Effect of 1,25-dihydroxycholecalciferol, cholecalciferol, and fluorescent lights on the development of tibial dyschondroplasia and rickets in broiler chickens

Effects of different dietary vitamin D combinations during the grower phase and the feed restriction phase on growth performance and sternal morphology, mineralization, and related genes expression of bone metabolism in Pekin ducks

Our study aimed to investigate the effects of different dietary vitamin D (VD) combinations during the grower (1-32 d of age) and feed restriction (33-52 d of age) phases on growth performance. We also evaluated sternal morphology, mineralization, and related genes expression of bone metabolism as well as absorption of calcium and phosphorous in duodenal mucosa and kidney in Pekin ducks. During the grower phase, we used 2 VD regimes (Group A: 3,160 IU/kg VD3; Group B: 400 IU/kg VD3 + 69 μg/kg 25-OH-D3). Each dietary treatment had 50 replicate pens of 10 ducks per pen. During the feed restriction phase, 30 replicate pens selected from Group A and Group B, repetitively, were redivided into 5 different dietary VD regimes to form a 2 × 5 experimental design. Each group consisted of 6 replicates, each with 10 ducks. During the feed restriction phase, we evaluated 5 different dietary VD combinations were as follows: T1: 2,000 IU/kg VD3 ; T2: 5,000 IU/kg VD3; T3: 3,620 IU/kg VD3 + 34.5 μg/kg 25-OH-D3; T4: 2,240 IU/kg VD3 + 69 μg/kg 25-OH-D3; T5: 1,800 IU/kg VD3 + 80 μg/kg 25-OH-D3). Results showed that Group B combinations with T5 had a better growth performance and breast meat deposition (P < 0.1). Regardless of 5 dietary VD regimes during the feed restriction phase, Group B significantly increased (P < 0.05) 52 d sternal depth and tended to increase (P < 0.1) 52 d sternal defatted weight, ash content, and phosphate (P) content of ducks. A significant interactive effect (P < 0.05) was observed on the mRNA abundance of DMP1 and Sost1 as well as RANKL/OPG in sternum and of VDR in duodenal mucosa of ducks at 52 d of age between dietary VD combinations during 2 phases. These results indicated that dietary VD regimes during the grower phase could affect the effectiveness of dietary VD regimes during the feed restriction phases; Dietary VD combinations of both phases could affect the genes expression of bone formation and the absorption as well as reabsorption of calcium and phosphorus in duodenum and kidney.

Leg disorders in broiler chickens: a review of current knowledge

Ensuring improved leg health is an important prerequisite for broilers to achieve optimal production performance and welfare status. Broiler leg disease is characterized by leg muscle weakness, leg bone deformation, joint cysts, arthritis, femoral head necrosis, and other symptoms that result in lameness or paralysis. These conditions significantly affect movement, feeding and broiler growth performance. Nowadays, the high incidence of leg abnormalities in broiler chickens has become an important issue that hampers the development of broiler farming. Therefore, it is imperative to prevent leg diseases and improve the health of broiler legs. This review mainly discusses the current prevalence of broiler leg diseases and describes the risk factors, diagnosis, and prevention of leg diseases to provide a scientific basis for addressing broiler leg health problems.

Application of Ultraviolet Light for Poultry Production: A Review of Impacts on Behavior, Physiology, and Production

The application of ultraviolet (UV) light in poultry production is garnering increased interest with the drive toward improved poultry welfare and optimized production. Poultry can see in the UV spectrum (UVA wavelengths: 320–400 nm) thus inclusion of these shorter wavelengths may be viewed as more natural but are typically excluded in conventional artificial lights. Furthermore, UVB wavelengths (280–315) have physiological impact through stimulation of vitamin D pathways that can then improve skeletal health. However, better understanding of the effects of UV supplementation must occur before implementation practically. This non-systematic literature review aimed to summarize the impacts of UV supplementation on the behavior, welfare, and production of laying hens, meat chickens (breeders and growers), and other domestic poultry species including directions for future research. The literature demonstrated that UVA light has positive impacts on reducing fear and stress responses but in some research, it significantly increases feather pecking over age during the production phase. UVB light will significantly improve skeletal health, but an optimum duration of exposure is necessary to get this benefit. Supplementation with UVB light may have more distinct impacts on egg production and eggshell quality when hens are experiencing a dietary vitamin D3 deficiency, or if they are at the terminal end of production. The relative benefits of UVB supplementation across different ages needs to be further verified along with commercial trials to confirm beneficial or detrimental impacts of adding UVA wavelengths. Further research is warranted to determine whether adding natural light wavelengths to indoor poultry production is indeed a positive step toward optimizing commercial housing systems.

Implications of Vitamin D Research in Chickens can Advance Human Nutrition and Perspectives for the Future

The risk of vitamin D insufficiency in humans is a global problem that requires improving ways to increase vitamin D intake. Supplements are a primary means for increasing vitamin D intake, but without a clear consensus on what constitutes vitamin D sufficiency, there is toxicity risk with taking supplements. Chickens have been used in many vitamin-D-related research studies, especially studies involving vitamin D supplementation. Our state-of-the-art review evaluates vitamin D metabolism and how the different hydroxylated forms are synthesized. We provide an overview of how vitamin D is absorbed, transported, excreted, and what tissues in the body store vitamin D metabolites. We also discuss a number of studies involving vitamin D supplementation with broilers and laying hens. Vitamin D deficiency and toxicity are also described and how they can be caused. The vitamin D receptor (VDR) is important for vitamin D metabolism; however, there is much more to understand about VDR in chickens. Potential research aims involving vitamin D and chickens should explore VDR mechanisms that could lead to newer insights into VDR. Utilizing chickens in future research to help elucidate vitamin D mechanisms has great potential to advance human nutrition. Finding ways to increase vitamin D intake will be necessary because the coronavirus disease 2019 (COVID-19) pandemic is leading to increased risk of vitamin D deficiency in many populations. Chickens can provide a dual purpose with addressing pandemic-caused vitamin D deficiency: 1) vitamin D supplementation gives chickens added-value with the possibility of leading to vitamin-D-enriched meat and egg products; and 2) using chickens in research provides data for translational research. We believe expanding vitamin-D-related research in chickens to include more nutritional aims in vitamin D status has great implications for developing better strategies to improve human health.

