Food for thought - feeding fillies - does diet make a difference in their performance

ROM a comparison of various elite human disciplines, it is estimated that men are about 11% faster than women and there are some obvious physical differences contributing to this in terms of stature, muscle mass, bone density, etc. In horses, fillies are generally slightly shorter and lighter than colts and they have a higher percentage of body fat. However, there are few studies that describe any appreciable differences in muscle mass, bone density, lung capacity, or heart There are certain trainers in the horseracing world who seem to be particularly adept at bringing talented fillies to the racetrack to produce winning performances, often over and over again. Some will even race following a quick return from the breeding shed, with great success. While inherent ability from their genetic makeup must be a huge factor in their success, the skill of the trainer and his or her team in knowing just how hard to push to achieve optimum training must also be key. Are fillies ‘dynamic divas,’ or should they be regarded as the ‘weaker sex’? Should we treat them any differently to colts when it comes to their feeding and management? In exploring these questions this quarter, I will focus on these real or perhaps perceived differences between colts and fillies. WORDS: CatheRine Dunnett BSC, PhD, R.nutR PhOtOS: ShutteRStOCK, BenOit PhOtOS, CaROline nORRiS, FRanCe GalOP/aPRh F size. Perhaps not surprisingly researchers suggest that the difference in speed between colts and fillies is only about 1%. Interestingly, however, the ability to tolerate muscle lactic acid, which is largely genetically controlled but which can be influenced by diet, is likely to be lower in fillies compared to colts. This is because muscle carnosine (a dipeptide involved in buffering lactic acid in muscle) is lower in fillies compared to colts. Evolution is likely to provide the reason for the comparatively small difference in running speed between fillies and colts. As an animal of flight, the fastest horses would have survived irrespective of their sex. So it would seem that the fillies can seriously take on the colts and compete effectively; however, for the biggest racing accolades there are procedural limitations. There may be an economic argument at play, since a top race winning colt is infinitely more valuable at stud than a similar broodmare that can only foal once a year. Temperament is another factor that has stereotypically defined fillies, with many being described as highly strung or nervous, although this should certainly not be taken as the norm. Multiple Grade/Group 1-winning fillies Ouija Board and Snow Fairy were described by their trainer Ed Dunlop as being tough and gutsy. He said, “They always galloped well and generally ate well – the exceptional ones are tough and will keep going.” However, where fillies do have a difficult temperament it can bring particular issues to training them successfully. They may be fussy feeders and while they eat up when they first come into training, finishing up a feed is a target that is not always reached as training work increases and pressure mounts. Fillies particularly can be very skilled at filtering out small pellets which they find unpalatable in mixes or sweet feed, which are unfortunately often the carrier for important vitamins and minerals. The addition of powdered supplements can add to the Snow Fairy, seen winning the 2012 Irish Champion Stakes, beating the colt Nathaniel into second place problem because these can be left at the bottom of the feed bowl. Adequate intake of forage can also go by the wayside as the season progresses, which can contribute to nutritionally related problems such as gastric ulcers and tying up. It has long been anecdotally believed in racing that tying up is more prevalent in fillies than colts, and data published by Dr. Sandra Wilsher and Dr. ‘Twink’ Allen demonstrates dramatically that this is indeed the case (Table 1). While accepting that genetics have a part to play, Dr. Stephanie Valberg of the University of Minnesota suggests that a frequent trigger for an acute episode of tying up can be any excitement or stress, such being held up at the rear of the string. Fillies can also be anxious travelers, sweating heavily and thus losing important electrolytes, the balance of which is vital for normal muscle function. Interestingly other issues such as fractures that can also be influenced by nutrition were significantly more common in fillies as two-year-olds but in colts as three-year-olds, while joint problems were more significant in older colts. Long distance travel can mean that continuity in feeding is difficult to achieve unless you take your own feed with you. It can take some fillies a few days to fit into a different feeding regime when racing abroad. Neophobia, which is essentially a fear of new feedstuffs, is a behavior that is commonly seen in other species and is sometimes described in horses traveling to other countries. Some fillies become seasoned travelers and by all accounts adapt well to their changing environment and feed. Pragmatically, It is always going to be difficult getting your exact feed when abroad and you just have to do the best you can and hope they will adapt well within the time frame. Energy requirements for horses in training are calculated using body weight and, because fillies will usually weigh less