1540 Effects of diets containing either traditional anionic salts or a commercial anionic supplement on feed intake and energy balance of prepartum dairy cows

Abstract

Anionic supplements are fed to prepartum (PP) dairy cows to reduce dietary cation–anion difference (DCAD) and improve calcium status at calving. Traditional anionic salts (AS) can reduce DMI, presumably due to poor palatability. Commercial anionic supplements purportedly are more readily consumed, but there is little research to support this assertion. Twenty-nine pregnant multiparous Holsteins were used to examine the effects of AS or a commercial anionic supplement (SoyChlor [SC]) on DMI and energy balance (EB) during the last 3 wk of pregnancy. The AS supplement consisted of 55% ammonium chloride, 29% magnesium sulfate, and 16% ammonium sulfate. At dry off, each cow entered a communal pen and was accustomed to a Calan gate feeder. The far-off dry period diet was a total mixed ration without anionic supplementation. At 21 d before expected calving date, cows were alternately assigned to a treatment. The AS or SC was incorporated into the diet to yield a calculated DCAD [(Na + K) − (Cl + S)] of −120 mEq/kg. Urine pH was monitored to ensure similar metabolic acidification among the two PP groups. Individual DMI was measured daily. Diet energy content (estimated using the CNCPS version. 6.5 model) and DMI allowed calculation of EB. Data were analyzed using the Mixed procedure of SAS. Post hoc testing of means was done using Bonferroni's procedure. Overall treatment and treatment by week effects for each of the three PP weeks were examined. Least squares means are in the table. Over the entire PP period, cows supplemented with SC had higher DMI (P < 0.001) and EB (P < 0.004) than cows supplemented with AS. Dry matter intake and EB declined for both groups as the PP period progressed toward calving.