Reducing the impact of condensed tannins in a diet based on carob pulp using two levels of polyethylene glycol: lamb growth, digestion and meat quality

Fourteen male Comisana lambs were divided into two groups of seven at age 45 days and were fed a diet containing 56% of dried carob pulp ( as fed basis). One group (P10) received a supplement of 10 g of polyethylene glycol ( PEG) for each kg of diet, while the second group (P40) received a supplement of 40 g of PEG for each kg of diet. Both diets were ground and supplied ad libitum. The experimental diet contained 2.1% of condensed tannins (CT) on a dry matter basis. The lambs fed the P40 diet had higher average daily gain than the P10 lambs (P < 0.05) and obtained higher live weights at slaughter (P = 0.08) although the dry matter intake was not different between the treatments. The increased level of PEG (P40 vs. P10 lambs) increased dry matter digestibility (P = 0.07) and nitrogen (N) and neutral detergent fibre (NDF) digestibility (P < 0.01). The carcasses from the P40 lambs were heavier and fattier than those from the P10 lambs (P < 0.05). Meat ( l. dorsi muscle) from the P10 lambs showed higher (P < 0.05) values of lightness (L*) compared to the P40 lambs. No differences in eating quality were registered among the groups. These results indicate that in a diet based on carob pulp (56%), 10 g of PEG per kg of diet are not sufficient to eliminate the effects of CT.