Mob grazing
At last we have the answer to demands for increased forage production, higher stocking rates, improved animal health, minimizing soil erosion and increased soil organic matter. Reversing climate change, feeding the 9 billion, reduced flooding and profitable business all wrapped in one! Or do we?
Alan Savory, initially in East Africa, developed the technique of “Mob Grazing” through years of practice and he subsequently wrapped it up in his concept of “Holistic Management”. A passionate advocate and in turns an inspiring and intensely irritating speaker, Alan Savory has travelled the world prostletising and gathering devotees to a system which entails grazing pastures with ruminants (usually cattle) using a radically different grazing strategy. Essentially it entails dense stocking on long forage for short periods of time and with long rest periods between grazings – of between 60 and 100 days. Mob grazers typically move cattle to new, small paddocks once or twice a day, in some cases more frequently. With high stocking levels on long pastures, for short periods of time, there is much selective grazing, trampling of forage and high grass residue left after grazing.
Claims that certain practices are a panacea, a universal solution, that can be applied to all environments, in all parts of the world, cause doubt in my mind; there are rarely universal practices even if there might be some universal principles to apply to agriculture. What bothers me particularly is the categoric claim that Mob Stocking will be universally more profitable, a claim made with no understanding of local farm conditions or economics. Such ill-informed claims are dangerous.
I have, therefore done a little investigation, met Alan Savory at a farm workshop in England, discussed with colleagues and visited farms practicing some of his techniques in Kenya and elsewhere. I find that there is as much forthright criticism as there is support for Mob Grazing.
Elements of Mob Grazing are similar to some widely used organic farming practices such as diverse swards including many species of herbs, grasses and legumes; other practices such as prolonged grazing intervals are also used successfully by those with extended grazing regimes who ensure winter cover and spring grass by shutting up fields in early autumn and by those on drier ground operating “foggage” systems, feeding standing grass over winter and of course by those using paddock grazing, moving cattle every one to two days. The latter is now standard practice amongst dairy farmers in the UK. The key differences are that Mob Stocking advocates routinely leaving very long rest periods, even during the spring and summer, grazing swards at greater height and leaving high residues of trampled grass.
The arguments made in favour of the system are that long grazing intervals will result in greater root biomass, that cattle will selectively graze, by picking the higher nutrient value parts of the plant, that by trampling the high plant residue back into the ground the soil carbon levels will be increased, resulting in increased water holding capacity, improved soil structure and overall forage yield and ultimately higher stocking rates with healthier animals in the long term.
Mob Grazing was developed to address problems of over grazing, deterioration of natural pastures, soil erosion and water stress in East Africa range lands and subsequently applied elsewhere in Africa and North and South America. Even if it is appropriate to dealing with these problems in those regions, is the system suitable for cool temperate maritime climates of the UK and does it deliver the claimed benefits?
Enthusiasts include Tom Chapman, see his Nuffield Scholarship report: Mob grazing cattle, the perfect arable break?
His study showed many of the benefits of organic farming – ley/arable rotations, and diverse swards including legumes, but it did not convince me that the claims for Mob Grazing of increasing stock carrying capacity by three times would necessarily be achieved in the UK.
On the other hand a 14-year study using satellite data across South Africa to compare grazing practices, while removing the dominant influence of rainfall/grass growth, found that the higher stocking rate of intensive mob stocking systems resulted in a consistent reduction in above-ground biomass when compared to non-selective grazing more typical of standard grazing systems.
While there is certainly some evidence that high post-grazing forage residue results in higher soil carbon https://members.niab.com/sites/all/modules/civicrm/extern/url.php?u=3100&qid=347339 what is the cost in terms of stocking rates and animal performance?
Mob Grazing is completely contrary to current thinking on optimum grassland management, particularly that for dairy cattle, which involves careful control of sward height at the start and end of grazing and operating a strict grazing rotation typically of 20 to 28 days, depending on growth rates, sward height and maturity. Such an approach is based on the understanding that after the grass plant has produced 3 leaves there is leaf senescence as subsequent leaves are produced. So optimum animal performance is achieved by a 20- 28 day rotation and a start height for grazing of 8 - 10 cms. and a residual height of 4cms. Reference
http://www.dairyco.org.uk/technical-information/grassland-management/pasture-walking/#.U1jbhzlkBUQ . This is certainly true of ryegrass and timothy, the predominant grass species used in the UK and observation will tell you that it is probably also true of white clover which, while holding its quality a little longer than grass species also deteriorates after 30 or 35 days, when senescence sets in.
There is some evidence to support our current shorter rotation and tight grazing management approach from the Agri Food Biosciences Institute at Hillsborough. Their work shows that if the sward at the commencement of grazing is around 8 -10 cms. (3000 kg DM/ha.), then the herbage will be higher in protein and energy e.g. 11.7 ME and that the higher energy also results in higher herbage intakes. The Institute found that excessively high pre grazing cover results in loss of 5 litres/cow/day due both to lower forage quality and lower quantity over the whole grazing period.
Current practices for beef cattle and sheep are based on similar principles, although grazing periods are frequently longer than the optimum one to two days due to the excessive fencing costs involved with paddock grazing for the relatively less profitable beef and sheep.
The principle remains the same for dairy, beef and sheep; long swards are lower in energy and protein and yield less over the year and high residual biomass of grazed swards results in “waste” and poor utilisation of the total herbage grown, slower recovery, poorer quality regrowth and lower stocking rates and animal production.
There may be advantages in increased root development from longer grazing intervals, and there is some evidence to that effect, with benefits to carbon accumulation and drought resistance. One way of exploiting that is by occasional longer rest periods and integrating silage/hay conservation and its long “rest” period with the grazed area.
It would seem that Mob Grazing with its long rest periods, grazing swards at greater height and leaving high residues of trampled grass may well increase carbon sequestration and possibly drought resistance. The main problem with Mob Grazing is that there is no evidence on how stocking rates and animal production compares with more intensive grazing; from what we know about forage in the UK it is likely to be significantly lower. A very real practical problem with Mob Grazing is that it limits the opportunity for topping for weed control; given that many permanent pastures and leys have varying levels of docks, creeping and spear thistles if you cannot top these at the optimum time then levels will increase though seeding and root spread.
We can of course agree that ruminants are the best means of producing food on both permanent and rotational grasslands and that, grazed by ruminants, they actually contribute to better soil structure and water retention and may well increase carbon sequestration and mitigate climate change rather than cause it, as some would argue.
Based on current evidence Mob Stocking cannot be advocated on commercial grounds for farms in the UK, indeed it runs counter to the experience of decades of grassland management which has shown that rotational grazing provides the optimum grassland productivity and livestock performance with its appropriate grazing intervals based on time of year, sward species and livestock type, short grazing periods of 12 – 24 hours and carefully managed pre and post grazing heights.
Mark Measures, mark@organicadvice.org.uk