Severity Of Tibial Dyschondroplasia Research Articles

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.

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.

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.

Earlier hatching time predisposes Cobb broiler chickens to tibial dyschondroplasia

Fertile eggs from Cobb 500 broiler breeder hens were incubated to provide low starting egg shell temperatures (EST; 36.9°C to 37.3°C) which were gradually increased to 37.8°C during the first 7 to 15 days of incubation compared with eggs incubated with a constant EST of 37.8°C (standard conditions) over the first 18 days of incubation. Time of individual chick hatching (measured at 6 h intervals from 468 h of incubation), chick weight, chick length and yolk weight were measured at take-off and BW was measured at 7, 14, 28, 34 and 42 days of age. Male birds at 34 and 42 days of age were assessed for their ability to remain standing in a latency-to-lie test. At 34 and 42 days, male birds were examined for leg symmetry, foot pad dermatitis, hock bruising and scored (scale 0 to 4, where 0=no lesion and 4=lesions extending completely across the tibial growth plate) for tibial dyschondroplasia (TD) lesions. The lower EST profiles caused chicks to hatch later than those incubated under the standard EST profile. Chicks which hatched at ⩽498 h incubation grew faster over the first 7 days than those that hatched later. There were significantly more birds (only males were studied) that hatched from the lower EST profiles with TD scores of 0 and 1 and fewer with score 4 at 34 days than those hatched under the standard profile. Male birds at 34 days with TD lesions ⩾3 stood for significantly shorter times than males with TD scores ⩽2. Moreover, male birds at 34 and 42 days with TD lesion scores of ⩾3 hatched significantly earlier and grew significantly faster over the first 2 weeks of age than did male birds with TD scores ⩽2. It appears possible to decrease the severity and prevalence of TD in the Cobb 500 broiler by ensuring that the birds do not hatch before 498 h of incubation.

Evaluation the Effects of Dietary Cholecalciferol Substitution with 1alpha-Hydroxycholecalciferol on Performance and Tibia Parameters in Broiler Chickens

2 Abstract: This experiment in broiler chickens was conducted to test the efficacy of feeding 1alpha-OH D3 as a replacement for cholecalciferol on performance, tibia quality and severity of tibial dyschondroplasia (TD). On the day of hatch 96 as hatched broiler chickens (Ross-308) were weighted and randomly allocated to two treatment groups, each with 4 replicate pens of 12 chicks. The dietary treatments were as follows: basal diet+5 µg/kg of 1alpha-OHD 3, or basal diet+5000 IU/kg vitamin D3. The broiler house was completely enclosed and lighting was provided by incandescent bulbs. No significant differences (p>0.05) were observed on daily feed intake, body weight and feed conversion ratio whereas it tended to improve in broilers fed basal diet supplemented with 5 µg/kg of 1alpha-OHD3 diet (p>0.05). No significant differences (p>0.05) were found between broilers fed basal diet plus 1alpha-OHD3 or the same basal diet plus cholecalciferol for any of tibia variables measured, whereas it tended to increase in broilers fed basal diet supplemented with 5 µg/kg of 1alpha-OHD3 (p>0.05). Treatments failed to induce any effect on TD scores at d 42, though it tended to increase in broilers fed diets containing 5 µg/kg of 1alpha-OHD 3 (p>0.05). In conclusion, the results indicate that supplementing 1alpha-OHD3 as a replacement for cholecalciferol could promote performance and tibia parameter and it increased severity of TD, whereas the results were not statistically significant.

Expression and identification of recombinant chicken vascular endothelial growth factor in Pichia pastoris and its role in the pathogenesis of tibial dyschondroplasia

