Western
Meeting of Poultry
Clinicians and Pathologists
|
Clinicians and Pathologists
|
|
Defective Down in Broiler Chicks
McCausland Consulting Services
A defective down syndrome in day old broiler chicks has occurred sporadically in British Columbia since 1987. This syndrome has resulted in significant economic loss to broiler hatcheries in British Columbia where hatching egg producers are paid on a per dozen basis. In one case in 1993, chicks affected with defective down and subsequently culled average 1`2 percent over the life of the breeder flock. Depressed hatchability also occurred. Defective down syndrome has also been called "clubbed down syndrome" in the field. The syndrome tends to reoccur in chicks hatched from eggs procured from the same breeder farm. The affected down takes on the appearance of grains of wheat with pointed ends. Many theories have been discussed in the field with respect to the cause of the defective down condition. No conclusion theories have been proposed. Dietary riboflavin level per se does not seem to be involved as suspect feed has continually been assayed to contain between 8 and 11 mg/kg of riboflavin (Arbor Ace management manual recommends 9.9 mg/kg). Riboflavin supplementation via the feed and/or water did not solve the problem. Chicks obtained from breeder flocks where a high incidence of defective down was present showed 6.03 to 6.34 mg/kg of riboflavin in yolk material. These chicks showed no gross evidence of defective down. Chicks from the same flock showing evidence of defective down revealed 3.46 mg/kg of riboflavin in the yolk material. Hatching egg size from flocks where defective down chicks was a problem did not appear to be a factor. Hatching egg weight from an affected flock was 67 grams, standard deviation of 4. This flock was 55 weeks of age. Water analyses have not revealed any significant findings, especially with respect to boron levels. Two farms known to have re-occurring cases tend to have large deposits of scaly material on the bell-type waterers. However this condition has not been seen elsewhere. Water softening did not eliminate or appear to reduce the condition. In one case large amounts of moldy feed was found in all feed storage bins. In two cases the author has noted a common set of factors that may be involved based on the simple theory that hens producing defective down chicks may not be receiving ample micronutrients. Common Factors Poor body weight uniformity. Slow feed delivery system (< 60 feet per minute). Crowded conditions (<5.4 birds per square metre). Hard drinking water. Other factors, which might have been implicated or involved in exacerbation of the syndrome, included a heavy infestation of roundworms. Gross necropsy of hens taken from the feed entry point revealed evidence of feed selection. The crops, gizzards and intestinal tracts contained what was considered an unusual amount of whole kernel grain (particularly wheat kernels). The droppings associated with these birds tended to be loose to wet in nature. Large numbers of adult ascarides were noted. All hens were in full egg production. Based on the above observations the author has made the following recommendations in the field: Follow breeder management guidelines with respect to body weight control. Considerable effort should be made to weight representative samples of chickens in order to maintain optimum body weights. Increase the speed of the feed delivery system to a minimum of 90 feed per minute. Re-calibrate all feed weighing systems. Feed the correct amounts at the correct times – do not miss feedings. Assess physical properties of feed in terms of grind. If necessary feed B Crumbles. Add additional B vitamins (eg.) to the feed, especially with respect to riboflavin and biotin (riboflavin 15 mg/kg of feed, biotin 0.50 mg/kg of feed). Administer multivitamins via the drinking water. Add approximately 4 to 5 mg of riboflavin and 80 to 90 mg of biotin in each litre of drinking water for 3 to 5 days continuously every 2 to 4 weeks. Treat with 30 PPM fenbendazol in the feed for 5 days. Repeat this treatment in 45 to 60 days. Use an effective worming program in the pullets and continue in the laying birds where necessary. Handle all hatching eggs with extreme care, and follow breeder management guidelines accurately. Clean feed storage bins and ensure that moisture does not enter bins. Depending on season ensure flocks begin egg production at the optimum age to avoid egg size problems. Drinking water source to be evaluated in detail (it is highly recommended that a water treatment station to remove water impurities be installed). All chicks subsequently hatched should be critically evaluated fro the degree of incidence of defective down.
Explanations for the defective down condition are numerous. Other factors, which may be involved, include a factor that impairs the metabolic utilization of riboflavin (infections or chemical agent) or the abnormalities are not related to a riboflavin deficiency.
|
|
To send us your comments or questions regarding this web site, click here. |