Effect of excess leucine in low protein diet on ketosis in 3-week-old male broiler chicks fed different levels of isoleucine and valine

A broiler study was designed to test whether or not the toxicity associated with high dietary Leu, is alleviated by the addition of Ile and Val; and if Leu toxicity is accompanied by ketosis. Dietary levels of 13.6 and 30.6 g Leu/kg, 8.3 and 11.6 g Ile/kg and 8.6 and 12.0 g Val/kg were used in a 2×2×2 factorial treatment arrangement with a complete randomized design. The isocaloric (ME=13.4 MJ/kg diet), and isonitrogenous (218 g crude protein/kg) diets were fed ad libitum to 1-week-old male broiler chicks for 14 days. Body weight gain, feed conversion, and β-OH butyrate level in plasma were determined at the end of the starter period. The diet based on 30.6 g Leu/kg in combination with the lower levels of Ile and Val reduced (P<0.05) weight gain, cumulative feed intake, and feed conversion ratio by 90 and 76 g, and 0.065 points, respectively. A complete restoration of these criteria was obtained by increasing Ile and Val by 40% above their initial levels. β-OH butyrate levels in the plasma of birds receiving all the treatments were not significantly different and the grand mean value was 55 mg/l. The results indicated that high Leu in a low protein diet reduced the overall performance of young birds but failed to induce ketosis.