March 31, 2011

English scientist warns about problems of overfeeding feed supplements

Blanket trace element supplementation as an insurance without proper understanding of actual deficiencies can easily make matters worse, according to Dr Liz Genever from the English Beef and Lamb Executive (Eblex).

The Eblex under the Agricultural Development Advisory Service (ADAS) looked into the use of the most economically important trace elements. The report confirmed that deficiencies of copper, cobalt, selenium and iodine can cause ill thrift and infertility in animals.

Animal stock is more likely to suffer from problems due to supplements, than from actual deficiencies. Eblex beef and sheep scientist Dr Liz Genever said, "As well as being a significant waste of money, blanket trace element supplementation as an insurance without reliable confirmation of actual deficiencies can easily make matters worse by causing detrimental mineral imbalances or interactions. This danger is heightened by the major variations commonly found in the trace element status of grass and forage with soil conditions, sward components, fertiliser use and the growing season; as it is by marked variations in the trace element requirements of different breeds, classes and ages of stock."

She said it is essential that herbage analysis is carefully interpreted because the sample may not be a good representation of what the animal is eating. Soil contamination can lead to wide variations in a single pasture. Dr Genever said that producers should recognise that compounds are generally well-fortified with trace elements and that overfeeding supplements can cause problems such as copper toxicity. "Confirm suspected deficiencies by herbage analysis and independent blood or tissue analysis before supplementing stock with extra trace elements," she said.

She also advised producers to remember that although free access minerals are useful, they tend to be the least effective method of supplementation because intake varies widely between individual animals.

Dr Genever also said it is important to monitor how individual animals respond to any supplementation to find out how effective the supplementation has been.

Eblex is now developing a series of detailed farm case studies using the findings of the ADAS report. The case study booklet will include practical advice on supplementation, and will be available free of charge to levy payers from next month.