Apparent Digestibility of Macronutrients and Fatty Acids from Microalgae (Schizochytrium sp.) Fed to Rainbow Trout (Oncorhynchus mykiss): A Potential Candidate for Fish Oil Substitution.

Aquaculture feed formulation has recently turned its focus to reduce the reliance on marine-derived resources and utilise alternative feedstuffs, as an approach to improve the environmental sustainability of the aquaculture sector. The fish oil market is highly volatile, and availability of this commodity is continuously decreasing for use in aquaculture. Currently, a growing number of commercial efforts producing microalgae are providing omega 3-rich oil for sustainable aquaculture feed. This study was focused to determine the nutrient digestibility of a marine microalga, Schizochytrium spp., which is rich in docosahexaenoic acid (DHA) and long-chain polyunsaturated fatty acids (LC-PUFA), as a novel dietary lipid source that could be utilized effectively by rainbow trout (Oncorhynchus mykiss). A whole-cell Schizochytrium spp. biomass was used in the digestibility experiment at two different temperatures, 8 °C and 15 °C. No significant differences were detected between the two temperatures for the apparent digestibility coefficients (ADCs) of the dry matter (94.3 ± 4.9%), total lipids (85.8 ± 0.0%), crude proteins (89.5 ± 1.8%), energy (83.1 ± 1.7%) and fatty acids (85.8 ± 7.5%). The ADCs of the nutrients, energy, DHA and other fatty acids showed that Schizochytrium spp. is a high-quality candidate for fish oil substitution and supplement of LC-PUFA in fish feed with vegetable oils.

Direct-fed microbial supplementation influences the bacteria community composition of the gastrointestinal tract of pre- and post-weaned calves.

This study investigated the effect of supplementing the diet of calves with two direct fed microbials (DFMs) (Saccharomyces cerevisiae boulardii CNCM I-1079 (SCB) and Lactobacillus acidophilus BT1386 (LA)), and an antibiotic growth promoter (ATB). Thirty-two dairy calves were fed a control diet (CTL) supplemented with SCB or LA or ATB for 96 days. On day 33 (pre-weaning, n = 16) and day 96 (post-weaning, n = 16), digesta from the rumen, ileum, and colon, and mucosa from the ileum and colon were collected. The bacterial diversity and composition of the gastrointestinal tract (GIT) of pre- and post-weaned calves were characterized by sequencing the V3-V4 region of the bacterial 16S rRNA gene. The DFMs had significant impact on bacteria community structure with most changes associated with treatment occurring in the pre-weaning period and mostly in the ileum but less impact on bacteria diversity. Both SCB and LA significantly reduced the potential pathogenic bacteria genera, Streptococcus and Tyzzerella_4 (FDR ≤ 8.49E-06) and increased the beneficial bacteria, Fibrobacter (FDR ≤ 5.55E-04) compared to control. Other potential beneficial bacteria, including Rumminococcaceae UCG 005, Roseburia and Olsenella, were only increased (FDR ≤ 1.30E-02) by SCB treatment compared to control. Furthermore, the pathogenic bacterium, Peptoclostridium, was reduced (FDR = 1.58E-02) by SCB only while LA reduced (FDR = 1.74E-05) Ruminococcus_2. Functional prediction analysis suggested that both DFMs impacted (p < 0.05) pathways such as cell cycle, bile secretion, proteasome, cAMP signaling pathway, thyroid hormone synthesis pathway and dopaminergic synapse pathway. Compared to the DFMs, ATB had similar impact on bacterial diversity in all GIT sites but greater impact on the bacterial composition of the ileum. Overall, this study provides an insight on the bacteria genera impacted by DFMs and the potential mechanisms by which DFMs affect the GIT microbiota and may therefore facilitate development of DFMs as alternatives to ATB use in dairy calf management.

Comparison of the impact of trans fatty acids from ruminant and industrial sources on surrogate markers of cholesterol homeostasis in healthy men.

SCOPE: Mechanisms by which trans fatty acids (TFA) from industrial (iTFA) and ruminant (rTFA) sources alter cholesterol homeostasis are virtually unknown. We compared the impact of dietary iTFA and rTFA on surrogate markers of cholesterol absorption (ß-sitosterol and campesterol) and synthesis (lathosterol) in healthy men. METHODS AND RESULTS: In a randomized, controlled double-blind crossover study, 38 healthy men consumed three experimental isoenergetic diets for 4 wk each. The three diets were (i) high in iTFA (10.2 g/2500 kcal), (ii) high in rTFA (10.2 g/2500 kcal) and (iii) control diet low in TFA from any source (2.2 g/2500 kcal). The sum of plasma ß-sitosterol and campesterol concentrations was significantly reduced after the iTFA diet compared with the control diet (-12%, p=0.050). The reduction in combined ß-sitosterol and campesterol levels was larger in magnitude after the rTFA diet (-29% versus the control diet and -20% versus the iTFA diet, p<0.0001). The TFA-rich diets had no impact on plasma lathosterol concentrations. CONCLUSIONS: Very high intakes of rTFA and iTFA decrease cholesterol absorption but have no impact on cholesterol synthesis. Consumption of rTFA reduces cholesterol absorption to a greater extent than iTFA, but this difference does not ultimately affect plasma cholesterol concentrations.

