Determining the preference, in vitro digestibility, in situ disappearance, and grower period performance of steers fed a novel algae meal derived from heterotrophic microalgae.

A series of 3 experiments were conducted to determine the in vitro and in situ disappearance, preference, and performance of steers consuming increasing concentrations of a novel feedstuff called algae meal (ALG). In Exp. 1 and 2, 3 ruminally cannulated steers (998 ± 103 kg BW) and 4 treatments were utilized: a dry-rolled corn-based diet (CON), or 15% ALG (A15), 30% ALG (A30), or 45% ALG (A45) as a DM replacement of corn. Experiment 1 was performed as a 3 × 6 unbalanced Latin square with six 5-d periods, and 6 paired diet combinations to determine steer preference, based on DMI for 4 h after feed delivery. Experiment 2 was conducted as a 3 × 4 unbalanced Latin square with 3 diets fed each period and four 14-d periods to determine in situ disappearance of ALG, soyhulls, corn, and hay as ALG increased in the diet. Experiment 3 utilized 48 individually fed steers (292 ± 22.4 kg; n = 12) in a 55-d grower trial, stratified by BW into 1 of 4 dietary treatments: a control wet corn gluten feed-based diet with no ALG (ALG0), or 15% ALG (ALG15), 30% ALG (ALG30), or 45% ALG (ALG45) in place of wet corn gluten feed on a DM basis. Digestibility of ALG was greater (P < 0.001) than soyhulls at 24 h, but was similar (P = 0.82) at 48 h, with hay being least (P < 0.001) digestible at 24 and 48 h. In Exp. 1, the proportion of total DM consumed by steers during the 4-h postfeeding was affected (P = 0.01) by paired diet combination. Steers preferred A15 or A30 diets over the A45 diet (P ≤ 0.008); however, no difference in preference between CON and A45 was noted (P = 0.76). Steers tended (P = 0.09) to prefer A30 over CON, but A15 and CON were not different (P = 0.75). No other paired diet combinations altered (P ≥ 0.23) DMI. In Exp. 2, inclusion of ALG in the diet did not affect (P ≥ 0.12) rate of, or overall in situ disappearance of, corn, soyhulls, or ALG. In Exp. 3, ADG tended ( = 0.06) to increase as ALG increased in the diet. There was a linear increase ( < 0.001) in DMI as ALG increased in the diet, and as a result, G:F linearly decreased ( = 0.01). In summary, ready consumption of the novel algae meal by steers and support of growth in steers at up to 45% of the diet suggest the algae meal is a viable feedstuff for ruminants.