Pasture-based dairying: challenges and rewards for New Zealand producers.

New Zealand dairying farm systems are principally pasture-based or seasonal supply. Features of these systems and their management are described, together with their advantages and limitations. The characteristics of reproductive management needed to attain satisfactory economic performance of these farm systems is discussed. The low-cost pasture-based seasonal system dictates that animals be bred over a very short period compared to many overseas countries and this is assisted in particular by the use of hormonal treatment for anoestrum. Oestrus synchrony is not widely used although uptake is increasing, particularly in large herds. The constraints imposed by the farming system represent a significant challenge to the application of embryo technologies as embryos must be recovered and transferred over the short period between calving and artificial insemination and farmers demand either a high pregnancy rate or a high value calf to compensate for the cost of the procedure and any delay in achieving a pregnancy.