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This is a very common problem on free range farms. Eggs are allowed to get too big. Ah, but I hear you say, "the price of large and extra large eggs encourages me to produce large eggs, so that is what I do". The reply to that is, "clearly profitability is reduced if eggs are too small but it is not necessarily improved by allowing eggs to get too large".



Therefore, what do "too large" and "too small" mean? In practical terms, it is wise to follow the recommendations in the breeders' manual. Obviously if the eggs are below their target, you could be reducing profitability, but very importantly, if the eggs are bigger than their breed can cope with, it is virtually certain that profitability will not be better than if the target had just been attained. I suspect that a maximum mean egg weight for the whole laying period for free range egg production with many of the current breeds being used should be about 65.5 - 66 g. Let's look at the evidence and see if I might be right. We need to be careful though because for some breeds this target may be a bit too high. Don't push them beyond their genetic potential. Profitability is certain to be reduced if the hens are stressed.

So we are back to that dreaded word "stress" again! In this context, what can sometimes happen is that hens that are laying eggs that are unrealistically large may die more readily. Many well managed and unstressed flocks have a cumulative mortality for the laying period of about 4 – 7%. Where egg weight has been too big, producers have been extremely happy up to about say 45 weeks but then could be depressed by an increasing mortality pattern in the second half of the laying period. However, usually it takes further interacting stressors to trigger the mortality increase. Stressors act cumulatively. At the time when the peak egg mass output (hen day production (%) x average egg weight / 100) has been reached (usually at about 40 weeks), all has been rosy with the bank manager. Towards the end of the laying period however, the cash flow would be poorer than it should have been. The following graph shows an example that thankfully is extremely rare of how wrong things can go if egg weight is allowed to get too big, in a flock that were underweight.

Despite the mortality as on the above graph, the performance of this flock was exceptionally impressive. Hen day production exceeded 90% for 27 consecutive weeks and peaked at 97%. When combined with the rapidly increasing egg weight, the egg mass output reached the danger zone of >60 g / hen/ day at 27 weeks (extremely early) and then peaked at 65 g at 39 weeks. What a happy producer he was at that time! However, the hens were less 'happy' because they were very stressed by this exceptional performance. The producer then was less happy when for welfare reasons the hens were depopulated early. Mortality as high as this is thankfully unusual and is most certainly unacceptable and the management of the flock must be geared to avoiding it.

So what lessons can we learn from this?

1. It is wrong to try to maximise egg production and egg weight in hens that have not been reared successfully. Pullets must have the correct physiology (liveweight) to be able to cope with the stress of every day life on a free range farm. Underweight pullets are better able to cope in caged units than on free range ones.

2. Nutrition plays an important role in its effects on egg weight. The two important constituents of the feed in this context are methionine (an essential amino acid / protein) and linoleic acid (an unsaturated fatty acid). It is essential to have a wide range of feed qualities available so that a step down feeding programme can be used. The timing of the changes is critical. It is a good idea to feed a very high quality feed until about 21 weeks old and then change to a good quality one until the egg mass output reaches about 60g / hen / day. A change of feed then is necessary so as to prevent the egg weight increasing as fast as it had been up to that point. When things are going well it is tempting not to risk changing the feed but it is invariably a mistake not to have done so. Further changes in the feed quality may be necessary later in the flocks' life too. With each nutritional step downwards, the methionine and linoleic acid would be reduced.

3. Everyone is used to post mortem reports coming back that say that the hens have died of peritonitis or salpingitis. This can be true where stress is involved from an egg weight that has been allowed to become too large. It can be extremely and depressingly difficult to stem escalating mortality in these cases.

4. The quantity of shell on eggs laid by each hen tends to be fairly equal throughout the hens' life. It therefore follows that with the same volume of shell being available when eggs get in the 68 – 71g range, as when they were smaller, they can become rather thin. These very large eggs are more likely to get cracked by impacts and crushed on the egg trays. Total Seconds can rise to financially disappointing levels towards the end of the laying period. As the hens are stressed at this time, eggs tend to be paler too with this exacerbating the second quality eggs problem.

The above table uses free range egg prices for each grade that have been paid to some producers recently. It looks at the effects of egg weight and the percentage of second quality eggs on the value / dozen eggs. At first glance it implies that the bigger the eggs the better the value but then one has to bring a dose of realism into it. If one assumes that Total Seconds for the whole of the laying period should be not more than about 7 - 8%, they could be about 12% or more if the eggs are too large.

For most free range producers i.e. those who receive a different price for each grade, it is clear that a mean egg weight of about 64g is likely to reduce profitability. However, shell quality should be good and there is unlikely to be any stress to the hens for producing eggs of this weight. But, a larger mean egg weight is attainable.

At the other extreme, if the mean egg weight was as high as 67g, increased mortality; a higher feed consumption and, most importantly, an increased number of seconds may occur. Bearing these interactive factors in mind, there seems to be no incentive for the mean to be above about 66g. Therefore the above evidence endorses my earlier target, that provided that the breed that you have chosen has been genetically programmed to produce eggs of this size, the aim is that the mean for the whole of the laying period should be between about 65 & 66g.

So what happens if the egg packers change the ratio between the prices that they pay for each grade and slant it to encourage more Medium sized eggs? Easy! Just alter the lighting and nutritional programmes and maybe change the breed that you use. You have control of this, so adapt your management accordingly.