Incidence Of Tibial Dyschondroplasia Research Articles

PSVIII-1 Identifying factors associated with the incidence of tibial dyschondroplasia in poultry

Abstract Selecting on increased breast meat yield and body weight (BW) is thought to be associated with the increasing prevalence of leg disorders. A disorder of particular importance is tibial dyschondroplasia (TD), which is characterized as uncalcified cartilage in the proximal area of the tibiotarsal bone, leading to increased lameness, reduced feed and water intake, and subsequently poorer production efficiency and increased pre-slaughter mortality. Although it is hypothesized that TD is more prevalent in fast-growing poultry, this relationship can vary across studies making it challenging to distill the relationship between BW and TD, especially as studies of TD span several decades. Therefore, a systematic literature search and meta-analysis was conducted to identify factors influencing TD incidence. To date, the systematic literature search has resulted in 21 eligible papers, although data are still being extracted from the literature. Data extracted from each study included TD incidence (%), BW (kg), species (turkeys vs. broilers), sex (male vs. female), and age (weeks) of the animals. Preliminary univariable models have been developed based on the current database. Univariable generalized linear mixed models were developed in SAS (PROC GLIMMIX) including study as a random effect to evaluate the relationship between TD incidence and BW, species, sex, and age. Turkeys (27.3 ± 0.08%) had a greater TD incidence than broilers (19.3 ± 0.03%); however, this difference was not significant (P = 0.3481). There was a tendency for age to influence TD incidence (P = 0.0553) and a significant effect of BW (P < 0.0001). TD incidence also tended to differ between the sexes, with greater incidence in males (22.9 ± 0.07%) than females (11.3 ± 0.05%; P = 0.0657). After extracting all available data from the literature, further analysis will be conducted to consider multivariable models to predict TD. As such, caution should be used when generalizing these results due to the preliminary nature of the database. With the currently available data, the results of this study support the relationship between BW/size and TD. Furthermore, this study illustrates that TD is a prevalent challenge in both major poultry species. Reducing TD incidence could significantly improve animal welfare and mitigate economic losses associated with pre-slaughter mortality.

Transcriptome analysis reveals the pathogenesis of spontaneous tibial dyschondroplasia in broilers.

Tibial dyschondroplasia (TD) is a severe bone disease that affects fast-growing broiler chickens and causes economic loss. Despite previous studies, the regulatory mechanism of TD remains unclear and is thought to be primarily based on thiram induction, which may differ from that of naturally occurring diseases. To better understand TD, a digital X-ray machine was used in the present study to determine its incidence in four hundred yellow-feathered broiler chickens. The results showed that the incidence of TD was 22% after 6weeks and gradually decreased after 8 and 10weeks. The body weight of broilers with TD decreased significantly compared to that of NTD broilers. In addition, the length and density of the tibia were reduced after eight and 10weeks, and the density of the tibia was reduced after 6weeks compared with the NTD chickens. This study also examined tibial quality parameters from TD (n = 12) and NTD broilers (n = 12) and found that bone mineral content, bone mineral density, bone ash content, calcium content, and phosphorus content were significantly reduced in TD broilers. Transcriptome analysis revealed 849 differentially expressed genes (DEGs) in the growth plate between TD (n = 6) and NTD groups (n = 6). These genes were enriched in ECM-receptor interaction, cytokine-cytokine receptor interaction, calcium signaling pathway, and TGF-β signaling. Genes encoding the alpha chain of type XII collagen, that is, COL1A1, COL5A1, and COL8A1) were identified as critical in the regulatory network of TD. Gene set enrichment analysis (GSEA) revealed that the pathways of cartilage development, circulatory system development, and nervous system development were changed in the growth plates of TD birds. In the blood transcriptome, 12 DEGs were found in TD (n = 4) and NTD chickens (n = 4), and GSEA revealed that the pathways from TD broilers' blood related to the phagosome, linoleic acid metabolism, monoatomic ion homeostasis, and calcium ion transport were downregulated. This study provides a comprehensive understanding of TD, including its effects on tibial quality, tibial changes, and the circulatory system, along with identifying important genes that may lead to the development of TD.

