Study of animal welfare through analysis and comparison of the presence of foot pad dermatitis in broilers raised in controlled environments in Brazil and Spain

Introduction

The poultry industry has been able to develop high-level technologies in these more than one hundred years of existence, reaching high zootechnical results. These advances have been obtained through a lot of financial investment in ambience, making the handling work more efficient. However, to offset this economic contribution, the producers were taken to increase the population density in aviary, mainly broiler chickens, currently one of the most discussed and questionable points regarding the BEA (Animal Welfare).

BEA has been a major problem in Europe over the past decades (Saraiva et al., 2016) and evolved throughout the world, yet the increase in BEA requirements generally results in an increase in production costs (GOCSIK et al., 2016). Industrial chickens type broiler, as well as the commercial laying hens to produce more and quickly, are genetically improved and submitted to an intensive confinement system with automated comfortable ambience, coupled with high density and nutritional diets high density, along with a sophisticated biosecurity to prevent diseases (BENEVIDES et al., 2013a, 2013b).

As a scientific interpretation for BEA, the representation most accepted is based on the five liberties, which are: (1) free of hunger and thirst; (2) freedom from discomfort; (3) free from pain, injury and disease; (4) free to express their typical behavior; and (5) free from fear and anguish (FAROUK et al., 2016).

In the category of productivity, Brazil occupies a great prominence place in the global poultry industry, because, as the third largest producer in constantly growing and largest exporter of poultry meat (ABPA, 2016), must always be excelling in their results. Parallel to the zootechnical progress, the demands of society such as food safety, traceability, environmental protection and sustainability, has also evolved, among these, we highlight the BEA as the focus of our work. In conventional production systems it is necessary to provide permanent access to food and water at a maximum density of 42 kg / m2, if the creations have adequate ventilation and heating (FAROUK et al., 2016). Furthermore, the high density in the production of broilers affects BEA, because it provides weakness in the legs, the shank and foot pads (Zhang et al., 2011), and also the increase in air temperature can cause serious problems related to thermal comfort

The commercialization of chicken feet, in Brazil, is directed to Asian markets (ABPA, 2016), this factor adds value to a low acceptance product on the intern market, favoring the profitability of Brazilian companies, however, pododermatite is a critical problem which can compromise exports of chickens (Teixeira et al., 2015), because they are eatable parts of the bird that are in high demand, especially in Southeast Asia (ZHANG et al., 2011). Chicken legs are considered a culinary delicacy in many cultures and became third most economically important part of the chicken, after the breast and wings, which are first and second, respectively (CHEN et al., 2016).

The pododermatitis or footpad lesions or contact dermatitis (Berchieri JR. et al., 2009), interacts directly with the BEA, because besides harming productivity and increase the sentences of broiler carcass parts in slaughterhouses is a disease that changes the behavior of birds raised on the floor and causes serious discomfort to the animals.

The lesions in the footpad can become a gateway for bacterial infections (for example Staphylococci), that will affect the health of the bird (Bassler et al., 2013), being the paws continuously on the chickens litter. Furthermore, the plantar cushion dermatitis demonstrated compromise the weight gain in the rate of 7.75% and feed conversion efficiency in 4.16%, respectively, in 37 days of production (DUNLOP et al., 2016).

The lesions usually begin with discolouration of the skin, followed by inflammation, erosions and hyperkeratosis of the skin, which can progress to ulceration and necrosis of the epidermis. (WEBER et al., 2015). The pododermatite was classified as an economic problem for the poultry industry of broilers and turkeys in the UK, North America and Australia, due to inadequate conditions of litter, especially the excess of humidity (SANTOS et al., 2002). Lesions that are caused by pododermatite are a concern to the poultry industry as the cause of the BEA is considered very important, especially in Europe (SHEPHERD; FAIRCHILD, 2010).

