The effect of cation-anion difference on calcium requirement, feed intake,body weight gain, and blood gasses and mineral concentrations of dairy calves

Our objective was to examine the effects of two diets with different cation -anion differences on Ca requirements in the growing calf. Holstein calves (n = 48, 24 males) were blocked at 56 to 70 d after birth (80 +/- 10 kg of body weight) according to sex and birth date and assigned randomly in a 2 x 3 factorial arrangement of dietary treatments containing cation-anion diff erences as meg (Na + K) - (Cl + S)/kg of diet dry matter and Ca content of 1) 0 and 0.35%, 2) 0 and 0.50%, 3) 0 and 0.65%, 4) 200 and 0.35%, 5) 200 an d 0.50%, and 6) 200 and 0.65%. Feed intake and average daily gain did not d iffer among treatment groups. Plasma pH and Ca were unaffected by dietary C a content or dietary cation-anion difference. Plasma Cl and P decreased lin early with increasing Ca content in the diet. Plasma HCO3 increased linearl y with increased dietary Ca content. Plasma HCO3 and partial pressure of CO 2 were higher in calves fed the 200 compared with calves fed the 0 cation-a nion difference diets. Plasma Cl was, however, lower in calves fed the 200 compared with calves fed the 0 meg diets. An interaction of Ca content and dietary cation-anion difference was detected for plasma P content. Urinary pH increased linearly with increasing dietary Ca content. Calves fed the 20 0 meg dietary cation-anion difference had higher urinary pH values than tho se fed the 0 meg diet. Urinary P excretion was not altered by dietary catio n-anion difference or Ca content of the diet. Calves fed the 0 meg diet had higher urinary cocnentrations of Ca and Cl when compared with those fed th e 200 meg diet. Bone ash, P, Ca, Mg, and K content of the 10th rib were not affected by dietary treatments. Breaking strength of the seventh and ninth ribs increased quadratically with increasing dietary Ca content. Dietary c ation-anion difference had no effect on the breaking strength of the sevent h and ninth ribs. Varying the dietary cation-anion difference from 0 to 200 meq/kg of dietary dry matter had no effect on Ca requirement of the growin g calf.