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Background and aims: Potassium (K), Calcium (Ca), and magnesium (Mg) are essential nutrients for plant and animal growth. The ratio of K/(Ca + Mg) in forage is considered as an indicator of grass tetany. While atmospheric nitrogen (N) deposition is declining or projected to decline in many countries, it remains unknown whether historical N inputs would have legacy effects on K, Ca, and Mg nutrition in soil and plants. Methods: After the cessation of 6-yr N addition with wide-ranging rates, we measured the concentrations of K, Ca, and Mg in soil and plants in a temperate steppe of northern China during three successive years from 2016 to 2018. Results: Soil K/(Ca + Mg) ratios were increased by historical N addition across the three years. Soil K/(Ca + Mg) ratios were higher than 0.08, indicating potential occurrence of grass tetany for ruminants. Plant mineral concentrations and K/(Ca + Mg) ratios at the plant community level showed no variation with increasing historical N addition rates in all the three years, except for the increasing K and Ca concentrations in 2017. All plant functional types showed strong stoichiometric homeostasis with respect to nutrient concentrations, which contributed to the stable forage K/(Ca + Mg) ratio under the N-induced increasing soil K/(Ca + Mg) ratio. Conclusion: Our results highlight the critical role of stoichiometric homeostasis in maintaining forage non-N mineral nutrition of natural grasslands under the background of soil nutritional alterations. [ABSTRACT FROM AUTHOR]

Simple Summary: Aluminium intoxication is poorly documented in ruminants and its symptomatology, compatible with grass tetany caused by hypomagnesaemia, is the most documented clinical manifestation of acute intoxication. However, there is no documented evidence of chronic aluminium intoxication in cattle. In a 50 dairy cow Belgian herd, excessive uterine bleeding at calving and decreased milk production were reported. The results of various analyses on 10 sick cows were compared with 10 healthy cows from another herd. The investigations of sick animals showed anaemia, marginal hypozincaemia, subclinical ketosis, hypomagnesaemia and a high aluminium/creatinine ratio (urinary excretion). The mixed ration contained a high level of aluminium. Based on the results and suspicion of chronic aluminium poisoning, it was advised to measure the soil pH, add salts to the ration to chelate the aluminium and support the cows with mineral supplements and propylene glycol. A visit was carried out 2 years later. The situation had improved, but all of the cows examined had subclinical ketosis. The grass silage had high aluminium and butyric acid concentrations. Aluminium could be incriminated in different stages, but it was probably not the only culprit. Chronic poisoning with metals and pollutants should be the focus of veterinary attention in the coming years. In ruminants, the main documented clinical manifestation of aluminium (Al) intoxication is similar to grass tetany. In a 50 dairy cow Belgian herd, the farmer reported excessive uterine bleeding at calving and decreased milk production. Dairy cows received a mixed ration (MR) with high Al concentration (453 ppm/kg of dry matter (DM)). Various analyses were sampled from 10 sick cows and compared with 10 healthy cows (from another herd). Sick cows presented anaemia and marginal hypozincaemia and 6/10 showed subclinical ketosis. Their urine analysis revealed hypomagnesaemia and a high Al/creatinine ratio. It was advised to determine soil pH, add salts to the ration to chelate the Al and support cows with mineral supplements and propylene glycol. A visit was carried out 2 years later and highlighted an improvement in the situation, but all examined animals presented subclinical ketosis. Grass silage Al content remained high (700 ppm/kg DM), as did butyric acid concentration (11.22 g/kg DM). Al could be incriminated at different stages: micronutrient deficiencies, anaemia and negative energy balance. However, Al was probably not the only culprit. This case report is a concern for future years in these areas due to droughts, scarcity of forage and an increase in contaminated soil ingestion. [ABSTRACT FROM AUTHOR]

