The effect of betaine and dl-methionine on growth performance and carcass characteristics in meat ducks

An experiment was conducted with meat ducks to determine if betaine could replace methionine in a methionine-deficient diet. In order to avoid the effects of betaine as a methyl-group donor or as an osmoprotectant or coccidiostat enhancer, sufficient amounts of methyl-donating compounds were added and clean conditions were used to reduce the coccidiosis challenge. A total of 576-day-old female meat ducks were fed one of four diets in a 2 (0 and 0.5 g betaine/kg) × 2 (0, 1.2 g dl-methionine/kg) factorial arrangement between 0 and 41 days of age. The basal diet contained 3.5 g methionine/kg (0–21 days), 3.0 g methionine/kg (21–38 days) and 3.0 g methionine/kg (38–41 days), respectively, and 3.4 g cystine/kg (0–21 days), 3.3 g cystine/kg (21–38 days) and 3.4 g cystine/kg (38–41 days). There were six replicates of 24 ducks per treatment. Performance was determined at 21 and 42 days. At the end, carcass yields, breast yields and abdominal fat were determined on nine ducks per replicate. There were no significant interactions between betaine and dl-methionine. dl-Methionine improved (P < 0.01) body weight and feed to gain at 21 days, and improved (P < 0.05) body weight at 41 days. The effect of betaine were also significant (P < 0.01) in term of bodyweight at 21 days and feed to gain. Betaine supplementation significantly decreased abdominal fat (P < 0.001) and increased breast yield (P < 0.01). Although there was a marked and significant response to methionine supplementation (1.2 g dl-methionine/kg) in breast yield (P < 0.01), the effect of methionine supplementation was not significant on abdominal fat (P > 0.05). These results suggest that betaine is more effective in improving carcass quality than methionine, and also effective in promoting growth and feed efficiency of starter ducks, provided the dietary levels of methionine are not marginally limiting.