Rethinking Feed ‘Shrink’ as we go to 2:1 feed conversion

This past week I participated in the Alltech Symposia in Lexington, KY. One of the speakers was Dr Tony Edwards, a consulting swine nutritionist from Adelaide, Australia. Tony’s task was to take us through the dynamics that are associated with improving feed conversion in future generations of pigs.

As an industry, we pay for feed based on the scaled weights at the feed mill. Any losses thereafter are the responsibility of the buyer. We’ve become increasingly aware of this ‘shrink’ in terms of transport and transfer losses. While he didn’t call it ‘shrink’, he had an excellent slide where he demonstrated ‘shrink’ once we get feed into the feeder.

When a pig goes to the feeder to eat, we’re all aware of the issue of feed wastage. We’ve made great progress in feeder design to help with this component of ‘shrink’. We used to talk of 10% wastage but I think with well designed feeder spaces and properly managed feeder settings we’re closer to 3% wastage today and in some situations maybe even down to 2%.

Now think of the next level of losses in terms of converting feed to lean meat. Once the pig injests a meal, one of the first losses impacting feed conversion in the indigestibility of components within each feed ingredient. This can range from various fiber components to phytic-acid forms of phosphorus.

The next drag on conversion efficiency is the cost of maintenance. If we have a 220 lb pig (100 kg), there is daily cost to maintain that body mass.

Another drag is absorption efficiencies. Intact proteins must be broken down in the gut by either enzymatic action or bacterial action before the various nutrients can be transported across the gut wall into the blood stream for circulation to the various cells in the body. A good example of this drag is the absorption rate of amino acids from intact proteins (think soybean meal) versus the absorption rate of synthetic amino acids.

The immune system has a cost. There is a cost to maintain the immune system associated with the bacteria that line the mucosa of the gut and the immune system associated with the whole body defenses. The immune system is vital to survival and vaccines and natural exposure leads to many activated mechanisms and pathways. However, there is now a lot of discussion of the costs associated with over activation of these mechanisms. Can we improve efficiencies by turning some of these systems on/off at selected times during the growth process?

After all of these needs are met the pig can begin using ingested nutrients for lean growth. Again, if the nutrients aren’t available in the correct ratios to each other, the pig must expend energy (think poorer feed conversion) to get rid of the excesses. Growth is also limited by the nutrient that is most limiting, whether it is a specific amino acid or calories in relation to an amino acid.

Dr Edward’s conclusion – as we make progress in understanding and limiting these causes of nutrient ‘shrink’ we will someday talk about pigs with a feed conversion well under 2:1.

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