152 Leveraging Rfid Technology to Investigate the Genetic Associations Between Feeding Behavior and Leg Health in Floor-Raised Broilers

Abstract Leg disorders (LD) pose serious welfare issues in broiler chickens. The objective of this study was to investigate the suitability of using feeding behavior (FB) traits as potential leg health indicators in floor-raised broilers. The data used were recorded from 95,711 pure-line chickens of both sexes. The individual FB was monitored continuously on a feeder visit basis with a radio-frequency antenna system. The visit-log data were clustered into daily observations for different FB traits and averaged for the 1st week period after the trial started. The FB traits were daily feed intake (DFI1), number of visits (NV1), time spent at the feeder (TSF1), visiting activity interval (VAI1), number of visited feeders (NVF1), and walked distance visiting feeders (WD1). The LD traits were tibial dyschondroplasia (TD), hock-burn (HB), footpad (FP), rotated legs (RO), bowed-in (BI), and bowed-out (BO) leg structure deformities. Multi-trait linear-threshold models were fitted using Bayesian inference for estimating (co)variance components. The heritability (h2) posterior averages and standard deviations (within parentheses) ranged between 0.09 (0.01) and 0.52 (0.03) for LD traits, and between 0.09 (0.01) and 0.47 (0.02) for FB traits. Genetic correlations (rg) between FB and LD traits ranged from null to weak. TD presented negative rg with NV1 (-0.13), TSF1 (-0.14), NVF1 (-0.11), and WD1 (-0.14), indicating that some alleles involved in broiler activity are favorably associated with a potential reduction in the risk of TD-caused bone lesions. Conversely, FP presented unfavorable rg with the same traits (ranging from 0.21 to 0.32), except for TSF1 (-0.08). When compared with the remaining FB traits, DFI1 generally presented the opposite relationships with TD and FP, with positive (0.16) and negative (-0.18) genetic correlations observed for the first and the latter, respectively. Angular and rotational deformities (RO, BI, and BO) did not present significant correlations with FB traits, apart from the weak correlation found between BO and TSF1 (0.11). General activity indicators such as NV1, NVF1, and WD1 could represent earlier selection criteria to reduce TD incidence, although the potential undesired selection response for FP must be further investigated.

Impact of litter on femur and tibial morphology, bone biomechanics, and leg health parameters in broiler chickens.

In this study effects of three types of beddings on broiler leg health and bone biomechanics were evaluated. A total of 504 male chicks (Ross 308) were randomly placed on three beddings (4 replicates/group; 42 birds/pen), zeolite-added litter (ZL), plastic-grid flooring (PF), and wood shavings (WS). On day 42, chickens were weighed, slaughtered, and samples (bone, muscle, and drumstick) were collected. Bones were subjected to leg health tests, morphometric measurements, biomechanical testing, and ash analysis. Broilers in PF and WS groups showed higher live weight than the ZL group (p<0.001), and the incidence of tibial dyschondroplasia (TD) and varus valgus deformity due to distal bending was significantly higher in PF (p<0.001). Multinomial logistic regression showed that bedding has a significant (p = 0.038) contribution toward the development of TD. Tibial strength (p = 0.040), drumstick width (p = 0.001), and total femur and epiphyseal ash contents (p = 0.044, 0.016) were higher in the ZL group. Chicken live weight was correlated with tibial length and weight (r = 0.762, 0.725). Flooring and the type of bedding material directly affect broiler bone length, strength and leg health. Plastic bedding improves the slaughter weight of chickens on the expense of leg deformities, and zeolite litter improves leg health and bone strength.

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 &lt; 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.

