Taking measures in time pays
Cellulitis develops after the intrusion of E. coli through a rupture in the broiler skin. Therefore, any damage to the bird skin can be considered an important infection route and an initiating factor for the problem. Ample evidence reveals that conditions that increase scratches will increase the incidence of cellulitis; therefore the practices related to flock management may play a decisive role in contributing to prevent the incidence of the problem. Within this context, several authors coincide in that the following factors or situations routinely found throughout the growing period may contribute, more or less, but not necessarily in the order they are listed here, to the incidence of skin damages and, ultimately, to the incidence of cellulitis:
1) Feed Restriction: “Out of feed” is one of the first factors to evaluate when there is a skin scratch issue. Birds out of feed due to delivery/logistic problems can induce birds to fight, pile and scratch each other when they regain access to feed. Hot weather feed management must be managed to prevent heat stress but allow for normal behaviour when the feed is permitted.
2) Nervous birds: Too much light, no dawn/dusk lighting programmes or sudden noises and flashing lights can cause birds to climb on each other.
3) Litter: Some operations struggle when weather and environmental conditions make it difficult to keep litter dry. Litter moisture control is critical, as increased moisture tends to increase lesion development in birds that are scratched versus birds that are scratched and placed on dry litter.
4) Nipple drinkers: With the increase in nipple drinkers over the past several years the incidence of cellulitis has decreased. This effect is most likely due to improved chick water management, improved litter management and the reduction of bacteria in the litter itself. Improved overall health is usually a recognised industry observation when nipple drinkers were brought in.
5) Ventilation: Ventilation especially in tunnel ventilated houses will instigate broilers to migrate to the cooler fraction of the house. Density patterns change as broilers struggle to reach an environmentally friendly zone. Increased densities create aggressive behaviours towards feed and water as bird ratios to management input change. Migration fences have alleviated this nomadic range in the broiler house.
6) Procurement: Cellulitis lesions could occur as early as 18 hours before processing. The period just prior to slaughter - feed withdrawal and transport - is a time where birds are particularly prone to being scratched.
7) Breed: Several managers have mentioned that cellulitis was more prominent in high yield, slow feathering birds than fast feathering breeds.
8) Breed sex: Males can be slower feathering allowing more skin injuries. However, pullets are known to have more tender skin; hence, prone to more scratches or skin trauma.
9) Calorie/protein ratio: If the ratio is too high (more energy) it could lead to lower intake of some essential amino acids. It could also lead to a higher deposition of abdominal fat. Deficient amino acids could lead to feathering abnormalities and increased energy or fat deposition could cause skin integrity issues leading to skin fragility.
10) Nutrition: Other nutritional entities are sometimes implicated as contributing factors. Low sodium levels may contribute to increased nervousness in a flock. Vitamin E, the B vitamins and some trace minerals such as selenium and calcium have also been suspected of contributing to the problem.
11) Density: Higher feeder, drinker and pen densities (>27 kg/m2) are also significant risk factors. It may be that increased densities lead to a higher incidence of scratches and feather breakage. This would also explain why nervous flocks are more at risk for a higher prevalence of cellulitis, since sudden mass movements in the chicken pen favours such skin and feather damage. Despite the evidences relating the incidence of cellulitis and the placement density, there are some controversies among some authors. Morris revealed that there was no pattern between levels of cellulitis in a complex and the size of the bird raised or the stocking density. Norton, however, reveals that birds under higher density will tend to have more scratches and therefore higher rates of cellulitis. Management of density should always be conducted on the basis of kg/m2 rather than birds/m2. The key is “manage density rather density manage you.”One cannot deny that skin scratches may be artificially created by high bird density by farm management. During hot weather birds may crowd to one end of the house trying to seek the ventilated cooler areas in tunnel houses. Partial brooding may encourage birds to remain in the brooding area. No doubt designing the house, locating the equipment and managing the flock to keep the birds spread out can and will reduce skin scratch challenges.
12) Last two weeks: Field data reveals that many management systems during the last two weeks of grow-outs is the time in which broilers experience the majority of the skin scratch lesions. This can ultimately, as mentioned, lead to the development of cellulitis. Broilers in this period are under a lot of stress, are crowded (more kg/m2) and become scratched as they move to feed, water, or “cool” house locations. This time is also a problem since feed restriction programmes or lighting programmes tend to cause the birds to be hungry, hence more agitated and stressed.
13) Bacterial contamination of the environment: Caked litter and higher litter humidity during the last weeks of the grow-out are also associated with a higher prevalence of cellulitis, whereas flocks with nipple drinkers were less at risk of developing cellulitis. Since humid litter is an ideal environment for bacterial multiplication, any measure decreasing the bacterial load in the environment should have a positive impact on the incidence of cellulitis. This also explains why it has been shown that chicken barns disinfected prior to chick arrival had a lower prevalence of cellulitis. For the same reason, a downtime period longer than 15 days has also been related to a decreased prevalence.