Abstract #348

# 348
Algae meal for ruminants: II. Growth and carcass characteristics of finishing steers.
Rebecca S. Stokes*1, Daniel D. Loy1, Stephanie L. Hansen1, 1Department of Animal Science, Iowa State University, Ames, IA.

De-oiled microalgae from large-scale production of heterotrophic microalgae can be combined with soyhulls to form a novel feedstuff called algae meal (ALG). To determine the effects of replacing corn in a finishing diet with ALG on growth and carcass characteristics, crossbred steers (168) were blocked by BW (432.2 ± 30.8 kg) into pens of 6 steers (7 pens per treatment) and assigned to 1 of 4 diets: a corn-based control (CON), 14% ALG (ALG14), 28% ALG (ALG28), and 42% ALG (ALG42). Corn was replaced by ALG on a DM basis. Steer BW were taken on d 0, 1, 28, 56, 74, 101, and 102, and steers were harvested on d 103. Pen was the experimental unit and DMI, ADG, and G:F data were analyzed as repeated measures. Two steers per pen were selected for sampling of blood and liver (d −1 and 96), and collection of rib facings at harvest. Overall DMI linearly increased (P < 0.01) as ALG increased in the diet (12.7, 13.4, 13.8, and 14.4 ± 0.15 kg/d for CON, ALG14, ALG28, and ALG42, respectively). There was a treatment by time effect for ADG (P < 0.01), with ADG linearly decreasing (P ≤ 0.03) in the first and third month, not differing (P = 0.95) in the second month, and linearly increasing (P < 0.01) in the fourth month as ALG increased in the diet. Final BW did not differ (P ­ = 0.74) between CON and ALG-fed cattle. There was a treatment by time effect for G:F (P < 0.01), with G:F linearly decreasing (P < 0.01) in the first 3 mo as ALG increased in the diet, while G:F linearly increased (P < 0.01) in the fourth month. Yield grade linearly decreased (P = 0.02), and there was a tendency for dressing percent and 12th rib backfat to linearly decrease (P ≤ 0.10) as ALG increased in the diet. Plasma Cu, Fe, and Mg concentrations were not different (P ≥ 0.31) in CON vs. ALG cattle; however, plasma Zn concentrations linearly increased (P = 0.03) as ALG increased in the diet. Total lipid, SFA, MUFA, and PUFA concentrations in the longissimus thoracis did not differ (P ≥ 0.13) between CON and ALG-fed cattle. It appears ALG has less energy than corn; however, minimal effect on carcass performance suggests ALG may serve as a potential replacement for corn in feedlot diets.

Key Words: algae, performance, cattle