What is the best way to feed a sow during lactation? It is a question that continues to be asked by researchers and producers alike. Survey data from a number of research studies show significant variability in average lactation feed intakes with ranges from 3.6 to 9.1 kg per day. Differences in genotype, herd size, lactation length, litter size and parity distribution can explain some of this variation. However, most of the difference is still due to feeding management.

From a nutrition perspective the energy, lysine and other nutrient requirements of a lactating sow depends on her weight, milk yields and the environmental conditions in the farrowing room. In a commercial setting, it is rare that we will know sow weight or milk yield, so we feed to appetite and ensure there is access to fresh feed at all times.

Research and practical experience tells us that the first week of lactation is absolutely critical. It is also where feed intake varies the most from farm to farm. Many farms have adopted a feeding programme that gradually increases sow feed allowance over the first 5 to 10 days of lactation. In many cases, this approach will reduce sow feed intake during the first week of lactation by 15 per cent, potentially leading to lower litter weaning weights and wean-to-oestrus intervals that are longer and more variable when compared to a more aggressive system of feeding (Aherne, 2004).

Restricted or gradual feeding in early lactation is commonly practised by those who believe that over-feeding sows in early lactation may cause udder congestion and hypogalactia, piglet scours and sow constipation, and may lead to sows 'going off' feed in mid to late lactation.

In a gradual feeding strategy, most lactating sows will be in an energy and amino acid deficit for the first week of lactation. Normally, this will not reduce milk production, but it will result in significant sow weight loss from both protein and fat. Clowes et al. (2003) demonstrated that if sows lose 9 to 12 per cent of their protein mass during lactation, they will have slower piglet growth rates and lower subsequent litter sizes (Table 1). Care needs to be taken with a gradual feeding strategy to ensure that the sows do not lose too much weight or condition.

Table 1. The effects of protein loss in lactation on sow reproductive performance
	Low	Moderate	High
Body protein loss, % of parturition mass	6.9	9.2	15.8
Follicles <4 mm diameter, % *	44.6	44.6	74.4
Follicles >4 mm diameter, % *	55.4	55.4	23.6

So what is the right lactation feeding strategy? It will vary from farm to farm but the major objective of farrowing room staff should be to maximize sow feed intake without upsetting the sow. Feed intake management is the key to optimizing litter growth and subsequent reproductive performance.

References

Aherne F.X. 2004. Feeding strategies for lactation sows. National Hog Farmer.
Clowes, E.J., Aherne, F.X., Foxcroft, G.R. and Baracos, V.E. 2003. Selective protein loss in lactating sows is associated with reduced litter growth and ovarian function. J. Anim. Sci. 81: 753-764.

February 2009