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Cage layer fatigue (CLF), which is commonly caused by calcium deficiency in the feed, leads to loss of structural bone and increase of bone fragility. In order to investigate the influence of low-calcium diets on bone quality and strength, histopathology, and egg quality, 72 laying hens were randomly allocated to 2 groups at 22 wk of age and received low calcium and control calcium until 34 wk, respectively. Egg production, feed consumption, BW, and egg quality were measured throughout. Bone mineral density, bone biomechanical properties, and histomorphology of femurs and tibias were assessed after birds were sacrificed in 26, 30, and 34 wk. The results showed that low-calcium (1.5%) diets decreased BW, feed consumption, and egg production. The broken eggs rate increased, and the eggshell strength and thickness were lower in treated birds than those in control birds at 30 wk and 34 wk. Femoral and tibial bone index and bone mineral density were lower, cortical thicknesses were thinner, and bone length were shorter over time when birds are in a low-calcium diet than those in control birds. In biomechanical properties, the values of stiffness, Young's modulus, and breaking strength were lower in both femurs and tibias in low-calcium hens at 30 wk and 34 wk than those in bones of control hens. In histomorphology of bone, the cortex turned thinner and there were more cavities in cortex and cancellous bone; the trabecular bone network was fewer, thinner, less cohesive, and generally fragmented; and trabeculae were less well-connected in low-calcium birds. Some cell nuclei in cancellous bone disappeared, and vacuolation was observed in bone cells. There appeared osteoid in cortex bone and cancellous bone in tibias. It was concluded that low-calcium diets could facilitate the development of osteoporosis characterized by an increase of osteoid and loss of structural bone and decrease the values of bone quality and strength, accompanied with a decrease in egg production and egg qualities, which may elucidate the developing mechanism of CLF.

Exogenous phytase supplementation increases P and Ca availability to allow for the dietary reductions without negative consequences on productivity or skeletal health. Effects of a Buttiauxella sp. phytase (BSP) supplemented in available P (avP)-reduced and Ca-reduced diets on performance, BW, eggshell quality, serum biochemical bone markers, and bone densitometry were evaluated in egg-laying hens from 68 to 78 wk of age. One hundred hens were fed 1 of 5 diets (n = 20/treatment), including a positive control (PC) with 0.35% avP and 3.5% Ca, and the PC moderately reduced in avP and Ca levels by 0.187 and 0.159% of the diet (by 53 and 4.5%), respectively, (NC1) or severely reduced by 0.231 and 0.275% of the diet (by 66 and 7.9%), respectively, (NC2). Other diets were the NC1 or NC2 supplemented with BSP at 600 FTU/kg (NC1 + BSP or NC2 + BSP, respectively). Egg production and feed conversion ratio were maintained by NC1 but were 11.9% lower and 12.3% higher, respectively, with the NC2 than the PC, which was alleviated by supplemental BSP. Diet effects on FI and eggshell quality followed a similar pattern. Body weight was 2.9% lower for NC1, and 6.1% for NC2 than the PC; BSP alleviated the decreased BW. Serum pyridinoline (bone resorption marker) was 20 to 27% higher in NC2 hens than in the other groups, with no effects on other bone markers. Total and trabecular space bone mineral density in the proximal metaphysis were 8.4 and 15.2% lower for NC1, respectively, and 12.1 and 26.7% lower for NC2, respectively, than PC. Supplemental BSP completely alleviated the decreased bone densitometry measures in NC1, but only partially in NC2. The NC1 hens maintained performance but had decreased BW and bone quality; phytase supplementation restored productivity, BW, and bone quality. The Ca and avP deficiencies in the NC2 hens relative to other groups were partially alleviated by the 600 FTU/kg BSP.

During the incubation period, the Ca-to-P weight (mg/mg) ratio in the yolk increases from 0.26 on day 0 to 0.92 on day 17.5 and to 2.9 at hatch. Moreover, the absolute Ca content in the yolk increases by 41%, whereas P content decreases by 87%, from day 0 to the day of hatching. Thus, at hatch and during the first days after hatching, there are high reserves of Ca relative to P in the residual egg yolk, risking hypercalcemia and hypophosphatemia. A growth performance study was conducted to explore the effects of reducing dietary Ca content in the prestarter phase (0–4 D) on BW and bone mineral deposition during the first days after hatch and at market weight (day 37). Four prestarter (0–4 D) diets were formulated to have 0.4, 0.6, 0.8, and 1.0% Ca content. After the prestarter phase, all birds were fed with the same commercial diets based on a 3-phase feeding program (starter, grower, and finisher). Growth performance (BW, ADG, ADFI, and feed conversion ratio [FCR]) was monitored throughout the study, and blood and tibia bone samples were collected on specific days. On day 4, BW and ADG decreased with dietary Ca contents higher than 0.6% (P 0.10). For the overall study (0–37 D), there were no differences in ADG and ADFI, but the FCR decreased with lower Ca contents (P 0.10). In conclusion, during the prestarter phase, BW increased with dietary Ca contents lower than 0.6%, most likely improving Ca–P balance; bone mineral deposition was reduced in this period. On feeding with a diet containing higher Ca content, bone mineral content was rapidly recovered.

Owing to selection for rapid growth and heavy muscle, bone deformities and injuries in broiler chickens are common and present a welfare concern. Recently, clinical quantitative computed tomography scans (QCTs) have been used for laying hens with significant, strong correlations between QCT-generated bone mineral content (BMC), bone ash, and analytical calcium. The objectives of this study were to determine if QCT-generated bone mineral density of tibias and femurs correlated to fat-free ash and if analytical Ca could be correlated to bone ash and digitally calculated density in immature broilers. Male broilers (Ross 708, n = 125) were raised from day 1 after hatching, and at 42 D, right leg quarters were collected from 50 randomly selected birds and frozen at -20°C until analysis. Leg quarters were scanned with muscle and feathers intact and arranged in rows on plexiglass, and each QCT included a solid Ca hydroxyapatite phantom. Tibias and femurs were removed from leg quarters after autoclaving, ashed, and weighed. Pearson's correlation analysis was conducted to understand the association between analytical bone ash and QCT BMC while paired t tests determined the amount of difference between QCT BMC and ash. Ash weight was strongly correlated to QCT BMC in both the femur (R = 0.86, P < 0.001) and the tibia (R = 0.91, P < 0.001). The average difference between the amount of actual ash weighed and BMC calculated from the QCT was 0.03 ± 0.22 g (P = 0.3) for the femur and 0.04 ± 0.22 g (P = 0.2) for the tibia. This study confirms that this technique can supply invaluable skeletal health information without sacrificing birds.

Vitamin D is essential for the metabolism of calcium (Ca) and phosphorus (P) in birds. The objective of the study was to evaluate the effect of different isoforms of dietary vitamin D on Ca and P utilization, egg quality, and bone mineralization of laying hens. A total of 42 Lohmann white laying hens at 57 wk of age were randomly assigned to 7 dietary treatments for 6 wk. Dietary treatments were: 3,000 IU/kg Vit D3 as control, and control with additional 3,000 IU/kg 25-hydroxyvitamin D3 (T1), 9,000 IU/kg 25-hydroxyvitamin D3 (T2), 3,000 IU/kg vitamin D3 (T3), 9,000 IU/kg vitamin D3 (T4), 3,000 IU/kg of vitamin D2 (T5), or 9,000 IU/kg of vitamin D2 (T6). Egg production and egg quality were measured weekly. Fecal samples were collected at weeks 2 and 6 to measure Ca and P utilization. After 6 wk, the left tibia and femurs were collected to measure bone mineral density (BMD) and bone mineral content (BMC). A 1-way ANOVA with Tukey HSD means separation test was used for statistical analysis. There were no significant differences in egg production, egg quality, BMD, or BMC of tibia and femurs among the treatments (P > 0.05). T6 significantly reduced feed intake (P < 0.05). The apparent total tract digestibility (ATTD) of Ca was higher (P < 0.012) in treatments supplemented with additional vitamin D, irrespective of forms. The ATTD of P was higher (P < 0.0001) in T5 compared to the other treatments at both time points. The utilization of Ca and P by laying hens can be improved through the addition of different isoforms of vitamin D in diets. However, additional vitamin D supplementation to laying hens, regardless of forms, had no effect on either bone mineralization or measures of egg quality.

