Most of the current crop of 2yo’s will now have been broken and are in the early stages of training proper in readiness for the forthcoming flat racing season. This period brings with it numerous problems for trainers and their staff, such as horses with high muscle enzymes, episodes of tying up, respiratory infections, various lamenesses and other skeletal problems or simply over exuberance.
Whilst such issues have many contributory factors, a good basal diet, with carefully selected extras can help to minimise some of these niggling problems. Overfed horses can become fat or too excitable During breaking, and pre- and early training the emphasis from a nutritional perspective should be on adequate but not excessive energy intake, whilst ensuring that a balanced diet is provided in terms of vitamins, minerals and quality protein. An overfed horse becomes either fat and so difficult to slim down for racing, or badly behaved and excitable, and thus more prone to injure itself or its rider. To avoid excitability, good quality hay or haylage fed in increased amounts will not only help to reduce the reliance on concentrate feeds, but may also reduce ulceration, especially in horses in their first season of race training. There are several concentrate feeds manufactured specifically for horses in early training or during a ‘lay off’ period. These are generally lower in energy than racing feeds, but still ensure an adequate intake of quality protein for young horses and provide a more concentrated source of vitamins and minerals, given that the intake of feed can be quite low at this time. Sometimes a more economical alternative to these tailored feeds would be a good quality low energy mix or cube, manufactured for the mainstream horse market.
However, reassurance should always be sought from the manufacturer concerned on the suitability of the main ingredients, including the protein and fibre sources and vitamin and mineral level for a horse in pre or early training. An further advantage of these two concentrate feed types for this stage of training, is that the energy provided is derived largely from digestible fibre and sometimes oil, with less emphasis on cereal starch. This is potentially beneficial for behaviour, and also for horses with a predisposition for tying-up or ‘set fast’. Not every raised muscle enzyme is a ‘set fast’ Raised blood levels of the muscle enzymes AST (aspartate aminotransferase) and CPK or CK (creatine kinase) are common place during early training. These enzymes are present at much higher levels in muscle cells than other tissues and therefore their leakage into the blood is considered indicative of muscle damage. The complication is that although muscle damage can result from an ongoing metabolic issue such as tying up, it may also occur as the result of transient over exertion. High AST and CK’s in blood are not always an indication of a horse having tied up and some horses that exhibit these blood results in the early stages of training will often work through it as training progresses.
Care should obviously be taken with horses, who show clinical signs of having tied up on one or more occasion. For such horses, diagnosis early in the season is beneficial, as their diets can be scrutinised more closely and key changes implemented that can in many instances reduce the severity or frequency of such attacks. These horses will often benefit from being fed a basal ration that is very low in starch (typically less than 15%) and so equally will need to be high in digestible fibre and oil to ensure adequate energy intake during training. Current research into tying up cannot yet explain why this dietary change helps, but widespread experience suggests that in many instances it does. Stephanie Valberg from the University of Minnesota suggests that it may be due to an effect on stress and the change in diet results in these horses becoming less ‘anxious’. However, trainers have in the past highlighted practical problems with this approach.
Some have reported that long-term palatability may be a problem with this type of diet, as horses seem to instinctively like the sweet, cereal rich coarse mixes and cubes, typical of traditional racing feeds. Measures that can be taken to avoid such problems include: 1. Identify problem horses as early as possible and adjust their ration to prevent them becoming accustomed to traditional racing feeds. 2. Feed 4 or 5 smaller meals per day rather than 3 larger ones. 3. Mixes are often more palatable than cubes 4. Some unmolassed sugar beet can improve palatability Most racing diets need supplementing with salt Electrolyte provision, including sodium, potassium, chloride, calcium and magnesium is an important dietary aspect to evaluate for all horses in the yard, not just those that tie up.
Racing diets generally meet and exceed the requirements of potassium and chloride, which are two of three the main electrolytes lost in sweat. The third, sodium, is in my experience never present in sufficient quantities in proprietary feeds for horses doing more than light work. This may be largely due to manufacturing constraints. However, sodium is easily supplemented by adding ordinary table salt daily to feeds (typically between 25-75g per day depending on work load). Whilst calcium and magnesium intake is usually adequate, the calcium to phosphorus ratio of the diet may not be optimal, especially if feeds are top dressed with oats.
It should also be recognised that, there exists quite marked differences between horses in their ability to absorb electrolytes and for this reason a creatinine clearance test can be useful in the further investigation of problem horses. This test (which involves taking paired blood and urine samples for analysis of the major electrolytes) helps the vet and nutritionist to take account of individual variation in electrolyte absorption and excretion and to modify the diet accordingly. Vitamin E intake can be low in some pre-training diets Vitamin E and selenium content of the diet should also be studied carefully. Racehorses that repeatedly tie up are not necessarily deficient in these two micronutrients, but may have a higher requirement due to increased free radical production. In my experience, selenium is usually present at appropriate levels in most racing rations, however the level of vitamin E provided can often be lacking.
