EFFECT OF DIETARY CATION-ANION BALANCE AND CALCIUM CONTENT ON GENERAL PERFORMANCE AND INCIDENCE OF LEG ABNORMALITIES OF BROILER CHICKENS

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Abstract
A factorial experiment with 1440 day-old Hubbard chicks was conducted to assess the interacting effects of dietary Na, K, Cl and Ca on general performance and incidence of leg abnormalities, especially tibial dyschondroplasia (TD). For Ca at 0.95%, all combinations of Na (0.17, 0.30), K (0.80, 1.10, 1.40), Cl (0.22, 0.44) were present; for Ca at 1.38% the combinations were the same except for K (0.80, 1.40). The various cation combinations produced 12 and 8 different meq kg−1 of (Na + K − Cl) for Ca at 0.95 and 1.38%, respectively. Body weight gain and feed conversion were affected by the main effects K, Ca and Na and also by their interaction. Both weight gain and efficiency of feed utilization were influenced by cation-anion balance as shown by significant Ca × K, Na × K, Ca × Na (feed conversion only) and K × Cl interactions. Increasing dietary K or Na increased litter moisture, whereas Cl moderated the effect of Ca. The incidence of TD was reduced by increasing dietary Ca, Na or K but their effects are interdependent on each other and on the level of dietary Cl as evidenced by significant Ca × Na, Na × K and Na × K × Cl interactions. Feeding diets with (Na + K − Cl) between 155 and 300 meq kg−1 had little effect on growth and feed conversion. Dietary Ca level changed both the pattern and response of birds for growth and feed utilization, suggesting that the term meq kg−1 (Na + K − Cl) is an inadequate measure of dietary cation-anion balance. Key words: Dietary cation-anion, calcium, leg abnormalities, broilers