In this article I will look at that last real peak of mortality in the young flock we have been studying, which seems to appear after the birds have gone out to grass. This peak appears quite high, and has a long tail. To start with, I hope to explain some of the factors that come into play at this time in the bird’s life
Firstly, going out is a stress, and the way the birds react to it can depend on the weather and the changes surrounding this phase. The heat is now off, they might be seeing grass and insects for the first time, and instead of the comfort of the hut they have known up to this point, their new shelter could be very different.
The actual stress of going out can be minimised by careful planning, and watching the weather. I know keeping an eye on the conditions is something most keepers like to do, but it is possible to get caught out.
As an example, last year a shoot local to me lost 60 per cent of its birds in one night because of a freak storm, and no amount of planning will combat something like that. What can help is making changes slowly, and one at a time. If this is a time for a change of diet, it may well be best to get the birds out and settled before you switch their feed.
It’s also worth doing something similar with drinker types, so a move from bells to nipples should be delayed for a few days. On the subject of nipples, we have had situations in the past where the nipple type needs to be changed at about this stage to allow a better flow of water for the birds as they start to drink in greater volume. If you are in any doubt, consult your supplier.
Having got it all going to plan in terms of reducing stress, what diseases await as the birds move outside, and do they play a part in this peak? The answer is almost certainly yes, there is a risk of a disease burden at this time, and for the rest of this article I want to look at what causes most of that peak of mortality.
The Eimeria (Coccidia) parasite has a life cycle of about seven days, depending on environmental and climatic circumstances. This runs from being picked up as the oocysts (eggs) from a contaminated environment, through several phases of reproduction in the cells of the gut wall, to finally reaching maturity and destroying the cell.
This releases vast numbers of oocysts to start the next cycle. Successive waves of the disease cause greater and greater contamination of the ground and increase the infective dose for the next flock placed on the ground.
The numbers involved are quite staggering, with one oocyst ingested resulting in the shedding of many thousands of oocysts, causing serious damage to the lining of the bowel in the process. The organism likes moist conditions, and can be found around the bases of drinkers or other patches of wet ground.
If the infective dose is small, there may be few signs besides the birds being a little dull and ruffled. In more serious cases, there may be weight loss, lethargy, dehydration, diarrhoea and death. In partridge the signs can come on as quickly as sudden death, and in chickens a severe case of the disease can result in blood in the droppings. Some keepers rely on chalky droppings as an indication of the disease, but this is not always a good or consistently reliable indicator.
In a previous article on this disease I mentioned that the 21 or 28 day ‘strikes’ are probably not the first the bird has experienced, and we have found the disease in birds as young as 14 days.
However, the clinical signs were very minor, with just ruffled birds who were food flicking. Birds certainly may already have cycled the disease once if not twice if they have had access to soil in the hut or sun porch.
We sampled birds weekly and the results are shown in the graph.
The massive rise in period four (from 28 days on) is an indicator of the massive numbers of oocysts produced by the birds as they go through a Coccidiosis challenge.
There is a difference between pheasant and partridge in the way they respond to the disease. Our sampling showed that pheasants seem to develop ‘street-wise’ immunity fairly quickly after the first major challenge, whereas partridge immune systems don’t seem to learn and will go on to suffer quite badly for one or two more cycles. No-one seems to know why this happens, but several of my colleagues have noticed the same effect so it is a question of ‘be warned’.
Treatment is relatively straightforward: a coccidiostats is usually placed in the food as a routine, but standard levels do not appear to control any major outbreaks or challenges. Increasing the dose in the food can lead to un-palatability, and overdosing can cause serious side effects, so the other option is a water-soluble drug to kill the coccidia. There are two of this type available, Baycox (Toltrazuril) or Amprolium, and your vet should be able to recommend which course of action is best.
Effective control is simply playing the numbers game, keeping the numbers of oocysts ingested to a minimum. This is mainly done by paying attention to the hygiene of the birds’ drinkers and feeders and the ground around them, not re-using old or infected pens or equipment and certainly not overstocking pens.
Also, I mentioned previously that many flocks will see a dip in food intake due to the stress of going out or a change of food around this time. If the birds’ food intake is dropping due to stress, then their intake of the in-food coccidiostats also drops accordingly, and this may be sufficient to make the difference between a challenge that you can see and one in which you only notice the birds becoming a bit ruffled.
Coccidiosis can be among your birds without you even realising. Clean ground will help reduce initial challenges, and keeping your birds as stress-free and healthy as possible will help them through if there is an outbreak.
Be aware that, even though pheasants might build up immunity, partridges will struggle to do this, so bear that in mind when choosing where to site your pens. If you do start to see Coccidiosis having an effect, there are treatments available for it that, combined with birds that are eating and drinking well, can keep your overall drug use to a minimum and reduce the severity of other challenges.
All these points should help to reduce that peak of mortality in the first week on the grass. Next time we will look again at those dreaded protozoans and see if there is anything new in the pipeline.