| dc.description.abstract | Lactation curves are a graphical representation of the milk production profile of a cow from parturition to drying
up. They provide information about the productivity of the cow and offer a means of explaining features of the
milk production patterns on the basis of the biology of mammary glands. 61,240 test day milk yield records
were used to evaluate the effect of non-genetic sources of variation in lactation curve traits. A univariate fixed
effect model was fitted to the data to evaluate the effect of the breed of the animal, parity/lactation number,
shape of the lactation curve, the interaction of the herd, year and season of calving (HYSc), age of the cow at
calving (in months) (CAGE) and days in milk at first test day milk sampling (DIM) on total lactation milk yield
(TMY), peak milk yield (MYmax), time of peak milk yield (DIMP) and persistency (S). All the sources of
variation fitted significantly influenced TMY. Breed, parity, HYSc and CAGE significantly influenced MYmax.
Parity, HYSc and DIM were significant for DIMP and S. Lactation curve traits were influenced by various
factors at varying thresholds. Therefore, these factors should be accounted for in a genetic evaluation process by
including them in the model as fixed effects. At farm level, management decisions such as selection and culling,
and feeding should made putting these factors into consideration. | en_US |