Vascular endothelial growth factor (VEGF) is an essential mediator of angiogenesis and endochondral ossification. To explore the role of VEGF in avian diseases such as tibial dyschondroplasia (TD), a typical disorder of endochondral ossification, we expressed and identified recombinant chicken VEGF (chVEGF) protein in Pichia pastoris and evaluated its effects on thiram-induced TD in broiler chickens. The SDS-PAGE showed that 2 recombinant proteins, with molecular weights of ˜46 and ˜70 kDa, were obtained. Western blot analysis indicated that the 2 proteins were recognized by rabbit anti-chicken and goat anti-human VEGF polyclonal antibodies. Moreover, the mixture of the proteins significantly stimulated angiogenesis in the chick chorioallantoic membrane. In 21-d-old broilers that had been fed a thiram-enriched diet (100 mg/kg of thiram for 2 d at 8 d old) to induce TD, intramuscular injection of the chVEGF proteins (at a dosage of 10 or 30 μg/kg) significantly reduced the severity of TD but had no effect on TD incidence or BW; decreased serum Ca and P concentrations and tartrate-resistant acid phosphatase activity and elevated serum alkaline phosphatase activity; enhanced the total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activities in the liver and kidney; upregulated the expression of type X collagen, matrix metalloproteinase (MMP)-13, and Runx2; and downregulated the Bcl-2 expression in the growth plates. In thiram-treated broilers at 15 d old, the chVEGF proteins upregulated the expression of MMP-13 and Runx2, and had different effects on type X collagen and Bcl-2 expression at different dosages. Our results indicate that exogenous chVEGF proteins promoted the recovery of TD-affected growth plates by improving the antioxidant capacity in the liver and kidney and by regulating differential expression of genes relating to endochondral ossification at different stages of TD development; VEGF deficiency in the growth plates was involved in the pathogenesis of TD.

ORIGINAL ARTICLE: Effect of the level of cholecalciferol supplementation of broiler diets on the performance and tibial dyschondroplasia

A study was conducted to evaluate four different cholecalciferol levels (NRC; modified), using diets supplemented with 200 (control), 1500, 2500 or 3500 IU/kg of cholecalciferol (VIT-D3). Each treatment was assigned to 3 pens of 17 broiler chicks of a commercial strain grown in an open-sided house with sidewall curtains. At 21 and 42 days, BW and feed conversion (FCR) were determined. At 42 days, five birds per pen were slaughtered to evaluate tibia and toe ash of the right leg, and incidence and severity of tibial dyschondroplasia (TD) of the left tibia and also measured dressing percentage and breast meat yield. Serum calcium and phosphorus concentrations were also determined. Haemagglutination inhibition antibody titre against Newcastle disease virus and lymphoid organs weight/body weight ratio were also determined. At both 21 and 42 days, the BW of birds fed 1500 IU/kg to 3500 IU/kg of VIT-D3 was significantly greater than birds fed 200 IU/kg. Similarly, better FCR was observed in birds those fed diets of high level of VIT-D3. No significant difference was observed for mortality at any age. Better dressing percentage and breast meat yield were noted in birds fed diets containing 2500 or 3500 IU/kg VIT-D3. Both tibia and toe ash contents were increased (p < 0.05) progressively with increased concentrations of cholecalciferol in feed. The incidence of TD (percentage of birds having TD scores greater than zero) was significantly (p < 0.05) influenced by level of 3500 IU VIT-D3/kg at 42 days. The severity of TD in birds fed diets containing 200 IU/kg VIT-D3 was apparently higher than birds fed diets with higher levels of VIT-D3. Concentrations of calcium and phosphorus minerals in the serum increased progressively with the high level of VIT-D3 supplementation to birds at both 21 and 42 days of age. Feeding levels of 1500 or 3500 IU of vitamin D3 did positively affect the immune system within the parameters measured. It may be concluded that performance, bone mineralization, blood chemistry and immunity against disease in broilers could be maintained when supplementing high level of VIT-D3 incorporated in broiler diets.

Mutation analysis of the aggrecan gene in chickens with tibial dyschondroplasia

Expression studies suggest that the incidence and severity of tibial dyschondroplasia (TD) in chickens, Gallus gallus, may be affected by the aggrecan gene, AGC 1. Here, results are described of a scan for single nucleotide polymorphisms (SNP) in AGC1 in genetic lines divergently selected for TD incidence in chickens. A total of 3,048 bp of DNA sequence obtained from amplicons produced by 4 primer-pairs designed from the GenBank AGC1 cDNA sequence were scanned for SNP. Among the 18 SNP detected and validated, only 2 were nonsynonymous. Allelic frequency differences between TD-affected and nonaffected birds were not statistically significant for all the SNP. The current results do not support an association of Gallus gallusAGC1 variation at the DNA level with the incidence of TD in chickens. The genomic resources described, however, including the SNP, could be useful in further evaluating AGC1 in other populations for association with TD or other skeletal abnormalities.

