CALCIUM AND CATION-ANION BALANCE EFFECTS ON FEED-INTAKE, BODY-WEIGHT GAIN, AND HUMORAL RESPONSE OF DAIRY CALVES

Our objective was to examine whether feeding low cation-anion diets al tered the Ca status of the growing calf. Holstein calves n = 32; 16 ma les) were blocked at 56 to 70 d after birth according to sex and birth date and assigned randomly to dietary treatments containing Ca conten t and cation-anion balances as milliequivalents of (Na + K) - (Cl + S) /100 g of dietary DM of .42% and -18, .52% and -18, .42% and 13 and .5 2% and T3. Feed intake did not differ among treatments. Calves fed he diet with cation-anion balance of 13 had higher gain (.85 vs. .71 kg/d ) than those fed the diet with balance of -18. Venous blood pH (7.374 vs. 7.323), partial pressure of CO2 (47.9 vs. 45.6 mm Hg), and bicarbo nate (28.3 vs. 23.3 mmol/L) were higher for calves fed the 13 versus - 18 balances. Plasma Ca and P were unaffected by Ca or cation-anion bal ance. Urinary pH was higher for calves fed the high than the low balan ce (7.442 vs. 6.047). Urinary Cl and Ca excretion was higher for calve s fed the low than the high balance. Breaking strengths for 7th and 9t h ribs were higher for calves fed the high balance and higher for the 7th rib only for calves fed the high Ca diet. Cation-anion balance alt ered Ca metabolism, but it is unclear whether Ca requirements were als o altered.