Lucerne Hay: Friend or Foe?

Lucerne hay enjoys a varied reputation amongst horse people, with some using it as a highly valued component of their horse's diet and others avoiding it with an almost religious fervour. But who is correct? 

Most experts in the field of equine nutrition today endorse the traditional view that Lucerne as a roughage should be used in moderation and should rather be fed in combination with grass or oaten hay in order for the total roughage component to
be at a ratio of about 3: 1 - i.e. 75% Grass or Oaten hay to 25% Lucerne hay. This ratio serves merely as a guideline but you will always be on the safe side by keeping your Lucerne portion below 50% of the total roughage component.

This newsletter article endeavors to shed some light on the advantages and risks associated with feeding Lucerne.

Lucerne Hay - What is it?

Lucerne hay is made from the Lucerne plant (Medicago sativa), a temperate perennial plant which originated in the Middle East. The Lucerne plant is a legu-minous plant species, meaning that it belongs to the family of plants that produce seed pods and have nodules on their roots that are capable of taking inert nitrogen from the atmosphere and converting it to organic nitrogenous compounds that are available to the plant.

The Lucerne plant may be cut to make Lucerne hay at various times during the plant's life cycle, but is most commonly cut at the 10% flowering stage. Lucerne hay, when it is produced and stored correctly is commonly green in colour and should, on closer inspection, contain a high percentage of leaf material and fine stems. Lucerne hay that has been weather damaged or baled when too dry will be dull green to brownish in colour, and will commonly contain a high percentage of stems and a much lower leaf content.

The Nutrient Profile of Lucerne Hay

Lucerne hay is a high protein forage and also contains more energy than grass hays like Teff and Eragrostis.  Lucerne also contains high concentrations of Calcium and Magnesium and, when fresh, also vitamins A and E.

Lucerne is however typically low in Phosphorous and depending on where it was geographically grown, contains varying concentrations of other macro and micro minerals. The table below shows an abbreviated nutrient profile of early bloom
Lucerne hay in comparison to grass hay and oaten chaff.

The table shows that between various cuttings Protein content can vary by 43% and the fibre content by 60%. It is also important to note that the Protein quality can be hugely affected with the lysine value dropping by 50% from 11.8g/kg to as low as 7.9 g/kg. The digestibility was also determined and reduced by 56% towards the last cutting.

Other studies shows that Lucerne grown in alkaline soils can have magnesium levels of up to seven times as high as the normal levels, again emphasizing the problems and risks involved with variations in composition.

Even with the large drop in values Lucerne remains a very nutritious fibre but this does partly explain why it is not recommended to use Lucerne as the sole source of fibre.

2) Imbalance in the Phosphorous to Calcium Ratio.

Most people are aware that Calcium is an essential nutrient and mineral in the development of a strong and healthy bone structure. The increased requirement for dietary Calcium in the nutrition of pregnant mares, young and growing horses (especially if in training), is well known by most owners and trainers. It is not so commonly known however that the ratio of Calcium to Phosphorus in the diet is as crucial as the inclusion of Calcium itself. It is also important to understand that certain foodstuffs contain Calcium and Phosphorus in forms that are unavailable to the horse. This is because certain chemicals in feeds such as oxalates and phytates bind Calcium so that the horse cannot digest it. Calcium is not only involved in structural components of the body such as teeth and bones, but is also extremely important in its dissolved form for processes such as muscle contraction, blood clotting and as a messenger molecule in cells within the body. So important is its role that the body keeps the amount of dissolved Calcium between strictly controlled levels through a process known as homeostasis. The body regulates the dissolved Calcium levels by drawing on Calcium in the bones in times of need, and by ensuring that excess Calcium is deposited in the bones in times of good supply. A hormone called the para-thyroid hormone regulates this homeostatic process. Parathyroid hormone in conjunction with vitamin D help to keep the balance of Calcium to Phosphorus in the bones in a ratio of around 2:1.

Why is Lucern's high Calcium content a disadvantage? When horses are fed Lucerne as the sole roughage, Calcium is supplied well in excess of their daily requirements. For example, 5kg of Lucerne supplies 70g of Calcium, which is more than twice the daily requirements of a 400kg horse at hard work. In response to this large and continuous supply of Calcium in the diet, the body will adjust its calcium-regulating hormone levels accordingly - the Calcitonin responsible for storing Calcium will increase, and levels of parathyroid hormone will decrease. From the body's point of view, there is no need to maintain high levels of a Calcium-mobilizing hormone when excess Calcium is consistently provided in the diet.

This supply-and-demand concept can become a problem during strenuous events. Since Calcium is required in large amounts for muscular contractions, plasma Calcium levels gradually fall as the duration and intensity of exercise increases. In response to falling plasma Calcium levels, the body calls upon parathyroid hormones to mobilize more Calcium from its storage depots in the bone. However, because the body has become accustomed to having excess Calcium available from the diet, it can happen that the concentration of parathyroid hormones is too low to adequately supply stored Calcium quickly enough to meet the sudden high demand. In other words, there are not enough workers available at a moment's notice to move Calcium from storage into circulation. As a result, plasma Calcium levels may continue to fall, increasing the likelihood of metabolic problems such as Tying Up and Thumps.

3) Other Mineral Deficiencies.

It also must be kept in mind that Lucerne hay is not a complete feed and will more often than not contain insufficient concentrations of trace minerals, in particular Copper and Zinc, to support sound musculoskeletal development.

•  Zinc is essential in bone, cartilage and hoof formation.  Deficiency can result in reduced appetite, retarded
   growth, dry thickened skin and hair loss in severe deficiencies.

