novel approaches to expression and detection of oestrus in dairy cows

produced by the ovulatory follicle can influence oestrous expression. Lopes
et al., (2007) concluded that larger pre-ovulatory follicles had greater
oestradiol concentrations and were associated with pregnancy. Therefore
increased activity at oestrus could be associated with increased oestradiol
concentrations and increased probability of conception.
From a management point of view, greater activity at oestrus can influence
the probability of pregnancy because oestrous detection is more likely and
the timing of AI relative to ovulation will be more precise. However a larger
data set is needed in order to draw meaningful conclusions about increased
oestrous expression and the probability of conception from these results.
2.5 CONCLUSION
In conclusion, important factors affecting expression of oestrus have been
identified in this study. Parity, oestrous number post partum and milk yield
were inversely related to the activity increase at oestrus. Time of year of
oestrus also influenced the activity increase possibly related to photoperiod
or day length. These results have largely confirmed the results of other
studies into factors affecting oestrous expression. Herein they largely agree
with the general consensus of opinion on factors that affect oestrous
expression, although few studies into the expression of oestrus have been
carried out using activity monitoring, highlighting the novelty of this study.
Therefore cow factors have been identified that can affect oestrous
expression. Further work is required to investigate variation in oestrous
expression, between individual cows to investigate if there is genetic
variation in the activity increase at oestrus.
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