G. N. Rowland

Calcium and phosphorus requirements of the very young Turkey as determined by response surface analysis

The first experiment was a central composite rotatable design with calculated calcium levels of 6.2, 7.0, 9.0, 11.0, and 11.8 g/kg diet and total phosphorus levels of 5.2, 6.0, 8.0, 10.0, and 10.8 g/kg diet (2.8 g phytin-P/kg by analysis). This design involved three replicates for each rotatable point and fifteen replicates of the central point. The second experiment was a 4 x 4 factorial design with calculated Ca levels of 8.0, 10.0, 12.0, and 14.0 g/kg diet and calculated total P levels of 7.0, 9.0, 11.0, and 13.0 g/kg diet (2.5 g phytin-P/kg by analysis). There were four replicates for each treatment. In both 16 d experiments maize-soya-bean diets were used and each replicate consisted of one pen containing 10-d-old broad-breasted, white tom turkeys. The Ca and total P requirements for optimum growth were estimated to be 12.5 and 10.0 g/kg diet respectively. Bone ash was adequate at these levels of Ca and total P, but maximum bone ash was not achieved until much higher levels of Ca and total P were employed. At the required levels of Ca and total P for growth the incidences of Ca- and P-deficiency rickets were very low. There were no treatment effects on feed efficiency. Increasing dietary Ca decreased the incidence of the Ca-deficiency lesion. There was a quadratic response due to dietary total P on both P-deficiency rickets and plasma dialysable P; intermediate levels of dietary P resulted in low incidence of the P-deficiency lesion and high levels of plasma dialysable P. There was a strong negative correlation between the incidence of P-deficiency rickets and plasma dialysable P. Percentage retention was very low at high levels of dietary P and low levels of Ca which corresponded with slightly higher P-deficiency rickets and low plasma dialysable P. No such obvious relationships existed between Ca retention, incidence of Ca-deficiency rickets, and plasma Ca. The incidence of tibial dyschondroplasia was very low in the present study. There were pronounced dietary treatment effects on phytin-P retention; at 14 d percentage phytin-P retention treatment means ranged from 18 to 46 in Expt 1 and from 0 to 40 in Expt 2 with the highest retention of phytin-P at low levels at both Ca and total P.

Effects of Increased Physical Activity on Juvenile Avian Bone

Commercial meat-type chickens (broilers) have become less active as production practices have increased the rate at which these birds gain weight. This inactivity could result in skeletal abnormalities that adversely affect animal health and production cost. This study investigated a treadmill regimen to increase the bone movement of broilers and force the broilers into an abnormally high level of physical activity. Beginning at 3 weeks of age, treatment birds were required to walk 5 days a week on a treadmill at a pace of 0.45 m/s for 30 min. The working hypothesis was that increased bone movement of broiler chicken accelerates skeletal development and strength. Results indicated that treadmill pacing did not affect the body mass of the bird during normal growth but did affect (p < 0.05) the length and width of the birds shank. The treatment reduced tibia length by approximately 8% and tibia midpoint cross-sectional area by 25%. The shear strength and bone mineralization of the tibia was not affected by the increased bone movement. Overall, the increased activity did not impact the structural integrity of the broilers tibiae.