Trace element supplementation

The study has highlighted the potential benefits of establishing the trace element status of livestock farms. The approach taken here was to assess the trace element content of grazed forage in conjunction with targeted blood and liver sampling in cattle and sheep.

Forage

• Establishing a reliable iodine value for forage proved to be difficult in this study although standard industry techniques gave a broad indication

• On some farms there was significant variation in the trace element content of different fields/areas of the farm eg Case study 7; sampling a good cross section of available grazing and conservation fields can help target supplementation

• On the majority of case study farms overall levels of trace elements tended to be higher in autumn forage samples

• The potential for pasture dressing to raise the trace element content of forage was demonstrated in Case Study 5

Blood and liver samples

Cattle

• None of the cattle blood samples taken had levels of cobalt (Vit B12) or T4 below the reference range

• Around a third of cattle blood samples (affecting six of the farms) had Cu levels below the reference range with twice as many cows as calves affected; liver samples give a more accurate indication of copper deficiency but were only available from cattle on two farms

• 13% of cattle blood samples were below the reference range for selenium although the vast majority were from one farm (Case study 3)

Sheep

• Very few (5%) of sheep blood samples had copper levels below the reference range and these were split fairly evenly between ewes and lambs and spring/autumn; twice as many samples (10%) showed marginally high copper levels

• 12% of sheep blood samples were below the reference range for cobalt (Vit B12) with the vast majority affecting lambs; it was only a problem for one farm in spring and two in the autumn

• Selenium (GSH-Px) levels in the spring were all satisfactory; in the autumn however 36% of samples were below the reference range affecting the breeding ewes on three farms and lambs on two. Liver samples of finished lambs from the two farms showed a marginal deficiency supporting the blood results

• T4 levels were marginally low in around 10% of samples, affecting twice as many ewes as lambs; the vast majority of these were sampled in the autumn with four farms affected

Methods of supplementation

• The farms studied employed a wide range of supplementation methods including free access minerals, trace element boluses, oral drenches and injections

• Over the life of the study two of the farms had either changed or were considering changing their supplementation method:

  • The first was using drenches for sheep and FA minerals for cattle but had changed to boluses this year

  • The second was considering changing from FA mineral blocks to boluses to ensure all cattle receive their requirements

• Following blood sample results from this study four farmers have given or will give additional supplementation:

  • Pre-tupping bolus for breeding ewes (Case study 4)

  • Copper bolus and slow release Se injections for cows and calves (Case study 3)

  • Co, Se and Cu bolus for calves (Case study 5)

  • Copper bolus for cattle at grass (Case study 7)

The Problem:

Many farmers use large amounts of mineral supplements as an insurance against mineral and trace element deficiencies but in many situations these are fed with no sound technical evidence of a problem – the belt and braces approach‘. In order to focus supplements where they are really needed and to improve the efficiency of beef and sheep production farmers should be encouraged to investigate the mineral status of their flock and to supplement only when needed.

Project Aims:

• To understand the best methods to determine if trace element deficiencies exist on farms
• To use four beef and sheep producers in England to act as case studies
• To produce a trace element budget for the case study farms
• To produce a technical booklet that could be converted into a manual

Approach:

To review current recommendations on trace element allowances by looking at the available literature and to make a thorough review of mineral status and supplementation on 6 farms across the country (4 in England and 2 in Wales).  Forage, blood and liver samples will be collected from ewes, lambs, cows, calves and finished cattle.  All supplementation will be recorded, including feeds, so a trace element budget can be produced.  Guidelines will be generated for all the farms involved.

Deliverables:

The case study farms can be used for events to communicate the project findings, and as part of stories in the agricultural press.  The technical report can be used as the basis for a manual on trace elements.

Planned activity:

The report and the case studies are being used to generate a BRP+ booklet, which should be available in May 2011.  We have used the findings at several winter evening meetings, and they will be used throughout the summer of 2011, including at the Uplands Conference on the 30^th of June in Penrith.