Cage layer fatigue is a common metabolic disease associated with a calcium and phosphorus imbalance, but recently we found this disease can be led by high fat diet. In order to elucidate the pathogenesis induced by a high fat diet, we randomly divided 88 White Shell Roman layers into 2 groups. There were 44 layers in each group. The control group was fed by a standard layer rations, and the high fat group was fed by completed rations mixing with 3% soybean oil. This study successfully constructed an animal model of osteoporosis caused by high fat. Bone samples were collected for bone mineral density, bone biomechanical properties which are all decreased at 26, 30, 34, and 38 wk old. We found the pathway of tryptophan-ERK-CREB from the perspective of metabonomics which promote the bone absorption. By metabolomics, we screened the significantly activated tryptophan pathway in high fat feed and detected the elevated tryptophan metabolite serum 5-HT at 26, 30, 34 and 38 wk old in the high fat group. At 38 wk old, we detected significantly elevated protein and mRNA levels of ERK/CREB/C-fos in bone tissue in the high fat group. So we concluded that high-fat were associated with a decrease in bone density and bone biomechanical index by disrupting tryptophan-5-HT-ERK1/2-CREB metabolism signaling pathways.

Coccidiosis penalizes calcium (Ca), phosphorus (P), and fat-soluble vitamin status, as well as bone mineralization in broiler chickens. We hypothesized that dietary vitamin D (VitD) supplementation in the form of 25-hydroxycholecalciferol (OHD), compared to cholecalciferol (D3), would improve bone mineralization in broilers receiving marginally deficient Ca/P diets, with more pronounced effects during malabsorptive coccidiosis. In a 2 VitD source × 2 Ca/P levels × 2 levels of infection factorial experiment (n = 6 pens per treatment, 6 birds/pen), Ross 308 broilers were assigned to an Aviagen-specified diet supplemented with 4,000IU/kg of either OHD or D3 between days 11 and 24 of age. The diet contained adequate (A; 8.7:4.4g/kg) or marginally deficient (M; 6.1:3.1g/kg) total Ca and available (av)P levels. At day 12 of age, birds were inoculated with water (C) or 7,000 Eimeria maxima oocysts (I). Pen performance was measured over 12 days post-infection (pi). One bird per pen was assessed for parameters of bone mineralization and intestinal histomorphometric features (day 6 and 12 pi), as well as E. maxima replication and gross lesions of the small intestine (day 6 pi). There was no interaction between infection status and Ca/avP level on bone mineralization. Bone breaking strength (BS), ash weight (AW), and ash percentage (AP) were highest in broilers fed the OHD-supplemented A diets irrespective of infection status. Eimeria maxima infection impaired (P

Broiler chickens have an extreme physiology (rapid growth rates) that challenges the correct bone mineralization, being an interesting animal model for studying the development of bone pathologies. This work studies in detail how the mineralization, chemistry, and structural organization of tibiae bone in broiler chickens change with age during the first 5 wk (37 D) from hatching until acquiring the final weight for slaughter. During the early growth phase (first 2 wk), the rapid addition of bone tissue does not allow for bone organic matrix to fully mineralize and mature, and seems to be a critical period for bone development at which bone mineralization cannot keep pace with the rapid growth of bones. The low degree of bone mineralization and large porosity of cortical bone at this period might be responsible of leg deformation and/or other skeletal abnormalities commonly observed in these birds. Later, cortical bone porosity gradually decreases and the cortical bone became fully mineralized (65%) at 37 D of age. At the same time, bone mineral acquires the composition of mature bone tissue (decreased amount of carbonate, higher crystallinity, Ca/P = 1.68). However, the mineral part was still poorly organized even at 37 D. The oriented fraction was about 0.45 which means that more than half of apatite crystals within the mineral are randomly oriented. Mineral organization (crystal orientation) had an important contribution to bone-breaking strength. Nevertheless, locally determined (at tibia mid-shaft) bone properties (i.e., cortical thickness, crystal orientation) has only a moderate correlation (R2 = 0.33) with bone breaking strength probably due to large and highly heterogeneous porosity of bone that acts as structural defects. On the other hand, the total amount of mineral (a global property) measured by total ash content was the best predictor for breaking strength (R2 = 0.49). Knowledge acquired in this study could help in designing strategies to improve bone quality and reduce the incidence of skeletal problems in broiler chickens that have important welfare and economic implications.

The large economic losses caused by leg disorders have raised concerns in the broiler industry. Several types of leg disorders in broilers have been identified, such as tibial dyschondroplasia (TD), femoral head necrosis (FHN), and valgus-varus deformity (VVD). In this study, phenotypic changes associated with VVD were examined using clinical diagnosis, anatomical examination, measured growth performance, bone traits, and serum indicators. The incidence of VVD among the chicken population at a commercial facility in Tangshan China was 1.75% (n = 52,000), distributed about 1:1 (n = 122), between females and males. A majority of chickens were characterized by a unilaterally abnormality, while appropriately 17.6% by bilateral abnormality. Approximately 97.9% of affected broilers were classified as the "valgus" type. Growth traits, including body weight, shank length, and shank girth, were significantly lower in chickens with VVD, while tibia and metatarsal bone indexes were about 1.3-fold higher in the affected birds than in the normal birds. Bone mineral density, bone breaking strength, and several serum indicators were significantly different between affected and normal broilers. Sparse and disarranged bony trabecular was observed in abnormal broilers by histological analysis. Generally, leg disorders are associated with compromised growth, bone quality, bone structure, and lipid metabolism. This study provides a reference for clinical diagnosis of VVD and lays a foundation for exploring its underlying mechanisms.

The present study was conducted to develop a non-traditional vitamin D3 (D3) intake bioassay with the objective of increasing the precision of D3 delivery to the chickens. For this purpose, newly hatched chickens (5 birds per cage) were allocated in battery brooders and randomly distributed into 8 treatments and 6 replicates per treatment. A basal corn-soy diet devoid of D3 containing calculated calcium and non-phytate phosphorus concentrations of 0.90 and 0.45%, respectively, was fed throughout a 21-D period. The first 9 D of the study served to deplete the maternal stores of D3 followed by a 12-h fasting period. From day 10 to the end of the trial, the birds were gavaged with graded levels of D3 obtained from a highly purified pharmaceutical grade D3 standard (99.8%) purchased from Sigma-Aldrich and dissolved in corn oil. Daily gavage treatments were based on estimated intake of 0, 50, 100, 200, 400, 800, 1,600, and 3,200 IU D3/kg of feed consumed over the last 12 D of the study. Precise cholecalciferol intake per kg of diet was adjusted based on actual daily feed intake per pen of birds. Performance data were evaluated from day 10 to 21. Percent tibia bone ash (TBA), tibia breaking strength (TBS), total mineral content, and total bone mineral density were obtained at day 21. The D3 treatments improved (P0.05) weight gain and feed efficiency. There was no linear or quadratic effect for any of the productivity performance variables. Graded levels of D3 improved (P0.05) TBA and TBS. Both were linearly increased (P0.05) in response to graded levels of D3. A quadratic response was observed for TBS only. Under the conditions of the present experiment and the average of 3 regression models, the D3 requirement for starter broilers was estimated at 285 IU D3/kg of feed when bone mineralization responses (TBA and TBS) were used as criteria to estimate the requirement.

Bone volumes and quality are related to their hormone levels in laying hens. In this study, we investigated letrozole (LZ) induced effects on the physicochemical properties of cortical bone in laying hens. After 9-wk LZ treatment, we observed that LZ could decrease estrogen level in laying hens. As a result, both the plasma tartrate-resistant acid phosphatase and bone Gla protein activities were suppressed significantly. In addition, carbonate substitution was inhibited significantly in humerus and femur confirmed by Raman spectroscopy. Meanwhile, the mineral density and yield load capacities of humerus and femur were improved. This study demonstrated that the high crystallinity and low carbonate substitution were tightly correlated with the relatively enhanced mechanical properties. Moreover, it elucidated biochemical mechanisms of estrogen in regulating mineralogical and mechanical properties of bones in laying hens.

This study evaluated the effects of crystalline arginine (Arg) on performance and body composition in male broilers. A total of 600 1-day-old Ross 308 broilers were distributed in a completely randomized design, with 5 treatments and 6 replicates of 20 birds. The treatments were given as a percentage of the Ross 308 requirement, and defined as 70, 80, 90, 100 (Ross 308 requirement), and 110% of Arg. Body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were evaluated at 10, 24, and 42 d. Bone growth was measured from 7 to 11 d using mineral apposition rate (MAR) technique. At 42 d, 2 birds per pen were euthanized for bone mineral density (BMD) and body composition measurement using dual-energy X-ray absorptiometry, and liver gene expression and muscle diameter size analysis. The means were subjected to ANOVA and, when significant (P ≤ 0.05), were compared by Dunnett's test. Regression analyses were performed to evaluate trends of Arg dose response. Birds fed 70 and 80% of Arg had lower BWG than the ones fed 100% of Arg (P0.001), with quadratic effects for all phases (P0.001, R2 = 0.94). The 70% of Arg group showed lower FI compared to 100% from 11 to 24 d and 1 to 42 d (P0.009), with quadratic and linear effects (P0.049, R20.72), respectively. The 70% of Arg group showed higher FCR compared to 100% (P0.0001) with quadratic effects (P0.002, R20.94) for all periods. At 42 d, the 70% of Arg group showed lower BMD, tissue, and lean muscle percentage than 100% of Arg. There was a quadratic effect of Arg levels on lean muscle (P = 0.046, R2 = 0.89). Therefore, the dietary supplementation with Arg is necessary as it leads to an overall body growth with increased lean deposition and BMD, without increasing fat accretion in Ross 308 broiler chickens.

