novel approaches to expression and detection of oestrus in dairy cows
novel approaches to expression and detection of oestrus in dairy cows
novel approaches to expression and detection of oestrus in dairy cows
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2.4 DISCUSSION<br />
The objective <strong>of</strong> this study was <strong>to</strong> identify fac<strong>to</strong>rs associated with the<br />
activity <strong>in</strong>crease at <strong>oestrus</strong>. Activity <strong>in</strong>creases at the time <strong>of</strong> <strong>oestrus</strong><br />
between 2 <strong>and</strong> 4 fold (Kiddy, 1977). In this study the <strong>in</strong>creases <strong>in</strong> activity<br />
were reported expressed as maximum activity at <strong>oestrus</strong> <strong>and</strong> the<br />
percentage <strong>in</strong>crease <strong>in</strong> activity from basel<strong>in</strong>e. There was a moderate<br />
positive correlation between percentage <strong>in</strong>crease <strong>and</strong> maximum activity.<br />
This could be expla<strong>in</strong>ed because some <strong>cows</strong> may have a high average<br />
basel<strong>in</strong>e activity but a small maximum activity <strong>and</strong> thus their oestrous<br />
<strong>expression</strong> is decreased, or vice versa where <strong>cows</strong> are generally <strong>in</strong>active<br />
yet at <strong>oestrus</strong> become very active. Several cow fac<strong>to</strong>rs were found <strong>to</strong> have<br />
a significant effect on maximum activity at <strong>oestrus</strong>; parity, oestrous<br />
number, time <strong>of</strong> year <strong>and</strong> milk yield (P