Abstract

Positive ruminant welfare is a sustainability principle, since it is strongly related to production efficiency, rumen health and diet composition. An efficient fermentation process improves nutrient utilization and increases ruminant productivity by decreasing methane (CH4) emissions intensity, without affecting methanogenesis. Crude palm oil (CPO) is used in cattle in tropical countries to overcome critical grazing seasons and improve body condition, fertility and welfare, however, there is little information on its effects on rumen fermentation (RF). The aim of the study was to identify the effects of low CPO concentrations on CH4 production and RF after 48 h incubation. Basal diet was 70% dry matter (DM) ryegrass-fescue hay and 30% DM concentrate without CPO. Treated diets included CPO (0.6, 1.2 and 1.8% DM). The design was a randomized complete block, with three repetitions and three runs (total bottles = 210). Data were compared by polynomial contrasts. Increasing CPO concentrations, linearly increased gas production (P=0.034), partitioning factor (PF; P=0.039), short chain fatty acids (SCFA; P=0.044) and metabolizable energy (ME; P=0.043), without affecting (P≥0.061) in vitro DM disappearance (IVDMD), pH, CH4 output and kinetics at 24 h. Improved PF, SCFA and ME suggest enhanced RF. Although, at 48 h CPO linearly decreased (P=0.023) IVDMD (-7.5%), it did not affect (P≥0.06) any other fermentation parameter. A reduction in diet digestibility was expected due to: (1) presence of unsaturated fatty acids in CPO (≈ 50%), which may adversely affect the fibrolytic bacteria; (2) a mechanical action, by coating fibre and preventing microorganisms from accessing it. In conclusion, adding low CPO concentrations to forage diets slightly decreased IVDMD, without reducing CH4 production. However, CPO supplementation increased PF, SCFA and ME, improving RF efficiency, and thereby potentially enhancing livestock production and welfare under climate change.