Uniformity in finished pigs

Typical variation in finishing pigs meeting specification at slaughter is between 20–30% nationally. It is important to be aware of and understand the variation on your unit.

Back to Finishing pigs

Variation occurs for many reasons: season, management, nutrition, feeding strategy, genotype, environment, gender and health. Look at three (or more) months’ worth of grading information and note the following:

  • Overweights
  • Underweights
  • Out-of-probe specification pigs
  • Percentage of pigs in the optimum box (target 85%)

When looking at grading information, choose a period of normal production, i.e. avoid data collected during movement restrictions, consistent hot periods or at Easter, Christmas and New Year.

Discuss what you have found with your marketing company/abattoir buyer to identify your problem areas.

Setting targets for your unit

Note your average deadweight and probe results and set targets relevant to your contract. Each unit will have different targets, depending on the contract.

You and your staff need to be aware of the current probe and deadweight specifications required by the contract. Discuss your targets with your marketing company or knowledge exchange manager to clarify what is ‘normal’.

Look at the slaughter data with your finishing staff each week/batch, so they can see progress being made and quickly implement changes, where needed. If you have control over it, improving the management of weaner/grower pigs will reduce variation from the offset.

Management guidelines

Weighing pigs

Weighing pigs on a routine basis throughout their life, i.e. weighing at routine pig moves/flow, gives you essential information that will help you improve uniformity.

The data will let you know when your weight spread shows too much variation or is considered outside of ‘normal’, or if growth rates are slowing. Solving these problems will rectify issues with uniformity early on in the pig’s life before they cannot be changed.

Establish routines/protocols with your vet and nutritionist if weight variation occurs at routine pig moves – this means staff can react quickly to problems.

Weight watcher pens

  • Pick out a number of pens from a week/batch of production, weigh and record average weights
  • This is an excellent way to gather useful information in a short period without having to weigh every pig
  • It will provide a good indication of growth rates and pre-warn you of slow- or fast-growing periods
  • If you group your pigs by size, make sure you pick representative pens, from the smallest to the largest pigs


Boars grow more quickly than gilts and tend to be leaner. If your analysis shows gender differences, consider different selection weights for boars and gilts.

Depending on the extent of the gender differences, it may be worth considering split sexing – talk to your vet and nutritionist about the advantages this could have on your unit.


Nutrition guidance for pigs

Incorrect diet specifications will increase the likelihood of variation in weight and probe measurements.

  • Consistent diet ingredients can reduce variation among pigs fed by-products and home-mixed feed
  • Feed to match genetic potential and health status
  • With ad-lib feeding, ensure hopper space is adequate for weight: 50 mm/pig, increasing to 75 mm/pig near finishing. Also check the hopper design and location in the pen allows equal feeding opportunities
  • With restricted feeding, ensure hopper space is adequate: 200 mm/pig, increasing to 300 mm/pig near finishing, to allow equal feeding opportunities
  • With restricted wet feeding, allow all pigs to feed at once but keep an eye out for queuing and vices
  • Remember the importance of water: water intake drives feed intake. Clean, constantly available and accessible water is vital to maintain feed intake. As with feed, equal drinking opportunity will reduce variation. Finishing pigs require 5–6 L/day, with a water flow rates of 1–1.5 L/min. See our pages on water guidance for pig farmers for more information
  • Any variation should be discussed with your vet and/or nutritional adviser

Water guidance for pig farmers

Remember the importance of water: water intake drives feed intake


If you are producing your own replacement gilts, there will be a percentage of dam line progeny in the finishing herd; these will probably introduce variation in both growth and grading results, especially at heavier weights. Identify the correct streaming and sale weight for these dam lines.

Physical environment

A poor physical environment will result in greater variation among pigs, i.e. temperatures that are too high or too low, with high levels of ammonia or carbon dioxide. Spend time observing your pigs’ behaviour, look out for early signs of stress. You can find more information about this in our online husbandry advisory tool (WebHAT).

Tail biting husbandry advisory tool (WebHAT)

All-in all-out systems are preferable, where possible, and a strict cleaning and disinfection protocol must be followed. Keep buildings and ventilation systems in good repair, check for worn bearings, burnt-out fans, blocked inlets, etc. and review opportunities to invest in low energy components to replace worn out parts.

If stocking densities are suboptimal, it can compromise growth and grading.

  • Overstocking can cause:
    • Heat stress
    • Unequal feeding and drinking opportunities
    • Extended days to sale and pen clearance
    • Increased vices (tail, ear and flank biting, etc.)
  • Understocking can cause:
    • Cold stress, especially in naturally ventilated buildings, and buildings with poor temperature control

Seasonal effects

Carcase weights tend to be lower during the warmer months and then increase as we move into autumn. Discuss any specific seasonality issues you have noticed on your unit with one of our knowledge exchange managers.

The better the health, the more chance the pig has of achieving its genetic potential. In relation to variation and grading, improved health can:

  • Increase growth rates
  • Reduce the spread of weights within pens
  • Lower the number of condemnations

Points to consider

  • An all-in all-out system will enable you to clean and disinfect all rooms between batches
  • Is it possible to keep pigs in the same group from weaning through to slaughter?
  • Reduce the number of movements post-weaning to improve pig flow by vaccinating sows and piglets with a PCV2 vaccine
  • It might be worth selling lighter, poor-growing pigs with the rest of the batch, rather than keeping poor growers back to reach target weight
  • Change diets between weaning and finishing with a phase-feeding programme, switching diets gradually on a daily basis