Growth of thoroughbreds fed a low-protein supplement fortified with lysine and threonine.

This research paper analyzes the effect of protein and certain amino acid supplements on the growth of Thoroughbred foals and yearlings. It found that, when given a low-protein diet supplemented with lysine and threonine, the horses grew at the same or greater rate as those on a standard protein control supplement.

Methodology

• The researchers tested two groups of Thoroughbreds: one group was given a control supplement with a traditional high protein content, while the other, an experimental group, was given a supplement with a lower crude protein content fortified with lysine and threonine. All foals were monitored over 14 months, with physical measurements and blood samples taken monthly to provide data.

Measurements

• Horses were measured for body weight (BW), average daily gain (ADG), body condition, wither height, hip height, body length, girth, forearm length, front and hind cannon length, and carpus and fetlock circumference.
• Blood plasma analysis was conducted to monitor levels of total protein, albumin, creatinine, and urea nitrogen. The variation that was observed from these measurements would subsequently be used to analyze the effect of the different diets on the horses.

Findings

• Over the course of the study, the researchers found no statistically significant difference (P > 0.05) in physical measurements or blood data between the control and experimental (Lys/Thr) groups.
• However, the foals on the Lys/Thr diet had significant differences in their average daily weight gain at specific times: November, December, and April.

Significance

• The results showed that lowering the protein content while adding lysine and threonine resulted in growth rates that were equal and sometimes greater than those receiving the traditional high protein supplement.
• This efficiency in growth implies that these specific amino acids, which are often lacking in high-protein horse diets, may play a critical role in optimizing protein use during growth and development. The study therefore provides further insight into the potential benefits of optimizing protein quality over simply increasing protein quantity in a young horse’s diet.