How to reduce the risk for grass staggers in cattle?

Grass staggers in cattle is a metabolic disorder caused by a shortage of magnesium in the cattle diet. It is also known as hypomagnesaemia or grass tetany. When turned out to fresh grass, cattle can also have problems with diarrhoea, as well a depression in milk butterfat percentage. This can be associated with a suboptimal balance of fatty acids, leading to rumen acidosis.

The question is “How to optimise dietary magnesium supply, sustain a healthy rumen pH, reduce the risk for grass staggers and maximize milk yield?”

Schonewille (2013) published an overview regarding magnesium requirements in dairy cow nutrition. The first conclusion is that the manure used to fertilise the soil may increase the risk on grass staggers, because it increases the levels of potassium (K) in grass. A high dietary potassium intake in ruminants inhibits magnesium absorption. Secondly, the source of magnesium is of crucial importance. The bioavailability to deliver soluble magnesium to ruminants varies tremendously. Schonewille et al. (2008) show in the Journal of Dairy Science that the average absorption of magnesium in dairy cows is on average 26.2%.

Cow signals of grass staggers:

  • reduced milk yield and milk butterfat
  • poor appetite, reduced intakes
  • diarrhoea
  • restless & nervous, e.g. hyperexcitability, ears pricked, eyes alert
  • stressed, e.g. sensitive to noise, nostrils flaring, head held high, raised heart rate
  • staggering & stiff movement, like walking on stilts
  • aggressive behaviour

Dietary factors reducing magnesium digestibility in cattle:

  • excessive sodium (Na) intake
  • high potassium (K) levels from liberal use of fertilisers
  • grazing from lush pastures increases the risk for rumen acidosis
  • poor solubility magnesium source at physiological rumen pH

Grass staggers & magnesium absorption

Magnesium is a major intracellular cation (positive charge) involved in metabolic pathways. It is also vital to nerve and muscle function as well as bone formation. Most magnesium is found in bone, but this is not a readily available source as bone turnover is controlled by calcium rather than magnesium homeostasis. Blood magnesium concentration should be 0.75 – 1.0 mmol/litre and is maintained by absorption from the diet rather than from body reserves.

The publication of Schonewille (2013) shows that the adult ruminant absorbs magnesium from the rumen and reticulum, rather than the small intestine as in monogastrics. Magnesium absorption is dependent on the concentration of soluble magnesium in rumen fluid (see figure). There is a sodium dependant active transport system for magnesium absorption across the rumen wall, as well as passive absorption down the concentration gradient. But, a surplus of potassium in the rumen will decrease magnesium absorption.

Weiss (2004) concluded that lactating dairy cows have to consume an additional 18 g of magnesium per day for every 1 percentage unit increase in dietary potassium above 1%. This is to maintain the same intake of digestible magnesium as that consumed when fed a diet with 1% potassium. Hence, high potassium levels may cause grass staggers. Increasing sodium and/or potassium will cause a decrease in magnesium absorption from the gastro-intestinal tract. As a result, magnesium concentrations in the blood of cattle drops.

In summary: surplus potassium in adult ruminant diets must be corrected with a magnesium source being soluble at physiological rumen pH.

Model of Magnesium absorption across the rumen epithelium

Magnesium absorption across the rumen epithelium (source: Schonewille 2013)

Acid Buf: rumen soluble magnesium to reduce the risk for grass staggers

Magnesium oxide (MgO) is commonly used to prevent magnesium deficiency, but the solubility of MgO varies greatly in practice. In Europe, levels of 20 – 30 g/head/day MgO are included in mineral supplements to lactating dairy cows to supply 10 – 15 g magnesium. However, Schonewille et al. (2008) demonstrated that over a range of studies that the average absorption of magnesium in dairy cows is 26.2%.

