Effects of dietary supplementation with Acacia mearnsii tannin extract on carcass characteristics and meat quality of lambs

Plant extracts are used as possible methane mitigants and to replace antibiotic feed supplements previously used prophylactically to improve the adaptation of lambs in intensive feeding systems. This study investigated the effects of Acacia mearnsii tannin extract used as anti-methanogenic feed additives on carcass and meat quality of lambs.

Forty Dohne Merino lambs, with an initial mass between 23.90 kg and 37.40 kg, were first stratified according to their initial body weight and thereafter one of the eight lambs with similar body weight were randomly assigned to four treatment groups (n = 10 lambs/treatment). The lambs were fed ad libitum with a basal total mixed ration. Four experimental diets were formulated: TMR diet (control); TMR diet with Rumensin^® at a dosage of 75 mg/kg of DM feed (Monensin; Positive control); TMR diet with raw condensed Acacia tannin at 20 g/kg of DM feed (Crude tannin); TMR with addition of encapsulated condensed Acacia tannin at 20 g/kg of DM feed (Encapsulated condensed tannins). The lambs were slaughtered at a live mass of about 50 kg after a 19 week trial period.

Dietary tannin additives did not affect the carcass composition or colour aspects of lamb meat. However, there were minor changes in fatty acid profiles, particularly in the intramuscular adipose tissue. The addition of encapsulated tannin extract resulted in a higher proportion of C18:2n6t (0.15% ± 0.03 vs. 0.19% ± 0.03; p < 0.05), C18.3n3 (0.24% ± 0.04 vs. 0.29% ± 0.04; p < 0.05), C22:6n3 (0.02 ± 0.01 vs. 0.05 ± 0.03; p < 0.05), in comparison to monensin. This improvement in fatty acid profiles is presumably beneficial for human health, but it could affect the sensory quality of meat.

Our results suggest that Acacia mearnsii tannin extracts can be included as anti-methanogenic feed additives in lamb diets without compromising product quality.