Polyethylene glycol as a means far reducing the impact of condensed tannins in carob pulp: Effects on lamb growth performance and meat quality

We conducted an experiment to evaluate the effects that a diet containing c ondensed tannins with and without polyethylene glycol (PEG) has on lamb gro wth and meat quality. Twenty-three male Comisana lambs were introduced to t he three experimental diets between 45 and 50 d of age. Eight were given a diet containing 56% of Ceratonia siliqua (carob) pulp (tannin group), anoth er eight received the same diet with a supplement of 40 g of PEG for each k ilogram of diet (PEG group), and the remaining seven lambs were given a con ventional maize-based diet (maize group). Voluntary feed intake and live we ights were measured until slaughter at 105 d of age, and digestibility meas urements were undertaken toward the end of the feeding trial. Carcass yield , meat quality characteristics, and a taste panel evaluation were conducted . The tannin-based diet contained 2.5% condensed tannins (DM basis), and la mbs given this diet had lower growth rates and poorer feed efficiencies (P < .01) compared with the other treatment groups. Daily gain was similar bet ween the maize and PEG lambs, although the efficiency of feed conversion wa s highest in the maize group. The digestibility of DM, N, and fiber was red uced (P < .05) by the condensed tannins. Lambs fed the tannin diet had a lo wer carcass yield (P < .05) and had less fat (P < .05), and the meat had a higher ultimate pH (P < .01) than those given the PEG; or maize diets. Cond ensed tannins affected meat color, which was lighter (L*) than meat from la mbs given the PEG-containing diet (P < .01). Sensory evaluation showed that panelists preferred meat from lambs receiving PEG and maize treatments com pared with those receiving the tannin diet, and this could be related to di fferences in meat ultimate pH and carcass fatness. These results show that condensed tannins from carob pulp are very detrimental to feed digestibilit y and lamb performance. Inclusion of 40 g of PEG/kg diet eliminated the eff ects of condensed tannins so that lamb performance and meat quality were si milar to lambs given a maize-based diet.