A higher daily intake of 1600-2400iu per day for a typical horse in training has been recommended in the scientific press. The range in vitamin E content of racing feeds is quite wide, typically between 250iu to nearly 500iu per kilogram of feed. So a horse in full work may receive anything between 1500 to 3000iu per day, excluding forage and supplements. However, many trainers rely on the use of non-specialist low energy feeds during early training and these are obviously fed at a much lower level of intake compared to racing feeds for horses in full work. This could therefore result in vitamin E intake during this period being nearer to 1000iu per day. Poor hoof condition is a common gripe for trainers and farriers Poor hoof condition is another common problem that develops in early training and which can often deteriorate as training progresses.
Whilst there are many conformational and biomechanical factors that contribute to poor hoof condition in Thoroughbreds, nutrition is an area that should not be ignored. It is true to say that most of the relevant nutrients such as quality protein, calcium, zinc, methionine and fatty acids are supplied in a typical racing diet. However, the micronutrient that has received most attention in the scientific literature with respect to improving hoof horn quality is biotin. Biotin, a B-group vitamin, is generally provided at a level of intake in most racing feeds that easily meets a horse’s basal requirement. However, the daily intake reported to improve horn quality is typically 10-20 times higher than this.
Biotin has been reported to improve hoof horn quality when fed daily at levels between 10 and 20mg per day. Patience however, is required with biotin supplementation, as benefits are unlikely to become apparent for 6-9 months. But remember that biotin is worth feeding for 12 months of the year – as the horn grown in the early winter will be raced on in the spring and summer. Getting the basics right for respiratory health Development of respiratory disease during early training is also a commonly encountered problem. I always compare a yearling’s first venture into a training or pre training yard to a toddler starting nursery for the first time, which can often involve consecutive colds and associated bugs for the first year or more.
Indeed, the adaptive part the mammalian immune system is strengthened through exposure to different infectious challenges. It is not surprising therefore, that avoiding some form of respiratory disease during pre or early training is an uphill struggle. Numerous nutrients that may support the immune system have been investigated by scientists in man and other species, such as glutamine, antioxidants including vitamin C and E, probiotics, prebiotics, omega 3 fatty acids, adaptogenic herbs, whey protein and others.
The vitamin C level in the fluid surrounding the lungs is reportedly decreased in horses suffering with Recurrent Airway Obstruction and other types of airway inflammation (e.g. bacterial infection), and some vitamin C supplementation can be warranted where a problem is identified. Glutamine is a major fuel source for cells of the immune system and whilst the merits of supplementation in horses have not been proven, a fairly recent study indicated that horses infected with the equine influenza virus exhibited a significant decline in blood glutamine 41 days after exposure. There may well be other nutrients amongst those cited above that could prove useful, however there are few if any products (or ingredients) that have extensive and unequivocal scientific evidence to support claims that they ‘enhance or boost’ the equine immune system. Before turning to nutraceuticals for all the answers, some fundamentals can be addressed.
Good clean bedding is essential, as are well-ventilated stables and clean forage. Whilst American hay has a good reputation for being clean, with very low mould and yeast counts on analysis, many trainers prefer to use English hay for early training and some will use it through the season. Unfortunately, our variable climate means that producing consistently clean hay can be difficult. Whilst haylage is a viable alternative to hay, as the process of fermentation keeps the level of mould and yeast to a minimum, it is not infallible and haylage that has been produced badly, or which has become contaminated is a serious issue.
I would recommend that before committing to a batch of hay or haylage, some basic analysis of moulds and yeasts is money well spent to ensure that potential respiratory challenges from forage are minimised. Total mould and yeast analysis cfu/g from forage sampled from racing stables Total Moulds Total yeasts Thermophilic spores Hay – English Timothy 270 150,000 150,000 150,000 <10 Haylage – English Rye 10 <10 30 * No visible spoilage was seen in any of these forage samples Retention of calcium is reduced in early training Finally a discussion of the problems of pre and early training would not be complete without reference to bone. Many of the problems encountered at this time relate to changes in bone strength and density during training. When a racehorse enters training for the first time their cannon bones have been shown to go through an initial period of demineralisation, which reaches its greatest severity at about 60 days into training (US based study). Remineralisation then occurs as training progresses.
The initial demineralisation phase results partly as part of the remodelling process but also as a result of a change in the nature of the diet (less forage and more cereal), as the horse moves from stud to training or pre training yard. Current thinking follows that adequate calcium content in the diet is especially important during the initial demineralisation phase, as the horse’s ability to retain calcium in the body seems to be reduced. Attention to the calcium to phosphorus ratio of the diet is also vital, especially if top-dressing with cereals. The dietary magnesium content should also be evaluated in this respect as it is sometimes overlooked. Silicon supplementation shows some evidence of efficacy in reducing some injuries in racehorses but its powder form as sodium zeolite has limited its use. A liquid form is now available and although promising, as the intake per day is very low, it does not as yet have a scientifically proven track record.