FIT NOT FAT ISSUE 23_Jerkins feature.qxd 31/01/2012 15:31 Page 3
VETERINARY Performance is linked to lean body mass For a horse to become overweight, there has to be a period of time where its energy consumption (calories in) is greater than their energy expenditure (calories used), which is simply a function of what is fed versus daily activity, including exercise. In youngstock, the combination of a plentiful supply of grass and good forage and concentrate feeds can lead to animals becoming overweight relatively easily. Horses in pre-training may arrive with the equine equivalent of ‘puppy fat,’ which can also be the result of over-conditioning during sales preparation. While the impetus is for youngsters to look their best for the sales ring, there is a balance to be achieved between fit and fat, as overweight yearlings simply cause issues for trainers and pre-trainers in their need to normalize body condition. While horses in full training are rarely described as being very overweight, they may be overweight for the job of racing. Trainers are generally very aware of the influence of bodyweight on racing performance and so strive to ensure that their horses reach the racecourse in optimum body condition. A body condition score of no more than 4 to 5 on a scale of 1 to 10 is generally regarded as being optimum for intense exercise such as racing. Body condition score assesses flesh coverage, mostly fat, over the various areas of the body and a score of 1 is extremely thin and 9 is obese. Studies in human athletes and also more recently in horses suggest that performance is
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Should we really be worried about obesity in racehorses? A quick glance around the paddock of most racetracks in North America would suggest not. However, while the number of horses racing with a much higher than optimum body weight may be low, this doesn’t represent the full story. When evaluating racehorse feed management, it is not uncommon for a nutritionist to hear the words “I have to work the horses harder to keep the weight off.” Also the question of over-conditioning in youngstock should perhaps be discussed in the context of its effect on horses once in training. WORDS: CatheRine Dunnett BSC, PhD, R.nutR PhOtOS: ShutteRStOCK.COM, WWW.hORSeWeiGh.COM, SaRah FaRnSWORth PhOtOGRaPhY
linked to lean body mass, or in other words, muscle. This makes absolute sense, as the greater the extent of the muscle mass, the higher the power-to-weight ratio becomes, which is important for intense exercise. Any large deviation in body condition score away from 4 to 5 in either direction is detrimental to performance. A significant fall in body condition score below 4 can mean the loss of lean tissue as well as fat and conversely a horse with a body condition score above 5 is probably carrying too much fat, which will reduce its power-toweight ratio.
Feed less, don’t exercise more It should theoretically be much easier to maintain a horse in training at ideal body condition, as we are firmly in charge of what they are fed. Some horses in training do however rise above their ideal body condition for racing and this can happen for a number of reasons. The most common reason for suboptimal body condition is that horses are not fed as individuals and their feed intake is not adjusted sufficiently to compensate for other factors. While a minimum amount of forage needs to be fed regardless of activity level (1-1.25% of bodyweight), this needs to be balanced with an appropriate amount of concentrate feed to prevent horses being underweight or overweight. Concentrate feed intake may actually need to be reduced if forage quality is particularly good, or if the horse concerned is proving to be a particularly good doer. Feeding by the scoop rather than by weight can also be an issue. Although cubes are convenient and a good choice, they are relatively easier to overfeed, as a bowl of cubes is significantly heavier than a bowl of mix. The difference, for example, between a flat and heaped scoop of cubes over time can make a big difference to energy intake. Another racing myth that needs to be exploded at this point is the idea that horses are not ready to race unless they are eating a certain poundage of feed. Different horses will require varying amounts of feed at different stages of training and generalizations are risky. Equally, the level of work should always be exclusively dictated by your training needs and should not be regarded as an additional method to reduce body condition. We should banish the thought that you have to work some horses on some manufacturer’s feeds harder to prevent