Report no. 816
16.05.2008
Heat during lactation
Abstract
Previously, lactating sows did not display heat before weaning.
There are several likely explanations of why many sows today
display heat during lactation; for instance the intense focus on
feed allocation in the farrowing facility, the increase in weaning
age, the increase in the use of nurse sows and the fact that many
pigs are moved late in the lactation period.
In this trial, heat in the lactation period was recorded in two
herds. In these herds, 12% and 16%, respectively, of the sows were
served before weaning. Blood samples collected pre-weaning revealed
that approx. 10% of the sows that were weaned without having been
served displayed heat during lactation. Overall, this demonstrates
that it would have been possible to serve approx. 25% of the sows
in the two herds pre-weaning had the procedures for heat control in
the farrowing facility been more efficient.
In herd 1, half of the 12% of the sows that displayed heat during
lactation were served after 24 days of lactation. In herd 2, half
of the sows that displayed heat during lactation were served by day
30. A sow that becomes a nurse sow later than 10 days after
farrowing is able to come on heat 4-7 days later. In herd 1, first
parity sows did not display heat as frequently during lactation,
whereas the 2-7 parity sows had the same occurrence of heat during
lactation. In herd 2, 1-3 parity sows were served an equal number
of times during lactation. Subsequently, the frequency
dropped.
In herd 1, the farrowing rate tended to be higher when the sows
were served in the farrowing facility compared with the sows that
were served after weaning. In herd 2, the sows served in the
farrowing facility had a significantly lower farrowing rate. When
the sows were served in the farrowing facility during lactation,
litter size was one pig smaller (significant) compared with sows
that were served immediately after weaning. The longer a sow had
been lactating when she was served, the larger the litter size.
Litter size was unaffected by whether the sow was weaned
immediately after service or whether she had had many days of
lactation after being served. If a sow is still willing to tend to
her piglets, it is recommended to let her stay in the farrowing
facility after service. In the two herds, 30% and 20%,
respectively, of the sows were weaned simultaneously with the first
service. It was not investigated whether the longevity of the sow
was affected by her being gestating and lactating at the same time.
It is unlikely that the few resources required by the embryos the
first two months of gestation influence resources required for milk
production.
Heat in the farrowing facility rarely follows the pattern of the
rest of the batch. If the sow is lactating for more than 40 days
(in total before and after service), the number of non-productive
days saved will pay for the reduction in litter size that is a
consequence of the sow being served during lactation.
The trial demonstrated that every fourth sow in the two herds
displayed heat before weaning. Almost half of the sows in heat were
not detected. In some cases, heat was triggered by factors such as
the sows functioned as nurse sows, were moved with the pigs to a
new pen (disinfection of the pen) or the pigs were weaned. Sows
that were used as nurse sows within ten days after farrowing
(two-step nurse sows) did not display heat more frequently during
lactation. Litter size drops by averagely 1-1.5 pigs when sows are
served during lactation. Litter size was unaffected by whether the
sow was weaned immediately after service or whether she continued
lactation while being gestating.
|
To the top