---

In western Canada, durum wheat cultivars (Triticum durum) have low to moderate lev-els of seed dormancy and are susceptible to pre-harvest sprouting. The aim of this study was to evaluate the dormancy level of Canadian durum wheat cultivars and to identify tetraploid wheat accessions with elevated levels of seed dormancy. First, the level of seed dormancy and length of after-ripening of 17 North American durum wheat cultivars were evaluated. The plants were grown under field conditions in 1995 and 1996, harvested at maturity (Zadok’s Growth Stage 92, ZGS 92), dried at room temperature for one week, and assessed for level of seed dormancy over seven weeks of after-ripening at 20C. Seed dormancy was characterized by the extent of germination at 20C. The results indicated that five durum cultivars exhibited moderate levels of seed dormancy at maturity while the remaining cultivars were non-dormant. Likewise, a rapid loss of dormancy (within 2-3 weeks of after-ripening) was characteristic of all durum cultivars. In a second experiment, 78 accessions of T. turgidum, T. turanicum, T. carthlicum, T. polonicum, and T. durum from the USDA germplasm collection grown under field conditions in 1995 and 1996 were evaluated for seed dormancy with the idea of identifying potential sources of increased seed dormancy. At ZGS 92, eighteen accessions were classified as dormant. Accession 93-282 was the only highly dormant genotype in this study. The seven most dormant acces-sions, identified in two years of field tests, were tested for length of the dormancy period. Accession 93-282 was the only genotype that had a longer period of dormancy than the durum cultivar, Kyle. The intensity of seed dormancy was quantified at five germination temperatures. A dormancy index was calculated from germination data at 10 and 20°C. The dormancy indices of tetraploid accessions 93-62 and 93-177 were 37% higher than that of the durum cultivar Kyle.

---

The objective of this study was to test whether the stimuli of osmotic pressure (OP), VFA or pH in the omasum would affect the passage of digesta from the rumen and feed intake in sheep. Five experements were carried out. Different solutions with specific, OP, VFA concentration and pH were infused into the omasal body. Rumen digesta volumes and outflow rates (liquid and solid) were measured by pulse dosing of liquid and solid marker into the rumen. Feed intake, solid and liquid outflow rates from the reticulo-rumen were (not always significant) reduced by increasing the (OP) of the infusate in the range of 400 to 2000 mOsmol/kg which gave calculated omasal OP up to 480 mOsmol/kg (perfect mixing with digesta was assumed). Feed intake and fractional ruminal liquid out-flow rate were significantly increased by increasing VFA concentration of infusate in the range of 50 to 250 mMol/l or calculated omasal VFA concentrations up to 150 mOsmol/kg with the suggestion of a decrease above this range. pH in the range of 5.0 to 7.0 was with-out effect. Serum OP was not affected by any infusate. There was no or only a weak re-sponse to abomasal infusion compared with omasal infusion when the same infusate was used. The study demonstrated that omasum responds to changes in the composition of di-gesta. Increasing OP reduced DMI (dry matter intake) and reduced digesta outflow from the reticulo-rumen. Increasing VFA concentration increased DMI and liquid outflow, high VFA concentration decreased DMI and liquid outflow rate. It can be concluded that omasum has a role in the control of digesta outflow from the rumen.