The aim of the survey was to determine whether feeding practices, the type and balance of feeds, and the use of nutritional additives and pre-race supplementation and management could influence the trend towards higher TCO2 levels generally reported in Standardbred racehorses following the analysis of pre-race blood samples.

A number of dietary surveys and feeding recommendations have been reviewed and published related to harness race horses in both Australia and overseas. (Bryden (1983), Carroll (1991), Kohnke (1991), Southwood et al (1993 a, 1993 b), Lewis (1995), Jackson (1996), Kohnke (1998), Kohnke, Kelleher and Trevor-Jones (1999).

The harness race horse generally has a higher major nutrient requirement for energy, protein and minerals compared to a thoroughbred racehorse. This is influenced by the smaller size of the typical Standardbred horse, the more intense training and physical and metabolic stress associated with conditioning programs traditional in the industry, and the increased frequency of race competition compared to thoroughbred racehorses.

The earlier surveys and nutritional reviews compared feeding standard practices to the scientific requirements published in the NRC (1978) and NRC (1989) guidelines for horses in intense training programs. The extent of the surveys were limited to either prominent trainers, a restricted locality or analysis of an established or traditional feeding program.

The survey initiated by the Australian Harness Racing Authority Inc.,(AHRA) is the first review of national feeding practices used in the harness racing industry in Australia.

The survey reviewed in this paper was carried out using a multiple choice question format. The survey questionnaire was designed to gather pertinent details of the types of feeds used, the relative amounts and proportions, the use of dietary supplements to either balance known low or inadequate levels in feeds, or perceived to be required by horses in harness training. It also encompassed questions on pre-race management procedures, including the practices of saline drenching and pre-race water withdrawal within the Standardbred industry.

The survey was structured to seek the accurate and representative information without bias or perceived identification of respondents, by providing alternatives in all categories of feed types, amounts and combinations. The survey was formatted to minimise the time required to complete the questions, avoiding additional written answers or explanations. The questionnaire was mailed to all registered harness racing trainers in each state of Australia, reflecting the need for a wide base of respondents and to counteract the customary low return rate of mail surveys.

The instructions on the methods of completion of the questionnaire emphasised the confidentiality of the data collected for identifying feeding practices that could influence the overall TCO2 levels in harness horses. The survey sought details relating to the state of residence of the respondent, and the approximate number of horses in training. The questionnaire was compiled using the SPSS (Statistical Package Software) to enable an accurate and statistically valid analysis of both the quantitative and qualitative responses given by the participants.

The number of questionnaires returned totalled 525, which approximates a return of 10%. This is considered a successful response for a mailed, voluntary questionnaire that has a stated return date, as compared to a personal interview form of survey. This return rate was also better than average, considering the length of the questionnaire and its relative complexity, albeit a multiple choice layout requiring minimal written response.

The return rate also exceeded general expectations, considering the profile of the industry and the possible issue of providing information to a controlling body of the industry, rather than to a research based institution seeking industry trends and feeding practices, such as carried out by Southwood et al (1993). The simplification of the questionnaire to avoid direct questions, which may have caused refusal to provide an accurate response, a product identification list and an exhaustive disclosure of feed ingredients, was instrumental in eliminating potential bias and reduce the rate of invalid or spurious responses.

The data obtained from the survey, which reflected an East Coast geographical concentration of the 525 respondents totalling 64.5%, was representative of the overall higher numbers of harness race trainers in the eastern states of Australia. Because of the voluntary nature of the mailed questionnaire, the success of the feeding programs adopted by individual trainers, and their direct influence on TCO2 readings could not be elucidated. However, the data on TCO2 levels is available from pre-race testing results based on state-by-state trends and locality of major harness racing tracks.

The results, as expected, indicated the widespread use of cereal grains as energy concentrates to fuel training exercise by horses within the harness racing industry. The amounts fed reflected the established energy and protein requirements for harness racing horses, based on their appetite limit and gut capacity in proportion to the intensity and duration of daily training programs and the higher frequency of racing for Standardbred horses. The data illustrated the widespread use of oats as the major source of energy in race diets. This reflects the results of earlier reviews by Bryden (1983), Carroll (1991), Kohnke (1991, 1998) and Southwood et al (1993(b)).

The use of whole or cracked corn to increase the energy density of the rations, in amounts up to 1.0kg daily (33.9% of respondents) and between 1-2 kg daily (13.3% of respondents), to help ensure horses are able to consume sufficient energy to meet the needs in a limited overall bulk of feed, reflected general recommendations of Bryden (1983), Carroll (1991), Kohnke (1991,1998), and the results of the Southwood et al (1993(b)) survey.

The limited use of flaked or boiled barley was not a trend reflected by earlier reviews, although in this survey, the rate of null or invalid responses on the use of barley generally, and co-incidentally cracked sorghum as an energy concentrate, was much higher than for the other two most common cereal grains. The use of grain sorghum as an energy supplement in horses is limited to geographical areas of Northern New South Wales and Queensland where the grain is more available. Generally its poor acceptance by horses further limits its popularity as an energy concentrate. (Kohnke, Kelleher, Trevor-Jones, 1999).