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English

The role of blood vessels in broiler chickens with tibial dyschondroplasia

Tibial dyschondroplasia (TD) is an intractable tibiotarsal bone disorder of rapid growing avian species, which leads to huge economic losses and compromised poultry welfare. However, the exact pathogenesis and treatment of TD remain largely unknown. Based on continuous research findings, we propose the TD pathogenesis hypothesis: during skeletal development of TD chickens, due to the absence of vasculature of proximal tibial growth plates (TGP), hypertrophic chondrocytes of the TGP are unable to complete calcification in normal bone development and less dead chondrocytes in the corresponding area can be timely transported through the blood vessels. Moreover, recent studies demonstrate that the TD formation mechanism gradually tends to a large number of dead chondrocytes in the TGP region or apoptosis occur due to various factors (such as, reduction of vascular invasion and blood cells, and increased weight or mechanical force of the tibia), while the reduction of blood vessels is insufficient to remove these chondrocytes and eventually leads to the TD formation. Recognizing the possible role of the blood vessels in the incidence of TD and can propose that the improvement in vasculature might be a novel therapeutic approach for ending TD in chickens.

Light-dark rhythms during incubation of broiler chicken embryos and their effects on embryonic and post hatch leg bone development.

There are indications that lighting schedules applied during incubation can affect leg health at hatching and during rearing. The current experiment studied effects of lighting schedule: continuous light (24L), 12 hours of light, followed by 12 hours of darkness (12L:12D), or continuous darkness (24D) throughout incubation of broiler chicken eggs on the development and strength of leg bones, and the role of selected hormones in bone development. In the tibiatarsus and femur, growth and ossification during incubation and size and microstructure at day (D)0, D21, and D35 post hatching were measured. Plasma melatonin, growth hormone, and IGF-I were determined perinatally. Incidence of tibial dyschondroplasia, a leg pathology resulting from poor ossification at the bone’s epiphyseal plates, was determined at slaughter on D35. 24L resulted in lower embryonic ossification at embryonic day (E)13 and E14, and lower femur length, and lower tibiatarsus weight, length, cortical area, second moment of area around the minor axis, and mean cortical thickness at hatching on D0 compared to 12L:12D especially. Results were long term, with lower femur weight and tibiatarsus length, cortical and medullary area of the tibiatarsus, and second moment of area around the minor axis, and a higher incidence of tibial dyschondroplasia for 24L. Growth hormone at D0 was higher for 24D than for 12L:12D, with 24L intermediate, but plasma melatonin and IGF-I did not differ between treatments, and the role of plasma melatonin, IGF-I, and growth hormone in this process was therefore not clear. To conclude, in the current experiment, 24L during incubation of chicken eggs had a detrimental effect on embryonic leg bone development and later life leg bone strength compared to 24D and 12L:12D, while the light-dark rhythm of 12L:12D may have a stimulating effect on leg health.

Effects of lighting, stocking density, and access to perches on leg health variables as welfare indicators in broiler chickens

An experiment was conducted to investigate the effects of lighting program, stocking density, and the provision of a perch on leg health variables as welfare indicators in broiler chickens. A total of 360 mixed sex Ross 308 1-D-old broiler chickens (180 male and 180 female) were placed in a completely randomized design with 2 × 2 × 2 factorial arrangement of lighting program (continuous or restricted), stocking density (12 or 18 birds/m2), and the provision of a perch (perch or without perch). At d 42, tibial dyschondroplasia (TD), valgus-varus deformity (VVD), footpad dermatitis (FPD), and hock burn (HB) were scored. In addition, tibio-tarsal index, robusticity index, bone weight-length index, tibia crude ash content, and fluctuating asymmetry (FA) and relative fluctuating asymmetry (rFA) of tibia width and length were measured. The incidence of TD increased in broiler chickens subjected to continuous lighting (P < 0.05) in comparison with those subjected to restricted lighting. Presence of a perch reduced the incidence and severity of FPD (P < 0.01) compared to without a perch. Restricted lighting tended (P = 0.093) to decrease the incidence and severity of HB lesions. The broiler chickens placed at low stocking density (12 birds/m2) and with access to a perch had lower incidence and severity of HB lesions (P < 0.01 and P < 0.001, respectively) compared to their corresponding opposite groups. Tibio-tarsal index was greater (P < 0.01) in broiler chickens subjected to restricted lighting regimen compared to continuous lighting whereas the provision of a perch tended to increase (P = 0.081) the tibio-tarsal index in broiler chickens compared to those without perch. There was a tendency of decreasing tibia crude ash content with increasing stocking density from 12 to 18 birds/m2 (P = 0.056). However, birds without perches had greater (P < 0.01) tibia crude ash content compared those with a perch provided. Continuous lighting increased the FA and rFA of tibia length in comparison with restricted lighting program (P < 0.05) in broiler chickens. In conclusion, it can be said that restricted lighting programs and provision of perches may help reduce the leg health problems thus contributing to improved welfare in broiler chickens.