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 × 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.

Comparison of Cholecalciferol and 25-Hydroxycholecalciferol in Broiler Diets Designed to Minimize Phosphorus Excretion

A study was conducted to evaluate 2 phosphorus regimes (NRC; modified), using diets supplemented with 1,000, 2,000, or 4,000 IU/kg of cholecalciferol (VIT-D3) or the equivalent amount of 25-hydroxycholecalciferol (25-OH-D3). Each treatment was assigned to 4 pens of 25 male broilers of a commercial strain grown in an open-sided house with sidewall curtains. At 21, 42, and 49 d BW and feed conversion (FCR) were determined. At 49 d, 5 birds per pen were killed to evaluate tibia ash of the right leg and incidence and severity of tibial dyschondroplasia (TD) of the left tibia. All remaining birds were processed at a pilot processing plant with agitated chilling and automatic evisceration to determine incidence of broken bones.No differences in BW were observed at 21 d due to dietary treatments. At 42 d, the BW of birds fed 4,000 IU/kg of vitamin D was significantly greater than birds fed 1,000 or 2,000 IU/kg; at 49 d the BW of birds fed 4,000 IU/kg of vitamin D was significantly better than that of birds fed 1,000 IU/kg with the BW of birds fed 2,000 IU/kg intermediate between these 2 levels. No significant differences in BW were observed at any age between source of vitamin D, phosphorus program used, or any interaction among or between vitamin D source, level, or phosphorus program. There were no significant differences observed for FCR and mortality at any age period or for tibia ash at 49 d. Birds fed 25-OH-D3 had a significantly higher severity of TD than birds fed VIT-D3, with no effect of vitamin D level and phosphorus program. Birds fed the modified phosphorus diet in combination with 2,000 IU/kg vitamin D had significantly lower incidence of TD than birds fed the NRC phosphorus diet with the same level of vitamin D. There were no significant differences among treatments for the number of broken bones during automatic evisceration in a pilot processing plant.

Effect of Source and Level of Vitamin D on Live Performance and Bone Development in Growing Broilers

Cholecalciferol (VIT-D3) and 25-hydroxycholecalciferol (25-OH-D3) were each used to provide 125, 250, 500, 1,000, 2,000, or 4,000 IU/kg of vitamin D activity in a nutritionally complete cornsoybean meal diet. Each treatment was assigned to four pens of 60 male broilers (Cobb 500) grown in an open-sided house with sidewall curtains. At 21 and 42 d, BW and feed conversion were determined. Samples of birds (8 per pen) were killed at the same ages; the right tibia was subjected to bone ash determination, and incidence and severity of tibial dyschondroplasia (TD) were determined on the left tibia.At 21 and 42 d, the BW of birds fed the 25-OH-D3 were significantly greater than those of birds fed the VIT-D3. At 21 d, vitamin D in excess of 500 IU/kg appeared necessary to maximize BW regardless of source. At 42 d, approximately 1,000 IU/kg was needed to maximize BW of birds fed VIT-D3, whereas no significant difference in BW was noted among birds fed the various levels of 25-OH-D3. Bone ash at 21 and 42 d was significantly greater for birds fed the 25-OH-D3 as compared to those fed the VIT-D3. Approximately 2,000 IU/kg of VIT-D3 was needed for maximum bone ash, whereas there were no significant differences in bone ash content of birds fed from 250 to 4,000 IU/kg from 25-OH-D3. The incidence and severity of TD was significantly lower for birds fed 25-OH-D3 and was reduced by increasing levels of vitamin D regardless of source. Results of the study show that 25-OH-D3 is more metabolically potent on a per unit basis than VIT-D3 for support of BW, tibia ash, and reduction in incidence and severity of TD. The differences were observed primarily at lower levels of vitamin D; at typical industry levels, few differences were observed between the two sources. Use of the 25-OH-D3 may allow for supplementation with lower levels or may provide a greater margin of safety.

