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Management Practices That Maximise Feed Efficiency

08 November 2013

Many improvements in feed efficiency management will be incremental – and often modest in size – but when considered together, they represent a tremendous opportunity to minimise the impact of higher feed prices on farm net income, according to John F. Patience of Iowa State University. He was addressing the 2013 London Swine Conference.


Feed efficiency is a very challenging indicator of farm success. It is a highly valuable measurement, providing essential information on a key component of the cost of production.

While it is important and valuable, it can also mislead and result in decisions that will achieve outcomes that actual decrease net income rather than increase it. So it is critical that the right measures of feed efficiency are utilized and applied correctly as decision-making tools.

Feed efficiency can be influenced by many variables, including the pig’s environment, genetics, herd health, diet composition and pig management. With so many moving parts, achieving the best possible feed conversion is very difficult but, like other challenging tasks, breaking it down into constituent parts is the best path to long-term success.

The financial rewards of improved feed efficiency, if undertaken properly, will be significant, and can mean the difference between profit and loss when margins are being constantly squeezed.

Feed Efficiency Targets

Before discussing how to maximise feed efficiency, we have to ask two very important questions. First, what do we mean by feed efficiency; it can be measured in many different ways. Following are examples:

  • Kg feed per kg live weight gain
    • Traditional approach that is familiar to everyone. However, it ignores differences in dressing percentage and thus can be misleading if higher fibre diets are used.
  • Kg feed per kg carcass gain
    • Increasingly common in the Midwest US and in research when diets differ in fibre content.
  • Mcal energy per kg (liveweight or carcass) gain
    • Is a crude measure of energy efficiency, but helps to put more focus on energy efficiency.
  • Feed cost per tonne
    • Terrible measure of efficiency because it means very little, since animal performance and net income are not part of the calculation.
  • Feed cost per pig placed
    • A useful measure of efficiency, in that it considers overall feed cost on a per pig basis. Not particularly useful when used alone, but is very useful when used in concern with some of the above measures of feed/energy efficiency.
  • Feed cost per pig sold
    • Similar to above, but takes into account the financial penalty of mortality.
  • Return over feed cost per pig place
    • Is a broad stroke measure of efficiency that, because it is expressed on a “per pig place” basis rather than “per pig basis”, acknowledges the impact of barn throughput.
  • Net income
    • A very broad brush measurement of “efficiency” but it represents the most important goal of pork production – to make money, or when the markets are down, to minimize losses. No matter which measures of efficiency are used, this should always be included, to avoid focusing on improving efficiency but inadvertently lowering net income.

The second question is very simple. Do we want to maximise feed efficiency? There is no simple answer, but there is a very real risk of focusing too much on feed efficiency and not on other aspects of the cost of feed or barn management. For example, one can easily improve feed efficiency by increasing diet energy content; however, there is no guarantee that this will improve profitability. Indeed, in many instances, it will have the opposite effect - but it will improve feed efficiency.

Feed Efficiency: Measurement

Measuring feed efficiency is relatively easy, at least in all-in-all-out production, but interpreting the results of the calculation is the really hard part. The following table (Table 1) illustrates this point. If feed conversion was calculated in the traditional manner, one would conclude that the two fills had essentially the same results. However, pigs in Fill B weighed less at entry and less at market, meaning they had an advantage over Fill A because smaller pigs typically will have a better feed conversion. Adjusting for entry and exit weights results in a very different conclusion: that Fill A had superior feed efficiency compared to Fill B.

Also, Fill B had lower mortality, and since mortality can influence feed efficiency, this needs to be taken into account. Once again, adjusting for mortality resulted in a differing conclusion about the comparison of Fill A versus Fill B.

Therefore, it is important to ensure that such comparisons within a farm or system are done correctly so that the right conclusions are drawn.

The situation is more complex when using bench-marking services to evaluate how one farm compares to its contemporaries. Differences in diet composition, entry/exit weights, particle size, mash versus pellets, etc. can also have a very substantial impact on feed efficiency and make comparisons among farms difficult.

Feed Efficiency: The Pig's Environment

The pig’s environment will have a substantial impact on performance. Temperature is an excellent case in point.