Effect of graded calcium supplementation in low-nutrient density feed on tibia composition and bone turnover in meat ducks.

Both genetic selection and increasing nutrient density for improving growth performance had inadvertently increased leg problems of meat ducks, which adversely affects animal welfare. We hypothesised that slowing weight gain with improving tibia quality probably enhanced tibial mechanical properties and alleviated leg deformities. Therefore, the present study aimed to evaluate the effect of graded Ca supplementation in a low-nutrient density (LND) diet on tibia composition and bone turnover in meat ducks. A total of 720 15-d-old male meat ducks were randomly assigned and fed a standard nutrient density positive control (PC) diet containing 0·9 % Ca, and four LND diets with 0·5, 0·7, 0·9 and 1·1 % Ca, respectively. Ducks fed the 0·5 % Ca LND diet and the PC diet had higher incidence of tibial dyschondroplasia (TD). When compared with the 0·5 % Ca LND diet, LND diets with ≥0·7 % Ca significantly improved tibia composition, microarchitecture and mechanical properties, and consequently decreased the incidence of TD. Furthermore, LND diets with ≥0·7 % Ca increased osteocyte-specific gene mRNA expression, blocked the expression of osteoblast differentiation marker genes including osteocalcin, collagenase-1 and alkaline phosphatase (ALP), and also decreased the expression of osteoclast differentiation genes, such as vacuolar-type H+-ATPase, cathepsin K and receptor activator of NF-κB. Meanwhile bone markers such as serum ALP, osteocalcin (both osteoblast markers) and tartrate-resistant acid phosphatase (an osteoclast marker) were significantly decreased in at least 0·7 % Ca treated groups. These findings indicated that LND diets with ≥0·7 % Ca decreased bone turnover, which subsequently increased tibia quality for 35-d-old meat ducks.

Effects of Tetramethylpyrazine and Icariin on tibial dyschondroplasia incidence, tibial angiogenesis, performance and characteristics via regulating HIF-1α/VEGF/WNT4 signaling in chickens (Abstract)

Effects of Tetramethylpyrazine and Icariin on tibial dyschondroplasia incidence, tibial angiogenesis, performance and characteristics via regulating HIF-1α/VEGF/WNT4 signaling in chickens (Abstract)

Icariin Ameliorate Thiram-Induced Tibial Dyschondroplasia via Regulation of WNT4 and VEGF Expression in Broiler Chickens.