Elevating levels of environmental lead (Pb) results in serious hazards to health of animals and human beings. In this study, daily diet with three different levels of Pb (Pb nitrate at doses of 1, 10, and 100 mg/kg body weight) were fed to ISA Brown layers. It showed that the kidney and liver have the relatively high Pb concentration (2.34 and 0.51 ppm) after culture, while the meat has the Pb concentration as low as 0.07 ppm (lower than the standard of Codex Alimentarius). It was also confirmed that egg laying worked as a potential pathway for hens to excrete Pb as Pb concentrations in eggshell and yolk increased from 0.10 to 3.11 ppm. However, the Pb concentration in egg white remains at a safe level (

This study evaluated the effects of high phytase doses and soybean meal (SBM) with different CP content on growth performance, ileal nutrient digestibility, digestible energy, plasmatic myo-inositol, phosphate release in vitro, and bone composition of broiler chickens. One thousand two hundred 1-day-old broilers were distributed in a 2 × 2 completely randomized factorial arrangement, with 2 phytase doses (1,000 and 2,500 phytase units [FYT]/kg of feed) and 2 SBM with different CP concentrations (45 and 47%), totaling 4 treatments with 12 replicates of 25 birds each. The chickens received feed and water ad libitum. Diets were based on corn and SBM, with different inclusions of soybean hull used to dilute the CP content of SBM according to each treatment. The inclusion of 2,500 FYT increased weight gain from 0 to 21 d (P

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 0.05). 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

Blood biochemistry and bone metabolism were evaluated to investigate the etiology and mechanism of spontaneous femoral head necrosis (FHN) in broilers. According to the femoral head score of the fourth, fifth, and sixth week old FHN-affected broilers, they were divided into 3 groups, namely Normal group, femoral head separation group, and femoral head separation with growth plate lacerations group, and then carried out a comparative study. The results showed that the liver function (alanine aminotransferase and aspartate aminotransferase) and lipid metabolism (high-density lipoprotein and triglyceride) levels of broilers with spontaneous FHN were significant changed compared with the normal group. At the same time, accumulation of lipid droplets appeared in the liver, which illustrated that the occurrence of FHN may be related to lipid metabolism disorders. Tibia and femur parameters showed significant changes in bone mineral density and bone strength. The distribution of chondrocytes in the articular cartilage of broilers with FHN was irregular and vacuoles appeared, which indicated that cartilage homeostasis was destroyed. TUNEL staining showed that the apoptosis rate of articular chondrocytes in broilers with FHN in 6-week-old was significantly higher than that of normal broilers. Meanwhile, the bone markers (bone glaprotein and bone-specific alkaline phosphatase) changed significantly, indicating that the articular chondrocyte apoptosis and bone metabolism disorder may occur in FHN-affected birds. Therefore, FHN in broilers may be caused by dyslipidemia and abnormal bone metabolism.

An experiment was conducted to evaluate the growth performance, bone mineral composition, diet utilization, and plasmatic concentration of myo-inositol (MYO) in turkeys fed different phytase doses from 1 to 28 d. A total of three hundred and twenty 1-day-old turkeys were distributed in a completely randomized design with 4 treatments and 8 replicates of 10 birds each. Treatments included a basal diet without phytase; reduced diet (reduced -0.15% available P and -0.18% Ca) without phytase; reduced diet + 2,000 units of phytase (FYT)/kg; and reduced diet + 4,000 FYT/kg. From day 26 to 28, partial excreta collection was conducted, and on day 28, 7 birds per replicate were euthanized for collection of ileal content and left tibia bones were removed from 2 of the same euthanized birds. Feed, excreta, and ileal digesta samples were analyzed to determine nutrient digestibility and metabolizability, ileal digestible energy, and AME. Tibia bones were analyzed for ash, Ca, and P content, and calculation of Seedor index. On day 28, blood samples were collected from 2 turkeys per replicate to analyze plasmatic MYO concentration. Feed conversion ratio was not affected, but phytase supplementation resulted in higher feed intake and body weight gain compared to turkeys fed the reduced diet (P < 0.05), and both doses were similar to the basal diet. Increasing the phytase dose had a linear effect (P < 0.05) on ileal digestibility of P and metabolizability of DM, CP, Ca, and Na, and also on AME. P content in the tibia bone increased linearly (P < 0.05) with phytase supplementation, and the same linear increase (P < 0.05) was observed for plasmatic MYO. In conclusion, the supplementation of turkey poult's diets with high levels of phytase up to 4,000 FYT/kg improves diet utilization by increasing P digestibility and dietary metabolizability, leading to higher P content in the bone and enhancing MYO provision and absorption.

The cage rearing model of the modern poultry industry makes the bones of birds more vulnerable to deterioration. In this study, at 8 wk of age, a total of 60 birds were randomly allocated to 2 groups, including the floor rearing group (FRD) and cage rearing group (CRD), and their body weight was measured every 2 wk. At the age of 20 wk, the tibia, femur, and humerus were collected from each group (n = 12) to determine the bone quality parameters such as weight, size, bone mineral density (BMD), breaking strength, cortical thickness, and area, ash content, calcium (Ca) content, and phosphorus (P) content. Meanwhile, the serum metabolome composition of both groups was detected by untargeted metabolome technology. The results showed that there were no significant differences in body weight, bone weight, and size between the 2 groups (P > 0.05), but the humerus mineral density and the breaking strength, cortical bone thickness, cortical bone area percentage of tibia, femur, and humerus of CRD was significantly lower than those of FRD (P < 0.05), indicating that the cage rearing system caused the deterioration of bone quality. Based on nontarget metabolomics, 49 metabolites were correlated with bone quality parameters, and 10 key metabolites were strongly correlated, including erucic acid, citric acid, and ketoleucine. In addition, the KEGG analysis showed that the caged system mainly perturbed amino acid metabolism, lipid metabolism, and energy metabolism, which led to changes in related metabolite levels, produced ROS, and altering energy supply, thus leading to a deterioration of bone quality of cage rearing ducks. Therefore, our findings were helpful to further understand the potential mechanism of the deterioration of duck bone quality in cage rearing system, provided a theoretical basis for reducing the occurrence of poultry osteoporosis, and ensuring the healthy development of poultry breeding.

We investigated the effect of photoperiod on eggshell quality, bone quality characteristics and bone metabolism related enzymes and factors in laying ducks. After adaption, 300 Jinding laying ducks (252-day-old) were randomly divided into 5 treatments, receiving 12L (hours of light):12D (hours of darkness), 14L:10D, 16L:8D, 18L:6D or 20L:4D, respectively. Each group had 6 replicates of 10 birds each. The feeding experiment lasted 8 wk. Compared with 12L:12D, the higher values of eggshell breaking strength occurred in ≥18 h photoperiods at the end of 6 wk, and in ≥16 h photoperiods at the end of 4 wk, with the common highest values in 18 h photoperiod (P ˂ 0.05). Besides, 18L:6D had higher values of ultimate load Fu and cortical cross-sectional area A in tibia, femur, and ulna (P ˂ 0.05), compared with 12L:12D. The higher values of proximal bone mineral content (BMC; tibia), distal BMC (ulna), total Ca (tibia), and cortical volumetric bone mineral density (vBMC; tibia and ulna) were observed in 16L:8D and 18L:6D treatments (P ˂ 0.05). Meanwhile, 18 h photoperiod group had the higher proximal BMC (femur) and total Ca in ulna (P ˂ 0.05). In serum, compared with 12L:12D group, the higher ALP activity occurred in ≥16 h photoperiods (0:00 and 18:00), with the highest values in 18L:6D treatment (P ˂ 0.05); the higher values of TGF-β (6:00) and OC (6:00 and 18:00) were simultaneously observed in 18 h photoperiod (P ˂ 0.05). Moreover, values of trACP activity, TNF-α and IL-6 contents decreased in ≥18 h photoperiods at 0:00 (P ˂ 0.05), compared with 12L:12D group. To sum up, an appropriate photoperiod could improve eggshell quality, bone strength and mineral content through increasing osteogenesis during the light time and decreasing resorption activity during the dark, and 18 h is an adequate photoperiod for the eggshell and bone quality of laying ducks.

