A comparison of temperate pasture species mixtures selected to increase dairy cow production and reduce urinary nitrogen excretion

Two short-term dairy cow grazing experiments in early lactation (spring) and mid-lactation (summer), were conducted in the Waikato region of New Zealand, to determine the effect of pasture species mixtures on urinary nitrogen (N) loss and milk solids production. The mixtures included four combinations of perennial ryegrass, tall fescue, narrow-leaved plantain and lucerne. All mixtures resulted in similar milk solids production within seasons. Where plantain (cv. Tonic) was included in the swards, apparent intake of plantain was 46-70% of daily dry matter intake and estimated water intake was increased by 4-21%. This led to significantly lower N concentrations of spot-sampled urine, by 38% in summer and 21% in spring. A decline in apparent N intake was also implicated in summer. The results show that effects on urinary N concentration, likely to be positive for reducing N leaching risk, can be achieved by including plantain in grass-lucerne swards, without detrimental effects on milk production.