Euroasia Congress on Scientific Researches and Recent Trends-VII, Baku, Azerbaijan, 6 - 09 December 2020, pp.578-579
Conventional systems where large numbers of chickens are raised in a small area for high egg production and profits have long been used in the egg production industry. However, animal welfare started to gain importance in Europe in the 1960s, and traditional cage systems were questioned as they caused movement restriction in chickens. This study aims to compare the tibiotarsal strength and some bone material properties to determine the welfare characteristics of laying hens kept in conventional cage (CC), enriched cage (EC), and freerange (FR). Four hundred eighty Lohmann Brown laying hens were placed in rearing systems at week 17 and reared through a production cycle that lasted until the 66th week. Chickens were randomly distributed in four replicates with 40 hens in each system (cage or pen). The same photoperiod (16h light / 8h dark) and standard commercial feed were used throughout the study. A total of 24 chickens from the groups were randomly selected and weighed. Body weights between groups were found to be similar in selected chickens (P> 0.05). Chickens were slaughtered, then the tibiotarsi of both legs were removed and dissected from surrounded soft tissues. Bone weight and bone lengths were also measured. Bone breaking strength was determined by a mechanical compression test using a tensile and compression testing machine.
Cortical area measurements were carried out through ImageJ image analyzing and processing software. Also, dry matter, ash, Ca, and P ratios of tibiotarsus were measured according to AOAC methods. It was observed that chickens reared in FR system had higher tibiotarsus breaking strength compared to CC and EC system chickens (P <0.001). However, the cortical area, dry matter, ash, Ca, and P contents were similar in chickens in all shelter systems (P> 0.05). Based on this experimental study results, some bone mechanical and material properties in laying hens were similar between conventional and enriched cages but different in the freerange system. Accordingly, chickens in the FR system had better bone properties compared to the CC and EC systems. These results show that chickens in FR system gain superior bone biomechanical properties due to their optimal comfort and space for motion.