Does post-grazing sward height influence sward characteristics, seasonal herbage dry-matter production and herbage quality?

摘要

Extending the grazing season through the production and utilization of high-quality forage is a key objective in grassland-based dairy production systems. Grazing swards to a low post-grazing sward height (PGSH) is a strategy for improving grass utilization. A grazing experiment conducted in Ireland investigated immediate and subsequent effects of PGSH on sward production, utilization and structural characteristics. Swards were grazed to 2.7 cm (severe; S1) or 3.5 cm (moderate; M1) from 10 February to 18 April 2010 (Period 1; P1). From 19 April, each P1 paddock was halved and grazed to either 3.8 cm (S2) or 4.8 cm (M2), until 30 October (Period 2; P2). The first grazing rotation was +7 d on S1 swards compared with M1 swards (45 d), due to greater herbage utilization (+0.22). Herbage production during P1 was not affected by PGSH but a severe PGSH during this period reduced subsequent herbage production: 13.9 (S1) vs. 15.5 t dry matter (DM) ha.1 (M1) by the end of the study. Leaf proportion was increased (+0.10) on S2 swards compared with M2 swards, but M2 swards produced 1.2 t DM ha.1 more herbage during P2. Despite the relatively lower level of sward utilization obtained from moderate grazing in P1 (3.5 cm) and P2 (4.5-5.0 cm), such levels of PGSH increased DM production while maintaining sward quality, compared with severe grazing (2.7 cm in P1 and 3.5-4.0 cm in P2).