The challenge is to define the lower and upper critical temperatures for growing and finishing pigs, so we can be certain that performance is not impaired by barn temperatures that are too lower or too high. For example, if the temperature drops below the pigs’ lower critical temperature, feed intake will increase by about 1.5 per cent per degree Centigrade NRC (2012).

The lower critical temperature is estimated to be about 23 to 24°C at 25kg body weight, dropping to about 15°C at 100kg (Renaudeau et al., 2012). These temperatures, especially at the heavier bodyweights may seem cold, because to humans, they are. However, pigs are eating as much feed as they can, and this generates a large amount of heat. Therefore, pigs will feel comfortable at cooler temperatures than most humans.

These lower critical temperatures assume that the pigs are healthy, the floor is dry and there are no draughts.

They also assume that the barn is well insulated. If any of these situations does not exist, then the LCT will be increased by perhaps 2 to 3°C to accommodate the chilling impact of dampness, draughts etc. Also, if pigs are not healthy – and therefore not eating to their full potential – their LCT will be much higher; this is why we see pigs in sick pens often huddling due to cold stress at barn temperatures that appear to be perfectly acceptable to other pigs in adjacent pens.

The limited data that are available suggest that feed conversion is minimally affected by elevated temperatures in the barn. As pigs become heat stressed, feed intake will decline by about one per cent (growing pigs) and two per cent (finishing pigs) for every degree above the upper critical temperature (Patience et al., 1995). The decline in feed intake is manifested in slower growth, such that changes in feed efficiency are smaller than one might expect (Renaudeau et al., 2011).

Feed Efficiency: Genetics

The North American model is to depend primarily on genetic selection of achieve lean, efficient carcass gain, as opposed to limit-feeding pigs. While limit feeding will reduce carcass fat, the associated slower growth is a penalty that most North American pork producers are unwilling to accept. However, selecting for feed efficiency can be problematic, as it can result in animals with poor feed intake and thus slower growth.

There are a number of solutions to this problem, one being multi-trait selection like BLUP that includes many criteria, one of which can be efficiency but also include growth rate or lean gain. Knap and Wang (2012) argue that the use of Residual Feed Intake (RFI) is another way to achieve rapid improvement in efficiency; essentially, RFI measures actual feed intake in a pig and compares that to what it should have eaten given its growth rate and carcass fat content (Cai et al., 2008).

The results of multi-generational selection by Dr Dekker's team at Iowa State University for RFI are presented in Table 2. Improved RFI resulted in a 13.2 per cent reduction in feed intake but only a 6.1 per cent reduction in growth rate. Feed efficiency was improved by about eight per cent and backfat was reduced by 14 per cent. These are impressive numbers, although no loss of growth rate would have been a more desirable outcome. In any event, these data demonstrate the improvement in feed efficiency that can be achieved through genetic selection.

Feed Efficiency: Herd Health

Pig health is widely recognised as having a profound impact on almost all aspects of animal productivity. This only makes sense but data to quantify this are surprisingly rare.

Dritz (2012) reported the results of a study undertaken in Sioux County, Iowa, which has the highest density of pig production in the US (722 pigs per square kilometre). Herds were characterised according to PRRS status (positive or negative), ileitis (positive or negative), biosecurity (pass or fail), site capacity (less than or greater than 2,500) and pig density (less than or greater than 5,000 pigs within a 2.4-km radius. The results are summarised in Table 3.

The herds that were PRRS-positive or had poor biosecurity procedures, had significantly poorer feed conversion than those that did not (P<0.05). They also reported poorer growth rate. These field data underscore the importance of strong biosecurity and herd health procedures if feed efficiency is going to be maximised.

A very recent dataset further emphasised the importance of remaining PRRS-negative. In a large, detailed study lead by Dr Nick Gabler of Iowa State University, in collaboration with Newsham and a private pork producer, pigs from a common sow source were split between two sites, with animals at one site being infected with the PRRS virus.

A large and detailed dataset is being generated by this unique study but the feed efficiency in Figure 1 illustrates the huge impact of a simulated PRRS outbreak in naïve pigs.

Figure 1. Impact of PRRS infection on feed efficiency in grower pigs
(Source: Gabler, 2013 - unpublished data)

Feed Efficiency: Diet Composition

Obviously, diet composition can have an important impact on feed efficiency. Indeed, nutritionists know that in order to improve feed efficiency, simply increase the energy concentration in the diet. This change may, or may not, benefit financial performance but it illustrates that improving feed efficiency through nutritional intervention is not a difficult goal to accomplish.