This study focused on analyzing the effects of inclusion of modern hybrid rye to corn-wheat diet on mechanical properties of bones and tendons. A total of 224 broiler chickens were fed a diet without rye inclusion or a diet containing 15% of hybrid rye cv. Brasetto. The diets were either unsupplemented or supplemented with xylanase (minimum activity 1000 FXU/g, dose 200 mg/kg of feed). Each dietary group consisted of 56 birds. On day 42, selected chickens (n = 7 from each group) were slaughtered. Tibia were analyzed for mineralization, geometry, and biomechanical characteristics of bone mid-diaphysis. The mechanical properties of digital flexor III tendon were also assessed. Bone mineral density and bone ash percentage did not differ when both diets were given without xylanase. Enzyme supplementation increased bone mineral density (P < 0.01) in both dietary groups, whereas bone ash percentage (P < 0.01) increased only for corn-wheat diet. Rye inclusion had no effect on bone mid-shaft geometrical traits related to tibia weight-bearing capacity (cross-sectional area, cortical index, and mean relative wall thickness). Performed bending test showed no effect of hybrid rye inclusion on bone mechanical endurance. When xylanase was supplemented, bone length (P < 0.01) and weight (P < 0.05) decreased, whereas yield load (P < 0.01), stiffness (P < 0.05), Young modulus (P < 0.05), elastics stress (P < 0.01), and ultimate stress (P < 0.01) increased, irrespective of rye presence. The tendon tensile strain test showed that in corn-wheat diet enzyme supplementation positively influenced rupture force (P < 0.05) and tendon stiffness (P < 0.01). Xylanase supplementation increased the value of energy required to tendon rupture, irrespective of rye inclusion (P < 0.05). Study showed that modern hybrid rye varieties can be introduced to corn-wheat diets of broiler chickens in the aspect of animal welfare related to the development and homeostasis of musculoskeletal system, irrespective of xylanase supplementation. The enzyme addition positively affected biomechanical properties of bones and tendons.

The effects of stocking density on the performance, egg quality, leukocyte concentration, blood biochemistry, corticosterone levels, bone mineral density, and noxious gas emission of laying hens were investigated. Eight hundred 34-week-old Hy-Line Brown laying hens (Gallus gallus domesticus) were randomly assigned to one of 4 treatments, each of which was replicated 4 times. Four stocking densities, including 5, 6, 7, and 10 birds/m2, were compared. A commercial-type basal diet was formulated to meet or exceed nutrient recommendations for laying hens from the National Research Council. The diet was fed to the hens ad libitum for 8 wk. Results indicated that hen-day egg production, egg mass, and feed intake were less for (P < 0.01) 10 birds/m2 stock density than other stock densities. Production rate of floor and broken eggs and eggshell strength were greater (P < 0.01) for 10 birds/m2 stock density than other stock densities. There were no significant differences in the level of leukocytes among densities. However, heterophils and the H/L ratio were greater (P < 0.01) for 10 birds/m2 than in stock density of 6 or 7 birds/m2. Serum corticosterone was greater (P < 0.01) 10 birds/m2 than stock density than other stock densities. Litter moisture and gas emission (CO2 and NH3) were greater (P < 0.01) for 10 birds/m2 than stock density than 6 and 7 birds/m2 stock density. Bone mineral content was not influenced by increasing stock density. However, bone mineral density was less (P < 0.05) for 10 m2 stock density than other stock densities. These results indicate that increasing the density beyond 5 birds/m2 elicits some negative effects on laying performance of Hy-Line brown laying hens.

Laying hen skeletal health continues to be an industry priority. Bone ash and bone Ca quantification in laying hen long bones provides valuable information on skeletal health. Unfortunately, these measurements can only be accomplished by sacrificing hens, thus making longitudinal measurements on the same hen impossible. Quantitative computed tomography (QCT), used with a calcium hydroxyapatite phantom, has been used to determine bone density of wings and legs as well as live hens throughout the production cycle by scanning with a calcium hydroxyapatite phantom. QCT has also been used to scan live hens throughout the production cycle. The purpose of this study was to determine how QCT calculated bone mineral content (QCT BMC) corresponds to analytical bone Ca and bone ash. Wing and leg quarters from 72-wk-old W-36 hens were QCT scanned along with a QCT Phantom. After scanning, humeri, femurs, and tibias were cleaned, divided into epiphysis (E) and diaphysis (D), fat extracted, ashed, and digested under nitric acid, and Ca was determined by atomic absorption spectroscopy was used to determine E, D, and whole bone Ca. Four bones/type were used for E and D, while 6 bones/type were used for whole bone measurements. A second set of bones were prepared to determine correlation of BMC to bone ash. QCT scans were analyzed with Mimics software (Materialise NV, Leuven, Belgium) to calculate bone volume and density in Hounsfield units. Utilizing the QCT phantom and bone volume, BMC was calculated for E, D, and whole bone. Data were analyzed with regression analysis and Pearson correlation coefficients were determined. Analytical Ca was correlated to QCT BMC for E (R = 0.84, P < 0.01), D (R = 0.99, P < 0.01), and whole bone (R = 0.97, P < 0.01). Whole bone ash was highly correlated to QCT BMC for femur (N = 47, R = 0.97, P < 0.001), tibia (N = 50, R = 0.94, P < 0.001), and keel (N 50, R = 0.94, P < 0.001). Whole bone ash and QCT BMC values of femur and tibia were not different (P = 0.39 and 0.22 respectively). Based on this information, QCT could provide relative quantitative assessment of total bone mineral in live birds proving useful in long-term studies.

This study aimed to evaluate the effect of photoperiod on growth performance and bone development in layer ducks during the pullet phase. A total of 480 11-wk-old Jinding layer ducks were randomly divided into 5 groups, receiving 6L (light): 18D (dark), 8L: 16D, 10L: 14D, 12L: 12D, 14L: 10D, respectively. Each group had 6 replicates of 16 birds each. The feeding trial lasted 80 d until 150 d of age. The results showed that 8L: 16D increased body weight (BW) and average daily gain (ADG; P0.05) compared with 6L:18D, whereas average daily feed intake, feed conversion ratio, and mortality rate had no difference among all treatments (P0.05). The midpoint perimeter (tibia and femur) and work to fracture (Wu; tibia) increased quadratically (P0.05), in response to photoperiod increment. Compared with 6L:18D, 8L:16D had higher tibia midpoint perimeter, ultimate load (Fu), and cortical cross-sectional area (P0.05), accompanied with higher content of total Ca, distal bone mineral content (BMC), and cortical volumetric BMC (vBMC; P0.05). A linear increase was observed in trabecular volumetric bone mineral density (vBMD) and vBMC (tibia and femur), elastic energy (femur), work to fracture Wu and young modulus of elasticity E (tibia) in response to photoperiod increase (P0.05), and treatment with 14L:10D had higher ultimate load Fu and total Ca of tibia (P0.05). Besides, estradiol and testosterone levels (serum), estrogen receptor gene mRNA expression (bone tissue), alkaline phosphatase and tartrate-resistant acid phosphatase activities, transforming growth factor-β, osteocalcin and tumor necrosis factor-α contents increased in ≥12 h photoperiods (P0.05). In summary, appropriate photoperiod increased BW, ADG, cortical bone generation, and bone mineralization, whereas only medullary bone formation increased with photoperiods. These results suggest that 8L:16D could be an adequate photoperiod for layer ducks' growth and bone development during the pullet phase.

The objective of this study was to determine the effects of a dietary synbiotic inclusion on broiler bone health under daily cyclic heat stress. A total of 360 Ross 708 broilers were randomly assigned to 1 of 3 dietary treatments (8 replicates per treatment): a regular diet (control) and the regular diet mixed with a commercial synbiotic product at 0.5 (0.5X) or 1.0 (1.0X) g/kg. The synbiotic contains a prebiotic (fructooligosaccharides) and a probiotic mixture of 4 microbial strains (Enterococcus faecium, Pediococcus acidilactici, Bifidobacterium animalis, and Lactobacillus reuteri). Room temperature was gradually decreased from 34°C on d 1 by 0.5°C/d for the first 14 d; then a cyclic heat stress episode (32°C/9 h/d) was applied from d 15 to 42. Gait score assessment and the latency-to-lie test were conducted when broilers were 40 and 41 d of age, respectively. The tibia, femur, and humerus were collected for measuring bone parameters at 42 d of age. The data indicated that bone mineral density, bone mineral content, and bone area were higher and the level of gait score was lower in the 1.0X group (P = 0.05) but not in the 0.5X group (P0.05) compared to controls. The proportions of broilers showing signs of lameness were ranked 1.0X group (25%)0.5X group (45%)control (54%). Compared to controls, broilers of 0.5X group stood longer (P = 0.03) during the latency-to-lie test. In conclusion, under the present conditions the synbiotic profoundly improves multiple indices of leg health of broilers subjected to the cyclic heat episodes, resulting in an improvement in walking ability.

