Effects of inclusion of licorice (Glycyrrhiza glabra L.) leaves, a tannin-containing plant, in a low-protein diet on feedlot performance and carcass characteristics of fat-tailed lambs

Abstract

The protein-sparing effect of condensed tannins (CT) was investigated in growing lambs fed a low- or high-protein diet during a 50-day period. Isocaloric diets containing 106 g crude protein/kg dry matter (DM) (low protein; LP) or 138 g crude protein/kg DM (high protein; HP) were formulated using 70 % concentrate, 15 % corn silage, and 15 % dried licorice leaves, providing CT (4.1 g/kg DM). Twenty-four crossbred male lambs (3-4 months old, 23.9 ± 5.2 kg body weight) were assigned to one of four diets: LP with polyethylene glycol (PEG; 40 g/kg DM) supplementation (LP + PEG), LP without PEG supplementation (LP - PEG), HP with PEG supplementation (HP + PEG), and HP without PEG supplementation (HP - PEG). The effect of dietary crude protein level and CT on feed intake was not significant (P > 0.05). However, a positive effect on daily gain (P < 0.001) and feed conversion ratio (FCR; P < 0.01) was observed in lambs fed with HP diets. An interaction effect between crude protein level and PEG was observed, and consequently, FCR was higher in group LP + PEG (10.1; P < 0.05) than in groups LP - PEG (7.3), HP + PEG (5.3), or HP - PEG (5.4). There was also an interaction effect between crude protein level and PEG on kidney, pelvic, and heart fat, presenting a higher relative weight in group LP + PEG (12.6 g/kg) than in group HP + PEG (9.2 g/kg; P < 0.05), but no (P > 0.05) in groups without PEG supplementation. These preliminary results suggest that the use of CT can minimize the negative effect of low-protein diets on FCR in lambs.

Effect ofCaesalpinia coriariaFruits and Soybean Oil on Finishing Lamb Performance and Meat Characteristics

“…The dietary concentration of CT in this experiment (0.42 g/kg DM) was lower compared to other studies; the experiment with lamb rations including fruits [ 15 ] with concentrations from 1.7 to 3.6 g/kg and daily gain was similar to the control diet, while, in other experiments with higher concentration silages (32 and 62 g/kg DM), the daily gain was reduced at the highest concentrations. The study [ 5 ] included Glycyrrhiza glabra leaves in lambs with a dietary concentration of 4 g/kg of DM and found a positive response only when PEG associated with the protein.…”

“…The effects of substrates containing tannins on ruminal fermentation are desirable if they do not alter VFA concentration and decrease both ammonia N and methane production [ 6 ]. The beneficial effects of condensed tannins in moderate dietary concentrations (20–40 g/kg DM) are associated with the improvement of amino acid supply to the small intestine [ 4 ] or by the protein sparing effect [ 5 ].…”

“…The inclusion of plants with condensed tannins (CT) in low or moderate levels in ruminant diets has demonstrated beneficial effects on lamb performance because the reduction in ruminal protein degradation improves the amino acid supply to the small intestine [ 4 , 5 ]. Tannins may also reduce losses of methane, and this could increase ME for growth; in vitro studies have shown that increasing graded levels of tannin-containing tropical tree leaves result in a linear reduction in methane concentration [ 6 ].…”