Watch minerals at grazing to maximise performance

4 February 2016

Grass grown on fields affected by flooding and waterlogging will require careful mineral supplementation to avoid problems with deficiencies or imbalances.

“Following the incredibly wet winter, farmers in many parts of the country are struggling to get to grips with the financial cost of flooding, especially as getting animals out to grazing early will be essential to help reduce production costs,” comments Rosie Miller, Ruminant Nutritionist with Trouw Nutrition GB. 

“While problems such as increased poaching risks are highly visible, there is a potentially more significant, but hidden, problem. Flooding and waterlogging can have a significant impact on the mineral content and balance of pasture.

“Grazed grass is at best a variable source of minerals, with levels directly dependent on the mineral content of soils. Typically, some minerals will be in short supply giving rise to potential deficiencies while some can be present at high levels and be antagonistic to other minerals.”

She says while farmers are aware of the problem of staggers associated with magnesium deficiency, there are other less well known mineral-related problems. Fresh grass can be high in iron and molybdenum which actively block copper uptake, making it less available to the cow. Copper deficiency can lead to poor conception rates so diets may need supplementation.”

She explains there are three specific reasons why flooding and waterlogging can further compromise mineral supply. The first is that in affected fields the levels of mineral leaching can be higher, resulting in poorer soil mineralisation. At the same time, damage to the soil structure will reduce the ability of the roots to absorb nutrients from the soil. Combined these may lead to lower forage mineral levels.

“In addition, farms may suffer the effects of increased level of heavy metals which are antagonists to more favourable metals due to the soiling of grassland caused by flooding and soil run off. Many fresh grass samples from pastures which were flooded in previous years show elevated levels of elements such as iron, molybdenum and aluminium all of which can cause problems.”

Ms Miller says a failure to supply the correct level and balance of minerals at grazing will result in disappointing performance from cows at grass. In addition to reduced milk yields, health and particularly fertility can all be affected.

“At a time when farmers are hoping for a boost to margins, mineral related issues could lead to the reverse being the case. Getting the mineral balance right across the entire ration will be essential if cows are to perform as well as possible, especially as reductions in concentrate feeding put more emphasis on the mineral supply from forages.”

“While cutting back on buffer feeds and parlour concentrates will reduce costs, this also reduces the opportunities to provide effective mineral supplementation. A short term gain in reduced costs will soon be wiped out if fertility suffers or conditions such as mastitis and lameness, both of which can be related to mineral deficiencies, increase.”

Ms Miller says where pastures suffered from flooding, major mineral deficiencies could be a problem, singling out calcium and phosphorus as particular concerns. Calcium deficiency during lactation reduces body reserves which could lead to increased incidence of milk fever while low phosphorus can impair fertility. She warns that aluminium on contaminated fields can further reduce phosphorus availability in cows.

Trace element deficiencies can also be a major problem. Zinc is required for foot and udder health, and low levels could result in more problems with lameness at a time when cows are expected to walk further, and with raised cell counts. Iodine, selenium and copper can also all be low in grazing produced from flooded pasture, leading to weak calves, increased retained cleansings and cell counts while raised molybdenum, sulphur or iron levels can reduce copper availability leading to generally poorer performance and lower conception rates.

Ms Miller believes if farmers take prompt action it will be possible to identify any problems and take action to prevent performance, health and margins being affected.

She advises farmers to having grazed grass analysed for mineral content as soon as possible, explaining that a mineral assay is the only way to understand the mineral levels in grazing and the precise risks stock may be exposed to. The aim must be to understand the specific problem and then to target supplementation from the most cost-effective solution.

“Using the analysis it will be possible to supplement diets precisely to supply the right minerals in the most appropriate form, addressing specific problems that exist.

“Supplementation could be from concentrates, free access minerals, water supplementation, minerals added to buffer feeds or specialist products such as boluses. The crucial thing is to take account of all mineral sources when assessing diets. Furthermore, it is essential to ensure legal maximum levels are not being exceeded.

“We would urge farmers to avoid blanket increases in mineral levels as this can result in feeding minerals above the required level which can just push up costs and can make issues with antagonism worse. The most cost-effective approach will be accurate supplementation based on the analysis of forage mineral levels and a mineral assessment of the whole diet.”

For further information, contact the Trouw Nutrition GB Ruminant Team.