Effects of a deficient magnesium supply during the dry period on bone turnover of dairy cows at parturition

Abstract

SUMMARY. The bone activity and bone mineral content in rib bones resected from 33 dairy cows between 3 and 8 h after parturition were measured, and the effects upon them of a deficient supply of dietary magnesium (Mg) during the last seven weeks of pregnancy were studied. The cows were fed a diet containing either 0.22% magnesium (low Mg) or 0.82% magnesium (high Mg) in the dry matter (DM), and the potassium content of both rations was increased to approximately 4.1% in the DM to reduce the absorption of magnesium. In the cows fed the low-Mg diet a fall in plasma Mg concentration was observed In the low-Mg, low-parity cows the plasma Mg concentrations at parturition were higher than in the low-Mg, high-parity cows, i.e. 0.83 mmol/l and 0.54 mmo1/1, respectively. After parturition four cows in the lowMg, high-parity group showed clinical signs of hypocalcaemia but none of the other groups did so. The bone formation in low-parity cows was significantly (P < 0.05) affected by Mg supply, with higher percentages of both trabecular surface covered by osteoid and osteoid volume in the low-Mg group. In the high-parity cows no significant differences in bone formation were found between the low-and high-Mg groups. An inadequate Mg supply resulted in a significantly (P < 0.05) higher Ca content in the bone ash of low-parity cows and a significantly (P < 0.05) higher bone ash percentage in the bone of high-parity cows.

Effects of Two Different Feeding Strategies During Dry-off on Certain Health Aspects of Dairy Cows

“…The Mg concentration was lower in primiparous cows than in older cows, but the reason for this is not clear. In contrast, van Mosel et al (1991) previously showed that lowparity cows fed a low-Mg diet had a higher concentration of Mg in plasma than did high-parity cows.…”

Dietary magnesium increases calcium absorption of ovine small intestine in vivo and in vitro

“…We took the samples for mineral balance studies during a short period. Most cows are rapidly in negative Ca balance during the early days of lactation [27]. In addition, the contents of intestine are stable after about 7 days from alteration of diet.…”

“…The tissue sheets, after washed fully with physiological saline solution, were attached on the Ussing chamber (exposed area 1 cm 2 ) to measure the 27 T. Kozakai et al…”

Perfil mineral de vacas mestiças Girolanda no período de transição em sistema semi-intensivo em duas estações do ano

“…A redução nos valores da concentração de cálcio no dia do parto foi similar às observações feitas por alguns autores que verificaram redução do mineral com a aproximação do parto e no dia do parto (Blum et al 1972, Wilson et al 1977, Van Mosel & Corlett 1990, Van Mosel et al 1991, Vanden Top et al 1995, Goff & Horst 1997a, Souza Júnior et al 2011, Buture 2009.…”