions.