Animal safety of a tall fescue endophyte (Epichloë sp.) in a perennial ryegrass (Lolium perenne) host

ABSTRACT

Aims

To assess animal health and production in sheep grazing perennial ryegrass (Lolium perenne) infected with a tall fescue endophyte (Epichloë sp.).

Methods

Three replicates of pure perennial ryegrass pastures infected with AR501 tall fescue endophyte (AR501 HE), AR1, AR37 or standard endophyte (STD) (all >85% infection) and a low endophyte control (AR501 LE) were grazed by 10 lambs for 7 weeks during late summer/early autumn, 2017. AR501 HE and AR501 LE were in the same tetraploid cultivar and the remaining treatments were in the same diploid cultivar. Lambs were weighed on Days 0, 19, 37 and 48 and assessed for ryegrass staggers on a 0–4 tremor scale nine times from Day 13. On Days 14 and 20, rectal temperatures and respiration rates were measured in lambs grazing AR501 HE, AR501 LE and STD under heat load. Pasture samples from each treatment were taken regularly (8 times) for analysis of known endophyte secondary metabolites.

Results

Peak mean ryegrass staggers scores for lambs grazing STD and AR37 treatments were 3.9 and 2.7, respectively, indicating environmental conditions were conducive to toxicity. Lambs grazing AR501 HE showed no ryegrass staggers at any date. The liveweight of STD lambs was up to 6.6 kg less than some or all other treatments on Days 19, 34 and 48, but there was no evidence of a difference between the liveweight of AR501 HE lambs and AR501 LE, AR37 or AR1 lambs on any date. Rectal temperatures and respiration rates of STD lambs were higher than AR501 HE lambs by 0.2°C and 26 breaths/minute, respectively. Apart from lower rectal temperature of AR501 HE lambs on Day 14, there was no evidence of differences between the AR501 HE and AR501 LE lambs. N-Formylloline was the only loline present in AR501 HE herbage (350–860 mg/kg). Peramine in AR501 HE herbage (42–77 mg/kg) was greater than that in STD and AR1 herbage on five and seven of the eight sampling dates, respectively.

Conclusion

Lambs grazing AR501 HE showed no ryegrass staggers, exacerbated heat stress or suppressed liveweight gain compared with lambs grazing AR501 LE in a season when endophyte-induced toxicity was evident in STD and AR37 pastures. This suggests AR501 tall fescue endophyte does not produce toxic concentrations of secondary metabolites.

Clinical relevance

This study suggests that there are no secondary metabolites produced by the tall fescue AR501 endophyte-perennial ryegrass association which affect animal health or production.

KEYWORDS:

• Endophyte
• alkaloid
• ryegrass staggers
• heat stress
• liveweight
• sheep
• Epichloë
• tremorgenicity

Acknowledgements

The authors would like to thank AgResearch staff that contributed to this research, specifically Trevor Knight for assistance in the field, Leo Liu and Yulia Morozova for chemical analysis of herbage samples, Anouck de Bonth and Jan Sprosen for the development of immunoblots. For data on DNA testing of seed, we thank Ian Grigg (PGG Wrightson Seed). The authors are also grateful to Gerald Cosgrove and Alison Popay of AgResearch, and John Caradus of Grasslanz Technology Limited, for reviewing the manuscript. Funding for this research was provided by Grasslanz Technology Limited, PGG Wrightson Seeds Limited and the Ministry for Primary Industries as part of the “Seed and Nutritional Technology Development” Primary Growth Partnership Programme.

Notes

1 A.J. Popay, AgResearch, Hamilton, NZ,

2 A.J. Popay, AgResearch, Hamilton, NZ.

Additional information

Funding

Funding for this research was provided by Grasslanz Technology Limited, PGG Wrightson Seeds Limited and the Ministry for Primary Industries as part of the “Seed and Nutritional Technology Development” Primary Growth Partnership Programme.