The Effects of Olive Cake Supplementation on Feedlot Performance and Longissimus Muscle Fatty Acid Composition of American Wagyu Steers and In Vitro Rumen Fermentation Characteristics

Wagyu cattle are well known for their greater intramuscular fat content which improves eating quality for consumers. These experiments were designed to investigate the impact of olive cake supplementation on Wagyu steer growth performance, longissimus muscle fatty acid composition, and in vitro rumen fermentation characteristics. We hypothesized that feeding with olive cake would improve animal performance and increase oleic acid (C18:1cis9) composition in the longissimus muscle. Experiment 1: Eighty-three American Wagyu steers (725 ± 10.7 kg) were used in this experiment. Steers were blocked by initial body weight (BW) and randomly assigned within blocks to one of two treatments. Treatments consisted of (1) control (basal ration with no olive cake) or (2) control diet + 5% supplemental olive. Steers were housed in feedlot pens (n = 4 steers/pen; 11 replicates/treatment) and fed a finishing diet typical for Wagyu cattle. Steers were individually weighed every 28 d throughout the 177 d experiment. Longissimus muscle samples were obtained for fatty acid analysis at the time of slaughter. Experiment 2: Rumen fluid from three beef steers (480 ± 10 kg) fitted with rumen canulae was used to investigate the impact of olive cake on in vitro rumen fermentation characteristics. Treatments consisted of (1) control (no olive cake) or (2) 5% olive cake. Results: Experiment 1: Steers receiving olive cake had a lower (<i>p</i> < 0.05) final BW and DM intake when compared to steers receiving the control diet. Longissimus muscle C18:2 and C22:6 n-3 were greater (<i>p</i> < 0.05) and C18:1cis9 tended (<i>p</i> < 0.06) to be greater in steers receiving olive cake when compared to controls. Experiment 2: Dry matter, acid detergent fiber, and neutral detergent fiber disappearance and molar proportions of short chain fatty acids were similar across treatments. The weight percentage of C14:1 was greater in in vitro rumen fluid fermented with olive cake when compared to controls. All other long chain fatty acids were similar across treatments. Under the conditions of this experiment, feeding olive cake at 5% of the diet DM reduced live animal performance and had minimal impacts on longissimus muscle fatty acid composition and in vitro rumen fermentation characteristics.