Reliability and validity of a modified gait scoring system and its use in assessing tibial dyschondroplasia in broilers

1. The gait scoring system for broilers developed by Kestin et al . ( Veterinary Record , 131: 190-194, 1992) has been widely used to evaluate leg problems. The many factors and measures associated with this scale have empirically established its external (biological) validity. However, published test-retest (within-observer) reliabilities are poor, and inter-observer reliabilities are unknown. We evaluated several modifications to this scale aimed at improving its objectivity and reliability. 2. Eighteen naïve observers scored a standardised video of birds exhibiting varying degrees of lameness, either using Kestin et al .'s system, or our modified system. 3. Test-retest reliability (0.906) for Kestin et al .'s system was higher than previously reported. Interrater reliability was also good (0.892). The modified system offered significantly better test-retest (0.948) and inter-rater reliabilities (0.943), without incurring costs in terms of time taken or difficulty of use. The systems were consistent, assigning individual birds the same score on average. 4. It is concluded that the modified system offers the advantages of reduced error within and between studies. 5. In a second experiment, we used our modified scoring system to examine the relationship between tibial dyschondroplasia (TD) and gait score in 267 selected broilers. 6. Neither the presence nor severity of TD affected gait score, suggesting that, at least in this strain of broilers, other leg problems like slipped tendons or torsional deformities had more influence on gait impairment than did TD.

Influence of Dietary Phytase Supplementation on Incidence and Severity in Broilers Divergently Selected for Tibial Dyschondroplasia

A study was conducted to determine the effect of dietary supplementation of phytase on the incidence and severity of tibial dyschondroplasia (TD) in chickens selected for high (HTD) and low (LTD) incidences of TD for 11 generations. By feeding a phosphorus-deficient diet (0.1% nonphytate phosphorous; nPP), HTD and LTD chickens were further identified as high-sensitivity birds (HS) and low-sensitivity birds (LS) to phosphorus deficiency based on mortality. Two hundred forty 1-d-old chicks from HTD and LTD lines (five replications of four birds per treatment) were randomly assigned to a control diet with 0.5% nPP and two treatment diets (0.1% nPP) with and without 600 phytase units (FTU) Natuphos® phytase/kg. Feed consumption and growth rate were measured for 3 wk, and both tibiae were scored for TD incidence, average TD score, and total number of TD lesions with the most severe form of the abnormality (lesions that were scored 3). The addition of phytase had no influence on TD incidence and lesion scores of 3 in HTD chicks. However, a nonsignificant reduction in TD incidence (P = 0.07), TD score, and no. 3 lesions (P < 0.01) were observed in LTD chicks. Interactions between sensitivity (to P deficiency) and phytase (P < 0.01) and sensitivity and nPP (P < 0.01) were observed for no. 3 scores in LTD chicks. These results indicate that phytase was effective in reducing TD incidence and severity in LTD chicks but not in HTD chicks.

The effects of ultraviolet light and cholecalciferol and its metabolites on the development of leg abnormalities in chickens genetically selected for a high and low incidence of tibial dyschondroplasia

Four experiments were conducted to investigate the effects of ultraviolet (UV) light exposure and several cholecalciferol metabolites on the development of tibial dyschondroplasia (TD) and other parameters associated with vitamin D metabolism in chickens selected for high (HTD) and low (LTD) incidence of TD. In Experiment 1, exposure of chickens to UV light reduced the incidence and severity of TD more in LTD chickens than in HTD chickens, as evident by the significant interactions (P < 0.10 and 0.04). In Experiment 2, the addition of cholecalciferol to diets that were deficient in cholecalciferol linearly decreased the incidence of vitamin D rickets and increased bone ash, but increased the incidence of severe TD. The LTD chickens had a higher maximal bone ash of 40.0 +/- 0.7% than did the HTD chickens, which had a maximal bone ash of 37.0 +/- 0.7%. In Experiment 3, the addition of 5 micrograms/kg of 25-hydroxycholecalciferol [25-(OH)D3], 1-alpha-hydroxycholecalciferol, or 1,25- dihydroxycholecalciferol decreased the incidence and severity of TD in the LTD chickens and had no effect on TD in HTD chickens. In Experiment 4, increasing dietary 25-(OH)D3 increased plasma 25-(OH)D3 levels in both lines, but HTD chickens had higher plasma 25-(OH)D3 levels at 20 and 40 micrograms/kg of dietary 25-(OH)D3. The incidence and severity of TD were reduced in the LTD chickens by dietary 25-(OH)D3, but little effect was noted in HTD chickens. The LTD chickens reached a maximal bone ash at 9.7 +/- 1.9 micrograms/kg and HTD chickens reached the same bone ash at 33.0 +/- 7.0 micrograms/kg. These results indicate that UV light and vitamin D metabolites are not effective in preventing TD in HTD chickens, but that altered vitamin D metabolism does exist between HTD and LTD chickens.