Investigation of different levels of cholecalciferol and its metabolite in calcium and phosphorus deficient diets on growth performance, tibia bone ash and development of tibial dyschondroplasia in broilers

This experiment was conducted to examine the effects of 1-α(OH)D3 alone or in combination with different levels of cholecalciferol on performance, and tibia parameters of one-d–old male broilers fed a tibial dyschondroplasia (TD)-inducing diet. A total of three hundred male broilers were randomly allocated to 5 treatment groups with 4 replicates. The dietary treatments consisted of TD inducing diet, TD inducing diet supplemented with 5 μg per kg of 1-α(OH)D3; TD inducing diet supplemented with 5 μg per kg of 1-α(OH)D3 and 1,500; 3,000 or 5,000 IU cholecalciferol kg-1 of diet. At 42 d of age, broiler chickens fed diets containing 1-α(OH)D3 and 1,500 IU cholecalciferol kg-1 of diet had higher body weight (p < 0.05). In the complete experimental period the best FCR and the highest daily weight gain were obtained in broilers supplemented with 1-α(OH)D3 and 1,500 IU cholecalciferol kg-1 of diet. Broilers supplemented with 1-α(OH)D3 and 1,500 IU cholecalciferol kg-1 of diet had significantly lower incidence and severity of TD in comparison with other groups. In conclusion, the results indicated that the supplementation of 1-α(OH)D3 in combination of 1,500 IU cholecalciferol kg-1 of diet could maximize tibia bone ash, performance and prevent TD in broilers fed TD inducing diet.

Vitamin D3 enhanced intestinal phosphate cotransporter genes in young and growing broilers

The influence of dietary vitamin D₃ (VD3) levels on growth, bone performance, and duodenal type IIb sodium-dependent phosphate cotransporter (NaPi-IIb) genes in broiler chicken were studied. One-day-old male Ross308 broilers (n = 432) were allocated into 6 treatment groups with each group consisting of 6 cage pens. Each treatment group received diet containing different amounts of VD3 (80, 200, 500, 1,250, 3,125, or 7,813 IU per kg of diet) from a day-old to 31 D of age. Dietary available phosphorus and calcium were kept the same across all treatments in each phase. At 14 D, influence of VD3 on BW gain was found in the birds that received VD3 of 3,125 IU/kg and 200 IU/kg (P < 0.05). Toe ash and tibia ash linearly increased (P < 0.05) at 14 D with increase in dietary VD3_. There was no significant influence of dietary VD3 on tibia breaking strength. In both phases, relative expression of duodenal NaPi-IIb linearly increased (P < 0.01) with increase in dietary VD3. At 14 D, highest expression of 3.2 folds was observed in birds treated with VD3 at 7,813 IU/kg of feed. At 31 D, birds that received VD3 levels of 3,125 and 7,813 IU/kg of feed showed 2.9 folds higher in NaPi-IIb expression compared with those fed lowest level of VD3 at 80 IU/kg of feed. When dietary calcium and phosphorus were maintained at the standard requirement, increase in dietary VD3 did not improve growth performance. For optimum growth and bone characteristics, dietary inclusion of VD3 at 500 IU/kg was adequate for both starter and grower broiler diets. Vitamin D₃ enhanced the expression of NaPi-IIb at higher doses and thus improving the tibia ash content in high VD3 treatment groups. This study reported for the first time an increased in the expression of duodenal NaPi-IIb in 31-day-old broilers in response to high dietary VD3 levels.

Evaluation of one-alpha-hydroxy-cholecalciferol alone or in combination with cholecalciferol in Ca-P deficiency diets on development of tibial dyschondroplasia in broiler chickens

This experiment was conducted to determine whether dietary cholecalciferol will alleviate a calcium and phosphorous (Ca—P) deficiency when one-alpha-hydroxy-cholecalciferol, 1α(OH)D₃, is supplemented, and to determine the effects of adequate and inadequate Ca—P when 1α(OH)D₃ is supplemented and vitamin D₃ is adequate. A total of 144 one-d-old broiler chicks (Ross 308) were allocated to 3 treatments. The dietary treatments were as follows: treatment A, adequate Ca—P + cholecalciferol + 5 μg/kg 1α(OH)D₃; treatment B, inadequate Ca—P + cholecalciferol + 5 μg/kg 1α(OH)D₃; treatment C, inadequate Ca—P + 5 μg/kg 1α(OH)D₃. All diets were mixed with 500 FTU/kg of phytase, and cholecalciferol was provided in 5,000 IU/kg except for treatment C that fed diets without vitamin D_3. The Ca—P levels in the adequate diets were 0.90% Ca, 0.66% total phosphorus (tP); 0.75% Ca, 0.59% tP; 0.69% Ca, 0.54% tP for the starter, grower and finisher periods. At d 42 of age, broilers were inspected for incidence and severity of tibial dyschondroplasia (TD). The results showed that inadequate Ca—P supplementation with cholecalciferol significantly decreased the incidence of TD, score and tibia ash compared with broilers fed the same diet in the absence of cholecalciferol (P < 0.05). The broilers fed inadequate Ca—P diets with cholecalciferol were unable to achieve the same tibia ash and incidence of TD as those fed Ca—P adequate diets (P < 0.05). In conclusion, this trial suggests that broilers fed an inadequate Ca—P diet with 1α(OH)D₃ and adequate level of cholecalciferol are unable to sufficient bone formation. There was no indication that 1α(OH)D₃ in the absence of cholecalciferol was effective in reducing TD whereas it could improve tibia ash.

