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A Low Dietary Cation-Anion Difference Precalving and Calcium Supplementation Postcalving Increase Plasma Calcium But Not Milk Production in a Pasture-Based System

J. R. Roche^*,,1, D. Dalley^*, P. Moate^*,2, C. Grainger^*, M. Rath and F. O’Mara

^* Agriculture Victoria Ellinbank, Victoria 3820, Australia
Department of Animal Science and Production, University College Dublin, Ireland

Corresponding author:
J. R. Roche; e-mail:
john.roche{at}dexcel.co.nz.

It was hypothesized that a reduction in the dietary cation-anion difference (DCAD) before calving, combined with an increase in Ca intake after calving, would reduce the incidence of periparturient hypocalcaemia and increase milk production in pasture-based dairy cows. Cows (n = 40) were assigned to one of two DCAD levels before calving (i.e., +7 and +50 mEq/100 g). Each group was then assigned to one of two dietary Ca concentrations after calving (i.e., 1.0 and 0.7%) in a 2 x 2 factorial design. The lower DCAD resulted in a nonrespiratory reduction in systemic pH as indicated by a lower urine pH. This acidosis resulted in an increased concentration of Ca in urine before calving. The lower precalving DCAD helped prevent the decline in blood Ca caused by the onset of lactation, even though blood Ca concentration was lower before calving compared with cows receiving a high DCAD. Supplementation of cows with Ca after calving increased plasma Ca concentration on the day of calving and during the subsequent 14 d. Milk production was not affected by pre- or postcalving treatments.

Key Words: dietary cation-anion difference • hypocalcaemia • pasture

Abbreviation key: Creat = creatinine, DCAD = dietary cation-anion difference, DMD = dry matter digestibility, HC = high postcalving dietary Ca, HD = high precalving DCAD, Hy = hydroxyproline, ICP-ES = inductively coupled plasma emission spectrometry, LC = low postcalving dietary Ca, LD = low precalving DCAD, ME = metabolizable energy, [SID] = strong ion difference, [SID_B] = strong ion difference in blood, [SID_U] = strong ion difference in urine

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