Effects of NaCl and NaHCO₃ on food intake, growth rate and acid-base balance in calves

Abstract

SUMMARY Calves were reared on milk replacer up to 5 weeks of age and given ad libitum access to pellets and chopped straw from 1 to 10 weeks of age. Major ingredients of the pellets were ground barley (B) or ground barley and grass meal in a 6:4 ratio (G). Included in these two basal diets were NaCl or NaHCO 3 , each at 2, 11, 20 or 29 g Na/kg D.M. Calves on G diets ate more than those on B diets but grew at a similar rate. The replacement value of grass meal for ground barley was 1·36:1. Most responses to Na inclusions were unaffected by the basal diets. Before weaning there were linear increases in food intake and growth rate related to Na level in the diet. At 29 g Na/kg D.M., total D.M. intake/kg 0.75 and growth rate were respectively 31 and 23% greater than at 2 g Na/kg D.M. After weaning there were differential responses to the two salts. With NaHC0 3 there were linear increases in food intake and growth rate up to 20 g Na/kg D.M., at which level total D.M. intake/kg 0.75 and growth rate were respectively 36 and 44% greater than at 2 g Na/kg D.M. With NaCl the only significant response was that total D.M. intake at 11 g Na/kg D.M. was 16% higher than at 2 g Na/kg D.M. Observations on acid-base balance and water intake indicated that inclusions of NaCl or NaHCO 3 up to 20 g Na/kg D.M. were well tolerated by calves. Above this level there was a sharp increase in water intake, and with NaHCO 3 there was a large base excess and high pH in the blood.