From by Bernard Peet

Some producers weaned successfully as early as 14 days, made possible by improvements in housing and nutrition. Very early weaning has also been used extensively in the USA in 3-site, SEW systems to control the transfer of disease from the sow to the piglet. However, most European countries have actually increased weaning age over the last 10 years or so. Although EU legislation forbids weaning at less than 21 days, typical weaning age in Britain is 25 days and in Denmark, 28 days.

In Western Canada, where I now live, few producers moved to very early weaning, partly because of the much better health status compared with the USA; 18-20 days is a more common weaning age. Recently though, several of my clients have asked whether this is economically the best time to wean and whether it would be better to increase weaning age. This is a complex question because of the interaction of weaning age with so many other performance and cost factors in both the breeding and feeding herd.

We know that as weaning age increases, wean-service interval decreases and is less variable, litter size gets bigger and farrowing rate tends to improve. Older (heavier) pigs eat more in the nursery, grow faster and therefore leave the nursery at a heavier weight. Where finishing space is fixed, which is increasingly the case, weight at slaughter is typically increased by 3-5kg for every 1kg increase in weaning weight. The down-side is the capital and labour costs of additional crates and the reduction in litters/sow/year.

Most of the research data looks at performance effects of weaning age or weight rather than the economic implications. It also tends to evaluate particular stages of production not the whole system. However, a series of three papers by Main et al, presented at a recent Swine Day at Kansas State University, report the results of trials carried out on a 7,300 sow unit with separate nursery and finishing sites, which looked at the economic implications of weaning ages from 12 to 21 days.

Table 1 shows the effect on nursery performance over a 42 day period, indicating the very large improvements in feed intake, growth rate and final weight as weaning age increased.

Table 1 Influence of weaning age on nursery performance
Weaning age (days)	12	15	18	21
Weaning weight (kg)	4.2	4.9	5.7	6.5
Av. Daily feed intake (g)	426	512	562	653
Av. Daily gain (g/d)	299	367	408	476
Feed/gain	1.42	1.39	1.38	1.38
Mortality(%)	5.3	2.8	2.1	0.5
Weight at 42d post weaning (kg)	16.9	20.3	22.6	25.8
From : RG Main et al, KSU Swine Day, 2002

Comparing pigs weaned at 15 and 21 days, each extra day on the sow increased weaning weight by 266 grams and 42-day weight by 916 grams, a ratio of 3.5:1. Main and his co-workers also looked at the finishing performance, costs and revenues of these pigs.

Increasing weaning age improved growth rate, reduced mortality and resulted in a slightly better carcass lean percentage, although the differences were much smaller than at the nursery stage. Standard costs for feed, housing and other inputs were applied to the performance data to look at the economic impact of weaning age in finishing systems with limited space and where space was non limiting.

Table 2 shows the results where finishing space was limited.

Table 2 Influence of weaning age on nursery performance
Weaning age (days)	12	15	18	21
Weaning weight (kg)	4.2	4.9	5.7	6.5
Kg sold per pig weaned	94.1	100.5	104.5	113.1
Revenue/pig weaned (US$)	88.17	94.19	97.86	105.94
Costs per pigs weaned (US$)	80.98	83.54	84.98	88.52
Income over variable costs per pig weaned (US$)	7.19	10.65	12.88	17.42
From : RG Main et al, KSU Swine Day, 2002

I have presented the data on a "per pig weaned" basis as it takes into account the differences in mortality from weaning to slaughter. The effect of the higher weight of carcass sold as weaning age increases has a huge impact on margin.

There is a large difference between the 18 and 21 day pigs, primarily because mortality dropped considerably for the later weaned pigs. The extra margin is US$4.54/pig weaned or US$104/sow/year if 23 pigs are weaned.

The cost of the additional crates necessary to increase weaning age from 18 to 21 days is about $60 per sow in the herd. Even if half the benefits of later weaning were achieved, the payback would only be just over a year!

The work at KSU also showed that in a finishing system where space was non- limiting, the extra margin was still US$3 for 21 day versus 18 day weaning.

One of the arguments for earlier weaning has been that farrowing crates are expensive and later weaning increases cost per sow place in the barn. The figures above suggest more crates are an excellent investment.

But what about the reduction in LSY and pigs/sow?

Table 3 Breeding herd performance in Denmark 2001top 25% herds
Average weaning age (days)	28
Average pigs born alive/litter	12.6
Average pigs weaned/litter	11.2
Litters/sow/year	2.33
Pigs weaned/sow/year	25.7
From: National Committee for Pigs, Annual Report, 2002

My own experience and farm recording data suggests that over the range 15-25 days, improved litter size, farrowing rate and fewer breeding problems more than offset a slightly longer breeding cycle and increase the potential for higher overall breeding herd output.

Danish producers, considered still to be world leaders in pork production, now wean at 28 days - not because they have to, but because they believe it makes economic sense. The top 25% breeding herds in the country average 25.7 pigs weaned/sow/year (Table 3) and get a whopping 12.6 piglets born alive/litter.

The best 25 of these herds produce between 27 and 29 pigs weaned and have average weaning ages of 24 to 32 days!

So is it time to re-assess weaning age? I think so.

This article first appeared in Western Hog Journal, Winter, 2003