Background

The key issue for sow breeders is to wean a large number of healthy and fast growing piglets. Sow prolificacy has improved considerably during recent years. As a result the rearing capacity of the sow is often exceeded. The increasing litter size at birth causes a lower average birth weight. A reduction in the piglet birth weight means increased risk of higher pre-weaning mortality rate.

Estimates of pre-weaning mortality in Germany, Ireland, Netherlands, France and Denmark are 16.7, 8.9-9.9, 13.4, 12.7 and 13.4%, respectively. The most common reasons for high pre-weaning mortality rates are crushing, starvation and diarrhoea. Pre-weaning mortality due to starvation and diarrhoea is caused by malnutrition and malfunction of the gastrointestinal tract of the newly born pig.

A novel approach to reduce pre-weaning mortality is supplementing sow feed with probiotics, that is feed additives containing beneficial live micro organisms. By means of stabilising the intestinal flora of the sow, a stable intestinal flora can be established in the piglets. Trend in pre-weaning mortality Pre-weaning mortality is positive correlated with litter size. Taking Danish pig production as an example the average number of live born piglets per litter has increased from 11.5 in 1999 to 12.3 in 2003, mainly as a result of selection for litter size.

During the same period litter size at weaning only increased from 10.2 to 10.7. This corresponds to an increase in preweaning mortality from approximately 12 to 13% over the considered time period as shown in Fig. 1. Factors behind pre-weaning mortality About 75% of all mortality in pig production occur during the first week after birth, 85% during the first two weeks after birth and 95% during the first three weeks after birth. The gastrointestinal tract of the newborn piglet is rather immature, but develops very fast and goes through dramatic changes.

It has a relative growth in length, weight and volume over the first three weeks of approximately 200, 300 and 600%, respectively, and reach maturity around 12 weeks of age. Consequently, the gastrointestinal tract is a very stressed organ during the entire suckling period and has a high risk of developing lethal malfunctions.

Besides crushing the main factors affecting mortality of suckling piglets are insufficient nutrient supply and low ability to utilise the supplied nutrients. Energy reserves in the newborn pig are limited, since only about 2% of body tissue is fat. With increasing litter size the individual piglet weight is decreasing and the smaller the piglets are the less deposited energy they have. Disturbed digestion therefore effects increased mortality, caused by starvation.

The immature gastrointestinal tract of the newly born pig is specialised for ingestion and digestion of sow milk. Creep feed will typically not contribute as a major source of nutrients before three weeks of age, so the newly born piglet is almost entirely dependent on milk supply. Unfortunately, the supply of sow milk per piglet decreases with increasing litter size. Furthermore, to a large extent decreasing parity number of the sow decreases milk supply per suckling piglet.

The above factors illustrate why starvation is an important cause of pre-weaning mortality. Starvation will lead to piglets with reduced thresholds towards disease, especially diarrhoea originating from a disturbed intestinal micro flora. The upset balance of the intestinal flora can lead to a reduced utilisation of nutrients. Reduced gastrointestinal function increases the risk of starvation and scouring, with all their consequences.

Prevention of pre-weaning mortality

Improving nutrient supply, digestion and absorption are central factors in preventing pre-weaning mortality. The gastrointestinal system of the newborn piglet is directed towards digestion of sow milk. This makes optimal feeding of the sow an important factor in prevention of preweaning mortality. The intestinal flora of the newborn piglet originates from its environment. Influencing the composition of the microbial environment by using probiotics may result in early establishment of a beneficial intestinal flora.

The early colonisation results in a colonisation barrier function, which prevents that non desirable germs gain dominance. Since the microbial flora of piglets originates mainly from the sow, it appears to be reasonable that feeding the sow a probiotic supplement will benefit not only the sow, but piglets as well. A probiotic, BioPlus 2B, was used in four trials with an average of 96 sows per trial. The trials were performed at research centres or on commercial test facilities, and conducted under the supervision of independent study directors from universities or research institutions. The effects on animal production of the probiotic were measured against negative control. The trial duration was from two weeks before expected farrowing until end of lactation. Sows were fed according to local practice and the probiotic was used in the recommended inclusion rate.

Statistically significant results

On average the control groups showed a pre-weaning mortality rate of 11.4% while the probiotic groups obtained an average of 7.1%. In three of the four trials the reduction in pre-weaning mortality was statistically significant (Fig. 2). The presented average reduction in pre-weaning mortality of 4.3% units obtained by the use of a probiotic corresponds to an economic contribution of about €22-34 per sow per year depending on piglet prices.

The reduction of the pre-weaning mortality by approximately one third is due to a probiotic effect on the gastrointestinal tract. Probiotic micro-organisms have been transferred from the sow to her piglets during farrowing. The probiotic micro-organisms secured the first colonisation with a stable intestinal flora, and this was maintained through the piglets’ continuous contact with sow faeces. As a consequence of the reduced preweaning mortality the litter size at weaning was higher in the probiotic supplemented groups than in the control groups in the four trials (Fig. 3).

The number of live born piglets per litter and piglet birth weight was almost identical in the two groups of sows. With identical starting points but being reared in larger litters it could be expected that piglets belonging to the probiotic sow groups would obtain lower weaning weights than piglets in the control groups. In contrast, the trials showed that piglets from probiotic supplemented sows were on average 7% heavier at weaning than piglets from non supplemented sows (Fig. 4).

It is well known and has been observed in the control groups, that pre-weaning mortality rate is increasing with increasing litter size. One additional piglet weaned was associated with an increase of approximately 2.5% units in preweaning mortality.

Comparing litter size at weaning and pre-weaning mortality rate in the probiotic supplemented groups shows that pre-weaning mortality rates were almost independent of litter size at weaning. One additional weaned piglet increased the mortality rate by only 0.3% units versus the 2.5% units in the control groups (Fig. 5).

Conclusion

Supplementing sow feed with a probiotic from two weeks before farrowing and during lactation reduced pre-weaning mortality rate and thereby increased number of piglets weaned per litter. The presented trial results demonstrate that supplementing lactating sows with a probiotic feed additive can remove the negative effect of increasing litter size on weaning weight. The above effects of the probiotic are due to improved functionality of the gastrointestinal tract mediated through a positive impact on the intestinal micro flora. It has been documented that the use of a probiotic is an effective tool to improve the health and nutrition of the suckling piglet and the sow breeders’ economy.

References

Dagorn et al., 1998. INRA Prod. Anim., 11, p212-213.
Jultved, 2003. Report 0325, Nat. Com. for Pig Prod., Denmark, 2pp.
Lentfohr, 2002. Schweinereport 2002. 8pp.
Marion et al., 2001. Digestive Physiology of Pigs, p34-36.
Martin, 2003. http://www.teagasc. ie/publications/2002/pig2002/paper06.htm.
Milligan et al. 2003. Prev. Vet. Med. 18; 56(2), p119-127.
Sorensen, 2000. Internal report no. 129, DIAS, Denmark.
Udesen, 2002, Notat 0235, Nat. Com. for Pig Prod., Denmark, 2pp.

Source: Chr. Hansen - March 2006