Open AccessProgress in breeding sheep for resistance to ryegrass staggers
Author(s) -
C. A. Morris,
N. C. Amyes
Publication year - 2007
Publication title -
grassland research and practice series
Language(s) - English
Resource type - Journals
eISSN - 2463-4751
pISSN - 0110-8581
DOI - 10.33584/rps.13.2006.3116
Subject(s) - lolium perenne , neotyphodium , biology , pasture , endophyte , perennial plant , heritability , flock , zoology , poaceae , veterinary medicine , agronomy , botany , genetics , ecology , medicine
Ryegrass Staggers (RGS) is predominantly a summer/autumn metabolic disorder of ruminants, caused by ingestion of the toxin lolitrem B. The toxin is produced by an endophyte (Neotyphodium lolii) found in perennial ryegrass (Lolium perenne). In clinical cases of RGS, animals experience neuromuscular uncoordination when under stress, e.g. when mustered by sheep dogs. Experiments with a standardised RGS scoring system show that resistance/susceptibility in sheep has a moderate/high heritability (0.37 ± 0.05). An AgResearch flock was established in 1993, with two lines bred for resistance (R) or susceptibility (S) to RGS. Annually, lambs are scored for susceptibility, when both lines graze together on high endophyte pastures, and are mustered by sheep dogs. In 2005 and 2006, 2% and 6.5% of R-line lambs, respectively, showed clinical staggers, compared with 94% and 91% of S-line lambs (P