Tibial dyschondroplasia (TD) is main bone problem in fast growing poultry birds that effect proximal growth plate (GP) of tibia bone. TD is broadly defined as non-vascularized and non-mineralized, and enlarged GP with tibia bone deformation and lameness. Icariin (Epimedium sagittatum) is a traditional Chinese medicine, which is commonly practiced in the treatment of various bone diseases. Recently, many researcher reports about the beneficial effects of icariin in relation to various types of bone conditions but no report is available about promoting effect of icariin against TD. Therefore, current study was conducted to explore the ameliorating effect of icariin in thiram-induced TD chickens. A total of 180 broiler chicks were equally distributed in three groups; control, TD induced by thiram (50 mg/kg), and icariin group (treated with icariin @10 mg/kg). All groups were administered with normal standard diet ad libitum regularly until the end of experiment. The wingless-type member 4 (WNT4) and vascular endothelial growth factor (VEGF) genes and proteins expression were analyzed by quantitative real-time polymerase chain reaction and western blot analysis respectively. Tibial bone parameters, physiological changes in serum, antioxidant enzymes, and chicken growth performance were determined to assess advantage and protective effect of the medicine in broiler chicken. The expression of WNT4 was decreased while VEGF increased significantly (P < 0.05) in TD affected chicks. TD enhanced the GP, lameness, and irregular chondrocytes, while reduced the liver function, antioxidant enzymes in liver, and performance of chickens. Icariin treatment up-regulated WNT4 and down-regulated VEGF gene and protein expressions significantly (P < 0.05), restored the GP width, increased growth performance, corrected liver functions and antioxidant enzymes levels in liver, and mitigated the lameness in broiler chickens. In conclusion, icariin administration recovered GP size, normalized performance and prevented lameness significantly. Therefore, icariin treatments are encouraged to reduce the incidence of TD in broiler chickens.

Effect of tetramethylpyrazine on tibial dyschondroplasia incidence, tibial angiogenesis, performance and characteristics via HIF-1\u03b1/VEGF signaling pathway in chickens

Tibial dyschodroplasia (TD) is a most common pathological condition in many avian species that is characterized by failure of growth plate (GP) modeling that leads to the persistence of avascular lesion in the GP. Tetramethylpyrazine (TMP) is widely used to treat neurovascular disorders and pulmonary hypertension, but no report is available about promoting effect of TMP against TD. Therefore, a total of 210 broiler chicks were equally divided into three groups; Control, TD and TMP. During the experiment mortality rate, chicken performance indicators (daily weight, average daily feed intake, average daily weight gain and feed conversion ratio), tibia bone indicators (weight, length, width of tibial and the size of GP) in addition to gene expression of HIF-1α and VEGF were examined. The results showed that TMP administration restore the GP width, increase growth performance, and mitigated the lameness in broiler chickens. The expression of HIF-1α and VEGF increased significantly in TD affected thiram induced chicks. Whereas, TMP treatment down-regulated HIF-1α and VEGF genes and proteins expressions. The present study demonstrates that the TMP plays an important role in angiogenesis during the impairment and recovery of GP in TD via regulation of the HIF-1α/VEGF signaling pathway in chickens.

Effect of Icariin on Tibial Dyschondroplasia Incidence and Tibial Characteristics by Regulating P2RX7 in Chickens.

Tibial dyschondroplasia (TD) is a disease of rapid growing chickens that occurs in many avian species; it is characterized by nonvascular and nonmineralized growth plates, along with tibia bone deformation and lameness. Icariin is widely used to treat bone diseases in humans, but no report is available regarding the effectiveness of icariin against avian TD. Therefore, this study was designed to determine its effect against TD. For this purpose, a total of 180 broiler chicks were distributed into three groups including control, TD, and icariin group. Control group was given a standard normal diet, while TD and icariin groups received normal standard diet containing 50 mg/kg thiram to induce TD from days 3 to 7 after hatch. After the induction of TD, the chicks of icariin group were fed with standard normal diet by adding 10 mg/kg icariin in water. Then morphological and production parameters analysis of tibial bone indicators, physiological index changes, and gene expression were examined. The results showed that icariin administration not only decreased the mortality but also mitigated the lameness and promoted the angiogenesis, which diminished the TD lesion and significantly increased the expression of P2RX7 (P < 0.05) in TD affected thiram induced chicks. In conclusion, present findings suggest that icariin has a significant role in promoting the recovery of chicken growth plates affected by TD via regulating the P2RX7. Our findings reveal a new target for clinical treatment and prevention of TD in broiler chickens.

