Yerba Mate (Ilex paraguarensis) as a novel feed supplement for growing lambs

Yerba Mate (Ilex paraguarensis), a plant known for its high antioxidant content, was fed to 20 of 40 lambs for 8 weeks. Lambs were randomly divided into two groups: one group (n = 20) was fed the control diet and one group (n = 20) was fed the control diet with 2.5% Yerba Mate. Lambs were group housed by treatment and fed ad libitum through automatic feeders that recorded individual food intake. Lambs received the dietary treatments for a total of 8 weeks and were monitored for live weight (LW), average daily growth rate (ADG), food conversion rate (FCR) and feed intake. Blood samples (8 mL) were taken from all lambs, on weeks 0, 2, 4, 6, and 8 and plasma analysed for total antioxidant capacity (TAC), advanced oxidation protein products (AOPP), non-esterified fatty acids (NEFA), triglycerides and cholesterol. Wool growth and cell-mediated immune status (PHA) were also measured. Overall, Yerba Mate (YM) lambs ate more (mean ± sem; 989 ± 68 g/d; P < 0.001) pellet than the control (CTRL) lambs (759 ± 63 g/d), however, LW (YM: 33.5 ± 1.1 kg and CTRL: 33.5 ± 1.2 kg) and ADG (YM: 207 ± 9.6 g/day and CTRL: 191 ± 8.4 g/day) were not significantly different between the two groups. FCR (g VFI/g ADG) was higher (P < 0.05) in the Yerba Mate supplemented lambs compared to the control ones (4.78 ± 0.45 and 3.97 ± 0.32, respectively). Wool growth rate was higher (P < 0.01) in the YM lambs (0.09 ± 0.005 g/cm2 and 0.07 ± 0.005 g/cm2, respectively). There was a significant effect of the interaction diet ×sampling time on plasma AOPP concentrations (P < 0.05), with Yerba Mate lambs presenting higher AOPP levels than the control lambs on weeks 4 and 5. Overall, plasma NEFA and triglycerides concentrations were similar in the Yerba Mate and in the supplemented group (NEFA: 0.15 ± 0.02 mmol/l and 0.17 ± 0.02 mmol/l, and triglycerides: 0.27 ± 0.02 mmol/l and 0.29 ± 0.02 mmol/l, respectively), however, a significant effect of the interaction time of sampling × diet on both metabolites (P < 0.05) was noted, with Yerba Mate supplemented lambs presenting lower NEFA and triglycerides levels than the control lambs on weeks 3, 4, 5 and 6 and on weeks 3, 4 and 5. No significant effect of diet was noted for PHA test, cholesterol and TAC levels, fat depth, eye muscle depth and muscle score. Our study indicates that although Yerba Mate supplementation can increase feed intake and wool growth in lambs, it did not result in significant differences in LW, ADG or body composition and had a significant negative effect on FCR. Further work is required to investigate the effect of Yerba Mate supplementation on lambs production and health.