The Centre of Biostatistics at the University of Limerick invites you to
its third seminar in the autumn series.

 

Noreen Quinn

Waterford Institute of Technology

"Modelling Lactation and Liveweight Curves for Irish Dairy Cows"

2:00pm, Wednesday 15th October

Room A2002


Abstract:
The purpose of this research was to examine techniques for estimating
the shape of lactation curves (for milk yield, milk constituents and
liveweight), which has the potential of reducing the cost of milk
recording in Ireland. The analysis was carried out on 15,506 lactation
records from commercial and experimental herds including both autumn and
spring calving animals. 'Goodness-of-fit' and adherence of the various
models to the assumptions of regression analysis were examined.  When
modelling milk yield, a severe problem of multicollinearity existed
therefore methods of reducing multicollinearity were investigated and a
new model was proposed that provided an acceptable level of accuracy in
representing the shape of the lactation curve for Irish dairy cows.
Numerous recordings were observed as being abnormal when examining the
fat and protein content in milk, therefore a method was proposed to
detect abnormal recordings of fat and protein content. As the ICBF  are
in the process of introducing an electronic do-it-yourself milk recorder
system, it will be necessary to have a scientific method of detecting
abnormal recordings in the near future. The method proposed is very
effective and abides by the guidelines outlined by ICAR . A model that
satisfied the assumptions of regression analysis and predicted the
actual content of the constituents to within 0.02% was also proposed. A
novel approach was used for modelling liveweight whereby splines were
used to find the dimensions of the data and principal component
regression was used to calculate the regression coefficients. This model
represented the shape of the liveweight curve and can be easily updated
for use by bio-economists.