The aim of every finishing enterprise should be to slaughter all pigs within plus or minus 5kg. from the average.

Therefore, the target range is 10kg. (i.e. 5kg. each side of mean), this equates to around 14 days of growth, assuming 685g/day average growth from weaning to 100kg. Given this weight spread it should be entirely feasible to get almost all pigs into the range over a two-week period.

That is the achievable standard - but reality is often far from this.

What can be done to minimise variation in Growth Rates?

Focus on - THE SOW:

Weaning weight for age has a close correlation with lifetime growth. Weaning weight for age is closely linked to birth weight and to sow's milk output. Sow milk output is closely related to feeding.
So lets break these three stages down.

The Dry Sow:
The widespread use of group housing of sows has meant that, on many units, young sows are run with older animals during pregnancy and it can be difficult to ensure that the smaller individuals achieve an accurate share of the food and space offered - another potential cause of variation in the size of piglets subsequently born.

Although research evidence is not too conclusive many units find that increasing feed levels, (to 150% of midpregnancy levels), in the final month prior to farrowing can help to increase birth weights and this is especially effective in those individuals which are of below-average body condition going into the final quarter of pregnancy.

Minimising Variation in the sucking: weaner phase - Key points summary

The Sow Wean and re-move sows in good condition - check lactation feeding. Check the condition of your sows in pregnancy - do you need to increase mid pregnant feeding levels? The Weaned pig Get the 'spaces' right - floor, feeder & drinker. Get the environment right - especially for the smaller pig. Don't move smaller pigs to the next diet too soon.

Feeding the Sow during lactation
Weaning weight depends on how well and accurately you feed the sow. The chances of achieving consistent birthweights when feeding levels are not matched to body condition is low and the need to wean sows, especially gilts, in the condition that they are farrowed in, is now well understood. Yet - too many sows, particularly those following their first litter, are re-mated in much poorer body condition than they should be in. In the effort to rebuild excessive lost tissue the contents of the uterus will suffer and lower birthweights are a common consequence.

The relationship between feed intakes and milk output in lactating sows is well established.

Too many tend to 'shrug shoulders' when sows display a tendency to limited appetite and simply assume that nothing can be done about it. Let us see what lessons we can learn from outdoor sows, which frequently eat over 10kg per day.

The differences between indoor and outdoor sows can be summarised:

• Outdoor sows have access to ad lib water from a trough that does not require the animal to "work" at obtaining water - as it would have to do from a bite-type valve.
• They often have feed available ad-lib rather than some, (often inaccurately), measured amount.
  It may well be worth reviewing precise farrowing house feeding methodology before assuming that nothing can be done to improve intakes - and, therefore, milk output and evenness of pre-weaning growth.

There is a correlation between farrowing house temperature, sow feed intakes, milk yield and weaning weight - as shown in Table 1. below:

Table 1	Farrowing House Temperature		% at 20oC
	30oC	20oC
Sow feed intake (Kg)	4.95	7.73	56
Milk Yield (kg/Day)
Week 1	6.34	8.54	35
Week 2	7.16	10.61	48
Week 3	6.13	10.92	78
Week 4	6.92	10.99	59
Mean Piglet weight (Kg)
Birth	1.51	1.52
Day 7	2.93	3.13	7
Day 14	4.59	5.52	20
Day 21	6.09	8.03	32
Day 28	7.64	10.36	36
Sow liveweight loss (Kg)	21.0	6.4
Sow backfat change (mm)	-3.0	+2.2
(Vidat et al 1991)

Disease and variation in growth rate

Any disease that effects a large % of your pigs will cause growth rate variation because the pigs use up food fighting disease rather than converting food into lean meat.

Respiratory Diseases and Diseases that effect the gut (enteric diseases) are particularly important because:

• They are infectious and will inevitably effect a large % of your weaner and grower pigs.
  
• They can be "subclinical" - no blatant signs - but they are doing enough to effect performance.

So what is your response?

Make sure you work with your vet to understand the disease status of your herd - prevention of respiratory and enteric disease is critical.

lleitis is one of the enteric diseases that can cause severe variation in growth rates and it is worth checking with your veterinary surgeon whether your unit is affected by this disease. Part of his investigation may be the use of the lleitest (11 blood samples from pigs of 80kg plus) which will confirm whether you have the cause of lleitis Lawsonia intracellularis - on your farm.

Minimising Variation in the Post Weaning Period

The penning of pigs according to their size is a well-established routine. However, the increasing trend to run larger groups of weaners together need not necessarily exaggerate any weight variations providing that certain rules are observed.

• Adequate floor space - overcrowding definitely exaggerates the variation in growth performance - see table 2.
• Adequate feeding and drinking space - the weaker pig is more likely to be pushed out if there is too much competition - and so variation in weight will widen.
• Feeding opportunity - the provision of feeders in two different parts of the pen can help to reduce competition.
  
• Drinking opportunity - the right number of drinkers in the right place with the right flow rate. The use of troughs or bowls may speed the intake of water and, as a result, encourage greater feed intakes.
• The correct diet - far too often pigs are disadvantaged by a change in diet being made prematurely. This has a considerable potential impact upon increasing growth variability as it is the slightly smaller individual that will be most affected by such a change. The use of choice feeding is a most valuable tool in mitigating this effect - this is where two, or more, diets are offered to a group of pigs allowing smaller individuals access to a denser diet for longer.
• Environmental control - the matching of air temperature and airspeed to size of the pig and the particular environmental circumstances created by the system of housing in use require intelligent and caring response. Again, getting adjustments and settings only slightly "wrong" will have a bigger adverse impact upon the less robust pigs in the group - another cause of widening variation.

Table 2 - Effect of Floorspace on Daily Liveweight gains in young pigs
Days after weaning	Light Pigs		Heavy Pigs
	0.22 sq.m/pig	0.30 sq.m/pig	0.22 sq.m/pig	0.30 sq.m/pig
0 - 7	0.165g	0.122g	0.169g	0.155g
15 - 21	0.446g	0.367g	0.594g	0.559g
29 - 33	0.537g	0.578g	0.592g	0.734g
(Penny 1998)

First Published in 'Pig Pages' - Elanco Animal Health's UK Newsletter.

Find out more about Tylan Premix^® or visit the Elanco Animal Health web site.

---

---

Tylan^® is a trademark for Elanco's brand of tylosin. ©2001 Elanco Animal Health
References available upon request.

NOTE: Reference to commercial products or trade names within information provided by thePigSite.com does not constitute an endorsement by the thePigSite.com and does not imply discrimination against any other similar products.