THE EFFECT OF UVB RADIATION ON SERUM VITAMIN D AND IONIZED CALCIUM IN THE AFRICAN SPOONBILL (PLATALEA ALBA)

Metabolic bone disease (MBD) was diagnosed in two chicks produced by a captive breeding colony of African spoonbills (Platalea alba). The birds were housed indoor during the winter breeding season and had no access to natural sunlight. When the index cases occurred, the nesting birds and chicks had a mean 25-hydroxyvitamin D (25-OHD) concentration of 9.9 ± 2.7 nmol/L and a mean ionized calcium (iCa) concentration of 0.98 ± 0.12 mmol/L (winter pretreatment). For comparison purposes, serum was collected the following summer; mean 25-OHD was 20.8 ± 3.9 nmol/L and mean iCa was 1.32 ± 0.05 mmol/L (summer). During the following breeding season, ultraviolet B (UVB) lighting was provided to the flock, resulting in a mean 25-OHD of 19.0 ± 5.6 nmol/L and mean iCa of 1.23 ± 0.06 mmol/L (winter treatment 1). Both 25-OHD and iCa were significantly higher compared with winter pretreatment, and 25-OHD was not significantly different from summer, indicating that treatment during the winter months succeeded in increasing 25-OHD levels to summer levels. However, winter treatment 1 and summer iCa were significantly different. During the next breeding season (winter treatment 2), the birds were exposed to a light with higher UVB output. The mean 25-OHD of the flock was 16.5 ± 7.2 nmol/L, and the mean iCa increased to 1.34 ± 0.04 mmol/L. Both were comparable to summer values. Healthy chicks were hatched during both breeding seasons, and no further cases of MBD occurred during the course of the study. Provision of a UVB light source to captive African spoonbills maintained indoors during the winter months can increase 25-OHD and iCa to levels equivalent to those seen in the summer months, when birds have unrestricted access to natural sunlight. UVB lighting is recommended for all breeding spoonbills that do not have access to natural sunlight.

Medical Management of Hypovitaminosis D With Cholecalciferol and Elastic Therapeutic Taping in Red-legged Seriema (Cariama cristata) Chicks

Three hand-reared, 50-53 day-old, red-legged seriema (Cariama cristata) chicks were evaluated for acute lameness and reluctance to ambulate. Two of the 3 chicks presented with angular limb deformities of the proximal tarsometatarsi and external rotation of the legs. Radiographs demonstrated decreased opacity of the long bone of the legs, with poorly delineated cortices and deviation of the proximal tarsometarsi. Serum concentrations of 25-hydroxycholecalciferol revealed all 3 chicks were deficient in vitamin D(3) at presentation. The chicks were administered injectable vitamin D(3) (cholecalciferol), oral vitamin D(3), and an ultraviolet B (UV-B) light was placed in their enclosure. Elastic, therapeutic taping was used to correct angular limb deformities present in 2 of the 3 chicks. Taping was continued until the angular limb deformities were corrected and lameness resolved. Hypovitaminosis D is a common cause of metabolic bone disease in captive avian species. Cholecalciferol administration, UV-B light supplementation, and elastic, therapeutic taping were effective treatments for osteodystrophy and secondary angular limb deformities due to hypovitaminosis D. This multifaceted treatment may be useful in other long-legged juvenile birds with similar clinical signs.

Super pharmacological levels of calcitriol (1,25-(OH)2D3) inhibits mineral deposition and decreases cell proliferation in a strain dependent manner in chicken mesenchymal stem cells undergoing osteogenic differentiation in vitro

The biologically active form of vitamin D₃, calcitriol (1,25-(OH)₂D₃), plays a key role in mineral homeostasis and bone formation and dietary vitamin D₃ deficiency is a major cause of bone disorders in poultry. Supplementary dietary cholecalciferol (25-hydroxyvitamin D, 25-OH), the precursor of calcitriol, is commonly employed to combat this problem; however, dosage must be carefully determined as excess dietary vitamin D can cause toxicity resulting in a decrease in bone calcification, hypercalcinemia and renal failure. Despite much research on the therapeutic administration of dietary vitamin D in humans, the relative sensitivity of avian species to exogenous vitamin D has not been well defined. In order to determine the effects of exogenous 1,25-(OH)₂D₃ during avian osteogenesis, chicken bone marrow-derived mesenchymal stem cells (BM-MSCs) were exposed to varying doses of 1,25-(OH)₂D₃ during in vitro osteogenic differentiation and examined for markers of early proliferation and osteogenic induction. Similar to humans and other mammals, poultry BM-MSCs were found to be highly sensitive to exogenous 1,25-(OH)₂D₃ with super pharmacological levels exerting significant inhibition of mineralization and loss of cell proliferation in vitro. Strain related differences were apparent, with BM-MCSs derived from layers strains showing a higher level of sensitivity to 1,25-(OH)₂D₃ than those from broilers. These data suggest that understanding species and strain specific sensitivities to 1,25-(OH)₂D₃ is important for optimizing bone health in the poultry industry and that use of avian BM-MSCs are a useful tool for examining underlying effects of genetic variation in poultry.

