The results of two recent studies on the effect of sow lactation weight loss on reproductive performance.

About 50 percent of all sows have a lower litter size in their second parity, compared with their first parity – and recent studies 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.

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

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. 

You can read more in the full version of the article in the magazine “Profitable Pig Production” issue 1, 2013.