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International audience; This experiment was designed to better understand the differences in enteric methane (CH4) emissions of ruminants in tropical and temperate areas. Two double 4 4 Latin squares using adult sheep were evaluated simultaneously in a temperate and a tropical site. At each site, two breeds (four Texel, temperate origin, and four Blackbelly, tropical origin) and four hay types (two C3 grasses and two C4 grasses grown, respectively, in temperate and tropical sites) were tested. High-(H) and low-quality (L) grass hays were tested within each type of grass. No difference in dry matter (DM) intake (g/kg BW/d) was observed between sites. Intake of C4 grass was lower than that of C3 grass. A breed site interaction was observed. In the tropical site, dry matter intake (g/kg BW/d) was higher in Blackbelly compared to Texel, whereas no difference was observed in the temperate site. The total-tract DM, OM (organic matter), NDF (neutral detergent fiber) and ADF (acid detergent fiber) digestibility values recorded in the temperate site were lower (P < 0.01) than those reported in the tropical site. Methane yield (g/kg DM intake) was not affected by site, whereas a breed site interaction was observed. In the tropical site, methane emission was lower for Blackbelly compared to Texel, whereas the opposite was observed in the temperate site. Differences in methane emissions between the temperate and tropical sites could only be the result of diet and breed interactions with the environment.

International audience; Microbial fermentation of carbohydrates in the rumen is largely responsible for the emis- sion of methane by ruminants. Ruminants fed tropical forages usually produce more enteric methane than ruminants fed temperate forages. The relative influence of forage type, breed and temperate vs tropical environment on rumen microbial populations is not known. This experiment aimed to separate these effects. We designed two parallel experiments in sheep in two sites: temperate (France) and tropical (French West Indies), using in each site two breeds, Texel (temperate origin), and Blackbelly (tropical origin) fed the same temperate forages (C3 carbon fixation, permanent grasslands of high and low quality) and tropical for- ages (C4 carbon fixation, permanent grasslands of high and low quality). We determined diet digestibility, ruminal end-products of fermentation and microbial groups: total pro- tozoa, methanogens and bacteria, and selected fibrolytic bacteria. Dry matter digestibility coefficient was higher in tropical site (612 vs 580 g/kg on average, P = 0.004) but no differ- ence was observed between C3 and C4 forages. There was no effect of site on total VFA concentration, but the acetate:propionate ratio was higher for the tropical site (4.30 vs 3.93 on average, P = 0.007). The acetate:propionate ratio was also affected by forage type with higher values for C3 than C4 forage (4.24 vs 3.99 on average, P = 0.03). Concentration of total rumen bacteria and methanogens was determined by qPCR targeting, respectively, the rrs (16S ribosomal RNA subunit) and mcrA (methyl coenzyme-M reductase) genes. For both groups, the number of gene copies per gram of DM rumen content was higher in the trop- ical site ( P < 0.001). For cellulolytic bacteria, higher number of rrs copies per gram of DM of rumen content were detected for Fibrobacter succinogenes in the temperate site ( P < 0.001), whereas no differences were observed for Ruminococcus flavefaciens or Ruminococcus albus numbers between sites, breeds and forage type. Protozoa numbers determined by counting did not vary between sites, forages or breeds, but a site × forage interaction was observed ( P = 0.01): there were more protozoa and R. albus in tropical sites for tropical forages. Our results suggest that rumen microbiota was mainly influenced by environment (temper- ate vs tropical) and that forage type (C3 vs C4) and breed had minor effects. However, an interaction between environment and forage type was observed for some variables

International audience; An in vivo trial was conducted in sheep to investigate the effect of three tropical tannin-rich plants (TRP) on methane emission, intake and digestibility. The TRP used were leaves of Glyricidia sepium, Leucaena leucocephala and Manihot esculenta that contained, respectively, 39, 75 and 92 g condensed tannins/kg DM. Methane was determined with the sulphur hexafluoride tracer technique. Eight rumen-cannulated sheep of two breeds (four Texel, four Blackbelly) were used in two 4 × 4 Latin square designs. Four experimental diets were tested. They consisted in a tropical natural grassland hay based on Dichanthium spp. fed alone (C) or in association with G. sepium (G), L. leucocephala (L) or M. esculenta (M) given as pellets at 44% of the daily ration. Daily organic matter intake was higher in TRP diets (686, 984, 1054 and 1186 g/day for C, G, L and M respectively; p < 0.05) while apparent organic matter total tract digestibility was not affected (69.9%, 62.8%, 65.3% and 64.7% for C, G, L and M respectively; p > 0.05). Methane emission was 47.1, 44.9, 33.3 and 33.5 g/kg digestible organic matter intake for C, G, L and M, respectively, and was significantly lower (p < 0.05) for L and M than for G and C. Our results confirm the potential of some TRP to reduce methane production. The strong decrease in methane and the increase in intake with TRPs may be due to their presentation as pellets.

International audience; Emptying the rumen of animals fitted with rumen cannulas is a regularly used experimental technique. This study in sheep aimed to evaluate whether total rumen emptying (TRE) results in disturbances in digestive parameters such as rumen pH, fermentation and microbial ecosystem, and whether it affects animal welfare. Eight adult wethers from two breeds offered hay and water ad libitum were rumen-emptied manually. Ruminal parameters were assessed 2 days before and 7 days after TRE. Welfare was assessed by measuring behavioural and cardiac responses to TRE involving human handling. Behavioural and cardiac measurements were performed (i) 2 h before, (ii) during and (iii) 2 h after the rumen emptying–filling session on wethers exposed to the same TRE operator. Results showed that TRE did not affect most of the digestive parameters analysed (ruminal pH, bacteria, methanogens) but did modify Dasytricha population and volatile fatty acid concentrations. Likewise, rumen emptying did not alter most behavioural and cardiac parameters, and we found no TRE-related change in fear reactions to the operator.