Apart from energy, the nutrients in the diet can influence feed efficiency as well. However, in this instance, nutrients would have to be deficient for any addition to result in improvement. Simply elevating amino acids levels in a diet will not improve feed efficiency, unless the diet was previously deficient in amino acids.

Obviously, the addition of certain feed additives and growth promotants can be used to improve feed efficiency.

In addition to the composition of the feed, the form of the feed can also play a role. Reducing particle size will improve feed efficiency, as will pelleting the diet. Indeed, pelleting has become more popular recently as producers seek to reduce particle size to less than 400 microns; for most farms, the only consistent way to make such feed flow through the feed delivery system is to pellet it.

Feed Efficiency: Pig Management

Delivery of feed to the pig may also play an important role. Poorly designed feeders, combined with poor management of the feeders, can lead to excessive feed wastage and poorer feed efficiency.

Inadequacy of feeder space may also result in poorer feed conversion (Figure 2; Weber et al., 2013). Their study showed no impact of feeder capacity until the pigs reached the final phase prior to marketing; given that the reduction in feed efficiency is modest and of short duration, it is unlikely that this reduction in feed conversion would warrant installation of new feeders in an existing barn. However, it could be a consideration in sizing feeders in new construction.

Sorting of pigs at any time during grow-out, including at placement, is a waste of time. It not only fails to improve pig performance but in fact results in slower growth and poorer feed efficiency. The only justification for sorting pigs would be to place very small or compromised animals in separate pens where they can receive special diets and daily care. Otherwise, it is a practice that is strongly discouraged.

Figure 2. Impact of feeder space allowance on feed efficiency in pigs during the final phase of growout
(Source: Weber et al., 2013).


Achieving the best possible – and most economical – feed efficiency requires the highest attention to detail on almost all aspects of pork production, including selection of the right genetics, proper diet formulation, management of barn environments and controlling disease.

Many improvements through management will be incremental – and often modest in size – but when considered in totality, they represent a tremendous opportunity to minimise the impact of higher feed prices on farm net income.


Cai, W., D.S. Casey and J.C.M. Dekkers. 2008. Selection response and genetic parameters for residual feed intake in Yorkshire swine. J. Anim. Sci. 86:287-298.

Dritz, S.S. 2012. Influence of health on feed efficiency. In: J.F. Patience, editor, Feed Efficiency in Swine. Wageningen Academic Publishers, Wageningen., The Netherlands. p. 225-237.

Gaines, A.M., B.A. Peterson and O.F. Mendoza. 2012. Herd management factors that influence who herd feed efficiency. In: J.F. Patience, editor, Feed Efficiency in Swine. Wageningen Academic Publishers, Wageningen., The Netherlands. p. 15-39.

Knap, P.W. and L. Wang. Pig breeding for improved feed efficiency. In: J.F. Patience, editor, Feed Efficiency in Swine. Wageningen Academic Publishers, Wageningen., The Netherlands. p. 167-181.

NRC. 2012. Nutrient Requirements of Swine. 11th rev. ed. National Academy Press, Washington, DC.

Patience, J.F., P.A. Thacker and C.F.M. de Lange. 1995. Swine Nutrition Guide. 2nd ed. Prairie Swine Centre, Saskatoon.

Renaudeau, D., J.L. Gourdine and N.R. St-Pierre. 2011. A meta-analysis of the effects of high ambient temperature on growth performance of growing-finishing pigs. J. Anim. Sci. 89:2220-2230.

Renaudeau, D., H. Gilbert and J. Noblet. 2012. Effect of climatic environment on feed efficiency in swine. In: J.F. Patience, editor, Feed Efficiency in Swine. Wageningen Academic Publishers, Wageningen., The Netherlands. p. 183-210.

Weber, E.K., K.J. Stalder and J.F. Patience. 2013. Interaction of feeder space availability and corn DDGS inclusion level on grow-finish pig performance and total tract digestibility in a commercial setting. J. Anim. Sci. 91: Suppl. 2):70.

Further Reading

You can view other papers presented at the 2013 London Swine Conference by clicking here.

November 2013

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