Q: Does lime pose any danger to my animals? A: Lime has real benefits for improving animal health, but caution is needed when animals come in contact with pastures after liming.

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This article outlines how to avoid possible animal health problems.

1. Lime is not normally toxic on its own. Animals can be exposed to lime most of the time without any adverse effects.
2. The area where risk exists relates to cows in the pre-calving period, and to the potential for physical damage caused by direct intake of coarse lime particles.
   1. Pre-calving. To minimise the risk of calcium deficiency (milk-fever) after or at calving, the cow must prepare herself to mobilise large amounts of calcium. The calcium will come from: increased absorption from the gut, re-absorption from the kidneys, and the bones. To help her prepare, we need to avoid unnecessary intakes of calcium and alkaline substances such as lime, and keep the DCAD (Dietary Cation Anion Deficit) as low as possible. We can reduce DCAD by avoiding high potassium and/or sodium diets (such as pasture recently topdressed with potassium or dairy shed effluent). Three ways liming could increase the occurrence of milk-fever are through:
      1. Direct intake - of lime particles remaining on pastures where they can be eaten by stock. The alkaline lime may raise the DCAD level in the feed reducing the ability of the cow to mobilise calcium around calving.
      2. Ingestion of soil and lime - This can occur if springer cows are grazed too hard. Ingestion of soil contaminated with lime could raise the DCAD of the diet and increase blood calcium levels at the wrong time.
      3. Reduced pasture magnesium content - Is caused by the release of calcium into the soil which can reduce plant magnesium uptake. As magnesium aids calcium absorption from the gut this reduction could affect calcium absorption and increase the incidence of milk fever.
   2. Post calving. Immediately after calving, the cow needs an increased calcium intake. Risks associated with liming and the post-calving cow relate to the effects a recent lime application may have on plant nutrient availability in the soil, and the effect lime contamination may have on pasture palatability. Generally pasture dusting with high quality lime flour is a recommended method of supplementary calcium to lactating cows.
      1. Trace element availability - Soon after lime application, the pH level in the upper few millimetres of soil can be raised to a level high enough to reduce the availability of trace elements such as copper. Low copper levels in the diet interfere with milk production and reproduction, so copper deficient cows may not milk well and may be slow to come into season.
      2. Grass staggers - High concentrations of calcium in the upper topsoil straight after liming can reduce plant magnesium levels if the soil temperature is below 15°C. This can lead to an increased incidence of magnesium deficiency - grass staggers or hypomagnasaemia - in the cows. While severe magnesium deficiency is fatal, sub-clinical deficiency can reduce milk production by up to 20% and cause irritable behaviour in the herd.
      3. Pasture contamination - Pasture spread with agricultural lime may be unpalatable, reducing intakes and possibly inducing ketosis and mineral deficiencies, especially of copper and magnesium.
   3. Physical Damage - Where the lime (or any other fertiliser) has a large particle size, ingestion of large abrasive hard pieces may damage the rumen wall, resulting in reduced absorption of volatile fatty acids, which means that there will be less energy available to the cow. This could lead to ketosis. The damage could also cause ulcers, which may lead to a fatal abdominal haemorrhage. Note:High quality calcium carbonate, with very small particle size, is extremely safe to use as a calcium source in animals requiring additional calcium, except immediately pre-calving. (See the pre-calving notes above).
3. Recommendations
   1. Timing of capital liming - applications of over 500kg lime/ha.
      1. Avoid applying lime to pastures which are likely to be grazed by springer cows before the lime has been washed off the pasture and become incorporated into the soil.
      2. Do not force springer cows to graze pasture that has been recently limed (but where the lime is washed off into the soil) to residual heights of less than 7.5cm.
      3. To achieve this, do not apply lime less than 8 weeks pre-calving.
         1. For spring-calving herds, this usually means that lime should not be applied after mid May.
         2. For autumn calving herds, this usually means that lime should not be applied after mid February (for a mid-April calving).
         3. If lime has to be applied late, leave sufficient paddocks unlimed to allow the springer cows access to unlimed pasture.
         4. Where lime has been applied within six months of calving, check:
            1. Animal trace element status at calving and supplement with any trace elements that the results indicate are needed. Seek qualified veterinary advice as to the best methods of supplementation to use.
            2. Pasture magnesium levels in the pasture being fed to both springer cows and newly-calved cows. If magnesium levels are low give a suitable magnesium supplement. (Higher soil temperatures in autumn mean that magnesium deficiency is not likely to be a problem for autumn-calving herds, but if the soil cools down early be prepared to administer a magnesium supplement).
   2. Timing of maintenance liming - application of less than 500kg lime/ha.
      1. As maintenance liming is designed to keep soil pH where it is, rather than to cause large changes, the potential effects on animal health are unlikely to be significant. Follow the same recommendations as apply to normal fertiliser applications:
         1. Do not apply fertiliser to paddocks being grazed by animals.
         2. Do not graze fertilised paddocks until sufficient rain has fallen to wash all traces of lime and fertiliser off the leaves.