Valine requirement of female Cobb broilers from 8 to 21 days of age

Abstract

Summary: Valine is the fourth limiting amino acid (AA) in corn–soybean meal–based diets for broilers, and any deficiency of this AA in the diet would result in impaired growth performance. As feed-grade Val became commercially available, the focus is now on satisfying the needs of this AA in broiler diets. The purpose of this study was, therefore, to estimate the minimum requirement of digestible Val in ratio to Lys in practical diets of female Cobb-500 broilers during the starter phase (8–21 D). A dose-response experiment was conducted using 540 female broilers in a completely randomized design. A corn–soybean meal diet was formulated to be deficient only in Val, and crystalline L-glutamic acid in the basal diet was gradually replaced by L-Val, creating 6 different ratios of digestible Val to Lys. The feed intake, BW gain, feed conversion ratio, carcass parameters, bone parameters, and nitrogen excretion were evaluated. The results of this study showed that BW gain and feed conversion ratio were significantly improved by increasing the dietary digestible Val-to-Lys ratio but not feed intake. The bone parameters and nitrogen excretion showed no response to different dietary digestible Val-to-Lys ratio. Within the carcass parameters, only abdominal fat differed between treatments. The minimum requirement of the digestible Val-to-Lys ratio for optimum live performance and carcass parameters was estimated using nonlinear models and quadratic regression equations. Based on the results of the present study, it is concluded that the minimum requirement of the digestible Val-to-Lys ratio for female Cobb-500 broilers is 0.78.

Keywords

• amino acid
• dose-response
• ideal ratio
• valine