Acidogenic mineral additions increased Ca mobilization in prepartum sows1,2

Increased sow milk production is associated with an increase in unexplained sow mortality during prepartum and early postpartum periods. This association has led to purported claims of hypocalcemic disorders. Assuming similar responses as dairy cows, feeding anionic mineral salts in late gestation and early lactation may reduce potential hypocalcemia related disorders in sows. Two experiments using CAD-MATE (Granco Minerals, Petersburg, VA), an acidogenic mineral supplement (AMS), were designed to determine the amount required to increase urinary Ca excretion and to identify renal compensatory responses to acid loads in sows. In Exp. 1, 30 multiparous gestating sows (Landrace × Large White) were fed 1 of 6 diets with either 0, 0.5, 1.0, 1.5, 2.0, or 2.5% AMS additions for 14 d. Diets provided a range (33 to -216 mEq/kg) of cation-anion balance, calculated as Na + K - Cl - S. Two 24-h urine samples were collected via bladder catheters for mineral analysis. One venous blood sample was drawn from 2 sows per diet on d 14. In Exp. 2, twelve sows were fed 1 of 3 diets to provide either 0, 1.5, or 2.5% AMS. Three 24-h composites of urine and fecal excreta were collected and analyses were used to calculate apparent mineral retention. Venous blood pH (range 7.41 to 7.33) and base excess (range 5.4 to 0.5 mmol/L) decreased (linear, < 0.10), but blood ionized Ca (range 1.28 to 1.37 mmol/L) increased (linear, < 0.05) proportionally to dietary AMS additions. Blood anion gap was not affected by diet. Urine pH decreased (linear, < 0.10) with additions of AMS (range 7.47 to 5.52). In Exp. 2, urinary SO (range 134 to 396 mEq/d) and NH (range 84 to 323 mEq/d) excretion increased ( < 0.05) with AMS additions. Urinary Mg, Na, and K excretion did not differ among treatments. Fecal excretion of Ca, Mg, and P increased ( < 0.05) in sows fed diets with 2.5% AMS. Fecal K, Na, and Cl excretion did not differ among treatments. Apparent Ca retention decreased ( < 0.05) with AMS additions, but apparent Mg and Cl retention increased ( < 0.05). In conclusion, AMS induced a renal compensated acid load as exhibited by urinary ion excretion patterns and maintenance of blood gas values within physiological ranges. Feeding diets with 1.5 or 2.5% AMS increased urinary and fecal Ca excretion and decreased apparent Ca retention implying an increase in mobilization of body Ca pools in prepartum sows.