Pig International - November 2012 - 20
Avoiding second parity slump
Sow studies found that weight loss from first lactation results in smaller
litter sizes and lower farrowing rates.
By Dr. Lia Hoving
About 50 percent of all sows have a
lower litter size in their second parity,
compared with their first parity - and
recent studies have indicated that
second parity litter size and litter
size could be related to subsequent
litter sizes and farrowing rates.
However, by altering management
and sow nutrition pig producers may
be able to reverse this trend and
improve second - and subsequent
- parity reproductive performance.
Sow body condition
Reduced reproductive production
in second parity sows has been related
to excessive weight loss during the
first lactation. During the past decade,
litter size and number of piglets weaned
have increased, as shown in Figure 1.
As a result, this has increased the
metabolic demands on first litter sows.
However, due to genetic selection on
lean grower and finisher pig traits,
sow feed intake has not increased.
This discrepancy can easily result in a
high sow weight loss during lactation
which can reduce follicle development
and oocyte quality. As a result,
subsequent farrowing rate, litter size
and litter quality can be affected.
The effects of weight loss on sow
reproductive performance seem to
have shifted over the years. Studies
from the 1980s and 1990s show that
lactation weight loss had a big influence
on weaning to oestrus interval, while
more recent studies show that sow
weight loss during the lactation affects
ovulation rate and embryonic survival.
TABLE 1: Effects of sow weight loss during lactation
on embryonic survival and development
1 (Patterson et al. (2011))
2 (Hoving et al. (2012))
Weight loss (kg)
Weight loss (%)
Days into gestation at slaughter
Ovulation Rate (n)
Number of embryos (n)
Embryonic survival (%)
Embryonic weight (g)
* Control: 90% ad libitum, restricted: 60% ad libitum; ** LWL = low weight loss (≤13.77%), HWL = high weight loss (>13.77%)
A,B signifi cance <0.05; § signifi cance < 0.1
The results of two recent studies on the effect of sow lactation weight loss on
The results of two recent studies
on the effect of sow lactation
weight loss on reproductive
performance are shown in Table 1.
Gilt feed intake studies
An image of sow loin muscle depth.
In the first study, gilts' feed intake
was restricted to 60 percent and 90
percent of ad libitum feed intake during
the last week of 20-day lactation. Feed
allowance was not different in the
weaning to oestrus interval and gestation.
In the second study, gilts were only
mildly restricted, which is different
from most experiments on the effects of
weight loss on subsequent reproductive
performance. Feed allowance (kg)
was calculated based on 1 percent of
body weight + 0.4kg per piglet, with
a maximum of 7kg. Maximum feed
intake was reached on Day 14 after
farrowing. Sow lactation length was 26
days. Results from both studies showed
that weight loss had a negative effect
on either embryonic weight (Study
1) or embryonic survival (Study 2).
The lack of effect on embryonic
survival in Study 1 could be due
to the relative low weight loss of
sows, compared with Study 2. This
indicates that weight losses of up to
11 percent probably do not influence
embryonic survival and eventually
litter size in second parity sows.
Piglet birth weight can, however,
be affected. The conclusion is that a
weight loss of more than 11 percent
negatively affected embryonic
survival and possibly embryonic
weight and should be prevented.
www.WATTAgNet.com | November/December 2012