The effect of initial spring grazing date and subsequent stocking rate on the grazing management, grass dry matter intake and milk production of dairy cows in summer
2006
Kennedy, E. | O'Donovan, M. | Murphy, J.P. | O'Mara, F.P. | Delaby, L.
The objective of this study was to investigate the effects of an early (February; F) or delayed (April; A) primary spring grazing date and two stocking rates, high (H) and medium (M), on the grazing management, dry matter (DM) intake of grass herbage and milk production of spring-calving dairy cows grazing a perennial ryegrass sward in the subsequent summer. Sixty-four Holstein-Friesian dairy cows (mean of 58 d in milk) were assigned to one of four grazing treatments (n = 16) which were imposed from 12 April to 3 July 2004. Cows on the early spring-grazing treatment were grazed at 5·5 cows ha⁻¹ (treatment FH) and 4·5 cows ha⁻¹ (treatment FM) while cows on the late-grazing treatment were grazed at 6·4 cows ha⁻¹ (treatment AH) and 5·5 cows ha⁻¹ (treatment AM). The organic matter digestibility and crude protein concentration of the grass herbage were higher on the early-grazing treatment than on the late-grazing treatment. The cows on the FM treatment had significantly (P < 0·001) higher milk (24·5 kg), solids-corrected milk (22·5 kg), fat (P < 0·01, 918 g) and protein (831 g) yields than the other three treatments. Cows on the FM treatment had a higher (P < 0·001) DM intake of grass herbage by 2·3 kg DM per cow per day than cows on the AH treatment, which had a DM intake significantly lower than all other treatments (15·2 kg DM per cow per day). The results of the present study showed that grazing in early spring has a positive effect on herbage quality in subsequent grazing rotations. The study also concluded that early spring-grazed swards stocked at a medium stocking rate (4·5 cows ha⁻¹; FM) resulted in the highest DM intake of grass herbage and milk production.
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