Studies on the replacement policies in dairy cattle IV. Influence of seasonal variation in performance and prices.

J.A.M. van Arendonk

Research output: Contribution to journalArticleAcademicpeer-review

33 Citations (Scopus)

Abstract

The optimum policy for inseminating and replacing cows, taking into account seasonal variation in biological factors and prices, was determined by the dynamic programming technique. The decision to inseminate a cow was based on comparing the expected income when the cow conceived with that when the cow was left open and replaced at the optimum time in the remainder of the lactation period. In the model, cows were characterised by their lactation number, stage of lactation, time of conception, milk production level and month of calving. The month of calving influenced the production of milk, fat and protein, the probability of conception, feed costs and the price of milk, calves and culled cows. Under Dutch conditions, heifers calving from September to November yielded the highest income while those calving in May or June gave the lowest. The difference in expected income between October and June was 277 Dfl. The minimum production for insemination to be optimum was largely dependent on the time of year. Lowest production was found when insemination took place from February to April. The consequences of the differences in the optimum policy in months of calving for the average length of the calving interval and the probability of replacement during the first lactation, and the expected herd life of heifers, were quantified. Seasonal differences in production, feed costs and calf prices were the main sources of the differences in the expected income from heifers. The optimum policy for inseminating and replacing cows was greatly affected by the seasonal variation in production and, to a much smaller extent, in calf prices and feed costs.
Original languageEnglish
Pages (from-to)15-28
JournalLivestock Production Science
Volume14
DOIs
Publication statusPublished - 1986

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