Besides causing the degradation of the leg quality and economic loss, the appearance of lesions on the legs, is now used as an evaluation criterion of BEA in poultry production systems in Europe and the USA (CHEN et al., 2016). Due to the value of this product on the market also as the growing issues of BEA, are the main interests of the poultry industry to reduce sentences for this cause in industrial abattoirs (SHEPHERD; FAIRCHILD, 2010). Studies conducted in the United Kingdom report an average prevalence of 14.8% of pododermatitis in 86 batches of 21 conventional chicken farms, and the average prevalence of 98.1% was found in 128 batches of 23 organic chicken farms (ASK, 2010).

Repeated use of litter is being a common practice in Brazilian aviaries, mainly due to factors such as difficulty and replacement costs as well as this destination at the end of each created broiler batch (MENDES et al., 2004). However, this practice, even with appropriate management, after an excessive period, can cause a hardening of litter and take to more frequent appearance of pododermatite (Berchieri JR. et al., 2009), which worsens as the birds gain weight and it occurs with a higher proportion from 28 days of age.

Factors such as high humidity and consequent increase in ammonia in high population density, especially in the modern environment of computerized aviaries controlled by exhausters, nebulisers and coolers type cooling (Mendes et al., 2004), can be considered as aggravating the occurrence of foot pad dermatitis, when the birds are also on reused litter.

The appearance of lesions in the footpad of the bird begins with an inflammation of the skin that is in permanent contact with the litter, which associated with corrosive factors present in it, speed up a ulcerative process, because as exist a lot of faeces on the litter, caused by the high densities in commercial poultry production, the results can be evolutive and progressive.

The pododermatite is an important marker of degradation of poultry litter, due to the high density accommodation that is severely criticized by animal welfare associations (Bernardi, 2011), mainly associated with repetitive use of litter for several creations and even for years, being removed often only partially when it exceeds the low walls of the aviaries

These modern aviaries are already used around the world, whether in areas of high or low temperatures and with relative humidity varies according to the region, however, we do not know if these external environmental factors can change and provide an effect or not the occurrence of foot pad dermatitis.

Pododermatitis is a condition of the broilers legs which is diagnosed by the observation of a dark brown color stained on its feet, at the broiler, the lesion can also be found in the hocks (MARTRENCHAR et al., 2002).

The pododermatitis has been considered as a kind of footpad contact dermatitis in chickens since it occurs at the points of contact with the ground (HASHIMOTO et al., 2011). The lesions usually begin with discolouration of the skin, followed by inflammation, erosions and hyperkeratosis of the skin, which can progress to ulceration and necrosis of the epidermis (WYNEKEN WEBER et al., 2015).

These foot lesions are associated with various environmental and nutritional factors (Gleice & Alves, 2013) such as diet, nutritional deficiencies, wet litter, types of sand materials, sex, weight of the birds, the season and density (Wyneken Weber et al ., 2015), noting that Martrenchar et al. (2002) observed that this last item increases the prevalence of pododermatitis in industry broilers.

The cushion plant lesion in broiler chickens is one criterion of condemnation on health inspection during slaughter, where these economic losses can be a significant loss for the company and integrated, and also for the export market (SINCLAIR et al., 2015).

To evaluate with a single standard of podermatitis injury scores, according to Ask (2010), there are different types of scores for classification in industrial abattoirs inspected. Hashimoto et al., (2011), classified the footpad lesions in 4 types of scores, where 0 was no injury, score 1 for injuries in some areas (<50%) of the footpad, a score of 2 for lesions large areas (between 50% and 100%) of the paw and score 3 to injuries throughout the area the footpad and around. Despite being a subjective analysis by macroscopic observation, as occurs in industrial poultry slaughterhouses, the important thing is not escape of standards already established by some authors. Therefore, there is not yet a single rule for evaluation of scores of injuries to pad dermatitis, however, all authors, always consider a lack the presence of severe injuries, gradually and progressively, which can start at zero or 1, going up to 4 or 5 respectively. In the histological aspect, we see in Figures 1 and 2 a moderate fibrosis in the subcutaneous tissue that we can consider as score 1, with an increase of fibrous tissue around the adipose tissue that composes the footpad.


Figure 1: Fibrosis (multiplication x20)		Figure 2: Fibrosis (multiplication x100)