Economic Consequences of Different Calving Intervals

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Abstract
The study sought to answer the questions: when is the optimal time of conception for a given type of cow? and what is the economic cost of deviations from this optimum? The general approach was to model the incomes and costs over two consecutive lactations for a cow with certain given characteristics, namely calving month, parity and production level. The effect on net return per year (NRPY) of changing the time of conception, from 60 to 220 days postpartum, for such a cow was then studied. For all combinations of characteristics early conception was the most profitable. The effect on NRPY of a delayed pregnancy by one day varied from 0.3 Sw. kr to 11.6 Sw. kr depending on calving month, stage of lactation, parity and production level. A change in the two former substantially affected the loss in NRPY per day of delayed pregnancy. An increase in the two latter gave a small but consistent increase in the loss per day of delayed pregnancy. The seasonal variation in milk price had a large impact on the relationship between NRPY and time of conception.