Abstract

This study was conducted to evaluate the effects of three diets with different cation-anion differences ((DCAD: mEq[(Na + K) − (Cl + S)]/100 g of dry matter)) in far-off and close-up period, on milk production and blood mineral of Holstein cows. Eighteen pregnant cows (220 - 225 d) were fed a base diet with three DCAD (+13 (control), 0, −13/100 g dry matter) for 60 ± 5 days. Control diet consisted of 170 g/kg corn silage, 396 g/kg alfalfa hay and 424 g/kg concentrate mix (dry matter basis). For decrease DCAD, two anionic salts such as ammonium chloride and ammonium sulphate were used. Production of milk and 3.5% fat corrected milk (FCM) were increased with decreasing DCAD. However, milk composition and yield of milk fat, protein and lactose were not affected by diets containing +13, 0 and −13 DCAD. In addition, prepartum dry matter intake, BCS change and body weight gains were similar for cows fed the three diets with different cation-anion differences. At calving, plasma calcium concentration was 6.55, 6.46 and 6.78 mg/dl for cows fed diets containing +13, 0 and −13 DCAD, respectively. Blood pH and concentration of K, Mg and Na were not affected by dietary cation-anion balance. Urinary pH of cows was affected by diets and was decreased linearly with decreasing DCAD. The mean urinary pH was 7.99, 6.81 and 6.11 for cows fed diets containing +13, 0 and −13 DCAD, respectively.

Key words: Metabolic disorders, pregnant cow, anionic salts.

Abbreviation

DCAD, dietary cation-anion differences; BCS, body condition score; FCM, fat corrected milk.