We know that the correct minerals and trace elements are essential for good health of sheep, goats and alpacas – but how do we know what to do about this?
Firstly we need soil tests. These are easier than you might think – you should take about 30 samples diagonally across the field, mix in a bucket to get a representative sample of the whole field then put some in a bag to post off for a soil test. Ideally, soil testing should be done every two years, as rain, grazing and hay or silage cutting will all affect the soil balance.
Before bothering about exactly which nutrients are there, it is vital to test the pH of the soil – the acidity or alkalinity of the soil strongly affects the availability of nutrients. Most are available between 5.0 and 6.5 pH, and the ideal is 6.5. Unless the pH is corrected, adding fertilisers or dressings might be expensive.
The chart below illustrates this.
Next, the soil itself must be in good condition: compaction reduces the ability of grass to grow well and of worms to travel through and aerate the soil – compaction will kill and drown them. Compacted soil will smell “off”, musty and have rusty stains in it and in the worst cases will simply be like concrete. There should be around 20 worms for every spade full of earth to indicate good quality. Soil should crumble – grass roots can then travel deeply and densely and absorb the nutrients for your animals to eat. Compaction can be addressed when the ground is dry using a flatlift machine, but not too aggressively.
Picture credit to Wikipedia where there is a great article on earthworms!
If you have poor quality grass, you need to consider whether to re-seed completely or simply add the relevant plants: you can add clover by feeding it to the animals, so that the seeds arrive at ground level already fertilised! White small clover is especially good for sheep and is also good for the soil – as it is not grazed out like some of the other types. Clover may be up to 80% of a seed mix and completely wasted if it dies due to compaction. White clover may manage to take over on good soil and can be slowed down by added nitrogen. You may need expert advice on the correct mix of grass for the land, the location, your purpose and your timescales. Then you should walk the land and compare fields, compare the hay or silage yields and observe what is going on to see what works and what does not.
Fertilisers: the first additive is dung, then the things to be bought in, such as lime and more specialised fertilisers. Remember that not only will the soil only yield its nutrients at the correct pH, but also the combination of elements will affect uptake by the animals.
- Rumen copper for instance is important for sheep, particularly when in lamb, though too much can be toxic, particularly for North Ronaldsay, Blue-faced Leicester and Texels, and to a lesser extent to Zwartbles, Charolais and Suffolk/Lleyn. Medium risk are the rest of breeds, including Cheviot and Scottish Blackface. However, too much molybdenum, sulphur or iron will inhibit uptake of copper, so it may be more important to be the pH right before considering copper.
- Cobalt cannot be stored in the body, so has to be ingested continuously – a drench is therefore not effective, but a bolus will be and will enable vitamin B12 to be produced in the rumen.
- Selenium deficiency impairs fertility, growth, wool quality and immunity
- Iodine is needed for similar benefits to selenium as well as bone growth and again has to be ingested continuously.
So boluses are good because they are specific to each animal – licks, blocks and tubbies are said to be good by some but are not reliably used by every member of the herd or flock. The other option to boluses is adding nutrients to the feed, as most of the animals will compete to eat. However, if your soil is correctly balanced and not compacted, you may save a great deal by just letting the animals eat the grass! And eating the grass, and ingesting the nutrients is the first and best defence in building strong immune systems, adding to disease and parasite resistance.