Livestock Health and Soil Nutrition Tiffany Bennett Livestock Consultant Brian Hughes Senior Soil and Land Management Consultant NRM Pathways to Productivity Expo October 11 th 2012 Bordertown Civic Centre Mineral disorders in livestock 15 + essential mineral Major Ca, Cl, P, Mg, K, Na, S Trace Co, Cu, Fe, I, Mn, Se, Zn, Mo Ultra traces 15? As, B, Cr, Ni, Si, V, Key Issues SE Mg, Co, Cu, Se Soil pH and nutrient availability TOO MUCH: aluminium manganese Iron NOT ENOUGH: magnesium calcium potassium phosphorous molybdenum TOO MUCH: sodium Boron NOT ENOUGH: iron zinc manganese copper phosphorous Page 4 Introduction Complex interactions in the soil have important influences on the availability of an element in pasture. E.g excess of any element in the soil will reduce the uptake of others Address some common soil/animal interactions relevant to the South East of SA -Copper -Cobalt/B12 -Selenium -Grass Tetany -Phlaris Staggers Page 5 Grass Tetany (Hypomagnesia) Caused by low levels of blood magnesium. Generally affects stock in late autumn, winter and spring Can cause significant production losses even with no signs of illness Often occurs during lactation or late pregnancy due to increased body demands May occur in soils with adequate magnesium due to poor root development. Page 6 Grass Tetany (Hypomagnesia) Signs include -in coordination, restlessness, over alert appearance, excitable, aggressive, convulsions. -May be induced when animal are disturbed with a high mortality in affected animals. Grasses or cereal crops tend to have low magnesium and a high content of organic acids that tie up magnesium in the rumen. Thin animals or fat animals that are losing condition can be at high risk Page 7 Grass Tetany (Hypomagnesia) High nitrogen and/or potash fertilisation reduce the availability of magnesium from the pasture. Avoid grazing soon after fertilisation application. Cold, wet, windy weather intensify the problem due to short periods of fasting particularly in paddocks lacking shelter. Provision of hay during periods of lush, rapid pasture growth can help reduce the incidence. If magnesium is fed over a long period of time it is important to add dicalcium phosphate as magnesium can reduce phosphorus absorption. Page 8 Magnesium deficency Interactions High dietary levels of potassium and nitrogen will inhibit magnesium absorption from the rumen Diets low in sodium increase magnesium requirements by indirectly raising potassium concentrations in the rumen Increased dietary levels of calcium increase dietary magnesium requirements Predicting Grass Tetany Risk from Soil Tests K/ (Ca+Mg) > ie. Exchangeable Potassium divided by Exchangeable Calcium plus Exchangeable Magnesium use cmol(+)/kg figures Risk factor only on these soils as actual incidence based on many other factors Soil types at risk identified in the MLR/SE- either soils with very high K or fairly acid and low Ca/Mg Predicting Grass Tetany Risk from Plant Tests K/ (Ca+Mg) > 2.2 use % figures Risk factor only as actual incidence based on many other factors high N Will find legumes in the same paddock have a ratio approx of perennial grasses Annual grasses variable but similar in July samplings SE Study by Lewis and Sparrow in 1991 Looked at 3 soil types across 22 sites Solodised Solonetz- sandy loam over clay Rendzina- black clay over limestone Siliceous Sand- deep light sand Surveyed tetany deaths over previous 5 years SE Study by Lewis and Sparrow in 1991 Mean Results Soil TypeSiliceous SandSL over ClayRendzinaAt risk levels July Soil Indicator > July Legume Indicator > 2.2 July Perennial Grass Indicator >2.2 Death over last 5 years nil9 of 12 sitesnil Grass Tetany Can we improve the soil and plant levels and reduce risk? Study at Wistow Acid SCL over clay History of grass tetany Soil level 0.23 (very high aim