novel approaches to expression and detection of oestrus in dairy cows

1.3.2 Primary Sign of Oestrus
Standing to be mounted (see Figure
1.3) is the primary and definitive sign
that a cow is in oestrus and indicates
the period when the cow is in a
preovulatory and sexually receptive
state. As depicted in Figure 1.3 the cow
underneath is in oestrus as it is
allowing the other cow to mount it,
remaining stationary without
resistance. This is indicative of ‘true
oestrus’ (Orihuela, 2000).
Traditionally cows were visually
observed for standing oestrus at
Standing to be mounted
Figure 1.3 The primary sign of
oestrus; standing to be mounted,
the underneath cow remaining
stationary allowing the above cow
to mount (adapted from Van Der
Merwe, 2005)
periods throughout the day as an accurate form of detection for submitting
cows for AI at the correct time. Although duration and intensity of oestrous
behaviour has decreased (Dransfield et al., 1998), and not all cows display
overt oestrus (Harrison et al., 1990) and only 50% stand to be mounted
(Van Eerdenburg et al., 2002). Therefore not all animals that ovulate stand
to be mounted, which makes accurate oestrous detection increasingly
difficult. However, there are many secondary symptoms of oestrous
behaviour that cows display when they are sexually receptive.
1.3.3 Secondary Signs of Oestrus
There are many secondary signs of oestrus that facilitate detection (see
Figure 1.4a-f) which can be useful to supplement the diagnosis of oestrus
as the duration is often longer than the period of standing to be mounted
(Ranasinghe et al., 2009), which is only 1% of the whole oestrous period
(Senger, 1994). However, this poses problems in carrying out accurate
insemination as these signs and their duration are variable, unlike the
primary sign of oestrus, so they do not give an accurate time relative to
ovulation (Orihuela, 2000;Ranasinghe et al., 2009). The secondary
behaviours may be more useful in the modern dairy cow because she
expresses fewer signs of oestrus, with reduced standing behaviour (Dobson
et al., 2008). Although it has been reported that the duration of secondary
symptoms also decrease with reduced standing time (Yoshida and Nakao,
2005).
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