Biological Significance of Reed Canarygrass Alkaloids and Associated Palatability Variation to Grazing Sheep and Cattle1
- G. C. Marten,
- R. M. Jordan and
- A. W. Hovin2
Total basic alkaloid concentration of reed canarygrass (Phalaris arundinacea L.) is negatively correlated with palatability (selection when a choice is offered) of the grass to ruminant animals. The significance of these alkaloids to ruminants not offered a choice of pasture forage remained unknown. Our objectives were to determine whether alkaloid concentration and alkaloid type differences among reed canarygrass genotypes affect animal performance, grass intake, and health of gazing sheep and cattle.
Replicated pastures representing two primary alkaloid types (gramine vs. tryptamine-carboline) and two alkaloid concentrations were primarily established from eight clones of reed canarygrass. During 1973 and 1974, these pastures were grazed by lambs and during 1975, by steers.
Total alkaloid concentration of the grass was highly negatively associated with average daily gains by lambs and steers (r= −0.91, −0.90, and −0.91 for 1973, 1974, and 1975, respectively). Alkaloid concentration was highly negatively correlated with an estimate of voluntary intake (r = −0.85) by lambs not offered a choice of reed canarygrass genotypes, but alkaloid concentration was not usually overtly associated with voluntary intake by steers. Animals had more diarrhea when grazing high-alkaloid plants and when grazing tryptamine-carboline-containing compared to gramine-containing plants. This physiological upset may have been a major contributor to reduced animal gains.
Breeding or managing reed canarygrass cultivars for lower alkaloid concentration per se, and breeding for tryptamine-carboline-free (gramine-containing) cultivars, should provide pasture that has improved animal performance potential. “Phalaris staggers” or “sudden death” were not incited in sheep or cattle grazing exclusively reed canarygrass that had very high indole alkaloid concentrations. This indicated that these disorders, thought to be caused by indole alkaloids in animals grazing Phalaris species, are very likely not caused by indole alkaloids alone.
We have conclusively demonstrated that palatability differences and their associated alkaloid concentration differences among reed canarygrass genotypes have a substantial biological significance for grazing lambs and steers.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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