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The economics of feed efficiency in pigs

June 6, 2023

(Editor's note: This is part one of a three-part series on feed efficiency in pigs.)

There is no question that feed efficiency is a powerful benchmark and a key driver for many decisions. But are we utilizing these metrics to drive profitability?

We know the feeding program for pigs has a profound impact on profitability, as feed cost accounts for up to 75% of total production cost. Within the feeding program, energy alone represents 50% or more of the total cost. Thus, dietary energy is critical in swine diets, and it is essential to understand feed efficiency.

A key question we need to ponder: Is it the best decision to always improve feed efficiency? The answer: it must be economical! Whereas feed efficiency greatly influences financial returns, steps to improve it do not always lead to financial gains. A good example would be increasing dietary energy density; if we consistently increase feed efficiency, it could increase feed cost per pig and lead to financial losses.

Measuring feed efficiency

The classical definition of feed efficiency is simply body weight gain per unit of feed consumed, typically denoted as F/G or G:F. Another way to express feed efficiency is on a dietary energy basis as opposed to feed consumed; this is denoted as caloric F/G. These are simple expressions, yet they can lead to errors.

For example, feed consumed is frequently not measured, and feed disappearance is the actual metric. Feed disappearance and feed consumed can differ by up to 30%, driven by factors such as feed waste. Thus, feed disappearance does not reflect the pig’s actual feed consumed.

Another important factor to consider is weight range. Initial and final weight are major factors affecting feed efficiency. Fat deposition is less efficient than protein deposition, and the rate of fat deposition increases in relation to protein deposition as body weight increases. Thus, when comparing groups of pigs for feed efficiency, we must consider variation due to differences in the body weight at which the various animals are evaluated.

Furthermore, differences in dietary energy density can lead to errors and sometimes inaccurate energy loadings or energy systems utilized. As a rule of thumb, if energy values are accurate, a 1% increase in dietary net energy results in a 1% improvement in feed efficiency. Additionally, a common modification to this calculation is feed efficiency on a carcass gain as opposed to live body weight. This modification is driven primarily by how pigs are sold; thus it is more reflective of the actual financial impact.

Other factors impacting feed efficiency

Additional factors to consider when determining feed efficiency accurately include:

  • Mortality: If mortality occurs at midpoint of the finishing phase, for every 1% increase in mortality, F/G could worsen by up to 0.8%.
  • Pelleting: This improves F/G by about 4–6% when feeding pelleted diets with less than 20% fines.
  • Particle size: Grain particle size improves F/G by up to 1.2% for each 100-micron reduction.
  • Sex: Whereas gilts have 1.7% better F/G compared to mixed-sex, barrows have 1.7% poorer F/G compared to mixed-sex.

As described, a plethora of factors can impact feed efficiency. Fortunately, equations that consider these factors and aid with feed efficiency calculations are readily available.

Feed efficiency economics

How do we represent feed efficiency from a financial perspective? The most typically used expressions of feed efficiency in financial terms include feed cost per pig sold, yet this only takes into consideration the cost of the diets on a per-pig basis.

Other metrics, such as feed cost per unit of gain, represent the results of multiplying feed efficiency by feed cost per kilogram. The best application of this method, though, is for comparison between nutritional programs when there is an expected change in feed efficiency alone.

Other methods, such as income over feed cost (IOFC), calculate profit by subtracting feed cost from the revenue on a per-pig basis, most typically on a hot-carcass weight pricing basis. Facility cost can also be incorporated into feed cost to estimate the income over feed and facility cost (IOFFC). IOFC and IOFFC are accurate methods to determine the economic value of a nutritional program, and ultimately, they are good ways to assess the financial implications of manipulating feed efficiency.


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