Effect of altering dietary mineral balance on growth, leg abnormalities, and blood base excess in broiler chicks.

Broiler cockerels were used in four trials of 3-wk duration to investigate the effects of altering dietary cation:anion ratios on chick growth, leg abnormalities, bone, and blood parameters. Dietary cation content was changed using Ca and Mg, whereas the anions P, Cl, and S were included at various levels, giving several total cation:anion ratios with several levels of ions. Narrowing the cation:anion ratios increased 3-wk body weights and the incidence of both dyschondroplasia and varus deformation. Further increases in dietary anion concentration generally caused a slight depression of body weights. Supplementation of Ca or Mg to diets containing high levels of anion relative to cation decreased the incidence of leg problems and lowered 3-wk body weights. Blood pH was not significantly affected by dietary mineral alterations, although pH tended to decrease as anion content was increased. Addition of P significantly reduced blood HCO3 and base excess (meq/L). Base excess was negatively correlated (P less than .05) with the incidence of TD and 3-wk body weights. Two strain-crosses of broiler cockerels, fed diets which had previously increased the incidence of leg abnormalities, exhibited no significant differences in the incidence of varus deformation or dyschondroplasia. The strain-cross of chicks having the lowest base excess had higher incidences of both leg disorders, although body weights were identical.