Factors contributing to foot-pad dermatitis in broilers
Foot pad condition has become an indicator of bird welfare and it also affects the value of paws for export sales.
Nearly nine billion broilers were grown and transformed into a variety of value-added' products in the USA last year. Value, convenience, safety, purity, as well as social responsibility (animal welfare, environment, labor etc.) have become important marketing traits for poultry products as the consumer expectations continue to evolve in the marketplace. Over the past decade, a highly sizable and profitable export market for processed and frozen chicken feet (paws) has evolved.
The market value of paws is affected by both size and quality (i.e., grade). Size (count per pound) creates a price differential from small to large, with the largest paws (jumbo) bringing the highest price. While foot/paw size will be dictated primarily by bird size in a given broiler complex, quality considerations may be controlled to increase market share and profits in the premium paw market. General paw quality/grade factors include those that are related to live production phase (i.e., shank pigmentation, foot-pad dermatitis, bruises, etc.) and those that are attributed to processing errors (i.e., improper cuts, mutilation, cuticle, compound fractures, missing parts etc.).
FPD affects quality, welfare
The incidence and severity of dermatitis (paw burns) that occur on the foot-pads of broilers is of great concern to the industry, not only from a product quality but also from animal welfare standpoints. Foot pad dermatitis (FPD) is a type of contact dermatitis primarily affecting the plantar surface of the footpad. Histological lesions associated with FPD include non-specific dermatitis often accompanied by secondary infections. The lesions are superficial in mild cases but progress into deep ulcers when the dermatitis progresses, resulting in pain and discomfort to the bird. The occurrence of FPD is now used as objective audit criteria in welfare assessment of poultry production systems in both Europe and the US.
Information on the etiology of FPD is limited and points to a complex interaction of various risk factors, such as:
- market weight,
- bedding type and litter quality,
- flock health,
- nutrition, and
- feeding and management programs.
Effective flock and environmental management programs, as well as modifications in nutrition/feeding programs may help in improving the incidence and severity of foot pad dermatitis in poultry. Birds spend most of their life in close association with the bedding/litter material. Hence, the most obvious contributor to FPD is either limited quantity and/or substandard quality bedding material. It is a natural for chickens to peck, scratch and work the bedding/litter material. This behavior helps in aeration, further minimizing the size of the litter by breaking down large clumps.
However, large particle size bedding material, over-use, and excessive caking deteriorates litter quality resulting in less working up of the litter by the birds. Bedding materials with sharp edges (large particle size wood chips, chopped straw, etc.) may contribute to FPD by opening small puncture wounds on the foot-pad that can lead to entry of the bacteria and eventually to FPD.
Moisture control is essential
Litter management is an ongoing struggle for producers, involving cost and availability of fresh bedding materials, nutritional programs, brooding, house ventilation, evaporative cooling and drinker management. As birds grow, increasing amounts of moisture are cycled through the litter. Obviously, any stressors (physical, chemical, or infectious) that affect the integrity and optimal functionality of the gastro-intestinal system can initiate enteritis, diarrhea, malabsorption, and feed passage, all of which rapidly increase excessive nutrient and moisture excretion into the litter.
Wet litter becomes harder and harder to dry as the birds age. Ventilation is extremely critical to moisture removal from the house, as producers are challenged with extreme winter- (condensation) and summer-time (evaporative cooling) conditions.
Nutrition can also influence FPD directly and indirectly. FPD has been frequently observed in birds reared on relatively dry litter. Recent research has shown that high nutrient density feeds, high protein levels, and feeds formulated with high soybean meal inclusion can lead to increased levels of FPD in broilers.
Indigestible carbohydrates (i.e., non-soluble polysaccharides; NSP) from plant protein sources (soybean meal, wheat, barley) can contribute to FPD by increasing fecal viscosity and promoting fecal adherence to foot pads, even when litter moisture is within acceptable levels. Given optimal conditions (pH of >8, and moisture of <60%), urolytic bacteria in the litter convert excreted uric acid nitrogen into ammonia.
Dissolved ammonia creates a highly alkaline solution, which in turn causes chemical irritation of the foot-pads. Many of the commercially available litter amendments reduce ammonia volatilization through reduction of litter pH. These litter amendments can help reduce FPD incidence and severity, although most treatments do not last for the life of flock.
Dietary zinc may help
Of course, any factor that increases water consumption (i.e., ingestion of high levels of sodium, potassium, or magnesium via feed and/or water) will contribute to wet litter conditions in the house. Several mycotoxins increase water consumption and wet litter production, and should be ruled out as a contributing factor in the etiology of FPD.
Research has shown that dietary zinc from organic sources improves the incidence and severity of FPD under conditions of high stocking density. Addon treatments such as this will not cover up larger management challenges described above, but should be part of a coordinated plan to improve foot pad quality on a complex-wide basis.