PS13-1. Methane Emissions from Brangus Steers in Feedlots Fed with Different Levels of Olive Cake.

Abstract Olive oil byproduct (olive cake) has a high lipid content, presenting nutritional characteristics that can promote animal performance and reduce enteric methane emissions. This study aimed to evaluate the inclusion levels of olive cake on animal performance and enteric methane emissions. Thirty-two Brangus steers were used in a completely randomized experimental design, confined for 85 days, with the first 15 days for adaptation and the subsequent 70 days for data collection. The animals were divided into four treatments, receiving diets composed of pre-dried silage and ryegrass hay, and isoproteic and isoenergetic concentrates, used at a level of 1.2% of live weight. The concentrates contained inclusion levels of 0%, 5%, 10%, and 20% olive cake, replacing corn in the concentrate. Green matter intake was monitored daily, and the animals were weighed weekly. In two 5-day periods, methane emissions from 3 animals per group were collected using the sulfur hexafluoride (SF6) marker technique, with methane and SF6 concentrations determined using gas chromatography. Replacing corn in the concentrate with olive by-product dried at 60 °C did not affect the average daily weight gain of the animals up to the 20% inclusion level of the cake (p = 0.17), nor did it affect the average weight gain (p = 0.36). However, a reduction in dry matter intake (p < 0.01) was observed in animals that received 5% and 10% olive cake, compared to the control group and the group with 20% inclusion. Despite this, replacing corn with olive cake in the concentrate did not influence feed efficiency (p = 0.26) or residual feed intake (RFI) (p = 0.37). Furthermore, the inclusion of olive cake in the diet reduced daily methane emissions (g CH4/day; p < 0.0001). The same behavior was observed when calculating the emission intensity, i.e., the intermediate levels (5 and 10%) emitted less CH4/kg of dry matter consumed (p < 0.0002) and emitted less CH4 per unit of average daily weight gain (p < 0.0001). In general, the partial replacement of corn with olive meal in the diet did not affect weight gain and feed efficiency and reduced methane emissions.