Increasing dietary vitamin D3 improves the walking ability and welfare status of broiler chickens reared at high stocking densities

A study was conducted to evaluate the effects of varying dietary vitamin D3 and stocking density on growing performance, carcass characteristics, bone biomechanical properties, and welfare responses in Ross (308) broilers. Experimental diets, containing 1, 10, or 20 times the NRC recommended level of vitamin D3 (200 IU/kg), were formulated with low, medium, or high vitamin D3 levels for 3 growing phases. Two stocking densities were 10 and 16 birds/m(2). One-day-old hatchlings (1,872 males) were randomly assigned to 6 pens in each treatment. Results showed that high stocking density decreased the feed intake, BW gain (P < 0.01), breast muscle yield (P = 0.010), and tibial development (P < 0.01), whereas increasing feed conversion ratio (P < 0.001), and the scores of gait, footpad and hock burn, and abdominal plumage damage (P < 0.01), particularly toward the age when birds attained their market size. Increasing dietary vitamin D3 improved the birds' walking ability and tibial quality (P < 0.05), and reduced the development of footpad or hock dermatitis and abdominal plumage damage (P < 0.01), some aspects of which were age-dependent and appeared to vary with stocking density. These data indicate that increasing supplemental vitamin D3 has a favorable effect on walking ability and welfare status of high stocking density birds, but not on performance.

Performance and bone mineralisation in broiler chicks fed on diets with different concentrations of cholecalciferol at a constant ratio of calcium to non-phytate phosphorus

1. An experiment was conducted with broiler female chicks (720) to study the effects of graded concentrations (75, 15, 225 or 30 microg/kg) of cholecalciferol (CC) in diets containing varying levels of calcium (Ca) and non-phytate phosphorus (NPP) at a 2:1 ratio (4:2, 5:25, 6:3 or 7:35 g/kg, respectively), on the performance (2-35 d of age), bone mineralisation and mineral (Ca, P, Mn, Fe, Cu) concentration in excreta. 2. Body weight gain, food intake, tibia density and tibia ash increased, and leg abnormality score decreased with dietary increase of CC from 75 to 30 microg at 4 g Ca and 2 g NPP. However, this improvement was not comparable with the birds receiving the highest concentrations of CC, Ca and NPP (30 microg, 7 g and 3.5 g, respectively/kg diet). 3. Significant improvements in the majority of parameters noted with increasing CC up to 225 microg at 5 g Ca and 25 g NPP/kg, which was comparable to those fed the highest levels of CC, Ca and NPP. 4. Concentrations of Ca, P, Mn, Fe and Cu in excreta decreased significantly with increasing CC at all Ca:NPP ratios tested. 5. The predicted requirement of CC for most of the parameters ranged between 1625 and 25 microg/kg diet at 5 g Ca and 25 g NPP. 6. Considering the performance, bone mineralisation, and mineral concentration in excreta, it can be concluded that Ca and NPP levels in broiler diet could be reduced to 5 and 25 g, respectively, while maintaining CC at 25 microg/kg.

Effects of 25-hydroxycholecalciferol and soy isoflavones supplementation on bone mineralisation of quail

1. The effects of 25-hydroxycholecalciferol (25-OH-D(3)) and soy isoflavones supplementation on performance, carcase recovery, bone mineral density, and tibia ash, Ca, P, and serum vitamin D concentrations and alkaline phosphatase activity in the Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature were evaluated. 2. A total of 270 ten-d-old Japanese quail were randomly assigned to 9 treatment groups, 6 replicates of 5 birds each in a 2 x 3 x 3 factorial arrangement of treatments. Birds were kept in a temperature-controlled room at either 22 degrees C (thermo-neutral) or 34 degrees C (heat stress) for 8 h/d (09:00-17:00 h) and given a basal (control) diet or the basal diet supplemented with one of three levels of 25-OH-D(3) (0, 250 and 500 IU/kg of diet) combined with one of three levels of soy isoflavones (0, 400 and 800 mg/kg of diet). 3. Birds kept at 34 degrees C consumed less feed and gained less weight than control birds. An increase in body weight, feed intake (and improvement in feed efficiency and carcase recovery were found in soy isoflavones and 25-OH-D(3)-supplemented quail reared under heat stress conditions. Bone mineral density, tibia ash, Ca, and P were linearly improved by 25-OH-D(3) and soy isoflavones supplementation in both thermoneutral and heat stress groups. Serum vitamin D levels and alkaline phosphatase activity were improved by 25-OH-D(3) and soy isoflavones supplementation in both thermoneutral and heat stress groups in quail. 4. In conclusion, a combination of 25-OH-D(3) and soy isoflavones supplementation to basal diet significantly improved bone mineralisation in quail.

Effect of diet with thiram on liver antioxidant capacity and tibial dyschondroplasia in broilers

1. An experiment was conducted to study the effect of thiram on liver antioxidant capacity and incidence of tibial dyschondroplasia in broilers. 2. One hundred and twenty Avian commercial broilers were allotted at random to three treatments: control group, low thiram group (50 mg/kg) and high thiram group (100 mg/kg). 3. Blood samples were collected to determine the activity of AST (aspartate aminotransferase). At the end of the trial, broilers were killed and liver samples were collected to determine the activity of SOD (superoxide dismutase), GSH-Px (glutathione peroxidase) and MDA (malondialdehyde) content, while the right proximal tibiotarsi were dissected in longitudinal section for assessment of tibial dyschondroplasia (TD) incidence and TD score. 4. The results showed that thiram increased the incidence of TD and TD scores, increased serum AST activity and MDA content of liver, and decreased the activity of SOD and GSH-Px in the liver. 5. They suggest that thiram causes TD in broilers by reducing liver antioxidation capability and damaging liver function; this may be one of the mechanisms by which thiram causes TD in broilers.

