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The value of weaning weight

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Ioannis Mavromichalis
A most common question is 'what is the value of extra weaning weight?' Say, a supplier comes knocking on your door with the next additive for the lactating sow feed. It costs 20 euros per kilogram (huge gasp goes here!) and you need one such kilogram per metric tonne of feed. This will give you an extra 500 grams on your current weaning weight, which at 21 days of age is lamentably too low, at 5.5 kg per piglet (summer and all that, you know).

So, we assume the sow consumes a (hugely optimistic) 6 kg feed per day for 21 days, which is 6 grams per day of the said additive, for a total of 6x21=126 grams per lactation period, at a cost of 0.126x20=2.52 euros per sow per litter. Not an insignificant amount of money!

Now, let’s assume your pigs at weaning are indeed 500 grams heavier, just because of this new additive! How do we evaluate the return on investment? Indeed, there are many good ways that have to do with heavier weight at the exit of the nursery phase, lower mortality, better feed efficiency, reduced veterinary expenses, and so on...But, these calculations will have to wait until pigs are 20-25 kg body weight and these are still indexes, with little monetary value. We need an answer now!

What I find as most ‘acceptable’ by my customers is using the cost of piglet feed it would take to get these extra 500 grams post-weaning. Say, a super quality piglet feed costs 0.8 euros per kilogram (perhaps, not so super quality, but that’s what we have now). Assuming a 1:1 feed efficiency rate (I know, this is not entirely correct, but it is practical) we need 500 grams of this piglet feed to get those extra 500 grams of body weight. So, each piglet would need 0.4 euros of extra expense just for feed. Assuming the sow had a litter of 10 piglets, this makes the expense for extra feed equal to 4 euros per sow. Now, this is worst than the 2.52 we spent on the additive, so in this case the additive wins!

Now, this sow required 2.52 euros to spare us these 4 hypothetical euros, so we’re talking a return on investment of 4:2.52 = 1.58, which means for every euro spent on that additive, the farmer gets back his euro and on top of that (or it would make little sense to just swap euros around!) at least an additional 1.58 euros are deducted from the feed bill. Adding the extra benefits described above only make things better!

But, before you spend the 2.52 euros per sow, better make sure the additive really works!


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    Sergey Volkov

    A useful method to determine the cost-effectiveness of additives for lactating sows. Thank you!

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    Dr Nikolaos Kotrotsios

    So you mean the total feed cost per sow using the specific feed additive is 4+2,52=6,52 euros per sow per litter.The question is what�s the value for piglet getting those 500 gr heavier in body weight. If we say for example that the price is 30 euros for each piglet at the exit of the nursery phase (we don�t wait until pigs are 20-25 kg BW..but we need an answer now!!) and with the presence of the new additive are indeed 500 grams heavier then the selling price is getting 33 euros for each one of them. So the deduction in our calculations must be 3-6,52= -3,52 euros. The conclusion got a negative result and doesn�t make any difference in our expectations. Do you agree with this simple way of the hypothetical approach?

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    I am sorry, but that calulation of Mr. Kotrotsios does not Work. Because the piglets are not weaned yet, we don�t need the 4� for piglets diet. And even if we needed them, it would be 6,52� divided by 10, because we have got 10 piglets per sow. So it is 3�-0,65�=2,35� plus per piglet. Have a nice weekend. Regards Sebastian

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    Ioannis Mavromichalis

    Niko, in your calculations you assume the sow consumes the 2.52 euros worth of the additives and at the same time the piglets consume the 4 euros worth of piglet feed. In reality, and if things go as expected, it should one or the other. Consuming the additive produces more milk, piglets get heavier, and they don't need the extra feed. So, spending 2.52 euros up front to the sow, saves 4 euros later off the feed bill.

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    Dr Nikolaos Kotrotsios

    Ioannis, according to your calculations the piglets get heavier 500 gr through out the consumption of extra milk production and not from consuming extra feed..In other words the 2,52 is equal to 4 euros? I have to say that we are talking in a very approaching and hypothetical considerations..Anyway thanks for the explanations

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