Abstract
Abstract. The traits activity, milk yield, milk flow rate and electrical conductivity were analysed in preparation for automatic oestrus detection. Collection of data was performed on a commercial dairy farm and milking took place in a rotary milking parlour. Between February and December 1998 1,090,031 observations from 2,422 Holstein Friesian cows were accumulated. Around 30% of cows were milked thrice daily. For each trait and each cow a daily value was calculated. The fixed effects test day, parity, calving season, milking frequency, week of lactation and the random effect cow were considered in statistical analyses. With increasing number of parity, activity decreased and milk yield, milk flow rate and electrical conductivity increased. The milking frequency had significant influence on all analysed traits and for the effect calving season no consistent trend was found. All traits showed characteristic patterns during lactation. Between test days high variations were found for the trait activity. The remaining traits showed a steady level except for small fluctuations. Repeatability was 27.4% for activity and between 70 and 78.7% for the milk parameters. The repeatabilities verified the collected field data having a satisfying structure for application in automatic oestrus detection. The repeatability of the trait activity indicated high differences between and within cows. The right skewed distribution indicated the activity as a promising trait for further analyses.
Highlights
Income in milk production is directly influenced by reproductive performance
With exception of the fixed effect calving season for the trait activity, all fixed effects were highly significant for all traits (P
Lowest activity was measured for cows with calvings in 1997 and highest activity was measured for cows which calved in summer 1998
Summary
Income in milk production is directly influenced by reproductive performance. For example, increased calving intervals lead to a reduction of milk yield per cow and year, an increased number of replaced heifers, a reduced genetic impact on traits with economic importance and an increased amount of voluntary and involuntary culling (BRITT, 1985). An effective possibility to improve fertility performance is to intensify oestrus detection. Measurable traits promise successful oestrus detection results. Several traits for univariate and multivariate oestrus detection are presented in a literature review of FIRK et al (2001). In this investigation, the traits activity, milk yield, milk flow rate and electrical conductivity are analysed concerning the influence of the fixed effects test day, parity, calving season, milking frequency and week of lactation. In preparation for further analyses of automatic oestrus detection on the basis of field data, the reliability of data collection should be proved by calculation of the repeatability of the traits
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