Leg problems have become more frequent in fast-growing turkeys. The objective of this study was to evaluate the effects of common leg defects on kinetic parameters of gait and biomechanical properties of bone. Nine hundred, day-old, male, Large White turkeys were raised in 48 floor pens. At 42 d of age, turkeys were divided into four categories of leg condition as determined by visual evaluation: Normal, Crooked toes, Shaky legs, and Valgus. Fifteen toms were selected from each group and trained to walk on a pressure sensitive walkway. Gait kinetic data were collected at 92, 115 and 144 d of age. At 145 d of age, turkeys were sacrificed and bones were collected and frozen until analysis. Morphological measurements of femur, tibia and tarsus-metatarsus were recorded. Bone mineral density (BMD) and content (BMC) were obtained using DEXA. Bone strength of tibias was evaluated using a four-point bending test and femurs with a torsion test. ANOVA was used to detect differences among groups, and Tukey's test used for mean separation. There were no differences in BW among different leg conditions. Gait parameters changed as turkeys aged, and age-group interactions were observed on peak vertical force (PVF), contact time, step length (SL) and bipedal cycle. No differences (P0.05) were detected in morphological measurements of femur or tibia. Relative asymmetry of femur length was lower (P0.05) in Normal and Valgus turkeys than in toms with Crooked toes. There were no differences (P0.05) among groups for femur BMD, BMC or strength. Tibia BMD and the area moment of inertia of turkeys with Crooked toes were lower (P0.05) than in toms with Valgus. With all four leg conditions, femur strength was positively correlated with PVF and negatively correlated with SL; BMD and BMC were correlated with tibia strength and gait kinetic parameters. In conclusion, only crooked toes caused consistent differences in gait patterns, bone properties and bone strength, but in general, gait kinetics was correlated with bone biomechanics in turkeys.

The present study was conducted to evaluate four commercially available phytase sources supplemented at regular (R) and super-dose (S) levels on live performance, bone mineralization, and apparent ileal digestible energy. Broiler chickens were allocated in stainless steel battery brooders (six birds per cage and eight pen replicates per treatment). A basal diet formulated to contain 0.2% non-phytate phosphorus (NPP) and 0.7% Ca was subdivided to create 11 dietary treatments: (1) basal diet was kept as the negative control (NC); (2) NC + limestone and monoclacium phosphate to create positive controls 1 and 2 formulated to yield 0.3% and 0.4% NPP; (3) NC + phytase A (250 and 1,500 FTU/kg); (4) NC + phytase B (500 and 1,500 FTU/kg); (5) NC + phytase C (500 and 1,000 FTU/kg); (6) NC + phytase D (1,000 and 2,000 FYT/kg). Performance was evaluated on d 7, 14, and 22. Tibia bone ash, tibia breaking strength, bone mineral content, and bone mineral density were evaluated on d 22. Apparent energy digestibility was evaluated on d 24. At d 7, phytases A and C supplemented at S level improved (P < 0.05) body weight and weight gain when compared to the NC. At d 14 and 22, all phytase sources improved (P < 0.05) body weight, weight gain, and bone mineralization when compared to the chicks under the NC diet. Overall, phytase supplementation at S level improved 17% apparent ileal digestibility at 24 d. Throughout the grow out period, phytase super-dose yield (P < 0.05) better performance, bone characteristics, and energy digestibility than the regular dietary level. In conclusion, all phytase sources were able to compensate the phosphorus deficiency and promote performance and bone mineralization. High levels of phytase showed a higher response when compared to the lower levels of supplementation.

An experiment was conducted to determine the relative bioavailability (RBV) of P in high-protein sunflower meal (HP-SFM) fed to broiler chickens based on bone traits and to determine the effects of dietary phytase supplementation and increasing levels of HP-SFM as a P source on bone traits, growth performance, and apparent ileal digestibility (AID) of DM and nutrients. In total, 240 broiler chicks were randomly allotted to 1 of 10 experimental diets with 6 replicate cages of 4 birds each and fed experimental diets from day 14 to 21 of age. Diets included a corn-soybean meal-based basal diet (0.35% total P; P-deficient diet), or the basal diet supplemented with 0.05, 0.10, or 0.15% P from either monosodium phosphate (MSP) or HP-SFM. Another 3 diets were formulated by supplementing the HP-SFM-containing diets with 500 phytase unit/kg of phytase. The bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) of femur and tibia and tibia ash content increased (linear, P < 0.01) with increasing dietary P content from MSP. A linear increase in femur and tibia BMC, femur BA, and tibia BMD was also observed (P < 0.01) with increasing level of dietary P from HP-SFM. The RBV of P in HP-SFM based on femur and tibia BMC were 41 and 44%, respectively. Dietary phytase supplementation increased (P < 0.01) most of bone traits of the birds except for femur BMD. In addition, birds fed the diets supplemented with dietary phytase had greater (P < 0.05) BW gain, feed efficiency, and AID of P than those fed the diets without dietary phytase. In conclusion, the estimated RBV of P in HP-SFM to P in MSP were 41 and 44% based on femur and tibia BMC, respectively. Also, dietary phytase supplementation increased AID of P, growth performance, and bone traits of the birds fed P-deficient diets containing increasing inclusion level of HP-SFM as a P source.

Two experiments were conducted to investigate the effect of high dietary calcium (Ca) level on growth performance, Ca and phosphorus (P) metabolism, and nutrient utilization in ducklings subjected to normal and low P levels in diets. A completely randomized design was used with a factorial arrangement of 2 total dietary P levels [normal-P (0.60%) and low-P (0.45%) groups] × 4 dietary Ca levels [low-Ca (0.55%), normal-Ca (0.75%), medium-Ca (0.95%) and high-Ca (1.15%) groups)]. Compared to normal-P group, low-P group had lower (P

Improved bone development and mineralization in broilers have been attributed to the use of 25-hydroxylcholecalceiferol [25(OH)D3] as a dietary supplement. In this study, effects of the in ovo injection of 25(OH)D3 delivered in commercial diluent on 18 d of incubation (doi) on subsequent bone development and mineralization in male and female Ross × Ross 708 broilers were investigated. The variables investigated included bone mineral density and breaking strength, bone ash concentration, and calcium and phosphorus bone ash concentrations. In a single-stage incubator, with 6 treatments on each of the 10 tray levels, a total of 2,400 experimental broiler hatching eggs were evenly and randomly set. Eggs were treatment-injected and transferred to corresponding hatching baskets on 18 doi. Experimental treatment groups were those that received 0.2, 0.6, 1.8, or 5.4 µg of 25(OH)D3 that were delivered in 100 µL of commercial diluent. Noninjected and diluent-injected controls were also included. On 21 doi, chicks were pulled and placed in corresponding floor pens, and on each of d 0, 14, and 28 posthatch (poh), 2 birds of each sex from each pen were randomly selected for necropsy and extraction of both of their tibia bones. Bones from the right leg were subjected to mineral density analysis and those from the left leg were used to determine breaking strength and residual bone ash concentration. Furthermore, ash calcium and phosphorus concentrations on d 14 and 28 poh were determined. There was a treatment × sex × age interaction for bone breaking strength. Bone breaking strength in male birds on d 28 poh was higher in the 0.20, 0.60, and 1.80 µg of 25(OH)D3-injected treatment groups than in the diluent-injected control group. In conclusion, although the in ovo injection of 25(OH)D3 had no positive effect on the bone development of Ross × Ross 708 broilers through d 28 poh compared with noninjected controls, it may provide a benefit to those subjected to an injection of commercial vaccine diluent.

The aim of the current study was to investigate basic morphometric, geometric, and densitometric parameters of tibia and tarsometatarsus in 14-mo-old male and female ostriches, and interrelationships between these parameters. The study was conducted on 20 tibiae and 20 tarsometatarsal bones of the left pelvic limb derived from 20 healthy 14-mo-old ostriches (Struthio camelus): 10 males and 10 females. The following parameters were determined using peripheral quantitative computed tomography: bone mineral content (BMC), volumetric bone mineral density (vBMD), cortical content (CRT_CNT), cortical density (CRT_DEN), trabecular content, trabecular density (TRAB_DEN), bone area (TOT_A), trabecular area (TRAB_A), cortical area (CRT_A), cortical thickness (CRT_THK_C), periosteal circumference (PERI_C), endocortical circumference (ENDO_C), and strength-strain index (SSI) in the metaphysis and diaphysis of the bones. Statistical evaluation of the obtained results was performed using Student's t-test, and the Pearson correlation coefficient between the investigated parameters was determined. The obtained results have shown significant differences in proximal metaphysis between males and females when evaluating such parameters as CRT_DEN, TOT_A, TRAB_A, PERI_C, SSI in tibia (P0.05), and BMC, vBMD, TRAB_DEN, CRT_CNT, TOT_A, TRAB_A, cortical area, PERI_C, ENDO_C, SSI in tarsometatarsus (P0.05). Significant differences between the 2 sexes were found in all the investigated parameters of diaphysis of tibia, except for CRT_DEN and ENDO_C (P0.05). Significant positive correlations between BW and bone weight were found (P0.05). Furthermore, numerous correlations of morphometric, geometric, and densitometric parameters of metaphysis and diaphysis of the tibia and tarsometatarsus were stated (P0.05). In conclusion, the present investigation demonstrated sex-related differences in morphometric, densitometric, and geometric properties of tibia and tarsometatarsus in 14-mo-old ostriches. Numerous correleations observed between the investigated parameters have shown that ostrich tibia and tarsometatarsus may present a valuable model for further studies on bone tissue metabolism regulation in breeding birds.

