In mid to late summer, the poultry health focus changes from the disease of chicks, such as coccidiosis, to growth limiting diseases such as Mycoplasma. These are big names for the two common problems called Chronic Respiratory Disease, and Coryza. However these common names actually are all related and sometimes are called the "Summer Respiratory complex."
There are a number of contributory factors to these disease and they all tend to multiply the problem. What I mean, is that once the bird has one part of the complex, and it is treated for that part, there is a great tendency for the bird to simply "come down" with the next part of the problem. This leads to a rather frustrating problem which for all intents and purposes seems rather like a merry go round.
So, how can we break the cycle of sickness without constant cycles of treatment? I think I can outline a very simple program which will help.
Underlying many of these problems is a series of factors. Attention needs to be paid to each of these, not because any one of them is the problem, but because they all cause stress, and the stress opens the doors to a particular organism which leads to the other problems.
So the scenario runs like this:
As young chicks, the birds are infected with an endemic (it is everywhere) disease called Mycloplasma gallisepticum , or MG. On its own it is not a problem, but as the chick grows, this bug hides in the respiratory tract of the bird.
Then some factor triggers the disease off and it starts to multiply. Some of these factors are: infectious bronchitis, poor housing, changes to housing, overcrowding, lack of particular food nutrients, abrupt changes to food nutrients, wet litter coccidiosis, poor sanitation, changes in the weather, extreme heat or cold, travel or vermin. All these factors cause stress. The stress factors in themselves do not cause problems but they allow the MG to become active. The MG infection then reduces the immune system, and allows many other opportunistic invaders to attack the birds. The summer respiratory problems become apparent, with Fowl Cholera, coryza, gurgles, one-eyed colds, and a host of other local names for these problems. Often the birds get gurgles, become light, waste away or are just "poor doers".
So, what to do??
One way to do this is through vaccination for MG. Unfortunatley, this is of limited benefit with multi-age flocks, although certainly practical with commercial flocks. Small flocks have problems with vaccine quantity and application, and the vaccine cannot be used with birds already exposed to the wild disease organism.
Another way is to use antibiotics as a preventative to reduce the vigor of the MG.
There are many programs for the application of antibiotics as a preventative to reduce the possibility of development of the summer respiratory complex.
The program has one inportant part that is to treat at day old for the first few days of their lives to ensure the limiting of the organism from day one. The rest of the program is a little more flexible. It will not matter a lot if the birds get their dose at three weeks or four weeks or even five. So I would run a program that was very specific about the first 4 days of treatment, then treated all the birds in the facility for one day of drinking water a month.
Usually continuation of the program for 1 full season for all chicks hatched, all breeders in the sheds and all growers will mean the following season will be almost free of SRD.
Please note: Do not use antibiotics when other treatments are in use i.e. coccidiossis treatment (where coccidiostat is present in feed)