The Mineral Specialists

Transcription

1 % DM The Mineral Specialists HEADLINES: G R A S S S I L A G E M I N E R A L P R O F I L E PHOSPHORUS UP BY 16% DUE TO SLOWER GRASS GROWTH POTASSIUM REDUCED BY 10% AND CATION ANION BALANCE BY 19% SOIL CONTAMINATION DOWN BY 25% BUT IRON ONLY MARGINALLY LOWER MOLYBDENUM HIGHEST LEVEL FOR 3 YEARS RELATIVE COPPER ANTAGONISM HIGHER DUE TO INCREASED MOLYBDENUM LEVELS RISK FACTORS: LOWER POTASSIUM & DCAB HYPOCALCAEMIA RISK STILL PRESENT BUT SLIGHTLY LOWER THAN 2014 HIGHER MOLYBDENUM REDUCED COPPER AVAILABILITY, INCREASED MOLYBDENUM TOXICITY, SUPPRESSED FERTILITY IRON LEVELS REMAIN HIGH WITH RISK OF OXIDATIVE STRESS W e saw very different patterns of weather during the Springs of 2014 and started with mild weather which developed into a warm Spring. Temperatures were 1.3 C above the average and Spring turned out to be the third warmest in the last 100 years! This year s spring weather was characterised by a cooler than average pattern, as highlighted by the 0.8 C lower temperature in May compared to the long term average. Indeed, May was the coldest since However, temperatures in March and April were slightly above average, which encouraged early grass growth, but this was slowed down by a cold May. From May to August temperatures remained below average and coupled with an erratic rainfall pattern (dry April followed by a wet May) grass yields were significantly down compared to Slow and variable herbage growth rates inevitably influence mineral composition and the following changes highlighted in this report are a consequence of this season s poorer growing conditions compared with MACRO MINERALS Phosphorus Phosphorus % maize/whole crop silage. Because of the significance of Phosphorus as a key nutrient for energy utilisation, it is important to check grass silage levels to ensure supplementation is both appropriate to and well balanced in the total diet. Potassium & DCAB The trend of increasing Potassium and Cation Anion Balance (CAB) over the past few years has been arrested in 2015, as the cooler spring weather reduced vegetative growth and grass yields for silage. Consequently Potassium was 10% lower on Of all the major minerals, Phosphorus is the one most sensitive to soil temperature and grass growth rates. A combination of reasonable growing conditions in March and April stimulated an early flush of grass, which slowed down in May. This pattern is probably the cause of the 16% increase in Phosphorus this season, which is the highest for many years. In terms of the effect on supplementation, the reported higher Phosphorus level is equivalent to 3% P in a typical dairy supplement included in a predominantly grass silage based diet and 2% P for a diet containing similar levels of grass and -10% -19% Page 1

