Pasture species and drought impact on milk yield 1. Milk yield responses in the Waikato

Milksolids (MS) production of Jersey cows grazing different pasture species mixtures over summer and autumn is described for the first two years of a 4-year trial. Four pasture mixtures were established after cultivation in autumn 1996, and were compared with existing ryegrass-white clover pastures. The mixtures were: (1) high-endophyte perennial ryegrass-white clover (2) tall fescue, phalaris, cocksfoot, white clover, red clover (3) same as (2) plus paspalum (4) endophyte-free ryegrass, timothy, white clover, red clover and (5) existing high-endophyte ryegrass, white clover. Milk tests were in January-February of 1997 and 1998. Cows were offered a single pasture allowance. Cows on high-endophyte ryegrass mixtures consistently produced low MS yields compared with those on tall fescue mixtures and endophyte-free ryegrass. In 1998, responses for cows grazing ryegrass-white clover (5 and 1) were significantly less than from tall fescue-based pastures (2 and 3) (0.74 vs. 0.86 kg/cow/day), and responses from cows on ryegrass/timothy based pastures (4), were better than for all others (0.96 kg/cow/day). Important determinants of the MS responses were the high rust infection and low contents of white clover in the high-endophyte ryegrass (1) pastures, and the high contents of red clover in the tall fescue and endophyte-free ryegrass-based pastures. Keywords: cocksfoot, cow grazing, irrigation, milk production, pasture quality, perennial ryegrass, phalaris, red clover, tall fescue, timothy, triple mix, white clover