Effect of temperature during the incubation period on tibial growth plate chondrocyte differentiation and the incidence of tibial dyschondroplasia

Tibial dyschondroplasia (TD) is one of the most prevalent skeletal abnormalities in avian species, causing enormous economic losses and major animal welfare problems. Irregular cell differentiation of the chondrocytes that populate the growth plate has been hypothesized to be involved in the etiology of the disease. We evaluated the effect of incubation temperature at various stages of embryo development and bone formation on growth plate chondrocyte differentiation and the incidence of TD. Eggs were incubated either at a control temperature of 37.8 degrees C, or at 36.9 or 39 degrees C, each for 6 h/ d, during early (0 to 8 d) or late (10 to 18 d) embryo development. At 14 d of incubation and at hatch, tibias were collected and weighed, and their ash and calcium contents were determined. Growth plate chondrocyte differentiation was evaluated by alkaline phosphatase activity and collagen type II and osteopontin gene expression. In addition, the level of the heat-shock protein 90 (Hsp90) was evaluated by immunohistochemistry. The rest of the chicks were raised to 49 d and the incidence of TD was recorded. The incidence of TD increased only when the temperature was altered at the early stages of embryo development, and it was correlated with an increase in tibia ash but not with tibia weight or calcium content. Moreover, increased TD incidence was correlated with delayed chondrocyte differentiation. Early changes in incubation temperature caused an increase in the level of Hsp90 in articular and differentiated chondrocytes of the hypertrophic zone and in the numbers of distinct undifferentiated chondrocytes arranged in columns in the proliferative zone of the growth plate. In summary, the early stages of embryo development and bone formation are of utmost importantance for appropriate growth plate chondrocyte differentiation, and any temperature deviation will increase the subsequent incidence of TD. The increase in TD incidence is probably the result of delayed Hsp90-driven chondrocyte differentiation, supporting the hypothesis that TD is the result of abnormal chondrocyte differentiation.

The Vitamin D3 Requirement of Broiler Breeders

An experiment was conducted with 25- to 66-wk-old Ross broiler breeders in an environment excluding ultraviolet light to determine the cholecalciferol (D3) requirements for hen day egg production; hatchability; body weight of the progeny at 1 d; embryo mortality during the early (1 to 10 d of incubation), middle (11 to 15 d of incubation), and late stages (16 to 21 d of incubation) of development; egg weight; specific gravity; and body ash of the progeny at 1 d of age. Five levels of vitamin D3 (125, 250, 500, 1,000, and 2,000 IU/kg of diet) were fed to hens from 25 to 66 wk of age. One additional group was fed no supplemental D3 until 36 wk of age and was then changed to 4,000 IU/kg of diet. Separate regression analyses were performed for wk 27 to 36 (peak original design) and for wk 37 to 66 (postpeak production modified design). The D3 levels for the predicted maximum hen day egg production during peak and postpeak were 1,424 and 2,804 IU/kg, respectively. The D3 levels for the predicted maximum hatchability were 1,390 IU/ kg (peak) and 2,708 IU/kg (postpeak). The level of D3 that resulted in the minimum early embryo mortality was 1,288 IU/kg at peak; however, no significant effect was observed at postpeak. The D3 levels for minimum middle stage embryo mortality were 1,130 IU/kg (peak) and 2,568 IU/kg (postpeak) and for late stage embryo mortality were 1,393 IU/kg (peak) and 2,756 IU/kg (postpeak). The D3 level for maximum egg weight was 1,182 IU/kg (peak) and for specific gravity was 1,337 IU/kg (peak) and >2,000 IU/kg (postpeak). The D3 level for maximum body ash of progeny at d 1 was >2,000 IU/kg. Analysis of the data from the original design of the experiment (treatments providing 0, 125, 250, 500, 1,000, and 2,000 IU of vitamin D3/kg for the 27- to 36-wk-old birds) indicates a requirement of approximately 1,400 IU of D3/kg of feed for broiler breeder hens. When the data from the modified experiment (37 to 66 wk of age) include conversion of the treatment provided at 0 IU of D3/kg to a treatment providing 4,000 IU of D3/kg, the requirement may be approximately 2,800 IU of D3/kg.

The Effect of Maternal Dietary Vitamin D3 Supplementation on Performance and Tibial Dyschondroplasia of Broiler Chicks

A series of experiments was conducted to investigate the effects of maternal dietary vitamin D3 supplementation at 4 different times during the laying cycle, on the performance and bone quality of broiler chicks fed a diet that induced tibial dyschondroplasia (TD) or an adequate diet. Ross x Ross broiler breeder hens were fed a corn-soy diet with various levels of vitamin D3 from 24 to 66 wk of age. Eggs were collected at 39, 44, 53, and 64 wk of age and hatched. Chicks from hens fed 250 IU of D3/kg (low maternal D3 or LMD3) and 2,000 IU of D3/ kg (high maternal D3 or HMD3) levels were placed in battery brooders and fed the diets from 0 to 16 d. At 16 d, the chicks were weighed and killed; the left tibias were used for bone ash determinations, and the right tibias were used to score the incidence and severity of TD (0, 1, 2, or 3, where 3 is the most severe). Body weight gain and feed intake were significantly lower for the LMD3 chicks at wk 44 and 64, although there was no difference in weight at hatch. For the first 2 hatches (wk 39 and 44), the LMD3 and HMD3 chicks demonstrated high average TD scores (2.03 and 1.57 vs. 2.05 and 1.75 for the LMD3 vs. HMD3 chicks, respectively) and high average incidences of severe TD (50 and 35% vs. 45 and 34% for LMD3 vs. HMD3 levels, respectively). However, results from the last 2 hatches (wk 53 and 64) showed that HMD3 chicks, compared with LMD3 chicks, had reduced average TD scores (1.39 and 1.47 vs. 1.01 and 0.44 for LMD3 vs. HMD3 levels, respectively) and severe TD incidence (36 and 40% vs. 17 and 8% for the LMD3 vs. HMD3 levels, respectively). In this experiment, as egg production declined toward the end of the laying cycle, hens fed the HMD3 might have been able to deposit sufficient quantities of vitamin D3 in the egg to maintain excellent body weight gain at 16 d of age and reduce the incidence and severity of TD. Hens fed the LMD3 diet were unable to produce similar improvements.