The magnesium requirement for a lactating animal has been calculated by the NRC 2001 as follows;

  1. Endogenous faecal losses – 3 mg per 100kg body weight
  2. Growth – 0.45 g per kg body weight
  3. Foetal requirements – 0.33 g per day
  4. Colostrum – 0.4 g per kg
  5. Milk – 0.15 g per kg

So, a mature, pregnant 600 kg cow producing 40 litres milk requires at least 8.2 g available magnesium per day.  From this work, the NRC 2001 suggested a magnesium supply of 0.20 – 0.25% of the dry matter on the basis of 16.2% magnesium availability from feed ingredients. More recent data suggests an improvement in milk yield can be achieved by cows by increasing magnesium levels up to 0.28 – 0.35% of the dry matter, especially during the summer months.

Question is: “Do cattle need more MgO or a better rumen bioavailable source of magnesium?”

Acid Buf is a 100% natural animal feed ingredient. It meets the nutrient requirements for cattle nutrition. The basis is a marine mineral complex with 74 bioavailable minerals, including magnesium.

The average rumen retention time of a diet is around 9 hours. The Finnish research institute Alimetrics compared the rumen solubility of various commercial MgO sources to the efficacy of Acid Buf. Set-up was in a rumen simulated model.

After 4 hours, magnesium solubility in Acid Buf was 58% and close to 100% after 9 hours. Other MgO sources were far less soluble. Acid Buf showed to be minimum four times more effective as compared to conventional MgO sources. These results confirm in vivo trial data produced by Cruywagen (2010) in dairy cows. Results and further details of this work are available upon request.

Conclusion: Acid Buf provides rumen soluble magnesium and will save space in the diet to reduce the risk for grass staggers in cattle.

Video: magnesium solubility Acid Buf vs. MgO

Acid Buf reduces the risk for grass staggers in cattle

Irish research by O’Grady et al. (2008) has shown that the rumen pH can drop below 5.2 when cows are grazing. McBride (2007) has associated rumen acidosis with an increase in trans fatty acid production in the rumen and a reduction in milk butterfat percentage as a result.

A summer grazing experiment by the Scottish Agricultural College (2011) compared 60 g/head/day MgO against Acid Buf. Two groups of Holstein Friesian cows in early lactation were grazed as one group. The cattle trial ran over a six week period. Results showed that Acid Buf significantly increased milk butterfat yield by 8% and milk protein by 7%. Overall, Acid Buf increased milk yield by 1 kg/head/day to a level of 38.8 kg. These results has also been confirmed in two trails at University College Dublin (UCD). Acid Buf demonstrated a linear significant increase in milk butterfat and milk yield.

Results from the University of Stellenbosch (2004) in dairy cows has shown that 80 – 100 gram Acid Buf per cow per day improved rumen fermentation significantly through optimising the ratio of propionate to acetate. With Acid Buf, dairy cows increased milk production by 5 kg, up to a milk yield of 45 kg. For further details, read the article “How to reduce the risk for rumen acidosis?”.

Cruywagen et al. (2015) published in the Journal of Dairy Science the effect of Acid Buf in relation to rumen pH and milk yield. The results confirm that Acid Buf provided relief in the event of rumen acidosis. Hence, milk yield performance was increased and especially milk butterfat. Also, Acid Buf improved feed efficiency. More milk was obtained per kilo dry matter intake. For further details, read the article “How to increase milk butterfat?”

Conclusion: Acid Buf reduces the risk for grass staggers and will maximize milk production from grazed grass.

Video: Acid Buf enahnces long term optimum pH in the rumen (Cruywagen et al. 2015)

Conclusions

When dairy cattle are turned out on spring pasture, the risk for grass staggers increases and milk butterfat gets under pressure. Cause could be the liberal use of soil fertilizer. This increases the level of potassium. Hence, the uptake of magnesium is surpressed.

When optimizing the cattle diet, a magnesium source that is soluble at the physiological rumen pH of 5.5 to 7.0 is needed. Acid Buf is a marine mineral complex providing 74 bioavailable minerals to the rumen, including magnesium. Hence, Acid Buf reduces the risk for grass staggers. At the same time, Acid Buf enhances an optimum rumen pH to maximize milk output and drive milk butterfat from lush grass.

Acid Buf offers nutritional solutions for:

  • a bioavailable magnesium for the rumen
  • replacement of MgO saving space in the diet
  • reducing the risk for grass staggers
  • long term pH optimization in the rumen
  • driving milk yield and milk butterfat from lush grass

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