Onderwerp scriptie

Dairy calf characteristics and the association with performance later in life - Angeliek Coysman

Linking calf characteristics with later heifer- and cow performance is suggested to provide the opportunity to set up a list of early life indicators for better selection of the most promising replacement stock and a reduction of the maintenance costs, resulting in an improved functioning of the dairy sector.

To confirm this hypothesis the life stage performance was investigated and the link between life stage performance and lifelong performance was considered.  

This study used an existing database. Data was collected from 842 Holstein-Friesian cows by CRV (Coƶperatie Rundveeverbetering) and WUR Livestock Research. The Principle Component Analysis (PCA), was used to reduce numerous observed variables into a smaller set of components per life stage, explaining the largest percentage of variation of the original dataset. Correlations between pairs of measures were calculated with Spearman rank correlation, identifying possible relationships between performances throughout life stages, the relation to lifetime performance and also if performances were interrelated. 

Having access to a large dataset of cows, followed from birth to calving and onwards, was supposed to be a great opportunity to investigate lifetime traits. However, this was only true to a limited extend as all found correlations had low values. As calves, heifers and cows were exposed to different tests and circumstances per life stage, little correlation was found between behavioural and physiological performances. A small relation between consistent day to day activity patterns with fear was found in heifers and calves. The responses of the calves to the behaviour tests reflected their personality in terms of emotionality, stress responsiveness and fearfulness. Personality, however, only showed some negligible correlations with growth-, health- and fertility variables. Some small but definite relationships were found considering body dimensions and performance later in life. And lastly, all found relations between production, growth, health and fertility were negligible or small.  

As a result, no set of early life indicators, as a tool for the selection of promising replacement stock, could be derived from the results of this study due to small correlations between life stage- and lifetime performance.

Student: A Coysman

Supervisor: dr ir E Bokkers (APS) dr ir K van Reenen (ASG)

36 Ects