Farm Ireland

Saturday 25 February 2017

Pigs: Hitting correct kill-out weight

Focus on a target to aid profits at factory

Peadar Lawlor

There are reports that carcass weights in factories are averaging 81.5kg for the first four months of this year. Producers are asking, 'what is the optimum live weight at which to slaughter their pigs?' This is not an easy question to answer. The processor and individual deals done with processors are very important factors.

The slaughter weight of Irish pigs has increased in recent years. The average carcass weight of pigs slaughtered in Ireland last year was 80kg (table 1, below), up from 64kg in 1970. Most other EU countries routinely castrate male pigs destined for the meat counter, thus allowing much heavier weights without running the risk of boar taint. However, this practice is becoming less acceptable and alternatives are being considered. Ireland and the UK produce entire male pigs and, as our slaughter weights were traditionally low, this safeguarded us from boar taint problems.

What is the current


The slaughter weight of pigs in Ireland is dictated largely by the minimum/maximum weight limits set by the main processors. Each processor has its own distinct range.

Table 2 (right) shows the minimum and maximum carcass limits for pigs at one processor (each processor will have different weight thresholds). It also shows the maximum and minimum liveweight bands that producers should use to avoid price penalties.

Failure by a producer to supply pigs within the maximum and minimum weight range can be costly. Each processor has its own system for making deductions on overweight and underweight carcasses, but generally the further carcass weight is outside the optimum range the greater the penalty.

Meeting an upper carcass weight limit of 85.5kg

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The following example uses data from a trial conducted at Moorepark where pigs were slaughtered at five target liveweights between 80kg and 120kg. The weight limits from the factory in table 1, their penalty structure for overweight and underweight pigs, and the normal bonuses for lean meat percentage were used to calculate net pig price/kg carcass using a base price of €1.24/kg carcass. Feed costs were calculated using the Teagasc recorded feed prices for April.

In this example we found that targeting liveweight at slaughter of 110kg was the most economical strategy. Above this liveweight, the penalties incurred for overweight pigs were sufficient to severely reduce margin overfeed per pig. To maximise the number of pigs approaching this weight, and also to avoid pigs exceeding the upper carcass weight of 85.5kg, it would be advisable to target all pigs above 103kg live for slaughter on a given week.

Situations where the upper weight limit is more relaxed

Processors tend to accept pigs heavier than their maximum declared limit from specific customers and in times of short supply. Allowing this increase in slaughter weight without penalty is profitable for the producer, since the costs of sow feed and most non-feed costs associated with producing the pig have already been incurred.

The main costs associated with the extra weight is the additional finisher feed used and non-feed costs associated with the additional weight, such as interest on increased borrowings for additional accommodation, depreciation for that accommodation required, cost of disposing the extra manure produced and increased repairs and maintenance associated with increasing slaughter weight. This currently works out at €0.64/kg liveweight for feed and €0.13/kg liveweight for the additional non-feed costs, giving cost totals of €0.77 per marginal kg of pig liveweight or €0.59/day.

Is the incidence of boar taint likely to increase?

Boar taint is an unpleasant odour that is released during the cooking of pig meat from entire male pigs. Only a proportion of boars produce this odour and not all consumers are sensitive to it. Nevertheless, it is a potential problem for the industry, since one bad experience by a consumer could put a person, or indeed an entire family, off pork for life. Although we have previously found that the incidence of taint-causing compounds in the carcass increases as slaughter weight exceeds 100kg liveweight, the incidence of boar taint is more a feature of age rather than weight. However, we have no way of knowing the age of a pig at slaughter and so maximum carcass weight limits, though not entirely accurate, are the only practical safeguard against boar taint. An upper carcass weight of 85kg would seem prudent in this regard.


It is impossible to give one recommendation for an optimum target liveweight at slaughter. Each processor has different upper carcass weight limits, different penalty structures and, even within processors, different suppliers may have negotiated different upper carcass weight limits. Without an upper weight limit, each extra kilogramme produced is profitable. Where a carcass weight limit of 85.5kg is set then producers should target all pigs exceeding 103kg for slaughter each week to maximise profitability. However, the industry must always be mindful that increasing slaughter weight also increases the risk of boar taint raising its ugly head.

Irish Independent

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