Effect of the level of cholecalciferol supplementation of broiler breeder hen diets on the performance and bone abnormalities of the progeny fed diets containing various levels of calcium or 25-hydroxycholecalciferol

Four experiments were conducted using Ross x Ross chicks hatched from broiler breeder hens fed various levels of cholecalciferol (vitamin D3; 0 to 4,000 IU/kg of diet) to determine the effect of the maternal diet on the performance and leg abnormalities of the progeny. Chicks hatched from eggs laid by the hens at different ages were used in experiments 1 to 4. The studies were conducted in an ultraviolet light-free environment as split plot designs, with Ca levels or 25-hydroxycholecalciferol (25-OHD3) in the chicks' diet as the whole plot, and vitamin D3 in the maternal diet as a subplot. Chicks in experiments 1 and 2 were fed 2 levels of Ca (0.63% or 0.90%) and chicks in experiments 3 and 4 were fed 6 levels of 25-OHD3 (0 to 40 microg/kg of diet). Significant increases in body weight gain (BWG) of the progeny were observed in experiments 1, 2, and 4 as the vitamin D3 level in the maternal diet increased. Chicks hatched from eggs laid by hens fed the highest levels of D3 had the highest tibia ash. Significant reductions in Ca rickets incidence (experiments 1 and 2) and tibial dyschondroplasia (TD) incidence (experiment 1) were observed as the level of vitamin D3 in the maternal diet increased. Chicks fed lower levels of Ca had lower BWG and tibia ash and higher incidences of TD and Ca rickets than chicks fed higher levels of Ca. Increasing the level of 25-OHD3 in the chicks' diet significantly improved BWG, tibia ash, and plasma Ca and reduced TD and Ca rickets incidence. An overall evaluation of the study indicates that chicks from hens fed the highest levels of vitamin D3 and fed high levels of Ca or 25-OHD3 had the highest BWG, tibia ash, and plasma Ca, and the lowest incidences of TD and Ca rickets.

Twenty-five hydroxycholecalciferol as a cholecalciferol substitute in broiler breeder hen diets and its effect on the performance and general health of the progeny

An experiment was conducted with broiler breeder hens to determine the relative biological value of 25-hydroxycholecalciferol (25-OHD3) compared with cholecalciferol (vitamin D3) for hen-day egg production, hatchability, embryo mortality (early, 1 to 10 d of incubation, late, 11 to 21 d), and body ash of the progeny. The study was conducted with 73-to-90-wk-old molted Ross broiler breeder hens in an environment excluding ultraviolet light. A basal vitamin D3 deficient diet supplemented with 4 levels of vitamin D3 (0, 3,125, 12,500, and 50,000 ng/kg of diet) and 2 levels of 25-OHD3 (3,125 and 12,500 ng/kg of diet) was fed. The relative biological values of 25-OHD3 in comparison to vitamin D3, using slope ratio techniques, were 138, 133, 128, and 111% for hen-day egg production, hatchability, late embryo mortality, and body ash of the progeny,, respectively (average = 128%). When comparing 25-OHD3 against D3 at the 3,125 ng/kg level, the relative biological values were 209, 167, 400, and 108% for the same criteria, respectively (average = 221%). However, at the 12,500 ng/kg level no statistical differences between 25-OHD3 and D3 were observed (average = 108%). Four trials were conducted to determine the effect of the maternal diet on the performance and leg abnormalities of the hens' progeny. In experiment 1, no vitamin D was added to the corn-soybean meal basal diet fed to the chicks, and in experiments 2, 3, and 4 the basal diet was supplemented with 27.5 microg of D3/kg of diet. In the progeny study, the average relative biological value of 25-OHD3 at the 3,125 and 12,500 ng/kg levels were 115 and 101%, respectively. The potency of 25-OHD3 in relation to vitamin D3 depended on the level tested. When comparing vitamin D sources, 25-OHD3 had greater potency than D3 only at very low levels of supplementation.

Effects of vitamin D3 dietary supplementation of broiler breeder hens on the performance and bone abnormalities of the progeny

Six experiments were conducted using Ross x Ross chicks hatched from eggs laid by broiler breeder hens fed various levels of vitamin D3 (0 to 4,000 IU/kg of diet) to determine the effects of vitamin D3 level in the maternal diet on the performance and leg abnormalities of their progeny. Chicks hatched from eggs laid when hens were 27, 41, 29, 36, 45, and 52 wk of age were used in experiments 1, 2, 3, 4, 5, and 6, respectively. The studies were conducted in a ultraviolet (UV)-light-free environment. Experiments 1 and 2 were conducted as complete randomized designs with the maternal diets as the treatments, and experiments 3, 4, 5, and 6 were conducted as split plot designs, with vitamin D3 in the chick diets as the whole plot and vitamin D3 in the maternal diet as a subplot. Chicks in experiments 1 and 2 were fed a vitamin D3-deficient diet, whereas chicks in experiments 3 and 4 were fed 4 levels of vitamin D3 (0 to 400 IU/kg of diet), and chicks in experiments 5 and 6 were fed 6 levels of vitamin D3 (0 to 3,200 IU/kg of D3). The highest body weight gains and tibia ash were observed in chicks hatched from hens fed the highest levels of vitamin D3 in all experiments. Reductions in the incidence of Ca rickets were observed in experiments 3 and 6, whereas increases in tibia ash were observed in experiments 2 and 6 as the level of vitamin D3 in the maternal diet increased. Body weight gain and tibia ash increased and Ca rickets incidence decreased as the vitamin D3 level in chick diets increased. An evaluation of the study indicates that chicks hatched from eggs laid by hens fed 2,000 or 4,000 IU of D3/kg as the maximum level of vitamin D3 had the highest body weight gains, and chicks fed 3,200 IU had the highest body weight and tibia ash and the lowest TD and Ca rickets incidences.