Magnet Italian ryegrass (Lolium multiflorum L.), HiMag tall fescue (Festuca arundinacea Schreb.), and Mgwell orchardgrass (Dactylis glomerata L.) are the first cultivars bred for higher magnesium uptake (high-Mg) to reduce grass tetany risk for ruminants. The experiment was conducted to evaluate whether magnesium (Mg) uptake efficiency by high-Mg cultivars is limited to specific phosphorus (P) levels, and to optimize P level for individual selections of high-Mg grasses in nutrient culture. The high-Mg cultivars were compared with two existing commercial cultivars viz., Tachiwase and Waseyutaka, of Italian ryegrass, Kentucky-31 (Ky-31) and Fawn of tall fescue, and Akimidori and Okamidori of orchardgrass, respectively. One-month aged seedlings were grown in controlled conditions with three P treatments of 0.1, 1, and 5 mM for 10 days and nutrient contents were determined. Increasing P fertilization increased shoot weights of the grasses. Shoot potassium (K) content of the high-Mg cultivars was lower than the commercial cultivars. In contrast, the high-Mg cultivars were consistently higher in shoot calcium (Ca) and Mg contents when compared to the commercial cultivars, irrespective of species, over P fertilization. While the shoot Mg and Ca contents increased, the K content and K/(Ca + Mg) decreased with increasing P fertilization, regardless of cultivars. Across the P levels, the high-Mg cultivars always showed a K/(Ca + Mg) value lower than 2.2, a safer value for grass tetany in ruminants. Irrespective of grass species, increasing P level reduced the K/(Ca + Mg) and the value became lowest at 5 mM P level. The highest relative range for shoot Mg content was obtained in 5 mM P level for Italian ryegrass (37.6%), tall fescue (30.1%), and orchardgrass (47.9%). Our results indicate the effectiveness of using 5 mM P level for screening high-Mg cool-season grass seedlings. [ABSTRACT FROM AUTHOR]

Hypomagnesaemia (grass tetany) is a metabolic disorder of ruminants due to a reduced dietary intake of magnesium (primary deficiency), incorrect digestibility or associated metabolic factors reducing Mg intake (secondary deficiency). Grass tetany is a production disease responsible for important economic losses in beef herds from Argentina. Several factors influence the development of grass tetany in cattle, including physiological status, weather, soil and forage. This research described a retrospective analysis over the past 20 years, revising the cases of beef cattle clinical hypomagnesaemia registered at the Veterinary Diagnostic Service in INTA Balcarce, Argentina. [ABSTRACT FROM AUTHOR]

Grass tetany is a metabolic disorder in cattle and sheep due to low magnesium deficiency in the blood. The main cause of this disorder is the imbalance between the nutrient concentrations of the grasses grazing on the grassland. Therefore, it has become a necessity to know the macro nutrient concentration of grasses growing naturally in grasslands and their ratio to each other. In order to prevent this disease that threatens animal health, grass tetany risk situations in grasslands should be determined and appropriate fertilization programs specific to the region should be developed accordingly. In this article, the causes of grass tetany were evaluated by considering plant-soil-animal interactions, and grass tetany risk status of grasslands in our country was compared in line with previous studies. [ABSTRACT FROM AUTHOR]

Background: A 61-year-old male patient presented with cerebellar syndrome, which had progressively worsened for 10 days, followed by a tonic-clonic seizure. Phenomenology Shown: Blood analysis showed severe hypomagnesemia and a brain MRI showed T2 hyperintensity in the cerebellar hemispheres (Figure 1). Therefore, the final diagnosis was cerebellar syndrome and epileptic seizures secondary to severe hypomagnesemia. Educational Value: In cases of subacute onset of ataxia, the possibility of ataxia secondary to hypomagnesemia should be considered, as it can be diagnosed with a basic blood test and there are potentially life-threatening outcomes in the absence of treatment, with a reversible course following early supplementation. [ABSTRACT FROM AUTHOR]

