PAUCITY OF HORSE NUTRITION RESEARCH
A recent report revealed that the following man years ( One man year refers to one person working an entire year ) were devoted to U . S . animal research in 1961- 1962 :
Dairy cattle ________ 235.9 Poultry _____________ 184.1 Beef cattle __________ 124.6 Swine _______________ 95.6 Sheep and goats _____ 63.0 Fur animals _______ 9.9 Horses _____________ 0.9
It ’ s small wonder , therefore , that the “ unknowns ” far outnumber the “ knowns ” when it comes to horse nutrition .
In many cases , we have either ( 1 ) proportioned the ration of draft horses down to the size and weight of light horses or ( 2 ) extrapolated or calculated estimated horse requirements from those of cattle or other classes of farm animals . Of course , the chief fallacies to this sort of thing are : Draft horses are quiet , work at a walk , and are under little stress ; and cattle differ from horses anatomically and physiologically — horses have a smaller digestive tract , and their cecum ( the primary seat of bacterial action ) is on the wrong end . As a result of this situation in the horse , perhaps microbial activity gives only a limited assist in synthesizing proteins and vitamins , and there is reason to question the efficacy of absorption so far down . For these reasons , in giving the nutritive requirements of horses , they are usually prefixed by such confidence-shaking words such as calculated , estimated and assumed .
In the discussion that follows , frequent reference is made to National Research Council ( NRC ) publication 912 , Nutrient Requirement of Horses . At the outset , I wish to compliment the authors on having done so much with so little , and to acknowledge that no one could have done more .
Digestibility of Feeds
Few digestion experiments have been conducted with horses . In using digestion data obtained with cattle and sheep , it is assumed that fiber digestibility is lower in horses , but there may be other digestibility differences . Thus , the digestibility of the most common horse feeds needs to be determined . Metabolism
Little is known about the changes which take place in nutrients after they are absorbed from the horse ’ s digestive tract . How are they used for growth and repair , and how are nutrients oxidized for the production of heat and work ?
Energy Requirements
NRC Pub . 912 states that energy required for maintenance is judged to be equal to twice the basal metabolism rate ; and the energy requirements for light and for medium work are assumed to be 3.0 and 3.5 times , respectively , their basal metabolic rate .
It is obvious , therefore , that these figures can only serve as rough guides to feeding practices . Also , the nutrient requirements of horses at work are based almost entirely upon draft animals pulling heavy loads at slow speeds . Yet , light horses at fast speeds for short periods ( as in racing ) may use up to 100 times the energy used at rest .
Data on milk yield of mares are scant , and largely based on draft mares . Extrapolating from the cow , it is assumed that the horse converts digestible energy into milk energy with 60 per cent efficiency . Likewise , the energy requirements for growth are calculated from beef cattle and based on certain assumptions . Protein Requirements
Nutritionists recognize that protein and energy requirements go hand-in-hand ; thus , as the carbohydrate portion of the ration is increased with severity of work , the protein portion should be increased simultaneously . This points up the likely need for higher protein content rations than have usually been fed to horses in hard use . Also , it would appear that higher than normal protein levels for breeding horses may be in the nature of good insurance , because it is recognized ( 1 ) that a protein deficiency may affect mare and stallion fertility adversely and ( 2 ) that the daily protein requirement increases in the last quarter of gestation .
In NRC Pub . 912 , it is estimated that mare ’ s milk averages 2 per cent protein ; then it is recommended that an allowance of 35 per cent protein in excess of that appearing in milk will provide adequate digestible protein for lactation . Further , the protein requirements for growing , young horses is calculated from cattle and based on the assumption that 50 per cent of the digestible protein fed above maintenance will appear in the gain . Mineral Requirements
Few experiments upon which to base horse mineral requirements are available , despite the fact that $ 7,000,000 is spent annually for minerals for equines . It is known that horses can perform work for extended periods on rations of grass hay , farm grains and salt . From this , NRC Pub . 912 goes on to say that it is assumed that horses are less sensitive to trace element deficiencies than are ruminants .
( Continued on Page 31 )
28 VOICE of The Tennessee Walking Horse