Focus On Feed Conversion in pig feeding

Focus On Feed Conversion

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The following article is a special collaboration from AFMA (Animal Feed Manufacturers Association) We thank their kind support.

Feed constitutes the major variable production cost (70%) and skillful management of feed has a major impact on profitability (Brumm, 1994). If one looks at international published values of feed efficiency, there is a 20 to 25% variation in feed utilisation within the pork industry between good and bad production units (Lattz, 1997). South Africa is no exception with a national average Dead Weight Feed Conversion (DWFC) of approximately 4.2:1 while more efficient producers realise conversions of 3.6:1.

The current average cost of pig feed in South Africa is around R1000/t (this includes a mixing and milling fee). It follows that the feed production cost per kg pork may vary from R3.50/kg (R1000/t @3.5 DWFC) in the case of good units to R4.20/kg (R1000/t @4.2 DWFC) in the case of an average unit. The good units are competitive with international feed costs for pork production, which, according to Pig International (Nov, 1998), vary between R3.00 and R5.00/kg (Canada is the cheapest at R2.93/kg, the USA is at R3.70/kg, Argentina at R3.91 and the Netherlands at R4.97). Although it is recognised that the diet that results in the best feed efficiency may not be the diet that produces optimal performance and carcass quality at minimal cost, the available ingredients and costs are such that only minor changes in dietary density are cost effective. The achievable standards for growth and feed conversion are shown in Table 1.

Table 1: Slaughter pig standards for 1997 (Gadd, 1996):

Food Eaten
6 - 30
30 -100
Breeder Feed @55kg per pig produced
Total Feed per pig marketed

A suckling piglet would consume about 5kg of milk dry matter (Close, 1994) to be weaned at 6kg. A further intake of 208kg of feed (table 1) is needed to reach a live weight of 100kg. At a total feed intake of 213kg per pig the live feed conversion is 2.1:1. If the breeder feed is added (55kg per pig marketed) the live weight feed conversion increases to 2.7:1. This live weight feed conversion as well as the corresponding DWFC, at a 76% kill out percentage, is shown in Table 2. The DWFC standard is therefor about 3.5:1. 

Table 2: Total grower and herd feed efficiency expressed on an live and dead weight basis.

Feed Conversion
Live FC
100kg live weight
76 kg carcass
Growing pigs only
Growing and Breeding

It is important to notice that the breeding pigs consume approximately 20% of the total feed, whereas the growing/finishing pigs consume about two thirds of the feed (table 1). The most important factors that impact on feed efficiency are highlighted below:

Breeder herd
The productivity of the sows and the breeding policy of the unit affect the amount of breeder feed per pig marketed.

Productivity of sows
If the number of pigs sold per sow per year is reduced by 10%, sows will consume 10 percent more feed per pig sold. This will increase the breeder feed by about 6kg per pig sold and increase the DWFC by 0.07 points.

Breeding Policy
If replacement gilts are purchased (at 100kg live weight) and not reared on farm, the DWFC should be adjusted downwards by approximately 0.09 points.

Grower herd
The biggest overhead on a pig farm is the daily maintenance requirement, which uses feed but generates no saleable product. Studies reported by Close (1997) suggest that the maintenance requirement of modern genotypes represent almost 40 percent of the total feed intake, compared to only 25 percent of unimproved pigs. As the maintenance portion is mainly a function of live weight, is becomes clear that a slow down in growth rate towards the end of the growing period will invariably reduce feed efficiency.

Fast Growth rate
Fast Growth reduces the grow-out time and thereby the feed required for maintenance. Fast growth is always important, but more so at the end of the growing cycle when the maintenance cost's are highest. Some of the most important factors that may reduce the growth performance are listed below:

Fast growing pigs are very sensitive to high temperature especially during the last month of growth. A 1øC increase in temperature above the comfort temperature will reduce feed intake and hence growth by 30g. This is shown in table 3:

Table 3: Effect of temperature on growth performance of pigs (Ohio, 1991)


Stocking density
The actual space allowance per pig is more critical than the number of pigs in a group. The recommended stocking densities in the Canadian Code of Practice for the care and handling of pigs (Patience et al, 1997) are shown in table 4. At higher stocking densities feed intake will be reduced by approximately 3% per 0.1 m2 reduction in floor allowance.

Table 4: Recommended stocking densities in the Canadian Code of Practice (Patience, 1997)

Body Weight
Floor space

The synthesis of fatty tissue requires approximately 3.5kg feed per kg, while lean tissue only requires 1.25kg feed per kg (Whittemore, 1993). It follows that any reduction in grading (increase in fatness) will invariably reduce the feed efficiency.

Feed Wastage
Recent work has shown that the average Australian pig farm wastes approximately 10 percent of the feed. The local figure for feed wastage may be similar. The mechanical adjustment and repair of feeders should therefor be a daily management priority. A standard rule is that about 50% of self-feeder trough bottom should be visible. Trough bottoms that are completely covered with feed are probably wasteful.

Loss in Protein deposition
A pig's genetic merit is determined by its ability to deposit lean meat. Lean deposition follows a rainbow-like curve. For improved animals the lean deposition may peak higher and decline slower. Any decline in lean meat deposition during the finishing stage reduces feed efficiency.


The breeding herd consumes about 20% of all feed and is therefor a relatively small contributor to feed efficiency. Poor feed efficiency is almost always caused by the feeder herd.

Due to the high cost of maintenance of modern genotypes, fast growth rate is of utmost importance. It is important to ensure that there is no slow-down in growth towards the end of the growing cycle.

For good feed efficiency the difference between good and poor finishers should be known. "Cramming" pigs through inefficient growing/finishing facilities will only add cost and decrease profitability.


Brumm, M. 1994. Pork Expo, gopher://gopher.ext.vt.edu70/00/docs/aps/aps-522.
Close, W.H. 1994. Personal communication.
Close, W.H. 1997. Feeding new genotypes: Establishing amino acid/energy requirements pp123-140 In: Principles of Pig Science. Editors, Cole, D.J.A., Wiseman, J., Varley, M.A.,
Butterworths, London
Gadd, J. 1996. Slaughter pig nutrition. In: The Pig Pen. Volume 4, No 1.
Lattz, D.H. 1997. The Economics and Profit Potential of Hog Production.
Ohio, 1991 gopher://gopher.ext.vt.edu70/00/docs/aps/aps-522
Patience J.F., Thacker, P.A. and de Lange, C.F.M. 1995. Swine Nutrition Guide 2nd Edition.
Prairie Swine Centre inc.
Pig International Nov, 1998. The production cost comparison. Nov 1998, Volume 28, 11. Whittemore, C.T. 1993. The science and practice of pig production. Longman Group UK.

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