High muscle glycogen levels and high race participation in young horses fed forage-only diets
Sara Muhonen, AgrD
Sixteen young Standardbred trotters were studied from January as 2-year-olds till December as 3-year-olds. They were fed forage-only diets and half of them got a training program were the distance for high intensity exercise was reduced by 30%. During the entire study the horses were fed forage-only diets consisting of early harvested energy rich forage complemented with lucerne, minerals and vitamins. The horses consumed 1.7-2.6% DM of body weight, which corresponded to 19-28 MJ metabolizable energy per 100 kg body weight and day. Their BCS (body condition score) were 4.8-5 throughout the study and they had normal growth and weight gain.
The horses’ muscle glycogen levels (rested > 48 hours) were 588 mmol/kg dry weight as 2-year-olds and 620 mmol/kg dry weight as 3-year-olds and there were no differences between training groups. These muscle glycogen levels are in the normal range for what has earlier been reported for Standardbred horses fed concentrate.
Including both training groups the planned distance for high intensity training averaged 5368 m per week. This is shorter than reported from professional trainers that represented 13% of the Swedish population of Standardbreds in training where the distance for high intensity training averaged 6571 m per week. 100% of the experimental horses passed a preparation race as 2-year-olds and 94% qualified for races as 3-year-olds which was greater than for the rest of the cohort in training and greater than the experimental horses’ older siblings. 56% of the experimental horses raced as 3-year-olds which was equal to the cohort in training and siblings. Breeding index for sires to the experimental horses was lower than for sires of their siblings. In total, the experimental horses participated in 27 races and the drivers racing them earned more prize money per race with the experimental horses than with other horses they had raced during the last three years (4541 SEK vs. 3242 SEK per race).
In conclusion, feeding young horses with free access to only energy rich high quality forage containing enough protein (complemented with minerals and vitamins) and shorter distance for high intensity training implied no restrictions for muscle glycogen, growth, BCS or ability to qualify and race before four years of age.
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