Effects of anionic supplement source in prepartum negative dietary cation-anion difference diets on serum calcium, feed intake, and lactational performance of multiparous dairy cows

摘要

Incidence of subclinical hypocalcemia in early postpartumdairy cows continues to be an animal welfareconcern and an economic burden for producers. Feedingprepartum negative dietary cation-anion difference(DCAD) diets produces metabolic acidosis, which supportsmobilization of bone calcium and reduces the incidenceof hypocalcemia. Achieving a sufficient degree ofmetabolic acidosis without reducing dry matter intake(DMI) can be difficult. This study compared the abilityof MegAnion (MA; Origination O2D Inc., Maplewood,MN), a new DCAD supplement designed to be morepalatable than typical anionic salt sources, and anotherpalatable commercial DCAD product, SoyChlor (SC;Landus Cooperative, Ralston, IA), to reduce urine pH(a surrogate for metabolic acidosis) without reducingprepartum DMI. A secondary objective was to assessthe effect of these anionic supplements on postpartumserum calcium concentrations and DMI. Prepartummultiparous Holstein (HO) and crossbred (XX) cowswere blocked by breed and expected calving date andrandomly assigned within breed to total mixed rations(TMR) with MA or SC and DCAD values of −215mEq/kg of DM. Cows (n = 56; 15 MA-HO, 12 SCHO,15 MA-XX, 14 SC-XX) consumed the treatmentTMR for at least 19 d and completed the 28 d in milk(DIM) phase of the study. Urine and blood sampleswere collected weekly and at 1, 2, and 3 DIM. Datawere analyzed as a randomized block design by repeatedmeasures with week or DIM as the repeatedeffect. Prepartum urine pH decreased from 8.15 ± 0.27before treatment to 6.12 ± 0.14 during treatment, wasnot affected by anionic supplement, and increased immediatelyafter calving when all cows consumed thesame early-lactation TMR. Prepartum serum calciumconcentrations were not affected (2.34 vs. 2.33 ± 0.02mmol/L) by treatment, whereas nonesterified fattyacids were lower (86 vs. 120 ± 10 mmol/L) and insulinwas greater (215 vs. 174 ± 10 pmol/L) in cows fed MAthan in cows fed SC. These differences are supportedby the numerically greater prepartum DMI (1.2 kg/d)and energy balance (1.8 Mcal/d) of cows fed MA. However,pre- and postpartum DMI and other productionvariables, including body weight, body condition score,milk yield, and energy balance, were not affected bytreatment. This lack of difference indicates that MAprovides another effective source of anionic salts fordiets designed to reduce urine pH and induce metabolicacidosis in prepartum dairy cows.