Poultry behavior reactions and welfare (review)

In connection with the need to improve competitiveness with foreign poultry farming, the problem of ensuring the well-being of poultry and producing high-quality products is an urgent issue (Welfare Quality® Assessment for poultry, 2009; I.J.H. Duncan, 1981; J.A. Mench, 1992). Special attention on the way to improving the welfare of animals is given to the compliance of technology with the biological characteristics of animals (D.A. Orlov et al., 2016). The level of well-being of poultry is affected by many factors: illness, stress, nutrition, conditions of housing (D.C. Jr Lay et al., 2011). A bird within certain limits is able to adapt to various environmental conditions (M. Brantsæter et al., 2018). Inability to adapt is expressed in changes in physiological status, as well as behavioral disorders that can harm both animals and maintenance personnel. Stress sensitivity is manifested in the behavior of chickens, which serves as the best indicator of well-being. Strong manifestations of fear, such as panic or abrupt escape attempts, not only increase energy costs, but can also cause damage or even death when the birds start moving through obstacles and hurt each other (S. Waiblinger et al., 2006). Fear, like an unwanted emotional state, reduces the overall activity of animals. Regular negative stimuli inhibit social interactions between animals (J.A. Mench, 2004; B. Forkman et al., 2007). Human is one of the main sources of stress for animals, the fear of human affects their well-being and productivity (T. Kutzer et al., 2015; M.A. Sutherland et al., 2012; F. Barone et al., 2018). Relationships between humans and animals can include visual, tactile, olfactory, and group perception (S. Waiblinger et al., 2006). A hen is sensitive to visual contact with a person, but some neutral interaction, such as moving a person's hands to the side of a cage or approaching a bird, even for short periods, can decrease stress (J.A. Mench, 2004). Measuring the response of animals to humans leads to conclusions about how they perceive all people or a particular person. It depends on the type of animal and the housing system, on the nature of its interactions with a person (positive, neutral or negative), on the quality of care for animals and poultry (S. Waiblinger et al., 2006). Understanding behavior is an important aspect of the concept of poultry welfare (V.N. Tikhonov et al., 2008). From the point of view of ensuring the welfare of animals, it is significant to have the possibility of living their natural life through the manifestation of natural behavior and the presence of elements in the environment that bring it closer to the natural environment (Animal Welfare Issues Compendium; D. Fraser, 2008). Poultry have retained a significant part of the behavioral needs of the wild forms (M.S. Dawkins, 1988). The main needs for the behavior of poultry are nesting, food and drinking behavior, the provision of physical and comfort activity and social interactions (I.J.H. Duncan, 1998; T. Shimmura et al., 2018). The restriction of natural behavior leads to a deterioration in the well-being of the bird. Environmental factors, such as high light intensity and crowding, also contribute to the high likelihood of behavioral disturbances (M.C. Appleby et al., 2004). Animals that are kept in captivity may exhibit behavioral disorders, including “stereotypes,” such as repetitive fixed cycles performed for no apparent purpose, aggressive behavior, pecking eggs (G.J. Mason, 1991; M.C. Appleby et al., 2004; I.J.H. Duncan, 1998). Hens contained in traditional cage batteries (for 4-5 heads) are less prone to problems with aggressive behavior due to the smaller number of birds in the group (H. Lukanov et al., 2013). At the same time, in floor systems, the size of the group can exceed 1000 heads, which expands the possibilities of the exploratory behavior of poultry, but increases the risk of peck and cannibalism (D.C. Jr Lay et al., 2011). The behavioral prefer