Improved Lamb Performance Associated with Breeding for Alkaloid Reduction in Reed Canarygrass¹

Abstract

We earlier documented that indole alkaloid concentration of vegetatively propagated reed canarygrass (Phalaris arundinacea L.) clones was inversely associated with average daily gains of lambs and steers. Our objectives were to determine whether alkaloid concentration and type in two commercially available cultivars (‘Rise’ and ‘Vantage’) and in a low‐alkaloid, tryptamine‐carboline‐free strain (MN‐76) were associated with performance and health of grazing lambs. These seed sources of reed canarygrass were each planted in three pastures (0.27‐ha/pasture) in a randomized complete block design.Lambs that grazed MN‐76 gained from 51 to 95% more per day than did those that grazed Rise and from 14 to 87% more than did those that grazed Vantage during a 2‐year period. Rise contained a mean of 0.28 to 0.32% dry wt of a mixture of gramine and tryptamines‐carbolines, Vantage contained 0.20 to 0.33% gramine, and MN‐76 contained 0.09 to 0.12% gramine. The three grasses did not differ in most other quality components, but MN‐76 had up to 8% less cell walls and up to 9% more crude protein during the 2 years, as well as up to 28% more Ca during Year 1. The correlation between total indole alkaloid concentration of the grasses and lamb average daily gain was −0.97 in Year 1 and −0.66 in Year 2. Incidence of diarrhea among lambs was 4 to 26 times greater when they grazed Rise compared to Vantage or MN‐76.We conclude that the indole alkaloid concentration threshold in reed canarygrass at or above which lambs will show reduced gain is about 0.20% dry wt, that diarrhea in grazing lambs specifically caused by consumption of reed canarygrass is very likely due to tryptamine‐carboline alkaloids, and that MN‐76 is a biologically significant grass breeding advance.

Anti-quality factors associated with alkaloids in eastern temperate pasture

“…Total indole alkaloid concentration (gramine, tryptamines and carbolines) was inversely correlated with weight gains in lambs and steers (Marten et al 1976). Marten et al (1981) indicated that a total alkaloid concentration greater than 2.0 mg/g dry weight of forage reduces animal gains. Similarly, palatability was correlated with total alkaloid concentration (Simons and Marten 1971).…”

“…They reduce palatability of the grass, and thus serve as animal deterrants to prevent overgrazing (Marten et al 1976). The tryptamine and carboline alkaloids create digestive disorders resulting in a greater incidence of diarrhea in sheep compared to either the hordenine or gramine alkaloids (Marten et al 1981). Hordenine and gramine alkaloids simply reduce average daily gains.…”

ALKALOID CONTENT OF REED CANARYGRASS (Phalaris arundinaceae L.) AS DETERMINED BY GAS-LIQUID CHROMATOGRAPHY

“…The levels of gramine detected in these samples should not affect ruminant performance as Marten et al (1981) determined the values of indole alkaloids below 2 ^g g ' DM had no effect on the ruminant animal.…”

Studies on genetic variation in reed canarygrass, Phalaris arundinacea L. I. Alkaloid type and concentration

“…Animals had more diarrhea when grazing high-alkaloid plants and when grazing tryptamine-carboline-containing as compared with gramine-containing plants. MARTEN et al (1981) studied whether alkaloid concentration and type were associated with performance and health of grazing lambs, using cultivars with different alkaloid types and concentration levels. The strain MN-76 and the cultivars Vantage and Rise had mean alkaloid concentrations of 0.105,0.265 and 0.300 YO of the dry weight, respectively.…”