Do your sows eat enough in lactation? Their appetite is driven by a wide range of influences, but one of the most important factors is known to be the palatability of the feed. An off-taste due to mouldy grains will certainly mean that less is consumed.

It is an aspect especially worth bearing in mind at the moment, in the light of reports from various parts of the world that the latest harvest includes above-average proportions of grain contaminated by fungal toxins. The possibility of a mycotoxin alert had been raised earlier because climate conditions in 2008 were seen as often suitable for promoting mould growth.

Moulds in dietary components have long been described generally as likely to reduce feed intake. The difference today is that we have access to scientific evidence in support of that claim. Some of the most eye-catching examples have emerged from work led by Professor Trevor Smith in the department of animal and poultry science at the University of Guelph in Canada. 

Toxins in grains

This work has looked closely at the effect of feed-borne Fusarium mycotoxins on the consumption of feeds and the performance of the animals involved. Remember here that the term Fusarium covers an assortment of fungal types whose toxins are found commonly in the grains fed to pigs. In fact they share with aflatoxins the distinction of being the most abundant of the mycotoxin varieties encountered in temperate zones worldwide.

Consider, too, the fact that the two animal species most sensitive to a Fusarium contamination in their feed are pigs and horses. Investigators say such a sensitivity is unfortunate in several ways, not least because the contaminants are often difficult to detect and therefore to control. The long list of differing compounds that form this toxins group makes detailed analysis so complicated that the standard approach has become to use the compound called vomitoxin or DON (deoxynivalenol) as the marker for all others.

Some Guelph measurements using DON in the feed for lactating sows have underlined how greatly the daily feed intake of the sow can be reduced, as Table 1 shows. Other testing found that the reduction was lessened, but not totally alleviated, by including a mycotoxin adsorbent in the feed.

This was where the sows received the experimental feeds for a period of 21 days after farrowing. A similar DON inclusion in the diet given for the three weeks before sows farrowed was less influential on the amount of feed eaten daily (down to 2.12kg from the 2.41kg measured for controls), but there was still a significant impact on the sow's weight gain in that the contaminated feed meant an average increase of only 0.62kg per day whereas the control feed gave 1.14kg daily.

From Table 1, a sow in a 3-weeks lactation could potentially eat 30% less, due to mycotoxin contamination, and lose more than 12 kilograms of body weight, instead of gaining over 2kg on the contaminant-free diet.

Improving intake

Compare those indications with the effects that have been suggested in other countries for different influences on the quantity of feed consumed by a lactating sow. Advisers frequently put room temperature top of the list for potential impact. They like to see a farrowing room kept at 18-19 degrees C, on the basis that any warmer conditions will entice sows to eat less.

However, they believe a 20 degrees C room would drop intake by only about 0.2 kilograms daily, which would probably not equate to a reduction of more than 5%. There can be no doubt that the modern prolific sow needs to be eating as much as possible while in the farrowing house. An assessment published last year said that another 12-16kg of sow feed consumption would be needed for every extra piglet raised from birth to a weaning weight of 7.5kg. More milk produced means heavier weaners, of course. Sows eating more in lactation are also given credit for coming back into oestrus more quickly after weaning and for farrowing more liveborn pigs in subsequent litters.


Yet the whole subject of daily feed intake by sows in lactation is far from straightforward. For example, while under-consuming her feed may well reduce the sow's milk output, a high intake each day does not necessarily stimulate more milk to be produced. How to manage sow conditions for maximum consumption is also a hard question. Responses are often unexpected or disappointing.

The facts say that intake is firstly a factor of parity, because a gilt will eat less than a fully mature sow — around 20% less, on a Canadian calculation. Secondly, a figure that expresses quantity eaten per day as a herd average will trend higher as the weaning age increases. This relates to the time in lactation when the sow eats most. Surprisingly, the peak reached by ad lib fed sows can come as early as Day 8-9. Breed or genotype can also make a difference to the amount eaten, but more variation may be seen sow to sow or batch to batch than breed to breed.

Manipulating amounts comes back to a matter of feed management. Begin with presentation. The data from multiple farms confirm that meal beats pellets for volume consumed each day of lactation while wet feed outperforms dry. Feeding in liquid form could be worth an extra 0.5kg daily but an increase of this level is more likely to appear with first-litter gilts than with older sows. On the downside, a survey in Europe has been checking whether computerised liquid feeding might in some cases result in the nursing sow being under-fed.

Impacts of feeding practices

Feeding system considerations must start with frequency and the general acceptance that multiple (three times or more) is preferable to giving the feed once or twice daily. The experts also agree that trough design in the sow's area of the farrowing pen needs to be optimised. Most specialists like to see a rather deep trough offering easy access, with a watering device over it or next to it.

Ingredients in the feed certainly affect its uptake. Higher palatability scores tend to be awarded to mixtures containing fishmeal than to soybean meal, for example. Here too, however, generalisations often hide conflicting experiences. The attractiveness of lucerne/alfalfa would be a case in point, since some feed advisers insist it is not particularly palatable whereas there are European producers who deliberately give a blend of lucerne meal and oats to farrowing sows on the basis that it compensates for possible mycotoxin contamination in the wheat component of the feed.

More protein will bring more consumption if a relatively low-protein mix has been given to the same sows in their previous gestation. Adding fat and lowering protein can have benefits in warm weather. Putting more fibre in the lactation feed does sometimes work in persuading sows to eat more total kilos, but even so, it is likely to cut the concentration of energy intake.The two management actions on which everyone agrees are to remove any remnants of feed from the sow's trough every day and to have a different diet formulation exclusively for lactation so that a high nutrient density can be used to ensure an appropriate intake of energy and of amino acids. There tends to be more argument over the feeding scale to follow with lactating sows. But the old idea of delaying the introduction of full ad lib has lost many of its former advocates, as a delay now seems to achieve little more than limit the total volume of feed consumed in the complete lactation.

A typical scale might begin by feeding 2.5kg of a 14.5 MJ DE/kg diet, to quote a British example for sows raising 11 pigs to a weaning weight of 7kg. The starting amount would apply on Day 1 after farrowing. Afterwards it is increased by 0.5kg daily so that on Day 10 the sow receives 7kg. A variation from Canada calls for bigger daily increases of 1kg between Day 2 and Day 8, with the aim of maintaining the same total quantity per day in the time from Day 8 until Day 12 when intake is called most susceptible to fluctuations. Full ad lib or to-appetite feeding would therefore be introduced from Day 12.

Whatever method you follow, give time and thought to the task of measuring the daily feed intake of the sows in your farrowing pens. Such records will be needed to help in troubleshooting where problems arise and in determining whether the sow is receiving all the nutrients she needs.

Underpinning the calculation of her requirement is the energy that will go into supplying milk for growing piglets. This typically accounts for about two-thirds of the energy she consumes. The other third goes into body maintenance. Without the nutrient resources for both these functions, she will mobilise reserves in the sense of converting tissue into milk. From the most recent studies, around 65% of the total loss of body weight for a sow in lactation involves fat. Protein, by contrast, accounts for less than 15%. But the conversion of protein into milk is relatively inefficient, meaning that sow weight loss benefits neither mother nor progeny.

The only way to react to this situation is to take the two-pronged approach of having the right feed for composition with presentation and the most effective feeding method for maximum feed intake. These fundamental rules have not changed recently. The changes we need to note are the greater demands placed on the modern sow from extra prolificacy and the increased risk this year that there may be mycotoxins in the feed so not enough of it is eaten.