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 D3. 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.

Tibiotarsus bone characteristics and tibial dyschondroplasia incidence of broilers fed diets supplemented with leucine and valine.

Two experiments were conducted to study the effect of standardized ileal digestible (SID) leucine and valine levels on tibiotarsus bone characteristics and the incidence of tibial dyschondroplasia of broilers from day 1 to 21 (Experiment I) and day 21 to 42 post-hatch (Experiment II). Each experimental phase was evaluated independently. In both experiments, a total of 1,500 one-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design 5×5 factorial arrangement for a total of 25 treatments. The SID leucine and valine levels were ranged from 10.0 to 19.6g/kg, and 6.0 to 12.0g/kg from day 1 to 21 post-hatch, respectively, while day 21 to 42 post-hatch ranged from 10.0 to 18.0g leucine/kg, and 5.2 to 11.2g valine/kg. Serum calcium and phosphorus, bone concentrations of calcium, phosphorus and ash, diameter and Seedor index of the tibiotarsus were not affected (p>.05) by the treatments at 21 or 42days of age. There was an interaction (p≤.06) between the SID levels of leucine and valine on tibiotarsus breaking strength at 21days, but not at 42days of age (p>.05). Tibiotarsus breaking strength was maximized in broilers from day 1 to 21 with the dietary levels of leucine and valine at 14.2 and 9.0g/kg respectively. Dietary leucine levels reduced linearly (p<.05) the hypertrophic zone of tibiotarsus cartilage at 21days of age. Therefore, leucine and valine supplementation interact positively on bone strength of broilers from day 1 to 21 post-hatch. Leucine can be a useful amino acid for reducing the hypertrophic cartilage zone in broilers from day 1 to 21, but not from day 21 to 42 post-hatch.

Perches and elevated platforms in commercial broiler farms: use and effect on walking ability, incidence of tibial dyschondroplasia and bone mineral content

Modern fast-growing broilers spend excessive periods resting and their activity further decreases with age. Inactivity has been suggested to increase impaired gait and the incidence of leg disorders. Tibial dyschondroplasia (TD) is a common leg pathology in broilers. A more complex environment might facilitate more activity and improve leg health. Perches or elevated platforms bring variety to broilers’ environment and could motivate more locomotion. This study examined the impact of perches and elevated platforms on walking ability, the occurrence of TD and level of bone ash and mineral contents. The investigation was performed on four commercial broiler farms throughout six consecutive batches with platforms and four to five with perches. On each farm at least two separate houses were included, enabling the comparison of furnished flocks to control flocks during each batch. Plastic slats with ramp access elevated by 30 cm or wooden perches of 10 and 30 cm height were offered in the furnished house. Farmers recorded the platform and perch usage twice a week with a five-point scale. Gait was scored before slaughter on a six-point scale according to the Welfare Quality® assessment protocol for poultry. The severity of TD was determined using a four-point scale on farm from all birds gait scored as 3 and at slaughter from 200 birds/flock. Farmers estimated 50% to 100% of the platforms to be occupied in all flocks throughout the entire growing period. Only single birds were perching, thus perch structures were constantly evaluated to be empty. Due to the low use, the perch-equipped houses were excluded when analysing bone content, walking ability and TD. On average, 30% of the tested birds exhibited gait score ⩾3. Younger scoring age resulted in a lower mean gait score and a lower percentage of scores 3 and 4 to 5. Overall, 2.3% of the birds examined at slaughter and 3.5% of the birds with gait score 3 were affected by TD. Leg health was better in birds with access to platforms: mean gait score, the percentage of birds scoring 3, and TD percentage and severity were lower in birds in platform-equipped houses. Elevated structures such as platforms, offering additional possibilities for locomotion to broilers seem to improve their leg health.

