By Dr Colin Walker BSc, BVSc, MRCVS, MACVSc
The crop of healthy pigeons should empty within 12 hours if
fed twice daily and within 24 hours if fed once daily. Delayed crop
emptying can be the initial indication to the fancier that all is
not well with the team.
Often the problem is first noticed when birds are picked up for
a morning toss and are found to have food in their crops from the
day before. Alternatively birds may not appear normally hungry
and trap sluggishly simply because they still have food in their
crops, waiting to be digested, from their last feed.
And so what are the possible causes of delayed crop emptying?
I find it easiest to group potential causes into four categories,
namely, problems with the food, the crop itself, the environment
or the body generally.
The crop is the dilated area of the oesophagus (the tube from the
throat to the stomach). It is the initial place that swallowed
food comes to rest. In health it is a functional, contracting,
muscular sac. At the completion of the meal it begins pushing
boluses of food through into the stomach. Anything that inflames
the crop wall interferes with this function. Common infectious
causes include wet canker, thrush, and bacterial infections (often
E coli.). Microscopic examination of a sample of fluid taken
from the crop i.e. a crop flush, can be used to identify a problem.
Feeding poor quality food contaminated with bacteria, fungi, or
toxins will lead to a slow crop.
One of the initial subtle ways that race birds have of showing
us that all is not well is a crop that takes too long to empty.
Frustratingly the list of possible health causes is virtually
endless. The problem could be a disease elsewhere in the body
that is not immediately associated with crop function e.g. worms
or Coccidia. Alternatively it could be one of flock management
that indirectly effects the birds well being e.g. over-training.
Exposure to heavy metals such as zinc and lead is an often over
looked problem. Drinkers, storage drums or feed trays made of
galvanized metal can all expose the birds to these toxins. Quickly
absorbed but slowly excreted they accumulate over time leading
to a range of health problems including delayed crop emptying
and even infertility.
Basically birds from lofts that fail to provide a sense of well
being can be expected to experience delayed crop emptying. This
may be because they fail to provide an environment conducive
to health. For example they may be cold and damp. Alternatively
they may fail to provide a sense of security so that the birds
do not rest properly or may be poorly set up leading to excessive
territorial disputes etc.
What to do?
A crop flush should be done immediately, particularly during racing,
to identify any crop infection present and treatment given as
indicated. If no problem is detected, a thorough clinical examination,
together with microscopic examination of a faecal smear, may
give the answer. Medication is not necessarily indicated. The
birds recent management should be reviewed together with the
loft design relative to recent weather. If the birds have been
working hard and the weather is cold, no tossing for a few days
and some probiotics or vitamins may help. Slow crops correlating
with a recent change in a grain batch may indicate a feed problem.
Interestingly, at last years avian vets conference in Manly,
our guest speaker was Dr. Lorenzo Crosti, the veterinary director
of Loro Parque in Tenerife. Loro Parque is a world famous bird
breeding facility. Dr. Crosti stated that he had good results
treating birds that were otherwise healthy, with slow crops,
with fennel tea. Fennel tea bags can be purchased from health
food shops. Simply make a cup of fennel tea, as you would a cup
of normal tea for yourself. This can then be added to the drinker.
There is no strict dose rate. It smells like licorice but unless
mixed too strongly the birds drink it readily.