The survey also indicated that the use of commercial, ready-to-feed sweet feeds was widespread, with 74.7% of respondents indicating that they fed sweet feeds as a major or supplementary part of their racing rations. The adoptions of rice based and extruded commercial feeds and feed blends with minimal oats may reflect the higher risk of tying-up in Standardbred fillies, for which those forms of highly digestible starch, or minimal starch feeds are promoted as an alternative to oats and other raw grains to reduce the incidence of tying up. (Kohnke 1998).

The incorporation of concentrated sources of protein, such as provided by legume oil seeds and meals and sunflower seeds, was not reflected in the recommendations or trends shown in earlier reviews and surveys. However, in this survey the fact that 50% of respondents recorded an invalid or null response may have reflected confusion with the question format or the examples of protein concentrates listed as part of the question.

Generally, protein concentrates are used to make up perceived or known low or imbalanced levels of quality protein sources that are deficient in cereal grains for horses in hard work. However, the widespread use of lucerne hay, as the major form of long stem roughage, which in itself provides from 15-17% crude protein, as a source of protein to offset the less than optimum levels in cereal grains, may have reflected the lower inclusion of protein concentrate feeds in Standardbred rations as indicated in this survey.

The survey by Southwood et al (1993(a)) carried out by interviewing 25 Standardbred trainers in the Sydney and nearby provincial training areas, indicated that energy intake was within the recommendations of the NRC (1989) guidelines for horses of the bodyweight range and intake of Standardbreds. However, this survey reported that the crude protein intakes were significantly higher than those published in the NRC (1989) recommendations. The present survey, due to the design of a voluntary questionnaire, and limitations on the depth of the questions, was unable to substantiate the findings of Southwood et al (1993(a)) or the recommendations by Bryden (1983), Carroll (1991) or Kohnke (1998) for the inclusion and intake amounts of protein concentrates.

However, it is interesting to note that high protein diets generally increase the amount of fermentation ‘heat waste’ produced during hindgut digestion, which would be a disadvantage to harness horses trained for extended periods under hot conditions, leading to increased risk of "blowing’ or thick windedness and dehydration. High protein diets in excess of requirement may also reduce renal fluid excretion, concentrating the urine, which may increase the levels of ammonia and nitrogenous waste in the environment of stabled horses and TCO2 levels in the blood. More research into these aspects is required.

However, horses under stress where cortisone has a catabolic effect in reducing muscle mass, may benefit from protein supplementation to help maintain muscle size and strength and overall race performance.

Chaff and Hay

Chaff or chopped hay as a bulking agent added to concentrate feeds to increase the volume of feed to appetite capacity and limit the rate of intake of starch concentrate in grains was included in the feeding programs of 93.9% of respondents. Again this reflected the trends of the aforementioned reviews and surveys, and is generally peculiar to Australian and New Zealand feeding practices (Southwood et al (1993 (a)), Kohnke, Kelleher and Trevor-Jones (1999).

A total of 83.6% of respondents indicated they provided hay or long-stemmed roughage to their horses on a daily basis, with 44.2% of respondents of the 85% who completed the questions related to the practices of feeding hay, indicating that lucerne hay was the major roughage base used to balance the concentrate to roughage ratio. The survey did not elucidate in quantitative terms, the average concentrate to roughage ratios of the diets, but traditionally, Standardbreds are fed a 55-60% concentrate (grain, protein seed, oil) to 40-45% roughage (chaff, hay and pasture) in Australia. (Kohnke 1998).

Due to the length of the questionnaire and the need to focus on the use of dietary supplements that could influence blood TCO2 levels, the question relating to the use of fat (as vegetable oil) in Stanardbred diets was not included. However, the use of small volumes of vegetable oil is often recommended as a part energy substitute for oats and other cereal grains to increase the energy density of rations, and limit the bulk and risk of ‘tying-up’ in horses in hard training, especially those with a reduced appetite. (Kohnke (1998), Kohnke, Kelleher and Trevor-Jones 1999).

The survey indicated widespread use of mineral, vitamin and electrolyte supplements to correct low or inadequate levels in the diet of horses in training, or a perceived or justified use to ensure that optimum performance is realised.

Generally, the less than expected use of commercial ready-to-use sweet and other premixed feeds as a source of minerals, vitamins and salts, was contradicted in this survey by over 50% of the respondents reporting that they supplemented diets with a general mineral and vitamin supplement, 43% of respondents used a calcium supplement and 57.5% an iron or iron/vitamin additive, while 46.3% of respondents used a Vitamin E, Vitamin B group and Vitamin C supplement on a daily basis.