BONE CHARACTERISTICS OF BROILERS SUPPLEMENTED WITH VITAMIN D

Vitamin D is added to broiler diets to supply its physiological requirement for bone formation. The fast growth rate of modern broilers is often associated with poor bone formation. Increasing vitamin D supplementation levels and the use of more available sources have applied to try to prevent leg problems, to increase carcass yield, and to improve the performance of broilers. The present study evaluated three vitamin D supplementation levels (1) 3,500 IU (control); (2) control + 1,954 IU of 25-hydroxycholecalciferol; and (3) control + 3,500 IU of vitamin D in broiler diets supplied up to 21 days of age. The objective was to investigate if the vitamin D levels above the recommendations could reduce leg problems in broilers. In this experiment, a total of 1,296 one-day-old male and female Cobb(r) 500 broilers were used. A 2 x 3 factorial arrangement was applied, consisting of two sexes and three vitamin D levels. No difference was found between the levels of vitamin D (p > 0.05), the performance of males or females, the gait score, the valgus and varus incidence, the tibial dyschondroplasia incidence, the occurance of femoral degeneration, the bone colorimetric, and the carcass yield. Parts yield differences were found (p > 0.05), except for liver and intestine yields. We concluded that the lowest tested vitamin D level (3,500 IU per kilogram of feed) added to the diet was the best choice in terms of cost/benefit to help minimizing leg problems in broilers.

Genetic analysis of leg problems and growth in a random mating broiler population

Improvement in growth has been widely reported as the cause of increased incidence of leg problems in broiler chickens. We report herein the genetic relationship between growth and leg problems in a random mating broiler control population. The traits studied were valgus (VL), varus (VR), and tibial dyschondroplasia (TD), which were expressed on a binary scale of 0 (normal) and 1 (abnormal); growth rates from 0 to 4 wk (BWG 0-4) and from 0 to 6 wk of age (BWG 0-6); and residual feed intake from 5 to 6 wk of age (RFI 5-6). A threshold-linear mixed model was employed for the joint analysis of the categorical and linear traits. Incidences of VL, VR, and TD were 26, 4, and 2%, respectively. Heritability of leg problems ranged from 0.11 to 0.13. Phenotypic correlations alluded to an unfavorable relationship between growth and leg problems; however, the genetic relationship between growth and leg problems was extremely weak, ranging from 0.01 to 0.08. There is, therefore, a basis for genetic improvement in leg problems. However, improved management practices would also be important to reduce incidence of leg problems in broiler chickens.

Vitamina D3 e seus metabólitos para frangos de corte

Objetivou-se revisar os efeitos do uso da vitamina D3 e seus metabólitos na alimentação de frangos de corte. Na atualidade, a indústria avícola tem buscado programas nutricionais eficazes, para que as aves possam expressar o máximo desempenho produtivo. Para linhagens modernas de frangos de corte, a taxa de crescimento é extremamente elevada, iniciando sobre um suporte esquelético imaturo, o que acarreta um aumento na incidência de perdas no processo produtivo, decorrentes de distúrbios metabólicos e esqueléticos. A vitamina D através de suas ações no intestino, ossos, rins e glândulas paratireoides se faz de importância para a homeostase do cálcio e desenvolvimento de um esqueleto saudável. A vitamina D3 e seus metabólitos participam da regulação da homeostase de cálcio e fósforo, através do mecanismo que aumenta a captação intestinal destes, diminuindo as perdas renais e estimulando a reabsorção óssea, quando necessário. De modo geral, o uso da vitamina D3 e seus metabólitos nas rações para frangos de corte têm mostrado que seu uso influencia o crescimento do animal, melhorando o ganho de peso, prevenindo o raquitismo e diminuindo a incidência de discondroplasia tibial. No que se refere aos valores recomendados para as diferentes fases de criação de frangos de corte, ainda são necessárias pesquisas para o esta-belecimento dos níveis suplementares dos metabólitos da referida vitamina que poderão ser utilizados na avicultura industrial, de modo a assegurar o atendimento das exigências nutricionais e o adequado desenvolvimento ósseo.