Response to dietary nitrogen in ponies

Utilisation of nitrogen was studied in 4 crossbred ponies. A latin square design was used to study the effects of corn gluten meal, casein or urea when added to a low protein basal diet. Apparent nitrogen digestion, nitrogen retention, total plasma protein, plasma urea and plasma-free amino acids were measured. The addition of corn gluten meal, casein or urea to the basal ration increased apparent digestion of nitrogen. Casein produced a significantly greater (P less than 0.05) nitrogen retention than corn gluten meal or urea. Plasma urea nitrogen increased significantly (P less than 0.01) in ponies given the urea diet. Total plasma protein concentrations were essentially unchanged for all treatments. Elevated plasma levels of proline, valine, methionine, isoleucine, leucine, tyrosine, lysine, and arginine were observed with ponies receiving the casein supplement. The data support the hypothesis that the horse is capable of responding to quality of dietary protein.