The limitation on the size of the questionnaire restricted the response to the actual amounts of these supplements that were routinely used. In the interview survey by Southwood and colleagues (1993(b)), it was reported that Standardbred trainers fed an average of 253% (125-381%) of the NRC (1989) daily recommendations for iron intake, whereas thoroughbred trainers averaged 218% (range 85-461%) of requirements on a bodyweight basis in the rations of their horses. This may reflect the widespread belief that harness horses in training require a higher intake of iron to meet their needs and replace elevated amounts of iron (23-25mg iron/L of sweat) lost in sweat of Standardbreds in hard training (Kohnke, Kelleher and Trevor-Jones 1999).

A large proportion (83.2%) of respondents reported daily use of electrolyte replacers, including 21.0% who fed plain salt as a routine supplement. Of these; the major type of product used was a high potassium, no bicarbonate formulation that has been widely promoted as the electrolyte replacer suited to harness horses and horses that sweat heavily. The choice of this type of electrolyte formulation, which does not contain a direct source of an alkalinising agent in the form of bicarbonate, could reflect industry concerns related to pre-race TCO2 levels, or advertising to highlight this risk by commercial companies.

However, the response to the question related to the use of proprietary alkaline and other blood/muscle supplements was surprisingly high, with 27.4% of respondents indicating that they provided a daily dose of alkalinising agents, although 70.5% of the overall respondents reported that they did not use these types of supplements routinely. In the total survey return of 525 participants, only 11 returned an invalid or null response to this question. This may reflect a concern by trainers that alkalinising agents can elevate TCO2 levels.

The response to the question relating to the use of direct alkalinisers, such as sodium bicarbonate, and indirect alkalinisers, including sodium sulfate, sodium and potassium citrate, resulted in the rate of invalid and null responses exceeding 80%. A low number of respondents, (13.9%), allowing for an 81.1% invalid response, indicated they supplemented their horses with up to 30g of sodium bicarbonate daily in their rations. The question to determine the popularity of other indirect alkalising agents exceeded 96.2% invalid responses for pre-race administration of potassium citrate, sodium citrate and ‘tris’ buffer, all of which have been cited for their potential to elevate pre-race TCO2 if administrated in feed or by drench within 6-8 hours of racing (Auer 1999).

Although the survey suggested only minor use of alkalinising compounds a more direct interview based survey, such as carried out by Southwood and co-workers (1993 a), may have provided a more definite occurrence and frequency of pre-race usage.

Respondents reported a 46.5% daily use of commercial kidney tonics and proprietary muscle buffering agents, with only a 1.7% invalid response, suggesting that this practice to provide alkalinising action, usually predominately after hobbling up and fast work sessions, was accurately reported. However, interestingly, an overwhelming majority of respondents did not routinely administer post-race saline or electrolyte replacement drenches to their horses. Traditionally, this has been a historic practice by harness horse trainers as a means of replacing fluids and salts lost by travelling and racing, to correct dehydration, as well as the time honoured, but scientifically unsubstantiated, practice of "flushing" the system of lactic acid and other metabolicites after intense exercise.

The use of pre-race drips into the vein was reported by 4.0% of respondents, with 94.1% responding with a resounding negative to their routine use. This may reflect changing practices within the industry because of the widespread availability of oral electrolyte replacement drinks that can be used prior to racing, and the increased costs of intravenous drips that make the practice less attractive for the benefits, if any, that are provided.

The age-honoured practice by North American trainers of withdrawing water for up to 6-8 hours prior to racing to provide a haemoconcentration effect, reduce the risk of bleeding and lighten bodyweight, all of which may, for various reasons, help ensure optimum performance, appears not to be a common practice in Australia, as shown in the AHRC survey results.

Only 21.3% of respondents reported pre-race water withdrawal and deprivation. The majority of these indicated that water was withdrawn for up to 6 hours prior to racing. The low popularity of the practice may have been influenced by press reports of increased TCO2 concentrations that have been associated with pre-race deprivation of water (Auer 1999). The hot climatic conditions in Australia are more likely to increase the risk of dehydration and elevated metabolic stress factors in horses when water is withdrawn more than 4 hours prior to racing.

The AHRC survey of feeding practices provided a valuable insight and update of the feed types and supplement usage by Australian harness horse trainers as at the year 2000. The response numbers were within the expected range for a voluntary mail out survey, the information provided by participants was sufficiently detailed so as to allow an overview of feeding practices, including the use of alkalinising compounds, which was the ultimate aim of the survey.

The feeding practices were consistent with earlier reviews and the interview survey by Southwood and colleagues, published in 1993. The results of the survey raised a number of issues, the most prominent being the association of dehydration with high protein diets and water deprivation practices prior to racing, which may elevate TCO2 levels in pre-race samples. More research on this aspect needs to be carried out to substantiate any possible influence.

The contents and labelling of commercial products to highlight the inclusion of alkalinising compounds and their possible cumulative effects when combined with ready to use feeds in particular should be considered as an important service to trainers to reduce elevated TCO2 levels in pre race blood samples..

The assistance of trainers in completing this first national feeding survey is recognised and the AHRC should be acknowledged for this important industry initiative.

References