In Vitro and In Vivo Ruminal and Physiological Responses to Endophyte-Infected Tall Fescue

Abstract

Relationships between alkaloid compounds in endophyte-infected tall fescue and ruminal metabolism were studied in two experiments. In the first experiment, different combinations of the pyrrolizidine alkaloids, N-formyl and N-acetyl loline, were incubated with ruminal fluid for 0, 24, or 48 h. Rate of disappearance of N-formyl and N-acetyl loline increased over time. After 48 h, disappearance of N-formyl loline and combinations of N-formyl and N-acetyl loline was greater than N-acetyl loline. Significant amounts of N-formyl and N-acetyl loline were metabolized and converted to loline. In the second experiment, abomasally cannulated sheep were fed increasing amounts of endophyte-infected feed to compare diet digestibility, alkaloid metabolism, and physiological responses. Total tract DM digestibility was greatest for the endophyte-free diet, as were ruminal and total tract ADF, ruminal NDF, and total tract CP digestibilities. N-Formyl and N-acetyl loline recoveries averaged 5% from abomasal contents and 0% in feces. Sixty-eight percent of the pyrrolizidine alkaloids recovered in abomasal contents had been metabolizable to loline. Ergot alkaloids administered in the diet were recovered (50 to 60%) in the abomasal contents, but recovery was only 5% in fecal collections. No significant differences occurred in the physiological parameters measured. Results indicate that response to endophyte-infected tall fescue may be influenced by ruminal metabolism.

Anti-quality factors associated with alkaloids in eastern temperate pasture

“…Chestnut et al (1991) found no difference in organic matter digestibility of E+ and E-tall fescue in steers and Harmon et al (1991) found no endophyte effect on dry matter and nitrogen digestibility in steers. Others, however, found that diets containing E+ tall fescue had reduced dry matter and organic matter digestibility in sheep (Hannah et al 1990, Fiorito et al 1991, Westendorf et al 1993, cattle (Aldrich et al 1993a), and rats (Larson et al 1991), which could be ambient temperaturedependent (Hannah et al 1990).…”

Journal of Range Management, Volume 54, Number 4 (July 2001)

“…Chestnut et al (1991) found no difference in organic matter digestibility of E+ and E-tall fescue in steers and Harmon et al (1991) found no endophyte effect on dry matter and nitrogen digestibility in steers. Others, however, found that diets containing E+ tall fescue had reduced dry matter and organic matter digestibility in sheep (Hannah et al 1990, Fiorito et al 1991, Westendorf et al 1993, cattle (Aldrich et al 1993a), and rats (Larson et al 1991), which could be ambient temperaturedependent (Hannah et al 1990).…”

Ergovaline, an endophytic alkaloid. 1. Animal physiology and metabolism

“…In vitro fermentation studies with tall fescue have demonstrated that feeding rats a whole seed that was previously incubated with rumen fluid is less toxic than feeding a seed not incubated, which suggests that rumen microflora reduced the concentration of toxic compounds (Westendorf et al 1992). Using in vitro fermentation of rumen fluid containing added pyrrolizidine alkaloids, Westendorf et al (1993) reported that pyrrolizidine alkaloids were degraded by rumen fermentation. Also using in vitro fermentation, Moyer et al (1993) demonstrated a linear decline in ergovaline in the soluble fraction, but an apparent increase in ergovaline associated with the insoluble fraction over a 48-h incubation.…”

“…Because of an absence of a commercial source of ergovaline and a lack of necessary analytical methods, there are limited data that provide direct evidence that ergovaline is absorbed intact and there are currently no in vivo data that confirm this occurrence. Looking at total ergot alkaloids, Westendorf et al (1993) reported that 50-60% of fed ergot alkaloids (tall fescue-derived) were recovered in the abomasal contents, indicating a significant reduction of alkaloids in the foregut. Westendorf et al (1993) went on to report only a 6-7% recovery of fed ergot alkaloids in faecal excretion.…”

“…Looking at total ergot alkaloids, Westendorf et al (1993) reported that 50-60% of fed ergot alkaloids (tall fescue-derived) were recovered in the abomasal contents, indicating a significant reduction of alkaloids in the foregut. Westendorf et al (1993) went on to report only a 6-7% recovery of fed ergot alkaloids in faecal excretion. This led to two major conclusions, namely that (1) there was a significant alkaloid reduction in the foregut and (2) the majority of the remainder appeared to be absorbed or metabolised in the intestines.…”