Effect of intermittent activity on broiler production parameters

The use of intermittent lighting in broiler production has been shown to result in spurts of activity that appear to reduce lameness. Because intermittent lighting is difficult to achieve in curtain-sided houses, the objective of this study was to determine whether simple equipment used to increase activity in broilers would improve production variables. At 1 d of age, 840 male broiler chicks were placed in 24 floor pens. The four treatments (six replicates of 35 chicks each) were as follows: 1) Control-standard feeders, 2) Ramps and Toys-birds had to climb a slight incline ramp to reach feeder and had a hanging mobile, 3) Ramps only, and 4) Toys only-standard feeders. Two trials were conducted. Weekly group weights and feed consumption were recorded. Mortality was recorded daily. At 6 wk of age, birds were bled, euthanatized, weighted, and scored for ascites and tibial dyschondroplasia (TD), and relative heart, liver, and spleen weights were obtained. Blood samples were analyzed for blood gases, hemoglobin, red blood cell count, and clinical chemistries were performed. In Trial 1, during Weeks 2, 3, and 4, treatments with ramps had significantly heavier average bird weight and significantly lower feed:gain ratios. In Trial 2, treatments with ramps had no difference in average BW; however, these groups consumed less feed, resulting in significantly lower feed:gain ratios. Cumulative mortality was decreased by ramp treatment in Trial 2. Toys decreased the incidence and severity of TD in Trial 2. In general, organ weights, blood gases, hematologies, and clinical chemistries were not affected by treatments. However, birds in treatments with ramps had significantly lower serum calcium and smaller hearts in Trial 1, and significantly lower serum cholesterol and smaller hearts in Trial 2.

Effect of Dietary 1,25-Dihydroxycholecalciferol Level on Broiler Performance

Studies were conducted to evaluate the level of dietary 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] required to decrease the incidence of tibial dyschondroplasia (TD) in male broilers at 3 and 5 wk of age. The birds were reared in floor pens with wood shavings and fed a corn-soybean meal diet supplemented with 0, 3, 6, or 9 μg/kg l,25-(OH)2D3. The diet contained, by averaged analyses, 0.73% calcium, 0.74% total phosphorus, and 0.22% phytate phosphorus. There was no treatment effect on body weight or gain:feed at either age. The incidence and severity of TD and the percentage of severe lesions were decreased and bone ash was increased by 6 μg/kg l,25-(OH)2D3 at 3 wk of age. At 5 wk of age, the incidences of TD and severe lesions were decreased when 6 μg/kg l,25-(OH)2D3 was fed. Bone ash was increased by this level in one of the two experiments. Plasma calcium was increased at 5 wk when 9 μg/kg l,25-(OH)2D3 was fed, but there was no treatment effect on plasma dialyzable phosphorus or l,25-(OH)2D3. The results indicate that 6 μg/kg l,25-(OH)2D3 is effective for decreasing TD under practical rearing conditions.

Sodium Zeolite A: Influence on Broiler Carcass Yields and Tibia Characteristics

This study considered the effect of dietary sodium zeolite A (SZA) on processing yields and tibia characteristics of male and female broilers divergently selected over three generations for high and low incidence of tibial dyschondroplasia (TD). Genetic lines included high and low incidence of TD and an unselected control line. Birds (ten replicate pens/line; thirty-five birds/pen) were fed either a standard diet or SZA-supplemented diet at levels of 0.25% and 0.50% from 1-21, 22-50, and 51-56 days of age, respectively.After the study, the high TD line had significantly (P < .01) higher body weight, chilled carcass weight, and carcass part weights than the low TD line. However, the yields (% of live weight) of carcass, thighs, and deboned breast did not differ (P>.05) among the lines. The SZA effect was significant (P < .05) for the yield of Pectoralis minor. Significant (P < .05) interaction between diet and sex indicated improvement only in yields of male broilers fed supplemented SZA. Inclusion of SZA in broiler diets resulted in an increased percent tibia ash (P < .05), but did not affect the incidence or severity of TD.

