Agriculture Reference
In-Depth Information
(Rodriguez-Martinez, 2007). Only a small proportion of the sperm cells reach the sperm
reservoir (Rodriguez-Martinez, 2007), the majority being phagocytised in the uterus
and either taken up by the uterine tissue or discarded through the vagina (Steverink
et al.
, 1998; Woelders and Matthijs, 2001). When ovulation approaches, endocrine and
physiological conditions change and sperm cells start moving from the reservoir into
the oviduct. When insemination time precedes ovulation, sperm cells may age and lose
their fertilising capacity. On the other hand, when ovulation time precedes insemination
time, oocytes have aged by the time sperm cells reach the site of fertilisation halfway
into the oviduct. Studies in which ultrasound was performed at 4 h intervals to asses
time of ovulation, revealed that optimal fertilisation results are achieved when sows are
inseminated in the 8 h preceding ovulation (Figure 17.2). In this interval, 90% of sows had
a 100% fertilisation rate. When insemination is performed earlier or later, fertilisation
results drop, but inseminations in the 24 h period before ovulation allow fertilisation of at
least 80% of the oocytes in more than 90% of the sows. Since ovulation rate is rarely lower
than 20 for sows, this would result in at least 16 good embryos on day 5 of pregnancy.
Nissen
et al.
(1997) also showed that insemination in the 24 h before ovulation resulted
in the highest farrowing rate and litter size.
In practice, insemination time cannot be based on ovulation time, since ovulation time
can neither be predicted nor visualised. Insemination time must therefore be based on
the signs of oestrus because sows ovulate during oestrus (see 'reproductive physiology'
section of the current chapter). Unfortunately, oestrus duration varies largely, both
between farms (on average 40 to 60 h), and within farms (from less than 24 h to more than
n=74
n=80
n=56
n=18
n=49
n=28
n=36
n=15
100
100
81-99
61-80
41-60
21-40
1-20
0
80
60
40
20
0
-48 to -40
-40 to -32
-32 to -24
-24 to -16
-16 to -8
-8 to 0
0 to 8
8 to 16
Time of insemination relative to ovulation (h)
Figure 17.2. Distribution of fertilisation results in multiparous sows dependent on the time of insemination
relative to ovulation. Fertilisation rate is defined as the percentage of embryos of the flushed oocytes and
embryos on day 5 after ovulation and presented as the percentage of sows with 0, 1-20, 21-40, 41-60, 61-80,
81-99 and 100% fertilisation in 8 h insemination intervals (Kemp and Soede, 2005).
