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Abstract

Reducing the dietary cation-anion difference (DCAD) has been shown to be an effective means
of preventing parturient paresis in confinement systems where cows are offered a total mixed
ration containing DCAD-reducing mineral compounds (anionic salts). Such a supplementation
strategy is not possible in cows being group fed forages precalving, and little is known about
the effect of supplementing these cows with large amounts of anionic salts twice daily.
Eight non-lactating, pregnant Holstein-Friesian cows were allocated to two levels of DCAD
(–20 and +18 meq/100 g DM) for 24 d, with an intensive Ca balance undertaken in metabolism
stalls following a 2-week acclimatization to diet. The basal diet was 3 kg DM of crushed barley
and 7 kg DM of pasture-hay. Urine and faeces were collected separately, weighed daily for 5 d
and analysed for Ca content. Urinary Ca, creatinine and hydroxyproline concentration and
plasma Ca concentration were determined during the period of the balance study. The diurnal
pattern in urine and rumen pH was determined over 2 d. Decreasing DCAD reduced (P<0.001)
the pH of urine, and increased (P<0.05) Ca absorption. Plasma Ca concentration was not
affected by DCAD, and DCAD did not affect the output of urinary hydroxyproline, a marker of
bone resorption. Twice-daily supplementation of anionic salts was sufficient to reduce the pH
of blood and increase gastrointestinal Ca absorption. There was no diurnal variation in the pH of
urine, suggesting that time of sampling to determine efficacy of DCAD in reducing systemic pH
was not important.

Item Type:	Article
Authors/Creators:	Roche, JR and Dalley, DE and O'Mara, FP
Journal or Publication Title:	Journal of Dairy Research
Publisher:	Cambridge University Press
ISSN:	0022-0299
DOI / ID Number:	https://doi.org/10.1017/S0022029906002123
Additional Information:	Sherpa- Cambridge University press Publishers version/PDF may be used in an institutional repository or PubMed Central after 12 month embargo
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