Growth, Livability, and Feed Conversion of 1957 vs 1991 Broilers When Fed “Typical” 1957 and 1991 Broiler Diets

The relative contributions of genetic selection and dietary regimen on the performance of broilers was assessed. Body weight, feed consumption, mortality (M), and the degree of tibial dyschondroplasia (TD) were measured in the 1957 Athens-Canadian Randombred Control (ACRBC) strain of broilers and in the 1991 Arbor Acres (AA) feather-sexable strain when fed “typical” 1957 and 1991 diets. Energy and protein levels, vitamin and mineral packs, and the coccidiostats used in the two dietary regimens were chosen to be representative of those in use by the industry for the two time periods. Eight treatment groups, i.e., two strains, two sexes, and two dietary regimens, were assigned into four blocks of eight litter floor pens for grow out. The 1957 diets were fed as mash, and the 1991 starter and grower diets were fed as crumbles and pellets, respectively. Feed consumption and BW were recorded at 21, 42, 56, 70, and 84 d of age, a period covering the normal marketing ages for the two broilers. Mortality and the cause of death was recorded daily. The incidence and severity of TD was assessed using a Lixiscope® at 42 d of age.Average BW were 190, 508, 790, 1,087, and 1,400 g for the ACRBC on the 1957 diets vs 700, 2,132, 3,108, 3,812, and 4,498 g for the AA on the 1991 diets at 21, 42, 56, 70, and 84 d of age, respectively. The 1991 diets increased the BW of the AA by an average of 14% (20% at 42 d, but only 8% at 84 d) and of the ACRBC by 22%. The BW advantage for the 1991 diet over the 1957 diet for the AA was less for males than for females after 42 d of age, and the advantage decreased with age, probably due to the increasing incidence of leg problems. The M for AA was 9.1% vs 3.3% for the ACRBC at 42 d. Most of the ACRBC M occurred before 21 d, whereas M occurred throughout for the AA, with most after 21 d due to flip-overs and ascites. The feed conversion at 42 d for the ACRBC on the 1957 diet was 3.00 vs 2.04 for the AA on the 1991 diet. The AA on the 1991 diet had a 48.6% incidence of TD vs 25.6% on the 1957 diet. The ACRBC had approximately 1.2% TD on both diets. The TD was more severe with the 1991 diet.

The Interaction of Boron with Calcium, Phosphorus and Cholecalciferol in Broilers

Abstract Rossi, A.F., Butcher, G.D. and Miles, R.D. 1994. The interaction of boron with calcium, phosphorus and cholecalciferol in broilers. J. Appl. Anim. Res., 6: 151–160. Four hundred and thirty-two day-old Cobb x Cobb feather-sexed chicks were placed in batteries for 21 days and randomly assigned at one day of age to eight treatment diets. The basal diet contained 22.3 ppm of boron as determined by analysis. Tibia ash was significantly lower for birds fed diets with low calcium and phosphorus or with low cholecalciferol. Feeding diets low in cholecalciferol increased the severity of tibial dyschondroplasia (TD) and body weight depression. Body weight, tibia ash and TD were not improved by adding 60 ppm of boron to the diet.

Age-Related Changes in the Incidence of Tibial Dyschondroplasia in Turkeys

Age-related changes in the incidence and severity of tibial dyschondroplasia (TD) and its relationship to body weight and other bone pathologies were studied in turkeys from ages 2 through 15 wk. A steady increase in the incidence and severity of TD was observed from 11 wk onwards. Whereas there was no correlation between the body weight and TD in early ages, during Weeks 14 and 15 the turkeys with severe TD had significantly higher body weight relative to those without or with mild lesions. Starting from Week 13, hemorrhage was evident in the base of TD-affected growth plates of many turkeys, which increased linearly during the following weeks. Histological examination of these areas revealed mild necrosis with erosion in TD tissues accompanied by occasional bone formations, fibrosis, and the presence of multinucleate chondroclasts and large number of erythrocytes adjacent to lesions. Sporadic rod-like bacterial colonies were discernible in TD tissues and cartilage canals. These studies show 1) whereas the onset of TD may have an independent etiology, the severity of the disease may be influenced by a higher body weight; and 2) subepiphyseal hemorrhages possibly facilitate a healing-type response that leads to replacement of TD tissue by way of resorption, bone formation, and fibrosis, but simultaneously makes the tissue accessible to bacteria.