Danish pig producers reached the milestone of an average 25 pigs per sow during 2006/7, and that’s the figure for 30kg pigs produced, not numbers weaned per sow. However, sow longevity continues to be a problem, with an annual sow replacement rate of over 50% and sow death loss at a staggering 15%. Producer organization Danish Pig Production (DPP) is carrying out research which, it is hoped, will lead to a substantial reduction in sow wastage, according to its Annual Report.

Overall breeding herd performance averaged 24.9 pigs/sow/year, with the top 25% of producers reaching 27.8. Liveborn piglets averaged 13.5, with the top 25% of herds producing 14.0 per litter. However, the average number of stillbirths per litter remains high, at 1.7 per litter. Weaning age is around 30 days and weaning weight averages 7.3kg.

The Danish breeding program continues to focus on improving the number of piglets alive at five days of age (called LP5) and this strategy has been producing excellent productivity gains. Over the 4 years to 2007, there was a 0.34 pig increase each year in Landrace sows and 0.38 in the Large White breed. Recently, there has been much more emphasis on increasing sow longevity, defined as the number of litters produced per sow lifetime, which is included in the breeding objectives. Because this cannot be defined until the sow is culled, other measures are being used as an indication of longevity. One of these is conformation, which has been used for many years. More recently, the ability of gilts to reach breeding after weaning their first litter has been used and this is highly correlated with sow longevity. The Danish report notes that the genetic traits for carcass lean content and daily gain are negatively correlated with longevity, whereas conformation is positively correlated. These relationships are now being used when estimating breeding values for longevity.

An increase in the incidence of shoulder ulcers in sows has prompted DPP to launch an investigation to find out whether there is a genetic variation or resistance to shoulder ulcers and whether the incidence can possibly be reduced by genetic means. In the meantime, the DPP report stated that it wants to see the number of reported shoulder ulcers halved and entered into an agreement with the Danish Veterinary Association to try to achieve this. The herd vet must regularly check the prevalence of ulcers and, if this is high or increasing, formulate an action plan with preventive measures. DPP is also looking at the influence of types of treatment, nutrition and design of housing on shoulder sores. The use of rubber mats has been shown to reduce the incidence and severity of ulcers.

A reduction in sow mortality is also a key aim of DPP research to increase longevity. It points out that a high death loss is not necessarily an indication of poor sow welfare in a herd. Many sows that have to be destroyed today would have been sent to slaughter five years ago, DPP notes. Sow mortality, it says, is reduced through prompt intervention, good prevention and consistent handling of unthrifty, sick and injured sows.

Hospital pens must be used early on to minimize the recovery period. It has initiated a demonstration project involving 20 farms around the country where data on sow longevity will be gathered and the measures that lead to improvements identified, so that this information can be communicated to producers. Hospital pens for sows are a key weapon in the fight for higher longevity. Trials have shown that it is possible to reduce the percentage of sows that die or have to be destroyed if there sufficient hospital pens available and a treatment strategy is drawn up by the vet. Preliminary results suggest that lameness was the primary cause (75% of sows) for transfer to a hospital pen. Sows stayed in the hospital pen for an average of 22 days and 80% of sows were able to return to the gestation pens or move to the farrowing house. Of the sows that were due for culling, there were 25% fewer deaths or destroyed sows.

With high and increasing litter size the use of nurse sows is very common in Denmark and DPP has investigated many aspects of this practice. A recently reported trial looked at whether the use of Oxytocin after foster piglets have been placed on the sow affected piglet growth and survival. One-step nurse sows were compared with two-step nurse sows and sows that only suckled one litter. Oxytocin was given ten minutes and three hours after new piglets were placed on the nurse sow. The first successful suckling occurred after 5.6 hours for the nurse sows that did not receive Oxytocin and 6.3 hours for the treated sows. The report notes that 50% of sows stood up during the Oxytocin treatment and suggested that this could be the reason why treatment did not help to make sows accept the piglets more quickly. Piglets weighed 100 grams less at weaning for every hour’s delay between introduction to the sow and suckling. However, there were no differences in survival rate or weaning weight between the two groups.

DPP has also compared the impact of being a nurse sow on subsequent performance, comparing one and two-step nurse sows with those that suckled just one litter. One-step nurse sows had an average 51-day period, two-step sows had 32 days and sows that were not used as nurse sows suckled for 27 days. Nurse sows took an average of one day longer to come on heat after weaning, which the authors suggest could be due to loss of condition in the long lactation period or because the sows showed heat during lactation. They also tended to have a lower farrowing rate but the one-step sows had a significantly higher subsequent litter size. The report suggests that the lower farrowing rate may be because nurse sows do not suckle for 3-12 hours after piglet introduction, which can induce a “weaning heat”. These sows have a much more variable onset of post-weaning estrus and therefore staff in the breeding area should be made aware of the nurse sows so they can pay special attention to heat checking and serving them when in standing heat.

Photo caption: SowShoulderPad-2 – Shoulder sores are a major problem in Danish breeding herds and pads like this one are used for protection