In order to simplify the calculations and discussion terms like Kilocalories, Megajoules have been avoided and Carbohydrate and Protein replace Starch Equivalents and Protein Equivalents.
Annex A of the present Rural Stewartship Scheme provides the following table to calculate stocking density. (4.)
|Class of Stock||Livestock Units (per head)|
|Cows (including suckling calves)|
|Other Cattle (6 - 24 months)|
|Other Cattle (24 months and over)|
|Ewes (including suckling lambs)|
|Female Farmed Deer (including suckling calves)|
|Horses or Ponies (6 months and over)|
Standards are laid down in the scheme for Stocking Densities, which cannot be exceeded at any time. These are calculated by the number of Livestock Units divided by the area in Hectares which they occupy. It is clear that this is a very arbitrary table prepared to simplify administration of the scheme. It takes no account of season of year, environmental conditions, or specific breed of animal.
Accepting that the frame of reference for 1 LSU is a suckler cow with calf, and utilising figures published by the Ministry of Agriculture (1.). A 500 Kilograms adult cow like a Welsh Black would require 2.95 Kilos. Carbohydrate plus 0.32 Kilos. Protein per day to maintain body weight in normal conditions. With a calf suckling the cow, to produce only 5 Litres of milk per day for the calf, requires an extra 1.27 Kilos. of Carbohydrate plus 0.28 Kilos. Protein. So even with a relatively small breed:
1 LSU requires 4.22 Kilos. of Carbohydrate plus 0.6 Kilo. of Protein per day.
Larger breeds of cattle would require greater amounts than this. We confine our discussion to the situation in which an Exmoor pony apparently requires the same nutrition as a suckler cow with calf. Tables for equine nutrition (2.) (Recommended daily requirements for maintenance only, i.e. not working but walking about eating grass): -
|Body Weight of Equine||(Kilos.)||Carbohydrate (Kilos.)||Protein (Kilos.)|
Clearly a Shire Stallion requires only 85% of the carbohydrate and 60% of the protein required by a suckler cow. Compared to the suckler cow a grazing Exmoor needs less than 0.45 LSU.
An article in English Nature’s ENACT magazine (3.) states “that in a New Forest context one pony is equivalent to 2.5 cows”. The same article shows little knowledge of the comparative anatomy and physiology of equines and bovines let alone their nutrient requirements and biochemistry of digestion.
Equines are monogastric herbivores. Bovines are ruminants; they regurgitate undigested gastric contents for remastication, that is they chew their cud.
The equine digestive system can be considered as starting with a very efficient system for the prehension and mastication of food. The equine muzzle is sensitive and very mobile. The Hypsodont teeth are long crowned and adapted for a circular grinding motion, which pulverises material thoroughly before swallowing.
After swallowing, the masticated bolus arrives in a simple stomach and small intestine where partial digestion allows absorption of carbohydrate as glucose and proteins as amino acids. The remaining less digestible gut contents then pass to an enlarged caecum and large colon where micro-organisms breakdown the woodier parts of herbage containing complex polysaccharides and lignin. This involves the conversion of cellulose and hemi-celluloses to volatile fatty acids. An extensive small colon then absorbs this source of energy, along with water and other nutrients. Other monogastric herbivores, from rabbits to koala bears, practise corprophagia, ingesting their own faeces, recycling them through their digestive system, in order to absorb nutrients. This is seldom seen in equines, and then usually in foals. If it does occur it is generally an indication of a deficiency in vitamins and minerals rather than energy.
The bovine muzzle is much less sensitive and immobile. The Selenodont dentition is adapted to quickly shearing the more succulent species of grasses, which will be masticated later, the act of rumination. While bovines under about 18months old rely on this shearing action, older animals tend to wrap the tongue around herbage and tear it up.
Ruminant digestive systems are characterised by a complex of stomachs in which food is stored for rumination. In these ‘proventriculi’ there is fermentation by micro-organisms of the fibrous carbohydrates and simple carbohydrates in order to obtain energy. This process produces volatile fatty acids, instead of glucose, that are absorbed by the small intestine. This mechanism results in the production of a considerable amount of the gas methane, especially if the animal ingests a large amount of the more simple carbohydrates like starch, as happens on a high grain ration. This methane is lost by eructation to the atmosphere and represents a net loss of energy from the ruminant diet, up to 10% loss, that does not occur in the equine. Ruminants can utilise low quality feeds well but are less efficient than monogastric herbivores in making use of good quality forage. Indeed food conversion can be only half that of a monogastric animal.
The appetite of the animal is another consideration; it is usually defined as Dry Matter ingested expressed as a percentage of Body Weight. In the young bovine it is about 2.5%, in the larger fully-grown animal it could be as low as 2%. (1.) Nutritional tables for horses show a similar range of 2% to 2.5%. (2.) However research carried out in the 1950’s in the Anatomy Department of the Royal (Dick) Veterinary College on Exmoor pony cadavers revealed that a 12.2 h.h. Exmoor pony of about 330 Kilos. live weight had the same vital organ capacities as a horse of over 450 kilos. Meaning,
An Exmoor pony can ingest over 3.0% dry matter of its live weight.
3.0% of 330 Kilos L.W. is 9.9 Kilos. In order to ingest 1.85 Kilos carbohydrate and 0.2 Kilos protein a computed ration would require to contain: -
18.69% carbohydrate and 2.02% protein.
Approximately half the nutritional content of a sample of good meadow hay.
This capacity allows the Exmoor to survive and prosper in conditions were other species would not only loose condition but starve. Exmoor farmers know that in a severe winter the cattle starve first, then sheep, then deer, and last of all the ponies. This is a two edged advantage: -
This potential appetite is not utilised by the ponies all the time, certainly not during summer grazing, but only when physiologically required. Intake of forage by an Exmoor pony is influenced not only by nutritional need but also by hormonal changes relating to day length. This is well seen during the month of October when ponies feed themselves up for the winter period. By that time of year, after the September flush of grass, the more fibrous October herbage is eaten in such bulk as to pack the caecum and large intestine. Even geldings “look in foal”, but the swelling is high on the right flank indicating a full caecum, not low on the left side, the location of a pregnant uterus.
written by Alex.N.Copland
A. N. Copland © 2003