Hypomagnesemia in dairy cattle in Uruguay

Abstract

An outbreak of hypomagnesemia is reported in Holstein dairy cattle grazing lush oat (Avena sativa) pasture in Uruguay. Nine of 270 (3.3%) cows died in May-July (autumn-winter) 2017. These nine cows were from 2 to 9-years-old (1st-6th lactation), with 22 to 194 days of lactation and 15.8 to 31.4L of daily milk production. Two cows with acute sialorrhea, muscle spasms, lateral recumbency, weakness, opisthotonos, and coma, were euthanized and necropsied. No significant macroscopic or histological lesions were found. One untreated clinically-affected cow and eight out of 14 clinically healthy cows of the same group under similar management and production conditions had low serum levels of Mg (lower than 0.7mmol/L). Secondarily, both clinically affected cows and six out of 14 healthy cows had low serum Ca levels. The K/(Ca+Mg) ratio of two oat forages, corn silage, and ration was 5.10, 7.73, 2.45, and 0.85, respectively. A K/(Ca+Mg) ratio lower than 2.2 represents a risk for hypomagnesemia. The difference between the contribution-requirement of minerals in the diet was established and a daily deficiency of Mg (-0.36g/day), Na (-25.2g/day) and Ca (-9.27g/day) was found, while K (184.42g/day) and P (12.81g/day) were in excess. The diet was reformulated to correct the deficiencies and the disease was controlled by the daily administration of 80g of magnesium oxide, 80g of calcium carbonate and 30g sodium chloride per cow. It is concluded that hypomagnesemia is a cause of mortality in dairy cattle in Uruguay, and that the condition can be prevented by appropriate diet formulation.

Determination of Blood Glucose, Total Protein, Certain Minerals, and Triiodothyronine during Late Pregnancy and Postpartum Periods in Crossbred Dairy Cows

“…A drop in blood Mg concentration results in spontaneous muscle contractions or tetany in dairy cows [14]. Hypomagnesemia occurs during the postpartum period in dairy cows [15,16]. Parturition significantly influences the level of blood iron.…”

Influence of Functional Feed Supplements on the Milk Production Efficiency, Feed Utilization, Blood Metabolites, and Health of Holstein Cows during Mid-Lactation

“…The role of macro minerals such as Ca, Phos, and Mg are more important than other minerals, and their balance in the body improves animal health, reproduction, and production performance [47]. Hypomagnesaemia or hypocalcemia in high-producing dairy cows increases the risk of some disorders such as milk fever [53]. Hypocalcemia reduces milk production and increases diarrhea and vagus indigestion due to the inhibition of feed intake [54].…”

Hypomagnesemia in beef cattle

“…In Uruguay, hypomagnesemia was described in dairy cattle grazing lush, fast-growing forages in autumn (Doncel et al 2019). In beef cattle, an outbreak of hypomagnesemia occurred in association with prolonged transport without access to feed and water (Dutra 2009) and two other outbreaks occurred after confinement for long periods in pens without access to water and feed (Dutra 2010).…”

“…Hypomagnesemia is associated with improved pastures (Burns & Allcroft 1967, Allcroft & Burns 1968) and occurs when cows under intensive management practices graze on fast-growing grasses, particularly, but not exclusively, in the spring (Wilcox & Hoff 1974). Hypomagnesemia mainly affects lactating (lactation tetany) (Grunes et al 1970, Watson et al 2008, Doncel et al 2019 or pregnant dairy cows grazing lush, fast-growing winter grasses such as oat, wheat, or ryegrass. The disease also affects lactating and pregnant beef cattle (Metson et al 1966, Grunes et al 1970, Dutra 2009, Constable et al 2017.…”