Relationships between technical, economic and environmental results on dairy farms: an explanatory study.

Path analysis was used to model multivariate relationships between milk yield, reproductive parameters, replacement, milk contents, farm characteristics, net returns and N-surplus. Data from an economic information system and DHIA-data were available from 478 farms. Two models were constructed: one to analyze the gross margin per 100 kg of milk, and one to analyze N-surplus per ha. The first model showed that on the level of individual farms milk yield per cow in 305 days influenced reproductive parameters, the replacement rate and gross margin per 100 kg of milk. Besides milk yield, gross margin is highly dependent of quota per ha, concentrates per cow per year, percentage of protein in the milk and amount of silage bought per ha. Number of inseminations per pregnancy, births per cow per year, young stock per ha and the replacement rate had a small, but significant influence on the gross margin. In the second model N-surplus per ha was found to be highly dependent upon milk quota per ha and the amount of concentrates per cow per year. Weaker, but still significant relationships were found with replacement rate, young stock per ha and milk yield per co