Lupins have been cultivated for over 2,000 years, originally in Egypt and the Mediterranean region. Used extensively in other parts of the world as a forage and livestock feed, lupins also have been popular for farm animals in Australia for some time.
Lupins are, however, a relatively new addition to the list of feeds deemed suitable for horses. Considered a legume, lupins are similar to peas or beans, having a hard, tough outer coating requiring soaking, rolling, crushing, or grinding to enable the horse to properly chew them. Pelleting or heat-treating lupins increases their palatability and probably their digestibility, although little is currently known of the effects of processing on lupin digestibility.
In Australia, lupins are grown mainly in Western Australia, with some production in South Australia, Victoria, and New South Wales. Two major varieties exist, the bitter and the sweet. Only sweet lupins are suitable for horse consumption. When crushed, sweet lupins have yellow flesh and may be mistaken for corn in a mixed feed. They are easily discernible by their speckled outer seed case.
The bitter varieties contain high concentrations of toxic alkaloids that reduce palatability and can be harmful to horses. In other animals, productivity may drop if large quantities of lupins are fed.
Lupins are predominantly a source of protein (28-34% crude protein) but also contain some fat (around 5%) and digestible fibre. They have a lower lysine and methionine content than other protein supplements (see table) such as soybean meal, so more lupins would be required to supply the same amount of these essential amino acids.
Comparison of lupins and other popular protein supplements:
|Lupins||Cottonseed meal||Full-fat soybean||Linseed meal||Sunflower seeds||Tick beans||Lucerne hay||Soy meal|
|Digestible Energy (MJ/kg)||14.6||11.5||20||11.4||19||13.2||8.2||14.|
|% Crude Protein||28-34||38||38||34||20||25||16||45 -48|
|% Crude Fibre||12||11||4||9||29||8||26.1||5.8|
|% Fat||5.4||5||18||1.5||25 – 30||2||1.6||1|
However, lupins are more palatable than soybean meal, and because they are a grain rather than a meal, it is easier to feed larger amounts. The oil present in lupins consists of 35% monounsaturated fatty acids, 45% polyunsaturated fatty acids, and 2% sterols. These oils appear to be stable in the whole seed for long periods. Although it is thought that the effects of processing will reduce shelf life, there have been no studies regarding nutrient stability during storage after cracking or processing.
Because of their low starch and high fibre content, lupins are digested efficiently in the hindgut of the horse through fermentation. Similar high-fibre feeds used in other areas of the world include beet pulp and soy hulls, although these do not have the high protein or fat content of lupins and are not as energy-dense. These characteristics make lupins particularly suitable for horses that have a low tolerance for starch-rich grains, such as oats or corn, which are digested predominantly in the small intestine.
Horses with a predisposition to tying-up or laminitis, or those horses that get excitable on typical cereal grains, may benefit from the addition of lupins to the diet. Because lupins contain very little starch, they are often considered as an ideal “cool” feed, but their high protein content and the presence of alkaloids means that their inclusion should be limited to 2 kg (4.4 lb) for a 500-kg (1,100-lb) horse. Lupins are the current fad in feeding Standardbreds, and there are horses getting far more than 2 kg (4.4 lb) per day.
Lupins are therefore suitable as an energy and a protein supplement. As a protein supplement, lupins can be quite cost-effective and are usually considered good value compared to other commercial or synthetic protein supplements. They contain minimal lignin, and the protein has been shown to be highly digestible in other animals. Very little is known about the digestibility of lupins in horses. Further work is needed in this area, but the results of feeding lupins are a promising indicator of their value as horse feed.
The low starch and moderate oil content of lupins makes them a good choice for leisure and show horses, reducing the chances of nutrition-related behavioural problems and boosting coat condition. As a high-energy supplement, lupins are excellent for performance horses, racehorses, and endurance horses needing a palatable, energy-dense feed. Lupins are also a good source of energy for growing and breeding horses.
Horses find sweet lupins palatable in soaked, cooked, micronized, or extruded forms, and they are a good ingredient to include in pellets. It is not advisable to use lupins as the sole dietary concentrate component. The grain should be viewed as a protein or energy supplement in commercial concentrates or pellets, or as a supplementary grain in home-mixed diets.