Hens at age
The optimal economic lifespan of a layer has increased significantly the past few decades due to improved breeding programs, nutrition, housing etcetera. Today's layers are productive for up to 25 more weeks than in the 1970's. Keeping layers until past their prime can be very beneficial, however, it does ask for some specific measures to assure continued productivity.
In addition to the economic advantages, there are also advantages from an animal welfare point-of-view. One point of debate in this issue is 'the molt'. Molting is the process of shedding and renewing feathers. During this process no eggs are laid. Farmers who want to keep their layers for more than one round often opt for forced molting. This means that the molting is induced by reducing feed intake and water to control when it happens. To improve animal welfare it would be better to be able to prolong the economic viability of layers without a molting period.
Prolonging the laying period
Over the past decades the quality of eggs has increased and a laying persistence in layers has improved. For a nice overview see the table below.
|
(brown layers) |
1970’s |
2000 |
2008 |
2020, expected |
|
Eggs per hen housed (75 wks) |
239 |
319 |
337 |
361 |
|
Eggs per hen housed (100 wks) |
|
|
430 |
487 |
|
Egg mass (75 wks) |
14,9 |
20 |
21,2 |
22,9 |
|
Egg mass (100 wks) |
|
|
27,3 |
30,9 |
|
Feed conversion rate |
3,16 |
2,1 |
2,5 |
2,02 |
|
Laying % (75 wks) |
55 |
74 |
77 |
82 |
Other advantages of prolonging the laying period of hens include:
-
Slower depreciation of young layers
-
Low production costs for older layers
-
Less labor is involved with older layers (vaccinations, loading etc.)
Despite encouraging facts and figures the average laying period used varies greatly. However, keeping laying hens for 100 weeks or more is not yet common practice in most regions accept for North America where forced molting occurs around 65 weeks.
Effect of age on egg parameters
The parameters of the eggs laid by older hens decline. Measurements in several trials show a reduction in the thickness of the egg shell, a decline of the haugh units and an increase of the number of second quality eggs (commonly used in the food industry). Especially the egg shell is important because it protects its contents against microbes and mechanical impacts.
Need for nutrients of layers at age
When hens are kept longer, extra attention must be paid to the changed physiology of the animal by:
-
providing the hens with plenty of calcium to guarantee optimal shell quality. Hens must be provided with 2 different calcium sources: the highly available sources and the source with slow release of calcium like for instance shell grid. Slow-release calcium will be available during the formation of the shell.
-
guaranteeing proper availability of phosphorus and vitamin D3. These are also necessary for high quality of the egg shells. The absorption of calcium and phosphorus are interrelated and vitamin D3 is essential for proper calcium and phosphorus utilization. introducing phase feeding in accordance with the different age levels.
Minimizing the selective intake
When feeding the hens there is a difference in nutrients at the beginning of the house and at the end, due to selective intake and due to particle size.
Intestinal health
Most health strategies for vaccinations and other treatments are developed especially for the hens which are kept until molting. Why should a treatment be valid longer than necessary in this case? When a farmer decides not to molt, this can result in a new chance for growth of for instance Salmonella. It is important to support the animal in maintaining its intestinal health via feed or drinking water supplementation.
The addition of short chain fatty acids have a positive effect on the intestinal flora and the gut wall. Especially the combination of formic acid and propionic acid has proven to reduce the motility of Salmonella. These acids improve the calcium absorption by providing an energy source for the enterocytes (active calcium transport) and by improving the absorption capacity (important for the passive calcium transport).
The combination of short chain fatty acids with essential oils (ProPhorce® PH concept) not only reduces the motility but has also shown to significantly reduce the invasiveness of Salmonella into the gut cells and blood stream.
Summary
The trend in the market these days is moving towards keeping hens for a longer period of time without molting. Economical and animal welfare benefits are worth it. Feeding strategies and health need more attention in the last period. To improve shell quality in aging hens it is important to feed more slow-release calcium compared to highly available calcium. Introduction of short chain fatty acids in combination with essential oils into the diet or via drinking water has a positive effect on the intestinal flora and can help prevent Salmonella.