Growth Of Thoroughbreds Fed A Low-protein Supplement Fortified With Lysine And Threonine
Staniar, W. B., D. S. Kronfeld, J. A. Wilson, L. A. Lawrence, W. L. Cooper and P. A. Harris. 2001. Growth of Thoroughbreds fed a low-protein supplement fortified with lysine and threonine. J. Anim. Sci. 79:2143-2151.
Abstract
Growth and protein status were examined in Thoroughbred foals and yearlings offered pasture supplements with different crude protein contents and amino acid compositions. Both supplements contained 3.0 Mcal/kg DM, 10% corn oil, 1.4% calcium, and three sources of fiber. The control supplement contained 14% CP and 22% soybean meal, whereas the experimental supplement contained 9% CP and 3% soybean meal and was fortified with 0.6% lysine and 0.4% threonine. Physical measurements and blood samples were taken monthly for a period of 14 mo. Measurements included BW, ADG, body condition (BC), wither height, hip height, body length, girth, forearm length, front and hind cannon length, and carpus and fetlock circumference. Blood plasma analysis included total protein, albumin, creatinine, and urea nitrogen. Effect of diet and time were evaluated by analysis of variance with repeated measures.
Results suggest that the foals offered the Lys/Thr grew at the same or greater rates than foals on the control supplement. When a low-protein diet was fortified with the first two limiting amino acids, the protein was utilized more efficiently for growth and development. This study gives further insight into the role of protein quality during a foal’s 1st yr of growth.