Effectiveness of twenty-five-hydroxycholecalciferol in the prevention of tibial dyschondroplasia in Ross cockerels depends on dietary calcium level

Five experiments were conducted to evaluate the efficacy of 25-hydroxycholecalciferol [25-(OH)D3] to minimize the development of tibial dyschondroplasia (TD) and improve phytate phosphorus retention in Ross cockerels during the starter period. In experiment 1, chicks were fed a TD-inducing (0.67% calcium) diet with or without exposure to ultraviolet light and no supplemental cholecalciferol. Dietary 25-(OH)D3 was added at 0, 10, or 70 microg/kg for both light treatments. In experiment 2, 25-(OH)D3 was added at 0, 10, 40, or 70 microg/kg to a TD-inducing diet containing 27.5 microg/kg added cholecalciferol. Experiment 3 was similar to experiment 2 except a diet marginal (0.85%) in calcium was fed, and cholecalciferol was added at 55 microg/kg. In experiments 4 and 5, 25-(OH)D3 was added at 0, 18, 36, 54, 72, or 90 microg/kg to a diet marginal in calcium. Dietary 25-(OH)D3 decreased the incidence of TD similarly at 40 and 70 microg/kg 25-(OH)D3 and improved phytate phosphorus retention when the TD-inducing diet was fed. The incidence of TD was decreased when 70 microg/kg 25-(OH)D3 was added to a diet marginal in calcium in experiment 3 only. Phytate phosphorus retention was generally not affected by dietary 25-(OH)D3 when a diet containing marginal calcium, adequate phosphorus, and high cholecalciferol was fed. The effectiveness of 25-(OH)D3 to reduce the incidence of TD in young broilers was higher when the dietary calcium level was below 0.85%. The incidence of TD in Ross cockerels was low (< 25%) when dietary calcium was greater than 0.85%.

The expression of calbindin in chicks that are divergently selected for low or high incidence of tibial dyschondroplasia

Three experiments were conducted with broiler chicks that were divergently selected for low or high incidence of tibial dyschondroplasia (LTD and HTD, respectively) to determine if the expression of intestinal calbindin-28 kD mRNA and protein differed between the 2 strains. In addition, levels of intestinal vitamin D receptor mRNA and plasma thyroid hormone concentrations were also examined. In experiment 1, LTD and HTD chicks were fed a corn-soybean meal diet that was adequate in all nutrients except cholecalciferol (D3), which was titrated to 5 or 40 microg/kg diet in a completely randomized 2 x 2 factorial arrangement. At 4 and 8 d of age, HTD chicks fed 5 microg of D3/kg of diet had a lower (P < 0.05) expression level of calbindin-28 kD mRNA than the LTD chicks fed the same diet. At 4 and 8 d of age, HTD chicks fed 5 microg of D3 had the lowest intestinal expression of calbindin-28 kD protein. Expression of vitamin D receptor mRNA did not differ for broiler strains at either level of D3 supplementation. In experiment 2, there was no significant difference in the expression of calbindin-28 kD mRNA or vitamin D receptor mRNA between day-of-hatch LTD, HTD, and commercial broiler chicks. Experiment 3 was similar in design to the first experiment except that the birds were fed for 18 d. Calbindin-28 kD and vitamin D receptor mRNA expression levels at 18 d were similar to those observed in experiment 1. Plasma triiodothyronine and free-triiodothyronine concentrations were greater for LTD chicks, regardless of dietary D3 supplementation levels. These results suggest that divergent selection of broilers for LTD or HTD alters the physiological response to nutritionally inadequate levels of dietary D3.

Effects of u.v. irradiation of very young chickens on growth and bone development

Six experiments were conducted to study the effects of exposure of young chickens to u.v. radiation. Chickens were fed a cholecalciferol (D3)-deficient diet and exposed to u.v. radiation from fluorescent lights giving total radiance (285-365 nm) at 0.15 m of 99.9 mJ/s per m(2). In Expt 1, chickens had increased body weight, bone ash and plasma Ca and decreased incidence of rickets and tibial dyschondroplasia (TD) when exposed to fluorescent light radiation 24 h per d, 24 h every 2 d, or 24 h every 3 d starting with exposure on day 1 after hatching. However, when not exposed on day 1, but on days 4, 7, 10, 13 and 16, the bone ash was reduced, and the incidence of TD and rickets was increased, compared with chickens exposed on day 1 after hatching. When chickens were exposed at 1 d of age to radiation from two lamps, each of which gave a radiance (285-365 nm) at 0.26 m of 856 mJ/s per m(2), both the length of time of radiation and location of the lamps (above or below the chicken) influenced the response as measured by body weight, bone ash, plasma Ca and incidence of rickets. When chickens that received a TD-inducing diet were exposed to 30 min u.v. radiation from below at 1 d of age they developed significantly less TD than did those not exposed when fed either 27.5 or 55.0 microg D3/kg diet.

Graded levels of phytase past industry standards improves broiler performance

This study evaluated the overall performance of 0-to-16-d-old, mixed-sex, Cobb x Cobb broiler chicks when dietary phytase levels were supplemented in excess of industry standards. The experimental diet used consisted of a basal corn-soybean meal diet that contained an analyzed 22.2% CP, 0.88% Ca, a deficient total P (tP) level of 0.46% (phytate P = 0.272%), and calculated ME of 3.123 kcal/g diet on an as-is basis. In addition to a positive control diet [0.70% tP], the dietary phytase levels evaluated were 0, 93.75, 187.5, 350, 750, 1,500, 3,000, 6,000, and 12,000 U/kg of diet. Supplementing phytase from 0 to 12,000 U significantly increased body weight gain from 287 to 515 g/chick, feed intake from 381 to 595 g/chick, gain to feed from 0.755 to 0.866, plasma P from 2.5 to 7.1 mg/100 mL, tibia ash from 26 to 41%, tibia ash weight from 0.200 to 0.601 g/tibia, tP retention from 51 to 80%, phytate P disappearance from 40% to 95%, apparent N retention from 58 to 78%, AMEn from 3,216 to 3,415 kcal/kg diet, and reduced P rickets from 80 to 3%. Using nonlinear regression analysis on log-transformed phytase levels, gain to feed, apparent N retention, and AME, responded linearly with respective R2 values of 0.76, 0.82, and 0.72, whereas body weight gain, feed intake, plasma P, P rickets, tP retention, phytate P disappearance, tibia ash percentage, and tibia ash weight responded quadratically with respective R2 values of 0.93, 0.88, 0.85, 0.84, 0.91, 0.96, 0.96, and 0.98. Few statistical differences existed between response data for broilers consuming the positive control diet or diets containing 1,500 to 12,000 U of phytase (P > 0.05). This finding indicates that broilers consuming a tP-deficient corn-soybean meal diet can achieve maximum performance when phytase is supplemented to 12,000 U/kg diet and that current phytase supplementation levels within the poultry industry may need to be reevaluated.

