by Walter Scharlach

Since 75% of the total feed used on a pig farm is consumed in the grower-finisher phase, nutritional accuracy in this phase has a substantial economic impact. Traditionally very little attention is paid to growing/finishing pigs mainly because of a lack of appropriate record keeping. As better record keeping systems and performance monitoring systems become available, and as potential improvements in profitability become more apparent, more attention is paid to the feeder herd. The variation of more than 25% in feed costs among farms is proof that major savings can be achieved in this area.

The establishment of production targets is important. According to Gadd 1996 "Top third" producers on ad lib feeding are now achieving the standards as shown in table 1:

These targets should be used as guidelines. The overall objective is to maximize profit and establish farm specific goals for your operation. Once the goals have been established the feeding and management strategies must be developed which make the achievement of these goals possible.

On most farms, expensive dry feeds are used and it becomes very important to achieve a good feed efficiency. Efficiency is maximized when the greatest proportion of the feed energy is directed to lean growth rather than to maintenance or fat deposition. This is achieved by increasing the feed intake as far as possible above which is required for maintenance, within the range of acceptable carcass quality. Figure 1 illustrates how nutrients which are supplied in excess of maintenance can be used to support growth, either in the form of lean tissue or body fat.

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The steps needed to formulate farm specific diets accuratly, are as follows:

Protein deposition rate:

The protein deposition rate determines the genetic merit of the pig. The effect of increasing the protein deposition rate is shown in table 2 below:

*PDR = Protein Deposition Rate

The protein deposition potential should be supplied by the breeding company. It may also be estimated from the fat-free lean gain. With this method the fat free lean percentage is obtained from the processor. The fat-free lean gain is calculated by subtracting the estimated fat-free lean at the initial weight, from the fat-free lean at processing and dividing this by the growing days (NPPC, 1991):

Lean gain/day = Carcass muscle - Initial muscle*

Growing days

* Initial muscle (kg) = (0.428 x initial live weight)-1.66

If the fat-free lean gain is calculated, the current productivity of the herd is measured without knowing what the potential performance limit is. Under these conditions, nutrient levels should be set somewhat above those that support current performance levels. As new diets are fed, performance levels should be measured. If performance improves, nutrient levels can be adjusted progressively upward until the optimal level of performance is achieved.

Once the pigs’ protein deposition capacity has been determined target nutrient intakes should be calculated. This is shown in table 3 below:

In order to translate these target nutrient intakes into dietary specifications an estimate of feed intake is needed. Feed intake can be determined by measuring feed intake on a subsamle of pigs in a pen. It is recommended that feed consumption is measured for a 2-week period from at least 2 feeders during the different weight periods. Commercial feed disappearance can also be estimated by using the following formula:

Average daily feed disappearance = Total feed used

Pig days

Feed intake is very often determined by a physical feed intake capacity or "gut fill". This means that pigs often reduce their energy intake if presented by low energy feed. Feed intakes vary considerably between different pigs farms. In table 4 the commercial estimate of feed intake on 10 farms is compared to the NCR estimate. The low intake is the average of 8 farms while the high intake reprsents the average of 2 farms.

* Estimated intakes from overall feed usage

Feed formulation:

Once the animals’ nutrient targets are defined and the feed intake curve is known, the diets can be formulated. The lean growth of pigs is driven by energy intake and limited by the animals’ genetic ability to deposit protein. In young growing animals the capacity to consume is normally too low to reach the maximum lean meat deposition. The inclusion of ingredients that dilute the energy content should be avoided. On farms with low feed intakes, growth may be limited by an energy deficiency throughout the growing cycle.

Finishing pigs, on the other hand, may consume more energy than what is needed for maximum lean meat deposition, particularly those with poor lean growth potentials. These animals may deposit excessive amounts of fat. On these farms, lower density diets may be used successfully. The interaction between intake and diet density is shown in table 5.

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Table 5 shows the following: