My pigs are too fat – an investigation process



Define the problem

Look at backfat over time – check for seasonal impact

The P2 changes with the time of the year – pigs are fatter going into autumn as they eat more as the weather cools off and they are thinner in the early summer as they grow better.

Note the effect is also on the weaners growth and fat deposition

Look at back fat variation within the group of pigs – what is the required matrix



The green box represents the ideal matrix box. 

At this slaughterhouse the ideal matrix was 8 to 12 mm and 60 to 70 kg deadweight

The two graphs are the range of weights presented in the slaughterhouse and the P2 measurements in those pigs

In this population: Mean deadweight (headoff)  – 67.3 kg sd 7.3        Backfat P2 10.4 mm sd 2.82


What effect on back fat, and more importantly profit, if you change some parameters

Check the result of the population if:

Change in average weight up and down

Sell  pork or light weight pigs more efficiently (if this is available)

Decrease variation around the ideal point:  Raise the light pigs – give them an additional week

                                                                     Decrease number  of heavy pigs – weigh pigs

Pigs should be weighed every time they are moved – weaning/10 weeks and slaughter at least

Decrease the variation in back fat – note and sell heavy fat pigs, Paylean and PST

Increasing live weight at slaughter by 1 kg increases P2 by 0.2 mm

Note impact of chemicals – Paylean, PST or Improvac (for males) for example (if available)


When is the problem occurring- examine the growth rate of the pigs


Fat deposition is about feed intake, but this can be difficult to measure.

Monitor the growth rates of the pigs at various stages around the farm.

Pigs who grow slower in the nursery area will not deposit lean tissue.

Pigs that reduce their feed intake in the finishing house will be leaner.

Days to slaughter =  ((Total wean to finish pigs on the farm/pigs sold each week)+(weaning age in weeks)*7)

Growth rate          =  (Liveweight kg)/(days to finish) = g/day birth to finish


What is the spread of ages at slaugther?


How tight is the slaughterhouse weights and how long does it take for the farm to empty the finishing house?  Does the farm utilise a weigh scale to monitor liveweight. Note diseases present


Environment of the pigs

These pigs are exactly the same genetics as in point 2.  Here the pigs were housed on straw




As pigs are raised more controlled environments the backfat range and variation reduces.

These pigs on straw had a deadweight (head off) mean weight 72.2kg sd 7.1, P2 11.8 mm sd 3.5

But note heavier pigs have more backfat.  These extra 5 kg would be expected to raise P2 by 1mm.

Finishing long pen 3

Grower group eco au 2

The pigs from point 2 – slatted curtain sided

The pigs from point 4 – ecoshelter on straw


Are any provisions made for the small pigs at weaning – streaming.  This helps to reduce variation


Impact of sex – male, female or castrates

Male – on improvac


Deadweight kg mean 68.6kg backfat P2 10.5mm

Deadweight kg mean 66.4kg backfat P2 10.4mm


Basic production issues – pig flow

All farms batch.  What are the batch parameters being utilised/required?   Does the farm utilise all-in/all-out?  Monitor batch variations over the year – look for under-stocking and over-stocking


Feed factors

Examine the feed and feed quality

Increasing lysine by 1g per day – reduces back fat 0.1 mm

Increase protein intake in general – but this increases cost

Increase energy intake by 1MJ/DE per day – increase fat depths by -0.6 mm

Reduce feed intake 100g per day – decrease P2 by 0.6mm.

Note mycotoxins and other factors that impact feed intake

Carefully examine feeders and waterer.

Space and location within the pen


Environmental factors

Boar conformation 1

High conformation boar

Check the environment of the various accommodation.

When are the pigs moved?

Are the pigs mixed?

Note Water, Food, Floor and Air issues.

Are facilities suitable for the group – note over and under-stocking


Genetic factors

The boar in particular can have an enormous impact on feed intake, backfat, carcase composition and growth rates.
How do you check the suitablity of the boar?

But note:- the mother also provides half of the genetics to the finishing pig.  This can be a particular problem in home reared gilts.

Some clients with homebred boars will use a selection of boars on test sows.  The boars are then put on ‘ice’.  Following a review of the ofspring in the slaughterhouse – 9 months later – the best boar is brought out of retirement for the next year the others sold


Diseases and pathogens

Examine the pigs for any pathogen which is going to increase variation and affect feed intakes.

Ileitis (porcine enteropathy), lameness issues, respiratory problems.  Note Mycoplasma pneumonia may actually reduce P2 by limiting feed intake in the finishing pig!