With the current state of the industry, feed conversion ratio (FCR) is one of the most important numbers to control the feed cost/shipped pig.  With negative margins per pig it is important to lower the cost, in order to minimize losses. What are realistic targets for FCR in the finisher barn and what factors most influence FCR?  This is a big subject and we review some of the factors in this article.

Typical FCR

A typical FCR for finishing pigs would be around 3.0.  However, the range is huge, with variations from 2.6 – 3.4.  Realistically, most commercial herds are in the 2.8 – 3.2 range.

The cost of 0.1 feed conversion calculation would be:

0.1 x (shipping weight – starting weight) x price of feed/kg

Current example – 0.1 x (120 – 25) x 0.275 = $2.61

So the range of 0.4 could mean a difference of $10.44 /shipped pig.

Factors influencing FCR

FCR is simply feed used (not feed eaten) per kg weight gain. There are many factors that influence feed usage and weight gain and some are given below

1.  Feed wastage is notoriously difficult to measure but, where this has been estimated in studies, a range from 2.5-10% is not unusual, with floor feeding of meal being particularly poor (despite looking clean!). This range also applies to wet feeding.

• extra 7% wastage vs 2.80 feed conversion = 0.196 FCR = $ 5.12 /shipped pig

2.  Feed nutrient density in finishing feeds is generally lower than it was some years ago when fat was “cheap”.  A finisher trial conducted by the Prairie Swine Centre showed that raising the energy level from 3090 kcal DE/kg to 3570 kcal DE/kg (+ 15.5%) and maintaining the lysine:DE ratio, improved the FCR  by 14.1% (Table 1).   

Table 1: Effect of dietary energy density (3090, 3340, 3570 kcal DE/kg)

In this trial the FCR improved by 14.3% (3090 vs 3570), but to get there the feed cost increased by 30.2%, therefore always look at the balance of price of feed and FCR in order to get the lowest feed cost/kg gain

3.  Feed form (meal vs. pellets vs. wet) influences FCR through changes in energy digestibility, intake, gut health, and feed wastage. This is also compounded by particle size.  Prairie Swine Centre compared the differences between these different feed forms and in different feeders in an experiment (Table 2).

Table 2: The effect of feed form and feeder type on ADG and FCR

4.  Average Daily Feed Intake (ADFI) probably has the biggest impact on performance.  A higher feed intake impacts both energy and amino acid intake.  This impact is usually bigger than varying the nutrient density.  Studies at the University of Alberta showed a large difference in ADFI among pigs (gilts 50-100kg), which varied between 1.57 to 3.15 kg/day.

There are many factors affecting ADFI:

Health status

Dietary factors (energy density, amino acids balance, particle size, additives)

Water (type of drinkers, flow rate, ease of access, quality)

Feeding systems (wet/dry/liquid, pigs/feeder space, access to feeder)

Management (weight at entry, moving/mixing, stocking density, pigs/pen)

Genotype/sex

Environment in the barn (temperature, temp. fluctuations, drafts, air quality)

Production system (all in/all out, fill time)

(adapted from Whittemore, 1998)

ADFI in the early growth phase

It is critical to have a good intake in this stage.  Pigs normally can’t reach their maximum lean gain potential in this phase, because of insufficient intake. The growth in this phase is very economical because high lean gain, which contains a high percentage of water, has a very good feed conversion.  There is also less fat deposition at this stage, which is very high in energy and has a high feed conversion.

An example generated with the NRC model illustrates this very well (Table 3).

Table 3: Expected impact of intake on performance with NRC model

25 kg, high lean gain pigs (375g lean gain/day). 3300 kcal DE/kg, $300/ton

• Improving the feed intake will improve the ADG (mainly lean gain, limited fat gain) and   the feed conversion resulting in lower feed cost/kg gain.

ADFI in the finishing phase

In the finishing stage pigs can normally easily reach their maximum lean gain potential.  Once they reach their maximum lean gain, the remainder of the nutrients will be directed towards fat deposition.  The following NRC model generated table illustrates those dynamics (Table 4).

Table 4: Expected impact of intake on performance with NRC model

100 kg, high lean gain pigs (375 g lean gain/day), 3190 kcal DE/kg, $250/ton

• High intakes in the finishing stage will improve the ADG (almost exclusively fat gain),   which results in a higher feed conversion giving a higher feed cost/kg gain and less desirable carcass.

5.  Space allowance

Studies have found a negative impact of crowding on productivity and welfare, measured mainly on small groups.  Prairie Swine Centre conducted a study on the impact of crowding in small groups (18 pigs) and large groups (108 pigs).  Space allowance was expressed using an allometric approach relating bodyweight to floor area, as determined by the equation: k = area(m²)/BW (kg)^0.667.  Below k = 0.035, space becomes restrictive and growth depression begins (Table 5).

Table 5: The effect of space allowance on pig growth

Small group          Small group             Large group         Large group

                                    Uncrowded              Crowded                 Uncrowded Crowded

Overall, crowded pigs had a poorer FCR and lower ADG than the uncrowded pigs.  The first sign of growth depression in response to crowding occurred much sooner for the pigs in large groups compared with pigs in small groups.  In the large groups, the critical point (k value) at which crowding and growth depression began was k= 0.042, while k=0.035 was the critical point for pigs housed in the small groups.

In the different growth stages on farm, space allowance should be based on the end weights per phase, for optimal growth, feed conversion (Table 6).

Table 6: Optimal space allowance at different weights (m²/pig, (sqft/pig))

Weight of pig                           25kg                  50kg               75kg            100kg           110kg                                                                                                m² (sqft)             m² (sqft)          m² (sqft)     m² (sqft)        m² (sqft)

Small group (k=0.035) 0.30 (3.2)         0.48 (5.1)         0.62 (6.7)     0.76 (8.1)    0.80 (8.7)

Large group (k=0.042) 0.36 (3.9)         0.57 (6.1)         0.75 (8.0)     0.91 (9.7)    0.97 (10.4)

6.  Other factors

Environment

This influences energy requirements and thus feed intake. Pigs kept below their Lower Critical Temperature will eat more and convert more poorly.

High carcass fat

See above

Genotype

Pigs with a higher lean gain potential are better able to convert the nutrients efficiently into lean gain and will have less fat tissue gain, resulting in a better feed conversion.

Disease

This normally increases mortality, but also the immune response diverts nutrients away from lean growth towards fighting disease.  The reduction in lean growth leads to a deterioration in FCR.  This may be severe – as much as 0.5.  Feed intake is normally reduced, the extent depending upon the actual disease.  Feed intake depression is particularly acute with pneumonia.

Clearly there are a huge number of factors that influence weight gain, apparent feed intake, and thus FCR, so attention to these can help to reduce feed costs.