A meta-analysis was conducted to compare effects of C4 and C3 grasses as well as warm and cold climate legumes on CH 4 production of ruminants. For this purpose, a database was built using 22 in vivo studies containing 112 observations with 58 C3 grasses, 28 C4 grasses, 26 cold legumes and 12 warm legumes. Neutral detergent fibre (NDF), crude protein (CP) and total tract organic matter (OM) digestibility ranged from 415 to 753 g/kg DM versus 361 to 754 g/kg DM, from 24 to 254 g/kg DM versus 44 to 314 g/kg DM and from 0.51 to 0.71 versus 0.56 to 0.83 for C4 and C3 grasses, respectively. The NDF, CP and total tract OM digestibility ranged from 441 to 690 g/kg DM versus 252 to 684 g/kg DM, from 93 to 236 g/kg DM versus 141 to 269 g/kg DM and from 0.42 to 0.57 versus 0.38 to 0.79 for warm and cold legumes, respectively. Relationships between CH 4 production and forage characteristics were analysed by analysis of covariance. For grasses, the main factors tested as fixed effects were NDF and CP content of the diet, total tract OM digestibility, intake, animal species, forage family and random trial effect. For legumes, tannin level was included in the model. Results indicate that ruminants fed C4 grass produced 17% more CH 4 as L/kg OM intake (P<0.05) compared to those fed C3 grass. Animals fed warm legumes produced 20% less CH 4 (P<0.05) than those fed C4 grasses. In contrast, no difference in CH 4 production between C3 grasses and cold legumes. Use of some legumes in warm climates could be a strategy to reduce CH 4 emissions by ruminants.

Sugarcane cultivars are interspecific hybrids with an aneuploid, highly heterozygous polyploid genome. The complexity of the sugarcane genome is the main obstacle to the use of marker-assisted selection in sugarcane breeding. Given the promising results of recent studies of plant genomic selection, we explored the feasibility of genomic selection in this complex polyploid crop. Genetic values were predicted in two independent panels, each composed of 167 accessions representing sugarcane genetic diversity worldwide. Accessions were genotyped with 1,499 DArT markers. One panel was phenotyped in Reunion Island and the other in Guadeloupe. Ten traits concerning sugar and bagasse contents, digestibility and composition of the bagasse, plant morphology, and disease resistance were used. We used four statistical predictive models: bayesian LASSO, ridge regression, reproducing kernel Hilbert space, and partial least square regression. The accuracy of the predictions was assessed through the correlation between observed and predicted genetic values by cross validation within each panel and between the two panels. We observed equivalent accuracy among the four predictive models for a given trait, and marked differences were observed among traits. Depending on the trait concerned, within-panel cross validation yielded median correlations ranging from 0.29 to 0.62 in the Reunion Island panel and from 0.11 to 0.5 in the Guadeloupe panel. Cross validation between panels yielded correlations ranging from 0.13 for smut resistance to 0.55 for brix. This level of correlations is promising for future implementations. Our results provide the first validation of genomic selection in sugarcane.

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