A quick glance at Fig. 1 below confirms that piglet output from the breeding herd has increased over the past few years. While this data set may not be indicative of the situation on every farm, most producers will be able to identify with the trend it suggests.
Although significant increases in physical pig output have been achieved, the situation with regard to weight of piglets produced per litter appears to be more variable at farm level: some farms are reporting very high weaning weights while others are struggling to maintain the status quo. We are all aware of the positive correlation that exists between weaning weight and subsequent lifetime performance so, perhaps now is a good time to ask ourselves if we are feeding today’s hyper prolific sow in the same manner as we did her less productive mother of 5 years ago?
If the answer is yes, then we may be missing out on some of the potential that exists within our production system. In considering sow nutrition, we need to always be conscious that decisions we make today will have repercussions not only tomorrow but also in a few months’ time on both the sow and the piglet and its lifetime performance. Ultimately kilos of meat sold per sow is a major determinant of financial margin on our farms so if we can increase the numbers of piglets born and increase the weight output from our sows at the end of lactation then we will be giving ourselves a very good head start in the quest to maximise lifetime performance. In the next few paragraphs I aim to focus on different aspects of sow nutrition and how they can contribute to increased litter weaning weights.
Pregnancy – secure high numbers of viable piglets
The primary objective of pig production is to produce as many pigs as efficiently as possible from our breeding sows over a prolonged period/lifetime. Clearly the success of this depends on many variables, however the central role that nutrition plays is undeniable. When we look at nutrition of the pregnant sow it is fair to say that the fundamentals have not really changed very much over time: ultimately the function of pregnancy feeding should be to maintain or replenish the sow’s body mass as appropriate; grow the products of conception i.e. the placenta, uterine fluids and foetuses; and finally develop the udder in preparation for a prolific lactation.
1. Establish maintenance requirements.
Maintenance requirement is by far the greatest draw on nutrients throughout pregnancy (Fig. 2). Given the high requirement for maintenance, it follows that periods of over or under feeding, can have a significant effect on the outcome of pregnancy and lactation. In general, the weight of sows at maturity has increased over recent years with corresponding increases in maintenance requirements (Fig 3).
In many cases the difficulty with dry sow feeding is that the feed allowance or curve is set according to a subjective assessment of a group of sows’ condition or perhaps to the curve which has traditionally been in place on farm. This can lead to inaccurate assumptions on sow condition and therefore systematic under or over feeding. It is useful to periodically employ more objective measures of body weight or condition such as condition scoring; weighing or backfat testing in order to determine the maintenance requirements of the herd and by extension of the feed requirement. By doing this we can avoid having excessively fat or thin sows entering the farrowing area and the problems that accompany such sows.
In general we should strive to have between 18 and 22 mm of backfat cover on sows at the point of farrowing. Above 22 mm, sows are likely to have lower feed intake in lactation, lose more body reserves and be less prolific at next parity. Sows that are excessively thin are likely to be in a severe catabolic state meaning that lactation output will be compromised and subsequent reproductive performance will be diminished resulting in increased sow wastage.
2. Feed in the correct pattern
In most circumstances on farm, sows are fed according to either a U shape pattern or flat line pattern throughout pregnancy. Most nutritionists will recommend increased nutrient provision during late pregnancy in order to maximise performance and sow longevity. The reason for this is because the metabolic focus in the sow changes from replenishment of condition following weaning to development of the products of conception in late pregnancy. Recent research has indicated that foetal weight, foetal protein content and mammary protein content increase by a factor of 5, 18 and 27 respectively during the last 45 days of pregnancy (e.g. Fig. 4).
These dramatic changes in foetal weight and protein gain indicate a huge surge in nutrient requirement in late pregnancy compared to early pregnancy. Ignoring this dynamic and applying a straight line feeding policy in pregnancy will lead to possible over feeding during early pregnancy and certain under feeding in late pregnancy.
If we want to get good quality piglets born and if we want to get the udder developed for lactation, then we must increase our feeding levels at the back end of pregnancy to match the demands created by the growing litter and udder. If we don’t increase the feed allowance we risk compromising sow body mass and foregoing piglet vigour at birth. In terms of diet specification, the early part of pregnancy doesn’t really present any problems because sows are restricted at this time so assuming a properly balanced diet, it is easy enough to meet requirements.
The challenge occurs at the back end of pregnancy because the nutrient, in particular amino acid, requirements change dramatically both in profile and in quantity. Recent research work conducted in Canada has promoted the merits of feeding two diets in pregnancy in order to better match the nutrient requirements of early and late pregnancy. In practical circumstances this may prove to be unworkable at farm level but never the less there may be some adjustments that can be made in consultation with your nutritionist which may offer benefits, particularly in young or newly established herds where the sows are still growing themselves.
3. Maximise piglet vigour
Some French researchers have recently proposed that using dietary oil, as opposed to relying entirely on starch to contribute energy in pregnancy, can stimulate increased vitality and survival of piglets. It is proposed that this may be due to an increased level of body fat in the piglet as well as a greater ability to metabolise fat at birth. Another area of research that is yielding very encouraging results is the targeted use of fatty acids in sow diets.
4. Maximise feed intake and feed the correct density diet in lactation (70 days onwards)
With increased potential for milk production, management and nutritional factors must be changed to meet these demands for lactation. Sows can achieve and maintain high levels of milk production throughout life if given adequate nutrients. Milk production typically constitutes 70 - 80% of the piglet´s total nutrient needs during lactation thus a high nutrient intake during lactation is essential at this time if we are to maximise milk production and piglet weight whilst avoiding depletion of sow body mass.
Excessive mobilization of body tissues during lactation is hugely detrimental to herd productivity because it results in reduced milk production, prolonged weaning to service intervals and potentially smaller subsequent litter size. High nutrient intake can be achieved by increasing feed intake and/or increasing the nutrient density of the diet. In terms of increasing feed intake the message should be to start high and increase quickly. As a general rule we should try to get sows to eat the same daily quantity on the day after farrowing as was eaten in the last week before farrowing. The feed curve should increase rapidly thereafter by at least 0.5 kg/day and ideally by 1.0 to 1.5 kg/day. Research has shown that if feeding is too restrictive in early lactation then total lactation feed intake will be reduced.
There are two reasons for this: A: Feed intake in the last three weeks of lactation is not influenced by intake in early lactation; B: The feed intake foregone in early lactation cannot be recuperated in the later stages of lactation. In addition to this, research and farmer surveys have shown that 30-35% of sows will show a reduction in feed intake for 2-3 days in the second week of lactation, while 30% of sows show no feed refusal at all. Therefore, it is better to tailor feeding towards those sows which do not show a drop in intake and target appropriate management strategies for those that do, rather than the other way around.
The need for high nutrient intake means that more fibrous ingredients should be avoided for lactating sow diets because they tend to be lower in energy content than cereals. Furthermore, when formulating lactating sow diets there is a balance to be struck between the use of crude protein / oil / synthetic amino acids and speciality products such as NatuPro or Lipidol. In order to get the best out of diets like these we need to be sure that we don’t overload the digestive system with unnecessary protein and oil so judicious use of speciality products is recommended in order to supply all nutrients in the proper balance.
In summary, our sows today are very capable of producing large litters and of producing vast quantities of milk to feed their litters. However unless we provide these animals with the correct nutritional tools we will struggle to reach the potential that currently exists for litter size and weaning weight. The key areas to consider in order to maximise litter weaning weights are:
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