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This study was conducted to determine the effect of housing environment and laying hen strain on performance, egg quality, and microbiology of the cloaca and eggshell. A total of 1,152 Hy-Line Brown ( HB ) and Hy-Line W-36 White Leghorn ( W-36 ) hens were used. All hens were kept in conventional cages ( CC ) from 18 to 32 wk of age and then moved to either enriched colony cages ( EC ) or free-range ( FR ) pens or continued in CC. Hens were randomly allocated into a 2 × 3 factorial arrangement of 2 laying hen strains (brown and white) and 3 housing environments (CC, EC, and FR) in a split plot in time (hen age) design. The experiment was conducted from 32 to 85 wk of age. The experiment was divided into 2 phases: early phase (32–51 wk of age) and late phase (52–85 wk of age). A 3-way interaction was observed for hen day egg production ( HDEP ) among housing environments, hen strain, and bird age in the early phase ( P = 0.004) as well as in the late phase ( P < 0.0001). In both of the phases, HDEP was higher in CC and FR than in EC. Hy-Line W-36 hens raised in EC had the lowest HDEP compared to other treatments. A 3-way interaction was observed for feed intake ( FI ; P = 0.017) and feed conversion ratio ( FCR ) in the late phase ( P < 0.0001). The lowest FI and highest FCR were observed in EC for W-36 hens. Free-range hens performed in-between for eggshell quality when compared to CC and EC while HB had better egg quality than W-36. Free-range hens had higher cloacal bacterial counts for aerobes, anaerobes, and coliforms than CC and EC. Higher eggshell bacterial contamination was observed in eggs from FR versus eggs from CC and EC. These results indicate that both housing environment and laying hen strain affect performance and egg quality as well as cloacal and eggshell microbiology. Further studies should be conducted to determine food safety and economic impacts when using different hen strains and housing environments.

This study aimed to determine the effect of the housing environment and laying hen strain on tibia and femur properties. A 3 × 2 factorial arrangement of 3 housing environments (conventional cages [ CC ], enriched colony cages [ EC ], and free range [ FR ]) and 2 laying hen strains (Hy-Line W-36 [ W-36 ] and Hy-Line Brown [ HB ]) in a completely randomized design was conducted from 32 to 85 wk of age. Six left tibias were collected at 8 different time points (38, 45, 52, 59, 65, 72, 79, and 85 wk of age), whereas 6 left femurs were collected at 3 time points (38, 65, and 85 wk of age). Tibias were evaluated for tibia breaking strength ( TBS ) and ash percentage, whereas femurs were evaluated for bone mineral density ( BMD ), bone mineral content, bone volume as a fraction tissue volume, and porosity percentage from total, cortical, medullary, and trabecular bones. The higher TBS ( P = 0.0005) and ash percentage ( P = 0.045) was observed in hens raised in FR systems compared with those raised in the CC. Overall, TBS of W-36 hens was significantly greater than that of HB hens ( P < 0.0001); however, there was no difference in the ash percentage between the strains ( P > 0.05). An interaction between the housing environment and hen strain was observed for BMD ( P = 0.04), wherein W-36 hens raised in the FR system had higher BMD than HB hens. Similarly, hens raised in FR systems had higher trabecular bone volume than those raised in CC ( P = 0.022). Hen strain influenced total and cortical bone properties: BMD, bone volume as a fraction tissue volume, and porosity percentage, wherein W-36 hens had better properties than HB hens ( P < 0.05). Trabecular BMD was higher in W-36 hens than in HB hens ( P = 0.04), whereas bone volume was higher in HB hens ( P < 0.0001). The results suggest that raising laying hens in alternative housing systems that have provision for exercise such as FR reduces structural bone loss, stimulate structural bone formation, and improve breaking strength of bones; however, it varies with the strain.

Bone serves as a multifunctional organ in avian species, giving structural integrity to the body, aiding locomotion and flight, regulating mineral homeostasis, and supplementing calcium for eggshell formation. Furthermore, immune cells originate and reside in the bone marrow, sharing a milieu with bone cells, indicating a potential interaction in functions. In avian species, the prevalence of gastrointestinal diseases can alter the growth and the immune response, which costs a great fortune to the poultry industry. Previous studies have shown that coccidiosis and necrotic enteritis can dramatically reduce bone quality as well. However, possible mechanisms on how bone quality is influenced by these disease conditions have not yet been completely understood, other than the reduced feed intake. On the other hand, several mediators of the immune response, such as chemokines and cytokines, play a vital role in the differentiation and activation of osteoclasts responsible for bone resorption and osteoblasts for bone formation. In the case of Eimeria spp./Clostridium perfringens coinfection, these mediators are upregulated. One possible mechanism for accelerated bone loss after gastrointestinal illnesses might be immune-mediated osteoclastogenesis via cytokines-RANKL-mediated pathways. This review article thus focuses on osteoimmunological pathways and the interaction between host immune responses and bone biology in gastrointestinal diseases like coccidiosis and necrotic enteritis affecting skeletal health.