Performance response of lactating and growing rabbits to dietary threonine content

This study investigated the threonine requirements of rabbits. Five diets, containing from 5.4 to 7.2 g/kg crude threonine, were formulated by supplementing a basal diet with l-threonine. Feeding trials were carried out using 370 rabbit does and 1150 weanling rabbits, grown in individual (n = 190) or in commercial (n = 960) cages, and slaughtered at 2.035 ± 0.025 (SE) kg of body weight. Milk production was measured in 80 lactations. Carcass traits were determined in 115 rabbits. The apparent threonine digestibility (%) was 63.8 ± 1.3 in the basal diet and 93.0 ± 6.0 for l-threonine, as estimated by the difference method. A minimal dietary concentration of 6.4 crude and 4.4 g/kg digestible threonine should be included to maximize the performance of lactating does. For growing rabbits, these values were 6.0 crude and 4.0 g/kg digestible. An excess of dietary threonine tended to impair intake and performance and to reduce the weight of perirenal fat. The results of this study also demonstrated the need for using digestible rather than total values to express the threonine requirements of rabbits.