1. Forage quality and methane production of the grazing portion of grass produced under elevated [CO 2 ] A.L. Abdalla 1 ; R. Ghini 2 ; A.S. Natel 1 ; A.L. Abdalla Filho 1 ; H. Louvandini 1 ; M.C. Piccolo 1 (1) Centre for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil (2) Embrapa Environment, Jaguariuna, SP, Brazil International Conference Steps to Sustainable Livestock 12 – 15th January 2016, University of Bristol, UK

2. Brazil 355 million ha of arable land 2

3. Cerrado soils - extend over 200 million ha 25% of Brazil - increase food production - contribute to mitigating global changes Brachiaria grassland = 80 million ha - Potential to increase total soil OM - Soil C sequestration 3

4. Elevated [CO 2 ]: positive effect on crop yield; plant growth & C sequestration in plant biomass C4 plants less than C3 plants meta-analysis Mediterranean grassland forages increase NFC, reduction NDF and digestibility quality of tropical C4 plants??? 4

5. Objective to determine the effects of season and elevated [CO 2 ] upon biomass production, fiber quality and methane production of the grazing portion of Brachiaria decumbens 5

6. Site: FACE facility Embrapa Environment, Jaguariúna - Brazil Free-Air Carbon Dioxide Enrichment (FACE): Twelve 10m Ø rings in 7 ha coffee plantation Six rings control treatment Six rings pure CO 2 to increase the level of [CO 2 ]: controlled by automatic environmental sensors Increases of CO 2 began on August, 2011 Target level 550 ppm (Ghini et al., 2015) 6

7. Site: planting, sample collection 22 nd November 2011 2 plots 0.25 m 2 Brachiaria decumbens cv basilic standardization after 10 weeks cutting with scissors the grazing portion of the stand (at 20 cm height) forage availability estimated and collected every 21 days Jan 2012 through Feb 2014 7

8. Biomass production Forage quality Site: analysis CENA / USP, Piracicaba - Brazil 8

9. Performance of FACE system 9 Frequency distribution of daytime CO 2 air concentration measured in the center of the rings during 2012 and 2013 (a) and hourly concentration during December 2012 (b). Bars represent standard errors (Ghini et al., 2015)

10. Rainfall and Temperature Climatic condition at the FACE facility in which the forage samples were collected from February 2012 to January 2013. 10

11. Biomass production Biomass available (gDM/m 2 ) of Brachiaria decumbens grown under two contrasting concentration of CO 2 and harvested at 20 cm high every 21 days from February 2012 to January 2014. 11

12. Forage quality 12 springsummerautumnwinter SE + CO 2 ambient+ CO 2 ambient+ CO 2 ambient+ CO 2 ambient Fiber composition (g/Kg DM) ADF324317344335326 3043003.6 ADL7170656656 57 3.4 CEL253247279269270 2472433.9 NFC86957279807690944.5 In vitro degradability (g/Kg DM) OMD5735675545535585595695826.5 NDFD3753683663583723753763897.7 ADF: acid detergent fibre, ADL: acid detergent lignin, CEL: cellulose and NFC: non fibre carbohydrate. OMD: organic matter degraded, NDFD: NDF degraded after 24 h in vitro incubation

13. Forage quality 13 Net CH4 (mL/g OMD) after 24h in vitro incubation of Brachiaria decumbens grown under two contrasting concentration of CO 2 and harvested at 20 cm high every 21 days from February 2012 to January 2014.

14. Discussion -Long term observation (two years) for Brachiaria decumbens at 21 days interval: -Biomass production -elevated [CO 2 ]: -only tendency - 285 vs 261 g DM/m 2 (P < 0.10), -rain season (spring & summer): -increase in biomass production up to 14% (P < 0.01), -improvement of water use -growth limited by nutrient and water availability -Forage quality -C4 plant -differences on ADF, ADL and NFC (season) (P < 0.10), -No significant effect on OMD and NDFD. -C3 Mediterranean grasses meta-analysis -No differences on fiber composition -Reduction on digestibility 14

15. Conclusions Elevated [CO 2 ] and rain season: significantly increased forage production, contribute to sequester carbon in plant biomass. Tropical conditions and C4 grasses: feeding at its best protein and fermentable carbohydrate ratio for: advantages in the microbial synthesis methane production intensity (L/Kg OMD) 15

16. Acknowledgments The authors would like to thank the fellowship grant and financial support from CNPq, FAPESP and Embrapa project “CLIMAPEST”. 16 Thank you for your attention abdalla@cena.usp.br