Subsequent to banning of use of antibiotics as growth promoter sin poultry nutrition, numerous studies turned to finding of alternative solutions, i.e. other, natural substances, which would have positive effect on chicken growth and feed conversion. Today, several groups of these additives are in use, and most often probiotics, prebiotics, enzymes, acidifiers, antioxidants and phytogene additives. Considering that each of the stated groups has its own specificities, objective of this work was to present main mechanism of their action and to present their effect on production results in fattening of broiler chickens through review of research published in this field.

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In broiler production, stocking density, i.e. floor surface per chicken, is very important welfare factor which directly and indirectly influences and determines the level of growth of chicken body weight, but it is also related to other welfare indicators. Objective of the paper was to define the broiler welfare in different stocking densities by evaluation of their walking ability (gait score), feathering, incidence and degree of hock burns, foot pad lesions, and by determination of the biochemical blood parameters (glucose concentration, total cholesterol concentration), as indicators of condition of stress. One day old chickens of Hubbard genotype were housed in boxes in floor rearing system, in 3 stocking densities and 5 repetitions of each treatment. Treatment A scored stocking density of 10 birds/m 2 ; treatment B, 13 birds/m 2 and treatment C, 16 birds/m 2 . Results of the trial indicate absence of significance of differences between trial groups of broilers in regard to their walking ability, condition of skin and legs, and stress indicators. In general, broiler welfare in all trial groups was satisfactory. However, determined tendencies of worsening of the condition of litter, increase of the frequency of lower scores for walking ability (gait score), hock burns and foot pad lesions which occur with increase of stocking density, indicate the importance of this rearing factor and need to define limiting stocking densities from the aspect of broiler welfare but also economical efficiency of production.

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