Welfare of productive animals (review)

Modern industrial livestock farming is characterized by a high degree of animal use intensity, which causes problems of animal health and welfare. Animal welfare can be defined as the ability to successfully adapt to environmental conditions without suffering (B.O. Hughes, 1976; D.M. Broom et al., 2019; K. Carlstead et al., 2013). The criteria for assessing a high level of animal welfare are good feeding (absence of prolonged hunger and thirst), proper maintenance (temperature comfort and free movement), health (absence of wounds, illnesses and pain during operations), animal behavior (absence of fear, behavioral disorders and good interaction with a person) (R. Botreau et al., 2007). The ability to engage in normal behavior supports the animal's emotional state and includes both general husbandry requirements (social interactions, type of diet, adequate housing space to turn, stand and lie down) and the performance of species-specific behaviors (use of nesting boxes, material for digging for pigs, etc.). Welfare is complex. Good health does not mean a high level of well-being, although it is a necessary condition for it. It is impossible to focus only on individual components of well-being, although in different conditions they may have different significance (T. Grandin, 2010). The ability of animals to adapt and, accordingly, their well-being is influenced by age and physiological state. Features of metabolism, reactivity of the immune system, hormonal status, and behavior determine the possibility of maintaining acceptable well-being and the special requirements of animals to technological conditions. The homeostatic systems of the body that ensure adaptation are controlled by the genotype (T. Grandin et al., 1998). The components of a welfare assessment are, firstly, an assessment of technology factors affecting animals (housing, microclimate, feeding, mode of use, handling methods, etc.) and, secondly, an assessment of the condition of animals: behavior, fatness, hygiene, problems with limbs, wounds on the skin (Welfare Quality® assessment protocol for pigs, 2009), indicators of physiological status (heart rate, breathing, body temperature) (M. Serra et al., 2018). To deeply assess the condition of animals and verify welfare assessment protocols, more complex invasive methods that require laboratory equipment are used (studying the level of stress hormones, blood composition, morphological characteristics) (K.V. Zhuchaev et al., 2019). In intensive livestock farming environments, it is important to ensure a basic level of welfare where the animal is healthy, free of stress, growing, reproducing and producing. Achieving a higher level of well-being, implying the ability to carry out species-specific animal behavior, is obviously possible in biologized production systems.