There are numerous studies on the Gys-1 allele frequency in horses of different breeds. It varies between 0.5 % for Morgan Horses, 3.4 % for Quarter Horses, 11.7 % for Southern German draft horses, 18 % for Haflingers, 24.2 % for Belgian draft horses and 34.6 % for Percherons. Recently, Norikers were tested for the mutated Gys-1 allele. It was found a carrier frequency of 34 %. With regard to clinical relevance of the Gys-1 mutation, there are few studies on draft horses, in particular the Noriker horse. In this study, the effects of the Gys-1 mutation on exercise tolerance and performance potential of three-year-old Norikers were investigated. Twelve Noriker stallions (9 wildtypes R/R, 3 heterozygous R/H) were examined in riding and drafting. The exercise tolerance was determined by salivary cortisol. The exercise intensity was estimated based on maximal heart rate (HRmax). HRmax in the three heterozygous horses was 171±10 beats/min after riding and 169±20 beats/min after drafting. Salivary cortisol concentrations of these horses were 3.21±0.82 ng/ml after riding and 1.23±0.62 ng/ml after drafting. The nine wildtypes had at riding HRmax of 163±19 beats/min and salivary cortisol concentrations of 2.40±1.40 ng/ml, while at drafting HRmax was 160±32 beats/min and salivary cortisol was 1.02±0.35 ng/ml. As a next step we investigated 15 performance characteristics from 188 horses with already tested Gys-1 genotype. Horses without Gys-1 mutation R/R (N=120) and heterozygous horses R/H (N=61) had a significantly better exercise capacity than homozygous colts H/H (N=7). Noriker horses with two H-alleles had slightly but significantly worse gaits in trot than R/R and R/H colts. In conclusion, there are some indications that Norikers with an H-allele are less resilient and have worse exercise capacity. Therefore, the working hypothesis stating that Norikers with the mutation are better performers at the annual HLP performing test was not proven.
Publication(s) resulting from University thesis:
Valach, A; Brem, G; Palme, R; Van den Hoven, R
(2017): Are results obtained in the stallion performance tests of Norikers affected by the presence of the Glycogen Synthase 1 mutant H-allele.
Wien Tierarztl Monat. 2017; 104(11-12): 323-329.