Role of dietary calcium and available phosphorus in the aetiology of tibial dyschondroplasia in growing turkeys

Abstract

1. Large White male turkeys from a heavy commercial male-line were fed 16 diets containing 4 concentrations of calcium (6, 10, 14 and 18 g/kg) and available phosphorus (3, 5, 7 and 9 g/kg) in a 4 x 4 factorial experiment. There were three replicates (pens) of each treatment and the skeletal health, morphology and mineral status of 4 turkeys from each pen were assessed at 7, 10 and 13 weeks of age. 2. The prevalence of tibial dyschondroplasia increased after 7 weeks of age and was present in 50 and 71% of turkeys respectively at 10 and 13 weeks. The lesion was localised in the caudal aspect of the proximal tibiae. Dietary calcium and available phosphorus did not affect the prevalence of the lesion except in turkeys on the diet containing 6 g calcium/kg, where body weight and the incidence of tibial dyschondroplasia were low. 3. Histological investigation showed no evidence of rachitic changes. 4. Low dietary calcium was associated with lower tibial plateau angles at 10 and 13 weeks of age. Tibial torsion and the angle of rotation were not affected by dietary treatments or age. Tibial torsion and the angle of rotation were not affected by dietary treatments or age. 5. Increasing dietary calcium increased tibial radiodensity, cortical density and the widths of the cortex and proximal tibiotarsus. Radiodensities increased to 10 weeks and were significantly lower at 13 weeks of age. 6. Bone ash, calcium and phosphorus declined with age, particularly between 10 and 13 weeks, whereas bone calcium: phosphorus ratios were not affected by dietary treatment or age. 7. Dietary calcium was positively associated with blood calcium and calcium ion concentrations and was without effect on blood phosphorus. Available phosphorus was associated positively with increased blood phosphorus and lower calcium ion concentrations but had no effect on total calcium. Alkaline phosphatase activity was low at high concentrations of dietary calcium with low available phosphorus and there was higher activity on diets containing low calcium and high available phosphorus.

Reducing the phosphorus concentration in diets for turkeys between 10 and 22 weeks of age

“…No treatment effect was detected with regard to P concentration in toe ash and the Ca:P ratio in the toe (Table 7). Average values found in this study were almost identical with those determined in the tibia of turkeys that had been fed different P levels up to 13 weeks of age (Hocking et al, 2002b). These authors used a range in P supply between 3 and 9 g available P/kg diet and did not find an effect of P supply on tibia ash content.…”

“…5 g/kg. Although no data are published on the composition of BW gain for turkeys, bone measurements indicate that this decline in P concentration with increasing BW can be expected (Hocking et al, 2002b). No data are available on the inevitable P losses of growing turkeys.…”

“…73 of the NRC (1994) NPP requirement without phytase between weeks 5 and 16 did not negatively affect the performance of male turkeys (Atia et al, 2000). Hocking et al (2002b) varied available P between 3 and 9 g/kg in diets for turkeys fed until week 13 and did not find an effect on the prevalence of tibial dyschondroplasia in cases where dietary calcium (Ca) was sufficient. As judged by growth data, heavy male turkeys did not need more than 3 g available P/kg diet up to 13 weeks of age when the Ca content was 10 g/kg (Hocking et al, 2002a).…”

Quantifying genetic (co)variation and effects of genetic selection on tibial bone morphology and quality in 37 lines of broiler, layer and traditional chickens

“…Breeds, breed category, source, mean tibia weight and incidence of tibial dyschondroplasia at 6, 8 and 10 weeks of age (n ¼ 4 males per line at each age) Breed Category 1 Source 2 Tibial weight (g) TD 3 (n) 6 weeks 8 weeks 10 weeks the proximal extremity of the cnemial crest. The tibial plateau angle was measured between this perpendicular line and a line from the proximal cnemial crest across the surface of the condyles as previously described (Hocking et al, 2002). A comparison of the transverse axes of the proximal and distal articular surfaces provided a measure of torsion within the bone using the method of Corr et al (2003a).…”

Quantitative trait loci for bone traits segregating independently of those for growth in an F₂ broiler × layer cross

“…Tibial plateau angles were measured on X-ray images between a perpendicular line drawn at right angles to the long axis of the bone and a second line drawn perpendicular to the long axis at the point where it bisected the proximal extremity and the cnemial crest across the surface of the condyles as described by Hocking et al (2002). Torsion measurements (degrees) were calculated by comparing the transverse axes of the proximal and distal particular surfaces of the tibiae as described by Duff and Thorp (1985).…”