Department of Animal Sciences, Federal University of Lavras, Lavras, Minas Gerais, Brazil.
Alltech Inc., Nicholasville, KY.
J Anim Sci. 2018 Jul 28;96(8):3433-3445. doi: 10.1093/jas/sky210.
Heterotrophic production of microalgae biomass provides a consistent, high-quality source of docosahexaenoic acid (DHA; C22:6 n-3) in triglyceride oils that could be used as a ration supplement for feedlot steers to improve nutritional qualities of beef. Sixty Angus × Simmental steers (438 ± 6.4 kg) were allotted to two treatments (30 steers each, six pens, five steers/pen) to determine the effects of ForPLUS (DHA-rich microalgae Aurantiochytrium limacinum; 63.6% fat; 17.9% DHA; 30 mg/kg Sel-Plex; Alltech Inc.) on performance, insulin sensitivity, LM fatty acid composition, and meat quality. Steers were fed basal diets containing 45% corn, 30% distillers dried grains with solubles, 20% corn silage, and 5% supplement. Basal diets were formulated to contain 16.1% CP and 1.32 Mcal/kg NEg. Treatments were delivered to steers in a ground corn-based top-dress (454 g total/steer) and contained no microalgae for control steers or 100 g/steer daily of ForPLUS for microalgae steers. A glucose tolerance test (GTT) was performed 10 d prior to slaughter. Steers were slaughtered when a target pen BW of 621 kg was achieved. Fatty acid oxidation potential was determined by measuring thiobarbituric acid reactive substances (TBARS) on LM samples collected 24 h after slaughter and aged for 48 h or 21 d. Weight and BW gain did not differ during the study (P ≥ 0.13); however, steers fed microalgae remained in the feedlot seven more days compared to steers fed the control diet (111 vs. 104 d; P = 0.04). Overall DMI decreased (P = 0.002) and G:F increased during the second half of the study (P = 0.04) in steers fed microalgae compared to steers fed the control diet. Steers fed microalgae secreted less insulin (P = 0.01) and took longer to clear glucose (P = 0.01) during a 2-h GTT. Carcass traits did not differ between treatments (P ≥ 0.23). Microalgae had no effect on n-6 content (P = 0.67), but more than doubled the n-3 fatty acid percentage and the n-3:n-6 ratio of the LM (P < 0.0001). The percentage of n-3 fatty acids C20:5 and C22:6 were increased (P < 0.0001) 4-fold and 6.25-fold, respectively, by microalgae supplementation. Concentration of TBARS did not differ in LM aged for 48 h (P = 0.91); however, when aged for 21 d, steers fed microalgae tended to produce LM with greater TBARS concentration compared to steers fed the control diet (P = 0.08). In conclusion, DHA-rich microalgae decreased DMI of steers, and increased n-3 fatty acids and beef oxidation in steaks aged for 21 d.
异养生产的微藻生物量提供了二十二碳六烯酸 (DHA; C22:6n-3) 的一致、高质量的甘油三酯油来源，可作为肥育牛的饲料补充剂，以提高牛肉的营养价值。60 头安格斯×西门塔尔牛 (438 ± 6.4kg) 被分配到两个处理组 (每组 30 头，6 个围栏，每围栏 5 头)，以确定 ForPLUS (富含二十二碳六烯酸的雨生红球藻 Aurantiochytrium limacinum; 63.6%脂肪; 17.9% DHA; 30mg/kg Sel-Plex; Alltech Inc.) 对性能、胰岛素敏感性、LM 脂肪酸组成和肉质的影响。牛被喂食含有 45%玉米、30%蒸馏干酒糟与可溶物、20%玉米青贮和 5%补充剂的基础日粮。基础日粮的配方含有 16.1%CP 和 1.32McalkgNEg。处理组以地面玉米基添加剂的形式添加到牛中 (每头牛 454g 总添加物)，对照组牛不添加微藻，微藻组牛每天添加 100g/头 ForPLUS。在屠宰前 10 天进行葡萄糖耐量试验 (GTT)。当达到目标围栏 BW621kg 时，牛被屠宰。宰后 24 小时采集 LM 样本，并在 48 小时或 21 天老化后，通过测量硫代巴比妥酸反应物质 (TBARS) 来确定脂肪酸氧化潜力。在研究期间，体重和 BW 增重没有差异 (P≥0.13);然而，与喂食对照饮食的牛相比，喂食微藻的牛在饲料厂停留的时间多了 7 天 (111 比 104 天;P=0.04)。与喂食对照饮食的牛相比，在研究的后半段，牛的总采食量减少 (P=0.002)，G:F 增加 (P=0.04)。与喂食对照饮食的牛相比，喂食微藻的牛在 2 小时 GTT 期间胰岛素分泌减少 (P=0.01)，葡萄糖清除时间延长 (P=0.01)。屠宰特性在处理之间没有差异 (P≥0.23)。微藻对 n-6 含量没有影响 (P=0.67)，但将 LM 的 n-3 脂肪酸百分比和 n-3:n-6 比例增加了一倍以上 (P<0.0001)。n-3 脂肪酸 C20:5 和 C22:6 的比例分别增加了 4 倍和 6.25 倍 (P<0.0001)。微藻补充剂对 48 小时老化的 LM 中的 TBARS 浓度没有影响 (P=0.91);然而，当老化 21 天时，与喂食对照饮食的牛相比，喂食微藻的牛的 LM 中 TBARS 浓度有增加的趋势 (P=0.08)。总之，富含二十二碳六烯酸的微藻降低了牛的采食量，并增加了牛肉的 n-3 脂肪酸和老化 21 天的牛肉氧化。