•  Copper is required for the development of bone, joint cartilage and connective tissues but also plays a role with
   metabolic and tissue anti-inflammatory enzymes. Deficiency can result in lameness in growing horses as well
   as anemia.

To which horses can Lucerne hay be fed?

Lucerne hay may safely be fed to all classes of horses; however, due to its high protein and relatively high energy characteristics, it must be fed to horses in controlled quantities to prevent problems that may be caused by excess energy and protein in the diet. The suitability of Lucerne hay for different classes of horses is discussed in more detail below:

Growing horses

When feeding Lucerne to growing horses, the amount fed should not exceed the growing horse's energy requirements. Growing horses fed energy in excess of their requirements have a much higher chance of suffering from developmental orthopaedic diseases including osteochondritis dissecans (OCD). Feeding protein in excess of the growing horse's protein requirements does not appear to be detrimental as the protein can be utilised as a source of energy. Moderation seems to be the key, and again, a mixture of other hay and Lucerne (+/- 3:1) will keep you on the safe side.

Pregnant and Lactating Mares

When feeding the pregnant mare Lucerne hay, care must be taken not to exceed her energy requirements which will then cause her to become overweight. Conversely, Lucerne hay alone will not be capable of meeting the early lactation mare's energy requirements and her Phosphorous and trace mineral requirements will also not be met by a diet based mainly on Lucerne hay. Depending on pasture conditions, mares need to be fed a good quality concentrate to maintain body condition throughout lactation.

As with growing horses, excess protein in the diet of pregnant and lactating mares does not appear to be harmful, however, it is an unnecessary waste of this relatively expensive feed component and should be avoided if possible.

Performance Horses in work or training

With performance horses, as with growing horses and pregnant mares, Lucerne must be fed in moderation. Unlike the above classes of animals, excess protein in the diet of working horses, particularly those that are stabled, can be detrimental to their health and performance.

Excess protein intake will increase urinary ammonia production, which may in turn cause respiratory problems for horses confined to the stable and can contribute to dehydration due to water loss through increased urine production and excretion. Excess protein also increases the amount of heat produced during the digestion and utilisation of feedstuffs. A diet which contains protein in excess of the horse's requirement can increase the horse's water and electrolyte loss through sweating and can contribute to hyperthermia, and decreased performance or endurance capacity.

Does excess protein directly affect performance? Almost certainly. Although there are no scientific studies which specifically examine the effects of an all-Lucerne diet, there is significant evidence that diets with excess Protein are detrimental to endurance-type exercise. Dr. Sarah Ralston, PhD, DVM, (dACVN) has observed in both endurance and three-day event horses that as protein content of the ration increased, so did metabolic failure. Michael Glade (PhD), in observing feeding practices and racing performance in Australian Thoroughbreds, observed that horses ran slower as the protein content of the ration increased over requirements. And finally, many horse owners report that grouchy, temperamental, "hot" horses become calmer, steadier and more con-sistent performers when excessive Protein is removed from the ration.

It is important to understand that these effects are not as a direct result of feeding Lucerne, but can result from feeding too much Lucerne. They can be avoided by ensuring that a horse's protein requirement is adequately met but not unnecessarily exceeded. It is important to keep in mind here the big variation existing between Lucerne batches and again this explains why it is advisable to use a grass or cereal hay in conjunction with Lucerne hay.

Spelling or Idle Horses

Lucerne hay can play a role in the spelling or non working horse's diet, and will help to supply these horses with good quality protein and calcium in their diet. However, due to its high energy content in comparison to other forages, Lucerne hay is generally not suitable as the sole source of roughage for this class of horse as it can encourage excess weight gain.

Ponies

Ponies may be safely fed Lucerne hay, but again it must be fed in moderation because it can easily lead to ex-cessive weight gain in ponies, particularly those that are easy keepers. Feeding too much Lucerne hay may there-fore predispose ponies to laminitis which can occur when ponies become overweight.

Lucerne hay is particularly useful in the diet of aged ponies. As horses and ponies age, they lose some of their ability to digest fibre and protein. Feeding them an easily digested fibre and high quality protein source in the form of Lucerne hay will allow them to maintain bodyweight, particularly during winter. Moderation again, however, is important.

Some Quality Considerations

The Lucerne plant's stage of maturity when cut, its weathering and handling during harvest/drying and the length of time it is stored prior to being fed will all affect Lucerne hay's energy, protein, vitamin and mineral content. Thus, when including Lucerne hay in a horse's diet, it is important to assess the Lucerne's stage of maturity and quality, before feeding it. Care should be taken to ensure that the hay does not contain mould or dust which will make the hay unpalatable and may contain fungal spores capable of causing heaves, coughing and bleeders or mycotoxins which could result in abortion or death.

Take into consideration that a heavy bale is not necessarily a quality bale, as the weight can vary widely with moisture content, and could be a sign that the Lucerne was too moist when baled.

Conclusion

Lucerne is a valuable feedstuff for horses and is capable of providing them with energy, high quality protein and often much needed lysine and calcium. Lucerne hay has to be used correctly in the diet, however, to realise its full benefits.

Typical problems due to excess energy and protein are very real possibilities when Lucerne hay is not fed in moderation. These problems are not, however, as a direct result of feeding Lucerne hay, but rather, as a result of feeding too much energy and/or protein in the form of Lucerne hay.

Another definite risk involved with feeding too much Lucerne is the Calcium to Phosphorous imbalance. Using grass hays in conjunction with Lucerne hay to full fill the horse's roughage requirement will help to avoid some of the problems associated with feeding excess Lucerne hay and will additionally, in most instances, reduce costs considerably.

Thanks to Equus for this article.
You can find out more from there website at: www.equusfeeds.co.za