UKnowledge > College of Agriculture, Food and Environment > Plant and Soil Sciences > IGC Proceedings > Proceedings XXII > Track 1-12 > 5
Track 1-12: Managing Seasonality in Grassland Quality and Quantity
Immediate and Carryover Effects of Post-Grazing Sward Height Imposed in Early Spring on Sward and Milk Production
Elodie Ganche, Teagasc, IrelandFollow
Luc Delaby, INRA, France
Michael O'Donovan, Teagasc, Ireland
Tommy M. Boland, University College Dublin, Ireland
Emer Kennedy, Teagasc, IrelandFollow
A grazing experiment was undertaken to investigate the immediate and carryover effect of post-grazing sward height (PGH) in early spring on sward and dairy cow production. Ninety Holstein-Friesian spring calving dairy cows were randomly assigned across 3 PGH treatments: 2.7, 3.5 and 4.2 cm from February 14 to April 24, 2011. Following the experimental period animals were managed similarly until the end of the lactation. Grazing to 2.7 cm during the experimental period reduced milk (-159 kg/cow; P < 0.01) and milk solids (-16 kg/cow; P < 0.01) yields and increased BW loss (+13 kg loss; P < 0.05) when compared to the 3.5 and 4.2 cm treatments which performed similarly. Grass utilisation (>2.7 cm) increased (P < 0.001) by decreasing PGH from 4.2 cm (0.74) to 3.5 cm (0.82) and further to 2.7 cm (0.94). During the carryover period (April 24 to November 13), cumulative milk (3542 kg/cow) and milk solids (281 kg/cow) yields did not differ between the experimental treatments. End BW was similar across treatments (503 kg). Total lactation performance of cows grazing to 2.7 cm in spring was -24 kg milk solids (P < 0.05) than the total lactation production of the 3.5 and 4.2 cm treatments (405 kg milk solids) indicating that cows offered a restricted pasture allowance in early lactation do not recover lost production. This study recommends a PGH of 3.5 cm in the first 2 grazing rotations to achieve a compromise between sward utilisation and animal performance in early spring while also ensuring high subsequent lactation milk production.