Young horses and brood mares have a greater nutritional demand for high-quality protein than mature horses. During growth, pregnancy and lactation, ensuring an adequate supply of the essential amino acids needed to utilise dietary protein is particularly important for healthy development and optimum performance. Vetpro Lysine-T for Young and Breeding Horses provides lysine and threonine, the two limiting essential amino acids that help maximise the use of digestible protein already present in the diet.
Protein is in every cell in the body, muscles, tendons, organs, glands, hooves and hair.
Protein is a collection of amino acids, much like bricks in a wall. There are two types, essential and non-essential. The latter can be ingested or mainly created within the body of the horse. The essential ones must be taken up from the diet.
There are only two limiting amino acids, these are Lysine and Threonine. A limiting amino acid is one that if not present, will prevent protein from being made, even if other amino acids are present in adequate quantities.
Therefore, protein quality can be improved (released) by supplementing with these two limiting amino acids. So just increasing the quantity of protein fed to a horse will not improve the uptake and increasing the amount of protein (or a protein supplement) can be detrimental to the health of the horse.
It is sometimes considered that the growing horse needs extra protein to maximise condition and muscle. In particular, young Thoroughbreds are fed high grain diets to maximise growth for the early demands of racing.
Overfeeding this protein has negative influences on the health of the horse (Mok & Urschel, 2020). Also, overfeeding protein has an acidogenic effect, it results in an increase of lactic acid in the system (Graham-Thiers & Kronfeld, 2005).
Acidogenic means a lowered pH level of the blood resulting in compromised health of the horse.
Amino acid balance/protein quality is especially important for growing horses and pregnant/lactating mares, while adult horses are less sensitive to protein quality (National Research Council, 2007).
Scientific studies on young horses have shown that supplementation with Lysine and Threonine safely optimised growth rates (Staniar et al., 2001).
It was found that lysine intake appears to be a greater factor than energy or protein in influencing bodyweight gain of weanlings (Ott & Kivipelto, 2002).
Fortification of the diet with Lysine and Threonine can allow the total quantity of protein, and in particular grains, to be decreased while still promoting optimum growth and muscle mass (Graham-Thiers & Kronfeld, 2005).
It has been scientifically shown that Lysine and Threonine supplementation in grazing lactating mares enhanced milk production and improved milk protein and fat quality (Lin et al., 2024).
Foal growth during lactation is influenced significantly by the quality of protein ingested by the mare.
The dietary protein intake of the lactating broodmare should therefore contain sufficient high-quality protein to prevent depletion of her body reserves (van Niekerk & van Niekerk, 1997).
A measure for the daily requirement of lysine for a 500 kg horse is 27 g (National Research Council, 2007) and it has been calculated that threonine is 0.62 of that. So ideally 16–17 g (Mok & Urschel, 2020).
It is important to check the amount being fed in premix feeds and adjust the amount being supplemented accordingly. Adjust for the amount stated in the premix feed compared to the recommended amount as it shows a total amount.
For example, if you feed 2 kg of premix instead of a recommended 4 kg then halve the estimated amount of Lysine and Threonine actually in the horse’s feed.
Yearling horses should receive 1.9 g/Mcal daily (Ott et al., 1981).
This refers to the fact that if they are not available, and in sufficient quantity, it means that the protein that the horse eats will not be absorbed and that seriously affects the total health of the horse.
It can be, but it is very rare. The horse must excrete the excess and will drink more water and urinate more frequently. It can be noticed by an ammonia smell in the stable.
By improving the uptake of digestible protein which builds muscle as well as providing full health benefits.
Daily requirement (500 kg horse): Approximately 27 g lysine and 16–17 g threonine (National Research Council, 2007; Mok & Urschel, 2020).
Check the amount of lysine and threonine already supplied by premix feeds and adjust supplementation accordingly. For example, if feeding 2 kg of a premix instead of the recommended 4 kg, halve the estimated amount of lysine and threonine supplied by that feed.
Yearlings: 1.9 g/Mcal daily (Ott et al., 1981).
Graham, P. M., Ott, E. A., Brendemuhl, J. H., & TenBroeck, S. H. (1994). The effect of supplemental lysine and threonine on growth and development of yearling horses. Journal of Animal Science, 72(2), 380–386. https://doi.org/10.2527/1994.722380x
Graham-Thiers, P. M., & Kronfeld, D. S. (2005). Amino acid supplementation improves muscle mass in aged and young horses. Journal of Animal Science, 83(12), 2783–2788. https://doi.org/10.2527/2005.83122783x
Graham-Thiers, P. M., & Kronfeld, D. S. (2005). Dietary protein influences acid-base balance in sedentary horses. Journal of Equine Veterinary Science, 25(10), 434–438. https://doi.org/10.1016/j.jevs.2005.09.006
Lin, J., Jing, H., Wang, J., Lucien-Cabaraux, J.-F., Yang, K., Liu, W., & Li, X. (2024). Effects of lysine and threonine on milk yield, amino acid metabolism, and fecal microbiota of Yili lactating mares. Frontiers in Veterinary Science, 11, Article 1396053. https://doi.org/10.3389/fvets.2024.1396053
Ott, E. A., Asquith, R. L., & Feaster, J. P. (1981). Lysine supplementation of diets for yearling horses. Journal of Animal Science, 53(6), 1496–1503. https://doi.org/10.2527/jas1982.5361496x
Ott, E. A., & Kivipelto, J. (2002). Influence of energy and protein content of the concentrate and restricting concentrate intake on growth and development of weanling horses. The Professional Animal Scientist, 18(4), 302–311.
Staniar, W. B., Kronfeld, D. S., Wilson, J. A., Lawrence, L. A., Cooper, W. L., & Harris, P. A. (2001). Growth of Thoroughbreds fed a low-protein supplement fortified with lysine and threonine. Journal of Animal Science, 79(8), 2143–2151. https://doi.org/10.2527/2001.7982143x
van Niekerk, F. E., & van Niekerk, C. H. (1997). The effect of dietary protein on reproduction in the mare. II. Growth of foals, body mass of mares and serum protein concentration of mares during the anovulatory, transitional and pregnant periods. Journal of the South African Veterinary Association, 68(3), 81–85. https://doi.org/10.4102/jsava.v68i3.881
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