Differential dry matter production, nutritive value and grazing utilisation of perennial ryegrass varieties and mixtures evaluated within intensive grazing regimes

Significant differences in grazing efficiency were recorded between varieties evaluated under animal grazing, indicating that not all varieties are suited to intensive grazing systems. Tetraploid varieties displayed a clear advantage over diploids for grazing efficiency which was allied with the increased nutritive value (digestibility) and a favourable sward structure of tetraploids. The economic value for increased grazing efficiency was determined based on the additional herbage dry matter that a variety with superior grazing efficiency could utilise.

This resulted in a €44 difference between the most and least grazing efficient varieties. The performance of perennial ryegrass mixtures rarely exceeded that of the highest component monoculture but likewise never was inferior to that of lowest. <br><br>Routine variety evaluations must evolve to new farming practices and regulations. This thesis outlines a methodology for the assessment of grazing efficiency and its inclusion within the PPI which will allow farmers to increase levels of pasture utilisation on farm.