Locomotion problems in meat poultry have multifactorial etiology. A better understanding of normal gait and its influences on biomechanical aspects of leg bones among turkey genetic lines is important to prevent skeletal disorders and locomotion issues. The objective of this experiment was to determine the possible differences in gait kinetic and kinematic parameters of turkey strains and their effects on bone biomechanical properties. Four genetic lines, named A, B, C, and D, were obtained and raised in 48 floor pens with new pine shavings. Leg health issues were classified at 16 and 33 d of age. Fifteen turkeys from each strain with apparent normal legs and gait at 33 d of age were selected for gait analysis. These 15 turkeys were trained to walk on a pressure sensitive walkway and video was recorded to calculate articulation movements. These data also were analyzed to obtain kinetic and kinematic parameters of the gait cycle collected at 47, 84, 107, and 145 d of age. At 20 wk all turkeys were sacrificed, and legs were collected and frozen for analysis. Weights and morphologic measurements of the femur, tibia, and shank were recorded. Bone mineral density (BMD) and content (BMC) were obtained using DEXA. Femur and tibia strength were evaluated by a 4-point bending test and torsion test, respectively. Gait parameters changed as toms aged and some differences were observed among lines. Genetic lines differed on BMD, but not on BMC. Strain D had a higher BMD and smaller diaphyseal angle than strain C, characteristics that were correlated with stronger bones. Strain D also had the lowest incidence of leg problems while strain C had the highest. Furthermore, the D strain had a smaller vertical motion of the toe than strains C and B at 47 d and strain A at 145 d, indicating that the D strain had a more efficient gait. In summary, genetic strains differ significantly on gait parameters, which in turn impacts bone biomechanics.

The incorporation of carbonate has been recognized as an evident change in bone mineral (bioapatite) during aging. Laying hens (Gushi layer) at 4 stages of age (8 hens each stage) were studied by Raman spectroscopy and X-ray radiography to investigate the mineralogical changes and bone density, respectively. Cortical bones of the humerus and femur show a rapid increase of carbonate (∼1.9 wt.%) from sexual maturity to the peak of hens' laying period, while the densities of the cortical bones are relatively stable. Before sexual maturity, the density of the cortical bones increases considerably during aging. However, after the peak of the laying period, only femoral density continues elevating. Carbonate contents in the cortical bones reach the maximum at the peak of the laying period. Two pathways (halted growth of density and Ca-release due to the CO3 incorporation) could both contribute to the intense Ca requirement for egg laying. Crystallization, however, has no significant changes during aging and the laying period. This study could shed light on the mechanism of mineral losses due to CO3 incorporation, and also shows the advantages of Raman spectroscopy in tracking mineral loss in poultry bone.

Limited information on physiological characteristic of bones in ostrich skeleton are available, even though bone weaknesses in ostriches are commonplace. Thus, the aim of this study was to evaluate morphological, densitometric, and mechanical properties of pelvic limb long bones (femur, tibia, and tarsometatarsus) in 14-month-old female ostriches (Struthio camelus var. domesticus). After the slaughter procedure, all bones were isolated, cleaned of soft tissues, and bone weight and length were determined. Using dual energy X-ray absorptiometry (DEXA) bone mineral density (BMD) and bone mineral content (BMC) were determined. Volumetric bone mineral density (vBMD) and geometrical parameters of the bones were determined using the quantitative computed tomography (QCT) method. Maximum elastic strength and ultimate strength of the bones were determined using three-point bending test. Significant differences were revealed between morphological, densitometric, and mechanical properties of femur, tibia, and tarsometatarsus in female ostriches at the slaughter age of 14 months. Elaborated experimental model and determination of morphological, densitometric, and mechanical properties of femur, tibia, and tarsometatarsus in female ostriches may serve for further studies on metabolic regulation of skeletal system properties with environmental, physiological, dietary, pharmacological, and toxicological factors.

The prevalence of keel bone damage as well as external egg parameters of 2 pure lines divergently selected for high (H) and low (L) bone strength were investigated in 2 aviary systems under commercial conditions. A standard LSL hybrid was used as a reference group. Birds were kept mixed per genetic line (77 hens of the H and L line and 201 or 206 hens of the LSL line, respectively, per pen) in 8 pens of 2 aviary systems differing in design. Keel bone status and body mass of 20 focal hens per line and pen were assessed at 17, 18, 23, 30, 36, 43, 52, and 63 wk of age. External egg parameters (i.e., egg mass, eggshell breaking strength, thickness, and mass) were measured using 10 eggs per line at both 38 and 57 wk of age. Body parameters (i.e. tarsus and third primary wing feather length to calculate index of wing loading) were recorded at 38 wk of age and mortality per genetic line throughout the laying cycle. Bone mineral density (BMD) of 15 keel bones per genetic line was measured after slaughter to confirm assignment of the experimental lines. We found a greater BMD in the H compared with the L and LSL lines. Fewer keel bone fractures and deviations, a poorer external egg quality, as well as a lower index of wing loading were found in the H compared with the L line. Mortality was lower and production parameters (e.g., laying performance) were higher in the LSL line compared with the 2 experimental lines. Aviary design affected prevalence of keel bone damage, body mass, and mortality. We conclude that selection of specific bone traits associated with bone strength as well as the related differences in body morphology (i.e., lower index of wing loading) have potential to reduce keel bone damage in commercial settings. Also, the housing environment (i.e., aviary design) may have additive effects.

The addition of microbial phytase to diets for broiler chickens has been shown to improve the availability of phytate P, total P, some other minerals, and amino acids. In this study, the effect of a novel microbial phytase expressed by synthetic genes in Aspergillus oryzae on amino acid and mineral availability was assessed. Phytase was incorporated (1,000 and 2,000 U/kg) into low-P corn-soybean meal-based diets for broilers. Broilers received the experimental diets for 3 wk, and excreta were collected from d 18 to 21 for the determination of AME and mineral retention. On the 22nd day, the broilers were killed and the left leg removed and ileal digesta collected. Ileal phytate P and total P absorption, ileal amino acid digestibility, as well as the bone mineral content and bone mineral density were determined. Ileal phytate P absorption and absorbed phytate P content of the low-P corn-soybean meal diet were significantly (P < 0.05) higher after dietary inclusion of the novel phytase (49-60% and 65-77% higher, respectively). Apparent ileal total P absorption and apparent total P retention was 12 to 16% and 14 to 19% higher (P < 0.05), respectively, after dietary inclusion of phytase. The bone mineral content and bone mineral density in the tibia were 32 to 35% and 19 to 21% higher (P < 0.05), respectively, after dietary phytase inclusion. The apparent ileal digestibility of threonine, tyrosine, and histidine increased significantly (P < 0.05) by 14, 9, and 7%, respectively, after dietary inclusion of microbial phytase. Overall, the inclusion of a novel microbial phytase into a low-P corn-soybean meal diet for broiler chickens greatly increased phytate P and total P absorption, bone mineral content and density, as well as the digestibility of some amino acids.

Life cycle changes in bone mineralization and bone size traits of the tibia and humerus were evaluated in commercial male and female broilers using dual-energy x-ray absorptiometry (DEXA). Experiment 1 evaluated weekly changes in bone traits from 2 to 7 wk of age, whereas experiment 2 compared the bone traits of 4 strains of commercial meat-type chickens from 4 to 8 wk of age. Birds were restrained without anesthesia, and the humerus and tibia were scanned in vivo. After each scan, individual BW was determined. From the DEXA scans, bone mineral density (BMD), bone mineral content (BMC), as well as bone length, width, and area were determined. Bone mineralization and size traits were analyzed as an analysis of covariance with BW as the covariate. If BW was NS as a covariate, then an ANOVA was used. The BMD reached its peak at 4 wk of age. The BMC of the humerus changed little from 2 to 8 wk of age, whereas tibial BMC increased as the birds aged, especially in males (P < 0.0001). In experiment 1, bone length, width, and area also increased with age (P < 0.0001), with the tibia growing in length at a faster rate than the humerus. In experiment 2, the BMD did not differ among the 4 strains of commercial broilers. Interactions with strain of chicken were also NS, indicating that all strains of chickens responded similarly with respect to age (4, 6, and 8 wk of age), sex, and type of bone (humerus vs. tibia). Coefficients of variation for BMD ranged from 15 to 16%, indicating a potential use of DEXA for selection to improve skeletal integrity. In conclusion, the tibia continued to grow, especially after the initiation of the growth spurt at 3 to 4 wk of age, as indicated by bone length, width, and BMC, but it did not become denser in mineral after 4 wk of age as its surface area increased.