than colts of a similar age and stage of training, it is normal for them to require less feed to maintain condition. On the contrary some fillies will eat as much as a big strapping colt but this largely depends on their comparative body size. The picture is complicated where a filly is a fussy feeder and some increase in energy density of feed is needed. This basically means that more energy has to be packed into a smaller volume. Feeding a less than straightforward filly should mean that they receive a balanced diet that is suitable for intense exercise, but also one that keeps them occupied and stimulated psychologically and reduces stress and anxiety. Ideally meal times need to be regular and consistent, and meal size kept small and frequent. John Shirreffs, trainer of one of the greatest mares in Zenyatta, likes to feed small amounts five times times a day. He says “Always the trick is to keep trying feeds until you find something she likes and don’t train so hard that she won’t eat – they love attention so bring fun treats like dandelion, sweet potatoes, Guinness, or aloe vera juice.” Interestingly, he also said that he always likes to feed from the floor in a rubber trug bucket or rub, as he feels this is a much more natural position for feeding. Regard must be given not only to how much energy is provided from feed, but also where that energy is coming from in terms of the balance between fiber, starch, sugar, and oil. This is particularly important where temperament is an issue, or if there is a family history or previous incidence of muscle stiffness or acute tying up. For fillies in early training, a minimum of 1.5% of bodyweight in hay should be allowed as this will set up good eating habits for the rest of the season and will also reduce the reliance on concentrate feed. Forage intake can decrease as work increases but a minimum of 1% of bodyweight must always be goal. Feeding fillies different types of forage such as hay, haylage, alfalfa chop, and grass chaff in one sitting can help to tempt them to eat an adequate amount. During this time, a feed that is low in starch (20% or less) and sugar that also provides adequate quality protein (e.g. from soya) is desirable. While some low-energy feeds may be low in starch, they do not provide adequate quality protein to support muscle turnover in these elite athletes in my opinion. As training progresses, a higher starch feed can be introduced, but this is not always necessary or desirable, especially where the filly is of a very excitable disposition. Recent research in trotters suggested that ‘performance’ was not diminished in horses fed an exclusive foragebased ration. These findings need to be examined further because ‘in field’ performance is so different to treadmill tests and comparatively difficult to quantify, and intensity of exercise somewhat different between trotting and certainly flat racing. What is clear is that energy source has a far more evidence-based effect on behavior than many supplements. A ration that provides plenty of forage combined with a concentrate feed that is low in starch and sugar is much more likely to keep a stressy filly settled than a low-forage, high-starch, and sugar-based ration. If supplemental ‘calmers’ are effective and are acceptable within the rules of racing then they could be beneficial; however, most do not offer any tangible evidence of benefit. High-oil feeds for top dressing such as linseed and rice bran, or even straight vegetable oil, are excellent for increasing the energy density of the ration and so maintaining condition. Sugar beet, while not hugely popular in racing circles, is a great feed to add moisture and to help disguise powdered supplements or to carry those vitamin- and mineral-containing pellets. It has been suggested that hormones account for the large difference in the incidence of tying up between colts and fillies, but no study to date has unequivocally proven a causal link. There is no doubt in some individuals, however, that behavior and the ‘will to win’ may be affected by stages in the estrus cycle. Some fillies can be either cranky or too docile during estrus, either of which can have a negative effect on performance. Interestingly some really talented fillies may show little evidence of estrus and simply get on with their job. The stable hormonal state established following a visit to the breeding barn may explain the relative success of some great mares. Although it is not allowed under BHA rules, Regumate seeks to address this situation, with marbles inserted in the uterus to mimic pregnancy being used as a nonpharmacological option with relative degrees of success. There are also many supplements that seek to address so called ‘PMS’ in fillies and mares, most of which contain herbs including agnus castus (chaste berry). Agnus castus would appear to have some benefit in humans although its effect in horses has not been investigated fully. So it would seem that the fillies certainly have the talent, and when trained and fed sympathetically they are able to deliver at the highest level. John Shirreffs’ bottom line is to keep their ears forward and keep them happy! And if Black Caviar could speak, perhaps she would agree with another world-class female athlete: “Some people say I have attitude – maybe I do – but I think that you have to believe in yourself when no one else does – that makes you a winner!’’ – Venus Williams, a world-class tennis player. n