The aim of the present study was to measure the apparent absorption of magnesium (Mg) originating from Mg-butyrate. Six mid-lactation Holstein Friesian dairy cows were used with dietary treatments arranged in a cross-over design. Two different diets were fed during the experiment, consisting of a low Mg diet without Mg-butyrate (L -Mg, 3.1 g Mg/kg dry matter) or a high Mg diet with Mg-butyrate (H-Mg, 3.9 g Mg/kg dry matter). Cows offered the L -Mg diet ingested 54.7 g Mg/day while the cows fed the H-Mg diets ingested 66.3 g Mg/day (P < 0.001). The fecal excretion of Mg, however, was similar between the two experimental diets (P = 0.174). Consequently, apparent Mg absorption was found to be 7.9 % units greater (P = 0.038) when the cows were fed the diet supplemented with Mg-butyrate. The greater Mg absorption after feeding the H-Mg diet was, however, not reflected by a greater urinary Mg concentration (P = 0.228). The fractional Mg absorption from Mg-butyrate was calculated to be 71.6 %, which indicates that Mg from Mg-butyrate is readily available for absorption. In conclusion, Mg-butyrate is an attractive alternative to supplement dairy rations with Mg. • An adequate supply of magnesium is important to prevent milk fever and grass tetany in dairy cows. • Currently, magnesium oxide (MgO) is widely used to supplement dairy cows with magnesium. • In dry cow nutrition, magnesium butyrate can be considered as an alternative source of supplemental magnesium. • Magnesium butyrate is an attractive alternative magnesium source to supplement dairy rations with magnesium. [ABSTRACT FROM AUTHOR]

Pasture yield in dairy grazing systems is critical to supplying sufficient feed for milking cows and maintaining productivity. In the Australian dairy industry, ryegrass and clover are common grasses used in grazed pastures. Dairy shed effluent (DSE), the wastewater produced from washing down the dairy holding yards during and after milking, is generally managed through application to pasture as a fertilizer substitute/supplement following partial treatment in stabilization ponds. The aim of this study is to assess the benefits of applying sludge and supernatant collected from two-stage DSE pond systems to ryegrass pasture. A pot experiment was conducted which involved applying pond sludges and supernatant to soil seeded with ryegrass. The application rates of the pond by-products were set according to their labile (plant available) phosphorus content. Ryegrass yield and leachate generated from each of the pots were recorded, and samples were collected for analysis of nutrients and other parameters. The ryegrass grown in soil treated with pond sludge and supernatant yielded greater dry matter (DM) with higher nutrient content than untreated control pots. In addition, pots treated with pond sludge exhibited lower rates of phosphorus leaching from the soil compared with pots treated with supernatant. Thus, pond sludge retained more plant available phosphorus in soil than both the control and pond supernatant treatment. The potassium to calcium/magnesium ratios in the ryegrass in the pots treated with pond sludge and supernatant were below the recommended upper limit for grazing. Therefore, the application of pond sludges on the dairy paddocks was found to be superior to applying supernatant in terms of utilization and conservation of phosphorus within the dairy farm and presents low risks of groundwater pollution and grass tetany. [ABSTRACT FROM AUTHOR]

This presentation will highlight historic discoveries in mineral metabolism in ruminants. At least 15 minerals can be classified as essential based on their involvement in one or more metabolic functions in mammals. Deficiencies of all essential minerals have occurred naturally or have been induced experimentally in ruminants. Cobalt was shown to be essential for ruminants in 1935 based on its ability to correct naturally occurring deficiency signs in Australia. This discovery occurred 13 years before cobalt was shown to a component of vitamin B12. Low serum magnesium concentrations also were associated with grass tetany in cattle before magnesium was found to be essential for the rat in 1931. The value of supplemental salt for cattle was demonstrated in the 1800's and a salt deficiency was experimentally induced in dairy cows in 1905. Over 50 years later sodium was identified as the mineral primarily responsible for salt deficiency. Naturally occurring deficiencies of phosphorus and copper were observed in grazing ruminants shortly after they were reported to be essential for rats. Copper toxicosis also became recognized as a practical problem, especially in some breeds of sheep. Selenium was shown to prevent white muscle disease in 1958. Because of its known toxicity and lack of a specific metabolic function, it was not until 1979 that Food and Drug Administration approved the addition of 0.1 mg Se/kg DM (later increased to 0.3 mg/kg) from inorganic sources to ruminant diets. This approval occurred after the identification of glutathione peroxidase as a selenium metalloenzyme in 1972. In 2009, the Food and Drug Administration approved the use of chromium propionate as a source of supplemental chromium for cattle at levels up to 0.5 mg Cr/kg DM. The approval of chromium propionate was based on its safety and ability to enhance insulin sensitivity in cattle. [ABSTRACT FROM AUTHOR]