The efficacy of 3 local limestone sources as potential Ca sources for laying hens was studied. Limestone sources were assessed for in vitro solubility. Four Ca sources (control, A, B, or C) and 2 particle size combinations (ground, 100% ground; or mixed, 67% ground+33% large particle) was used. The control consisted of a commercial ground limestone for the ground Ca source and oyster shell of the large particle Ca source. DeKalb laying hens were randomly placed in 32 battery cage units (n=12/cage). At 19 wk of age, hens received 1 of 8 Ca source and particle size treatments (4 replicates/treatment) until 74 wk. Egg production, feed consumption, BW, and egg quality were measured throughout. Bone mineral density (by quantitative computed tomography), breaking strength, ash, and Ca were assessed at the end of lay. In vitro solubility was dependent upon Ca source and particle size (P0.0001) with oyster shell generally having a greater in vitro solubility than test limestone sources A, B, and C of similar particle sizes. Feed consumption (100 to 117 g/bird per day), BW (1,500 to 1,800 g), egg production (92% peak egg production), egg weight (55 to 67 g), and egg specific gravity (1.090 to 1.078) did not differ among hens fed the different Ca sources (P0.05). Tibia bone mineral density indicated the oyster shell treatment had a lower trabecular density than Ca source A; however, all other Ca sources had similar bone mineral density for all measures (P0.05). Hens fed the mixed Ca particle treatments consistently had greater feed consumption from 27 to 70 wk than those fed the 100% ground Ca source (P0.05). Bone mineralization was enhanced in hens that received the mixed Ca particle treatments (P0.05). Overall, the results of this study indicate that the local limestone sources A, B, and C would be suitable alternatives to current commercial sources of Ca for laying hens. In addition, large particle Ca did improve bone quality.

Limited opportunity for movement and load-bearing exercise for conventionally caged laying hens leads to bone loss and increased susceptibility to osteoporosis, bone fractures, and cage layer fatigue, all of which compromise hen welfare and have negative consequences for production. The objective of this study was to compare bone mineral density (BMD) and strength measures of White Leghorns housed in conventional battery cages (CONV), cages modified to incorporate a nest box and perch (MOD), and commercially available, furnished colony cages with (CWDB) or without (CWODB) a raised dust bath. Hens reared on floor litter were randomly allocated to 1 of 4 cage systems at 19 wk of age. Hen-day production and egg quality were measured between 20 and 64 wk. At 65 wk, hens were killed, and right femur, tibia, and humerus were excised. Bone mineral density was assessed using quantitative computed tomography, and breaking strength was measured with an Instron Materials Tester. In the femur and tibia, CONV hens exhibited lower total BMD, bone mass, cortical bone area, cortical bone mass, and bone-breaking strength than CWDB, CWODB, and MOD hens. Density and cross-sectional area of bone in the trabecular space was highest in CONV. In the humerus, total and cortical BMD and mass and breaking strength values were higher for colony-housed birds than hens in CONV and MOD. The MOD birds did not exhibit increased humeral BMD or strength measures over CONV hens. These findings provide evidence that hens housed in modified and colony cages, furnished systems that promote load-bearing movement, are better able to preserve cortical structural bone than conventionally caged hens and simultaneously have stronger bones. Furthermore, inclusion of raised amenities that encourage wing loading is necessary to reduce humeral cortical bone loss. The overall absence of correlation between egg production or quality and bone quality measures also suggests that improved bone quality in CWDB, CWODB, and MOD furnished cages is not the result of lowered egg production or quality.

The purpose of this study was to investigate the effects of varying ratios of n-6 to n-3 fatty acids in the diets of White Leghorn chickens on tibia bone characteristics [bone mineral density, bone mineral content (BMC), ash bone mineral content, bone morphology, and cortical thickness] and tibia bone strength parameters (ultimate force, bending stress, maximum strain, Young's modulus of elasticity, area under the curve, and moment of inertia). Seventy-five 16-wk-old female White Leghorn chickens were randomly assigned to 1 of 5 dietary ratios of n-6 to n-3 fatty acids: 47.8:1, 18.0:1, 7.6:1, 5.9:1, or 4.7:1. Corn oil was the n-6 fatty acid source, whereas flax oil provided the n-3 fatty acids. Bone density was measured on the left tibia via dual-energy x-ray absorptiometry (DXA) prior to killing and after excision. Bones were ashed in a muffle furnace at 500 degrees F. Tibia bones were broken by using a 3-point bending rig. Results showed no significant effect of diet on bone characteristics. There were no significant differences among diet groups for parameters of bone strength except cortical thickness (P < or = 0.01). Bone mineral content determined by ashing was significantly different by 9.2% (P < or = 0.0001) from BMC determined in vivo by DXA; however, there were no differences in ex vivo BMC and BMC ash, although they were highly correlated (r = 0.99, P < or = 0.0001). We concluded that there was no effect of n-3 fatty acids on tibia bone in mature White Leghorn chickens. The GE Lunar Prodigy DXA instrument significantly underestimated the in vivo BMC in chickens.

A study was conducted to evaluate the effects of alfalfa-based molt diets on molting performance and bone qualities. A total of 36 Single Comb White Leghorn hens were used for the study. There were 6 treatments: pretrial control (PC), fully fed (FF), feed withdrawal (FW), 90% alfalfa:10% layer ration (A90), 80% alfalfa:20% layer ration (A80), and 70% alfalfa:30% layer ration (A70). For the PC treatment, hens were euthanized by CO(2) gas, and bones were collected before molt was initiated. At the end of the 9-d molt period, hens were euthanized, and femurs and tibias were collected to evaluate bone qualities by peripheral quantitative computed tomography, mechanical testing, and conventional ash weights. The hens fed alfalfa-based molt diets and FW stopped laying eggs within 5 d after molt started, and all hens in these groups had reduced ovary weights compared with those of the FF hens. In the FW and A90 groups, total femur volumetric bone mineral densities (vBMD) at the midshaft were significantly lower, but those of the A80 and A70 groups were not significantly different from the values for the PC and FF hens. In cortical bone density, the midshaft tibial vBMD were significantly higher for FF and A70 hens than for PC hens. The medullary bone densities at the midshaft femur or tibia of the FW, A90, A80, and A70 hens were reduced compared with those of the PC hens. Femur cancellous densities at the distal femur for the FW and A90 hens were significantly reduced compared with those of the PC and FF hens. The FW, A80, and A70 hens yielded significantly higher elastic moduli, and the A80 hens had higher ultimate stress compared with the PC hens, suggesting that the mechanical integrity of the midshaft bone was maintained even though the medullary vBMD was reduced. These results suggest that alfalfa-based molt diets exhibit molt performance similar to FW, that medullary and cancellous bones are labile bone compartments during molting, and that alfalfa-based molt diets may be beneficial to maintain the mechanical properties of bones during molt.

Axial x-ray microcomputed tomography is a cost-effective technique with the potential to assess bone mineral density (mg/cc) in both cortical and cancellous bone in Single Comb White Leghorn hens. The technique requires little sample preparation and involves relatively simple data processing. The system described in this research is based on compact fan-beam type tomography, using a tungsten-anode x-ray tube with a relatively small focal spot (approximately 5 microm), coupled with a high-resolution x-ray detector system (approximately 10 microm). To produce a real 3-D data set using microcomputed tomography, x-ray projection views were acquired at 720 equally spaced angular positions (0.5 degrees) around the object of interest. These groups of views were then used to reconstruct a computed tomography image. A test grid with orthogonal test lines was used to calculate bone volume and bone surface. From these calculations, parallel plate equations were used to derive trabecular architectural parameters such as average trabecular plate thickness and average trabecular plate separation. Three-dimensional microarchitecture was evaluated using specialized stereological analysis software. Significant relationships between apparent bone mineral density (mg/cc) and 3-D structure were observed in femoral specimens from 66-wk-old Single Comb White Leghorn hens.

An experiment was conducted to investigate the effects of phytase and 2 levels of fructooligosaccharide (FOS) supplementation on growth performance, bone mineralization, and P utilization of broiler chickens. A total of 210 day-old male broiler chickens (Ross) were randomly placed into 7 dietary treatments consisting of 6 replicates with 5 birds per pen. The experiment was designed as an augmented 2 × 3 factorial arrangement with 0 or 500 U/kg of phytase and 0, 0.5% or 1% of FOS added to a reduced Ca (0.8%) and available P (0.25%) negative control diet (NC). A positive control diet (PC) that contained 1% Ca and 0.45% available P was also included. During the entire experimental period, phytase supplementation significantly improved (P < 0.05) the feed conversion ratio (FCR), BW gain (BWG), and feed intake. Birds fed the PC diet showed significantly higher bone mineral density (BMD) and bone mineral content (BMC) in both femur and tibia bones (P < 0.0001) than those fed the NC diet. Phytase supplementation increased femur BMD (P < 0.05), whereas FOS decreased femur BMD and BMC (P < 0.05). Phosphorus utilization was significantly higher for the NC diet (P < 0.0001). Phytase alone and in combination with 0.5% FOS increased P utilization significantly when compared with other treatments (P < 0.05). Fructooligosaccharides, especially at the level of 0.5%, increased P retention. In conclusion, phytase supplementation in low Ca and P diets improved growth performance, bone quality, and P utilization. However, supplementing NC diets with phytase and FOS did not result in bone mineralization values comparable with that of the PC diet. The application of dietary FOS alone had a negative effect on broiler bone quality.

