Freeze-dried Nannochloropsis oceanica biomass protects eicosapentaenoic acid (EPA) from metabolization in the rumen of lambs.

Eicosapentaenoic acid (EPA) from freeze-dried biomass of Nannochloropsis oceanica microalgae resists ruminal biohydrogenation in vitro, but in vivo demonstration is needed. Therefore, the present study was designed to test the rumen protective effects of N. oceanica in lambs. Twenty-eight lambs were assigned to one of four diets: Control (C); and C diets supplemented with: 1.2% Nannochloropsis sp. oil (O); 12.3% spray-dried N. oceanica (SD); or 9.2% N. oceanica (FD), to achieve 3 g EPA /kg dry matter. Lambs were slaughtered after 3 weeks and digestive contents and ruminal wall samples were collected. EPA concentration in the rumen of lambs fed FD was about 50% higher than lambs fed SD or O diets. Nevertheless, the high levels of EPA in cecum and faeces of animals fed N. oceanica biomass, independently of the drying method, suggests that EPA was not completely released and absorbed in the small intestine. Furthermore, supplementation with EPA sources also affected the ruminal biohydrogenation of C18 fatty acids, mitigating the shift from the t10 biohydrogenation pathways to the t11 pathways compared to the Control diet. Overall, our results demonstrate that FD N. oceanica biomass is a natural rumen-protected source of EPA to ruminants.

Effects of alfalfa particle size and starch content in diets on feeding behaviour, intake, rumen parameters, animal performance and meat quality of growing lambs.

Thirty-two crossbred Merino branco male lambs were randomly allocated to eight diets, combining two forms of alfalfa presentation (chopped or ground), with four barley grain levels (0%, 11.2%, 21.3% and 33% dry matter (DM)), balanced by low starch agro-industrial by-products (LSBP). The diets were supplemented with 6% soybean oil and included 40% of alfalfa in DM. The lambs were individually housed and the trial lasted six weeks. Intake of DM, average daily weight gain (ADG) and carcass weight were higher with ground alfalfa (P < 0.01). Replacing barley grain by LSBP reduced linearly DM intake and ADG (P < 0.001) but increased meat tenderness (P = 0.046). Regardless of the treatments, meat showed a healthy biohydrogenation fatty acid (FA) profile, with high proportions of t11-18:1, c9,t11-18:2 and a t10-18:1/t11-18:1 ratio clearly below 1. The reduction of barley in diet had a moderate positive impact on meat FA composition, decreasing t10-18:1, which was enhanced by the increase of forage particle size.