Effects of prepartum dietary calcium level on calcium and magnesium metabolism in periparturient dairy cows

Abstract

The aim of this study was to investigate the effects of dietary Ca level (4.9, 9.3, and 13.6 g/kg of DM) on Ca and Mg homeostasis in dairy cows around parturition. Cows of the Swedish Red breed (n = 29) with no previous veterinary treatment for milk fever were divided into 3 groups, and each group was fed one of the different diets during the last 15 to 32 d of gestation. Calcium was added as ground limestone, and the Mg concentration was 1.8 g/kg of DM in all diets. After calving the cows were fed similar diets. Plasma was sampled twice per week until calving, and 6, 12, and 24 h, 2, 4, and 7 d after calving. Spot urine samples were collected twice weekly until calving and creatinine was used as a marker of daily urinary excretion. Fecal samples were collected 2 times per day for 5 d starting 2 wk before expected calving, and acid-insoluble ash was used as an indigestible marker to estimate digestibility. Apparent digestibility of Mg and daily Mg excretion in the urine were lower in the dry period for cows fed the highest Ca level. Plasma Mg concentration was lower on 2, 4, and 7 d after calving in cows fed the highest level of Ca. Treatment groups did not differ in plasma Ca concentration, parathyroid hormone concentration, or bone mobilization, evaluated using crosslinked carboxyterminal telopeptides of type I collagen (CTx) as a marker. Plasma Ca concentration decreased and plasma CTx concentration increased 6 h after calving. The apparent digestibility of Ca during the dry period was not affected by dietary Ca, but the cows fed 4.9 g Ca/kg of DM excreted 1.2 g of Ca/d in the urine, which was higher compared with 0.4 g/d and 0.6 g/d for the cows fed 9.3 g of Ca/kg of DM and 13.6 g of Ca/kg of DM, respectively. The results show that feeding 13.6 g of dietary Ca/kg of DM impaired the Mg absorption during the dry period, and resulted in decreased plasma Mg concentration after calving, but prepartum dietary Ca level did not affect plasma Ca, parathyroid hormone, or CTx concentrations.

Effects of prepartum dietary cation-anion difference on aspects of peripartum mineral and energy metabolism and performance of multiparous Holstein cows

“…Plasma concentrations of Mg were lower in the 2 d after parturition for cows fed lower prepartum DCAD, consistent with other studies that have measured blood mineral responses shortly after parturition (Green et al, 1981;Kronqvist et al, 2011). Administration of exogenous PTH has been shown to decrease urinary Mg excretion, likely due to an increased renal threshold for Mg clearance by the kidneys induced by PTH.…”

Review: Endocrine pathways to regulate calcium homeostasis around parturition and the prevention of hypocalcemia in periparturient dairy cows

“…Minerals present in organisms in large amounts are calcium, phosphorus, magnesium, sodium, potassium, chloride and sulfur. In the specific case of calcium, several studies have detected a correlation between low circulating magnesium concentrations and low circulating calcium concentrations in humans (Classen et al, 1986;Paunier, 1992), mice (Zimmermann et al, 2000) and dairy cows (Kronqvist et al, 2011 and. Low magnesium concentrations have been shown to reduce the secretion of PTH (Suh et al, 1973), as well as decrease tissue responsiveness to PTH (Reddy et al, 1973;Rude, 1998).…”

Relationship between incidence of milk fever and feeding of minerals during the last 3 weeks of gestation

“…This is in agreement with Thilsing- Hansen et al (2002), who concluded that Ca intake had to be decreased to less than 20 g/day to decrease the incidence of milk fever. In addition, differences in Ca intake have been found to have no effect on the incidence of milk fever or subclinical hypocalcaemia in experimental studies when the minimum level exceeds 20 g/day (Goff and Horst, 1997;Kamiya et al, 2005;Kronqvist et al, 2011). Curtis et al (1984) found no effect of dietary Ca in commercial herds on the incidence of milk fever, although they concluded that all cows in their study were fed well above the recommendations.…”

“…However, more than 80% of the present herds that belonged to the lowest third in Mg intake received Mg at rates above the current Nordic recommendation (Nielsen and Volden, 2011), and the NRC (NRC, 2001) recommendations and the former Swedish recommendations (Spö rndly, 2003) recommend even lower levels of Mg. There are also other indications that the current recommendation is too low (Kronqvist et al, 2011). For example, Goff (2008) suggests more than twice the dietary Mg level stated in Nordic recommendations to ensure adequate Mg absorption during the dry period.…”