Effect of antibiotics on in vitro and in vivo avian cartilage degradation

Antibiotics are used in the livestock industry not only to treat disease but also to promote growth and increase feed efficiency in less than ideal sanitary conditions. However, certain antibiotic families utilized in the poultry industry have recently been found to adversely affect bone formation and cartilage metabolism in dogs, rats, and humans. Therefore, the first objective of this study was to determine if certain antibiotics used in the poultry industry would inhibit in vitro cartilage degradation. The second objective was to determine if the antibiotics found to inhibit in vitro cartilage degradation also induced tibial dyschondroplasia in growing broilers. Ten antibiotics were studied by an avian explant culture system that is designed to completely degrade tibiae over 16 days. Lincomycin, tylosin tartrate, gentamicin, erythromycin, and neomycin sulfate did not inhibit degradation at any concentration tested. Doxycycline (200 microg/ml), oxytetracycline (200 microg/ml), enrofloxacin (200 and 400 microg/ml), ceftiofur (400 microg/ml), and salinomycin (10 microg/ml) prevented complete cartilage degradation for up to 30 days in culture. Thus, some of the antibiotics did inhibit cartilage degradation in developing bone. Day-old chicks were then administered the five antibiotics at 25%, 100%, or 400% above their recommended dose levels and raised until 21 days of age. Thiram, a fungicide known to induce experimental tibial dyschondroplasia (TD), was given at 20 ppm. Birds were then killed by cervical dislocation, and each proximal tibiotarsus was visually examined for TD lesions. The results showed that none of these antibiotics significantly induced TD in growing boilers at any concentration tested, whereas birds given 20 ppm thiram had a 92% incidence rate.

Nutrition and skeletal problems in poultry

Several excellent reviews regarding nutrition and skeletal disorders have appeared in the last 20 yr. This review will cover several areas of vitamin D research, the area of feed deprivation, and bone abnormalities, because there has been considerable interest in these areas during the past 10 yr. Studies indicate that the quantitative requirement for cholecalciferol (D3) for broiler chickens is much greater than previously thought. Ascorbic acid may play a role in stimulating 1-hydroxylation of 25-hydroxycholecalciferol [25-(OH)D3], but the evidence is not clear under exactly what conditions this relationship is important in practical prevention of tibial dyschondroplasia. Studies indicate that dietary supplementation with 1,25-dihydroxycholecalciferol [1,25(OH)2D3] will reduce the incidence of tibial dyschondroplasia in three different strains of broilers bred to develop a high incidence of the disease. But it did not prevent the disease totally in the strains, unless high enough levels of 1,25-(OH)2D3 were fed to reduce growth rate. These studies indicate that these high tibial dyschondroplasia strains have a defect(s) in vitamin D metabolism. Studies continue to elucidate the role of ultraviolet light in preventing leg abnormalities. Only a few studies have been conducted on the efficacy of various vitamin D3 derivatives to prevent tibial dyschondroplasia. Feed deprivation continues to be an intriguing method of preventing tibial dyschondroplasia, and examination of exactly how this prevents the bone abnormality could open avenues for explaining the disease.

Vitamin D3 requirement of young chicks receiving diets varying in calcium and available phosphorus

1. Three battery experiments were conducted with broiler chicks during the 2nd and 3rd week of life. Graded amounts of cholecalciferol (D3) were added to maize-soyabean meal diets that were designed to be (a) severely deficient in available phosphorus (P), (b) marginally deficient in calcium (Ca) or (c) adequate in both available P and Ca. 2. With diets containing 1.0 g available P and 6.3 g Ca/kg (assay 1), graded doses of D3 between 0 and 37.5 mu/kg produced linear (P < 0.05) positive responses in both weight gain and tibia ash. With a D3 concentration of 1250 micrograms/kg, 250 times the requirement recommended by the NRC, bone ash was increased (P < 0.05) over that of birds fed 37.5 micrograms/kg, and neither weight gain nor food intake were reduced. 3. With a P-adequate diet (4.5 g available P/kg) containing 8.5 g Ca/kg (assay 2), weight gain and bone ash increased linearly (P < 0.05) upon supplementing the basal diet with 0, 2.5 and 5.0 micrograms D3/kg. Higher doses of D3 did not elicit further responses, and chicks fed on a diet containing 1250 micrograms D3/kg gained as fast and had bone ash values that did not differ from those of chicks receiving 5, 10, 20 or 40 micrograms D3/kg. 4. When the maize-soyabean meal basal diet was fortified with Ca and P to achieve adequate amounts of Ca (10.1 g/kg) and P (4.5 g available P/kg) in assay 3, dietary additions produced results similar to those obtained in assay 2 where P was adequate and Ca was slightly deficient. Again, chicks receiving a surfeit of D3 (1250 micrograms/kg) exhibited weight gains and bone ash values that were as great as those of chicks receiving 5, 10, 15 or 30 micrograms D3/kg. 5. It is apparent that young chicks have a high tolerance for excess D3, and chicks fed on diets that are severely deficient in available P continue to respond to D3 in excess of 37.5 micrograms/kg.