Dual energy x-ray absorptiometry (DEXA) was evaluated for use as a noninvasive tool to monitor skeletal integrity in live laying hens. The objectives of the current study were 1) to validate the use of DEXA in evaluating bone integrity in live birds as compared with excised bones under a normal nutritional regimen as well as in hens fed varying levels of dietary Ca and 2) to correlate densitometric scans with other bone strength criteria and egg traits. Densitometric scans were conducted on the tibia and humerus of live hens at 10-wk intervals from 17 to 67 wk of age. After each scan, bones were excised from euthanized hens to measure breaking strength characteristics and bone ash (experiment 1). Similar measurements were collected at 38, 48, and 58 wk of age from hens fed hypercalcemic (5.4%), control (3.6%), and hypocalcemic (1.8%) diets from 32 to 58 wk of age (experiment 2). The bone mineral density (BMD) and bone mineral content (BMC) between live and excised bone scans were highly correlated (r = 0.85 and 0.92, respectively, P < 0.0001, experiment 1). Densitometric scans of live birds were positively correlated with bone breaking force and bone ash (r = 0.68 and 0.73, respectively, P < 0.001) with little to no correlation with shell traits. In experiment 2, the excised tibial scan had lower BMD and BMC than the live bird (P < 0.01), whereas no difference was detected in densitometric scans of the humerus. The live and excised BMD and BMC of the tibia (r = 0.87 and 0.82, respectively, P < 0.001) and humerus (r = 0.94 and 0.93, respectively, P < 0.001) were highly correlated. Due to the high correlations between live and excised bone scans and the significant correlations of live scans to more traditional invasive bone measurement tests such as bone breaking force and bone ash, we concluded that DEXA is a useful noninvasive tool for evaluating skeletal integrity in live birds.

The purpose of this study was to validate dual-energy x-ray absorptiometry (DXA) for measuring the body composition of chickens in vivo. Four trials were conducted with broiler chickens using a DXA instrument (Lunar, DPX-L) and small animal total body scan software (version 4.7a). In the first 2 trials, the effects of scan mode (high resolution or detail slow), scanning position (ventral or dorsal), and the use of attenuating materials (AM) (2-mm polyvinyl chloride or 4-mm polystyrene) on the precision and values of the DXA parameters body mass, lean tissue mass, fat tissue mass and percentage, bone mineral content (BMC), and bone mineral density (BMD) were evaluated. The precision was highest for body mass and lean tissue mass, followed by BMC and BMD, and was lowest for fat tissue mass and percentage. The precision of the measurements was not influenced by scan mode, position, or type of AM. In contrast, the values for all DXA parameters except body mass were significantly influenced by the scan mode but not by the position. The high resolution mode gave significantly higher estimates of fat mass and BMC but significantly lower measures of lean tissue mass and BMD compared with the detail slow mode. A significant difference between AM was only observed for the DXA estimates of fat tissue mass and fat percentage. In trial 3, the accuracy of the DXA measurements was tested by comparison with chemical body composition analysis. Linear regression equations between the respective DXA and chemical parameters were established. High correlations (r > 0.9; P < 0.0001) were obtained for all parameters, except for fat percentage (r = 0.593; P < 0.05). The purpose of the validation trial was to compare the predicted body composition based on the DXA measurements with established equations and the chemical body composition. There was extremely good agreement for body mass, lean tissue mass, and fat tissue mass and percentage, but not for ash weight. It is concluded that, after proper methodological standardization and application of specifically determined regression equations, DXA can be used for estimating the body composition of chickens in vivo. However, the regression equations are strictly limited to one particular instrument, software version, and applied methodology.

Dual-energy X-ray absorptiometry has been validated in our laboratory as a noninvasive tool to assess skeletal integrity in live birds. The first objective of the current study was to determine if there were detectable changes in bone mineral density (BMD) and bone mineral content (BMC) while an egg was being formed in the oviduct. Implications from this experiment would define the time of day scans should be conducted for future experiments. Densitometric scans were conducted on the tibia and humerus of live hens undergoing active egg formation when hens were 0, 5, 15, and 20 h postoviposition at 24, 30, and 40 wk of age. No detectable changes in either the BMD or BMC of the tibia and humerus were observed as the egg was being formed in the reproductive tract at any age measured. These results suggest that densitometric scans may be conducted on bones in live birds at any time during the day, irrespective of the stage of egg formation. The second objective was to monitor the change and degree of variation in skeletal integrity of live birds during the first cycle of egg laying. The humerus and tibia of White Leghorns were scanned repeatedly at 10-wk intervals from 15 to 65 wk of age. The BMD of the humerus increased from 15 to 65 wk of age, whereas the BMD and BMC of the tibia increased from 15 to 55 wk of age, resulting in a bone-by-age interaction (P < 0.001). The BMC of the humerus did not change from 15 to 55 wk of age but increased at 65 wk of age. Age-related increases in BMD and BMC may be due to the inability of dual energy X-ray absorptiometry to distinguish medullary from structural bone. The CV for BMD and BMC of egg-type chickens was greater than 10% after 25 wk of age, which suggested that bone densitometry could be used as an indicator tool in genetic selection with a potential for improving skeletal integrity of birds.

The genetic component of osteoporosis in caged laying hens is large, and a method for detecting hens susceptible to fracture could be useful in breeding programs. A radiographic absorptiometry film method was modified by video digitization from an image intensifier and computer analysis and termed digitized fluoroscopy (DF). Humeral and ulnar DF values were measured in 165 hens during lay. Relationships (P < 0.001) were seen between DF assessments from 25 wk onward and postmortem measurements at 70 wk. We conclude that DF can detect poor bones in hens early but is problematic. Quantitative ultrasound was also investigated. We measured amplitude-dependent speed-of-sound (Ad-SoS) in the third toe in hens. Nutritional studies revealed Ad-SoS values correlated with postmortem peripheral quantitative computerized tomography, (control group, r = 0.48, P < 0.001; treatment group, r = 0.39, P < 0.001). In caged and free-range hens, Ad-SoS correlated with shear strength (r = 0.33, P < 0.001, all hens) and radiographic density values (r = 0.53, P < 0.001, all hens) measured postmortem. The Ad-SoS values were higher in free-range than in caged hens (1,904 vs. 1,850 m/s, P < 0.001). Ad-SoS measurements were made in hens from a study where divergent genetic selection has produced high and low bone index lines with 92% difference in tibia strength. The value in high bone index hens was higher than in low bone index hens at 32 (P < 0.001), 42 (P < 0.001), 52 (P < 0.05), and 62 wk (P < 0.001) in generation 8. In an Ad-SoS heritability study, heritability estimates ranged from 0.15 to 0.39. We conclude that Ad-SoS is a heritable trait, reflects other bone measurements, and rapidly detects poor bone quality in hens.

Transforming growth factor-beta (TGF-beta) belongs to a large family of multifunctional growth factors that regulate a broad spectrum of biological activities involved in morphogenesis, development, and differentiation. The current study was designed to investigate the effects of TGF-beta genes on chicken growth and body composition traits. The Iowa Growth and Composition Resource Population was established by crossing broiler sires with dams from two unrelated highly inbred lines (Leghorn and Fayoumi). The F1 birds were intercrossed, within dam line, to produce two related F2 populations. Body weight and body composition traits were measured in the F2 population. Primers for TGF-beta2, TGF-beta3, and TGF-beta4 were designed from database chicken sequence. Polymorphisms between parental lines were detected by DNA sequencing, and PCR-RFLP methods were then developed to screen the F2 population. The TGF-beta2 polymorphisms between broiler and Leghorn and the TGF-beta4 polymorphism between broiler and Fayoumi were associated with traits of skeletal integrity, such as tibia length, bone mineral content, bone mineral density, and the percentage of each measure to BW. The TGF-beta3 polymorphism between broilers and Leghorns was associated with traits of growth and body composition, such as BW, average daily gain, weight of breast muscle, abdominal fat pad and spleen, as well as the percentage of these organ weights to BW, and the percentage of shank weight and length to BW. The current research supports the broad effects of TGF-beta genes on growth and development of chickens.