Effects of chestnut bark (Castanea spp.) tannin extracts on selectivity, dry matter intake, weight gain, and enteric methane emission from llamas (Lama glama) under grazing conditions in the high Andean grasslands

The present study's objective was to evaluate the effects of chestnut bark (Castanea spp.) tannin extracts on selectivity, organic matter intake, dry matter intake, weight gain, and enteric methane emissions from llamas as a mitigation strategy. The study was carried out from August to September 2016 at the Experimental Centre IVITA-Marangani-Cusco-Peru (4200 m above sea level). Twenty young female llamas (4.1 ± 0.34 years old) with an average live weight of 99.2 ± 5.21 kg at the beginning of the experiment were used. The llamas were allocated to two treatments (control and tannin). Organic matter intake was calculated from organic matter excretion and organic matter digestibility, the dry matter intake was calculated by using percentage of ash content of the diet, and methane emissions were determined using the SF₆ tracer technique over seven days, while the llamas grazed 9 h per day on a native pasture dominated by Festuca rigescens and Calamagrostis amoena. The tannin group was provided with tannin extract derived from chestnut bark at a dose of 12 g/day orally before grazing. The selectivity in both groups was similar (P > 0.05), consuming 91.5 % of grasses and graminoids, 84.5 % of leaves and stems and 61.5 % of green matter. The control group's feed intake was 1614.64 g/day, while that of the Tannin group was 1624.70 g/day (P > 0.05). Weight gain at 31 days was similar for both groups (P > 0.05) (5.7 and 5.2 kg for the control and tannin groups, respectively). Enteric methane emissions were 27.35 ± 1.573 g/day for the control group and 19.32 ± 1.057 g/day for the tannin group (P < 0.001); showing the same tendency when methane emissions were compared according to llama live weight with 0.24 ± 0.012 and 0.17 ± 0.008 g/kg LW/day for the control and tannin group, respectively, (P < 0.001). It was concluded that the use of tannins in the present study reduced methane emissions by approximately 30 % without affecting selectivity, Dry matter intake, and weight gain in llamas.