2 G R A S S S I L A G E M I N E R A L P R O F I L E average this season relative to In turn, CAB was reduced by 19% to +375meq/kg DM. While this decline in one of the key risk factors for hypocalcaemia is welcome, it remains relatively high. In most cases the Dietary Cation Anion Balance (DCAB) of the total diet will be calculated within the target range of +200 to +400 meq/dm for a milking cow and the lower value in this season s silage crop will make it slightly easier to achieve a DCAB of less than +200 meq/kg DM for dry cow diets: For close up or Transition diets for average to high yielding herds the challenge is greater to achieve a DCAB of around zero for a partial anionic diet and less than 100 meq/kg DM for a full anionic diet. Failure to achieve these DCAB targets will increase the risk of Hypocalcaemia which includes: Retained cleansings Uterine infections Displaced abomasums Depressed Dry Matter intake Poor milk initiation Ketosis Milk Fever The occurrence of Hypocalcaemia will inevitably depress milk production, fertility and health in the forthcoming lactation. Consequently it is a key action point to analyse grass silage for minerals from which a Cation-Anion Balance can be calculated to be used in balancing pre-calver diets with the purpose of minimising Hypocalcaemia. TRACE ELEMENTS Trace elements are generally lower on average in this season s grass silage compared to 2014, with the exception of Molybdenum. Iron Compared to the very high level of 2014 (456 mg/kg) Iron has slightly fallen by 8% to 419 mg/kg, it must be noted though that the Iron level still remains high, well above 2013 levels, with the associated risks of pressure on Copper and other trace elements another indicator of soil contamination. The disparity between Iron and Soil Contamination, as measured by Titanium, undoubtedly results from higher anaerobic activity in soils, which would solubilise Iron resulting in a higher uptake by grass. The fact that Soil Contamination has not increased at a time of unsettled weather when cutting grass is a welcome development and hopefully indicates more care is being taken to avoid soil pick up at harvest. Published research demonstrated that within silage clamps Iron contributed by soil contamination becomes solubilised which makes it more reactive and oxidative. In this highly active form Iron will readily bind with Copper and Sulphur in the rumen to form insoluble Iron-Copper Sulphides, thereby reducing Copper availability and increasing the dietary requirement. In addition, reactive Iron will increase oxidative stress in cattle to the detriment of health and productivity. To limit damage check forage Iron levels and use the data to estimate total dietary levels. Provide a balanced mineral supplement containing Novus MAAC chelates of Copper, Manganese and Zinc, which are well protected from Iron competitive pressures and absorbed at different gut sites. Molybdenum A striking feature of the 2015 grass silage survey is the 13% increase in Molybdenum. Of all the elements Molybdenum is +13% Iron competes for gut absorption, with Manganese which has shown a drop of 17% in 2015 levels compared to Soil contamination is a primary source of Iron, and while Iron has declined by 8%, Soil Contamination is down 25% which is confirmed by a similar reduction in Aluminium; this being most sensitive to anaerobic soil conditions. In well aerated soils Molybdenum is oxidised which renders it insoluble, thereby making it difficult for plants to absorb through the roots. Once air is excluded from soils by excessive water supply then it rapidly dissolves and becomes extremely available for root absorption. As a result grass Molybdenum levels will vary widely from farm to farm and from season to season dependent largely on rainfall patterns. This year s high rainfall from May to August has clearly much to do with this increased level. Of course other soil factors play a part in determining Molybdenum solubility in the soil, but the most important is air. Molybdenum is well recognised as a Copper antagonist which reduces the availability of this essential element through the formation of Page 2

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4 Forage Year No. of Samples % Difference 2015 v 2014 Calcium % Phosphorus % Magnesium % Potassium % Sodium % Chloride % Sulphur % CAB meq/kg Iron mg/kg Aluminium mg/kg Manganese mg/kg Copper mg/kg Zinc mg/kg Cobalt mg/kg Iodine mg/kg Selenium mg/kg Molybdenum mg/kg Relative Copper Antagonism High High High - Soil Contamination Titanium mg/kg Data covers the period 1st June to 7th September. Results are expressed on a Dry Matter basis. Page 4

5 G R A S S S I L A G E M I N E R A L P R O F I L E insoluble compounds. An increased dietary Copper requirement results. The antagonism from Iron and Molybdenum on Copper availability requires additional Copper in a mineral supplement, to overcome the combined suppression of these antagonists. While recognition of the increased antagonistic challenge to Copper availability in the forthcoming winter season is important, the longer term strategy to reduce both Iron and Molybdenum lies in both soil improvement and practical actions at grass harvesting. Actions based on analytical information are also important to prevent both Copper toxicity and the more prevalent and economically damaging Copper deficiency diseases. SUMMARY The 3 key mineral risk factors to cow health and productivity are Potassium, Iron and Molybdenum. While Potassium and Iron have declined, they remain at levels well in excess of the dietary requirement for ruminant livestock. Coupled with the significant increase in Molybdenum, the probability of involvement in Hypocalcaemia, Infertility and Oxidative Stress remains a real possibility. Only through the regular analysis of grass silage can these risk factors be identified and a balanced mineral supplementation developed. In the longer term, forage mineral risk factors to cow health and productivity can be reduced through soil improvement and adopting an appropriate nutrient management plan for grassland. Having an integrated approach to the mineral nutrition of soils, grass and cows is the answer to improving grass and cow productivity in a sustainable and profitable manner. This review relates only to the mean of the first 400 Grass Silage samples analysed from this year s 1st Cut. The mineral status of silage is extremely variable and the only certain way of establishing the mineral content from an individual farm is by regular analysis. MINERAL ACTION PLAN To ensure cow health, fertility and production is not compromised by unidentified Mineral Risk Factors use: T&J Forage Mineral Analysis Service T&J Mineral Check to formulate nutritionally balanced supplements T&J Soil Action Plan to improve soil fertility, grassland production and forage mineral balance THOMSON & JOSEPH LTD The Mineral Specialists Phone: Fax: enquiries@tandj.co.uk Page 5

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