Fish oil diets do not improve insulin sensitivity and secretion in healthy adult male pigs.

The effects of long-term dietary supplementation of fish oil (n-3 PUFA-rich) in adult male pigs on body condition as well as insulin sensitivity and secretion were examined. Fifteen Duroc boars aged 204.5 (sd 9.4) d (body weight 145.8 (sd 16.8) kg) received daily 2.5 kg basal diet with a supplement of: (1) 62 g hydrogenated animal fat (n 5); (2) 60 g menhaden oil containing 10.8 g DHA and 9.0 g EPA (n 6); (3) 60 g tuna oil containing 19.8 g DHA and 3.9 g EPA (n 4). Rations were balanced to be isoenergetic. After 7 months of treatments, oral glucose and meal tolerance tests were conducted after insertion of a catheter into the jugular vein. Dietary supplementation with n-3 PUFA altered the blood plasma profile: DHA and EPA increased whereas arachidonic acid decreased (P < 0.01). Plasma glucose, insulin and C-peptide responses to oral glucose and the test meal were not affected by treatments (P>0.34). For all animals, total body fat estimated from body weight and back fat thickness was correlated with both beta-cell function (by homeostasis model assessment (HOMA); r+0.63) and insulin sensitivity (index of whole-body insulin sensitivity and by HOMA; r - 0.63 and r+0.66, respectively). In conclusion, long-term supplementation with dietary n-3 PUFA did not affect insulin metabolism in healthy adult male pigs. The relationship between body fat and insulin sensitivity, well documented in human subjects, suggests that the adult male pig could be a promising animal model for studies on insulin metabolism.

Study of the effect of trans fatty acids from ruminants on blood lipids and other risk factors for cardiovascular disease.

BACKGROUND: The intake of trans fatty acids (TFA) from industrially hydrogenated vegetable oils (iTFA) is known to have a deleterious effect on cardiovascular health, the effects of TFA from ruminants (rTFA) are virtually unknown. OBJECTIVE: The purpose of the present study was to compare the effects of rTFA and iTFA on plasma LDL concentrations and other cardiovascular disease risk factors in healthy subjects. DESIGN: In a double-blind, randomized crossover controlled study, 38 healthy men were fed each of 4 experimental isoenergetic diets lasting 4 wk each. The 4 diets were high in rTFA (10.2 g/2500 kcal), moderate in rTFA (4.2 g/2500 kcal), high in iTFA (10.2 g/2500 kcal), and low in TFA from any source (2.2 g/2500 kcal) (control diet). RESULTS: Plasma LDL-cholesterol concentrations were significantly higher after the high- rTFA diet than after the control (P = 0.03) or the moderate- rTFA (P = 0.002) diet. Plasma LDL-cholesterol concentrations also were significantly (P = 0.02) higher after the iTFA diet than after the moderate-rTFA diet. Plasma HDL-cholesterol concentrations were significantly (P = 0.02) lower after the high-rTFA diet than after the moderate-rTFA diet. Finally, all risk factors were comparable between the control and the moderate-rTFA diets. CONCLUSIONS: These results suggest that, whereas a high dietary intake of TFA from ruminants may adversely affect cholesterol homeostasis, moderate intakes of rTFA that are well above the upper limit of current human consumption have neutral effects on plasma lipids and other cardiovascular disease risk factors.

The effect of drinking milk containing conjugated linoleic acid on fecal microbiological profile, enzymatic activity, and fecal characteristics in humans.

BACKGROUND: The primary objective was to determine whether consumption of conjugated linoleic acids (CLAs) affected the fecal microbiota composition, fecal enzyme activity or fecal composition. METHODS: Human subjects consumed (1 L/day) cows' milk (4% fat) containing (5 mg/g fat) cis-9, trans-11 CLA (CONT), (32 mg/g fat) cis-9, trans-11 CLA (NAT) and (32 mg/g fat) trans-10, cis-12 CLA and cis-9, trans-11 CLA (SYN) for 8 weeks, in addition to their normal diet. Milk feeding periods were separated by 4 week washout periods. Fecal samples were obtained at the beginning (day 0) and the end (day 56) of each milk feeding period. Fecal samples were analysed for microbiological profile, enzyme activity, pH and short chain fatty acid content. RESULTS: Samples taken at day 0 and day 56 indicated that the numbers of lactobacilli and bifidobacteria significantly decreased after consumption of all experimental milks; total aerobes, total anaerobes, enterobacteria, and enterococci + streptococci did not change. At day 56, the activities of beta-glucosidase, nitroreductase, and urease enzymes had decreased compared to samples taken on day 0 for all treatments. beta-glucuronidase activity did not change. Fecal pH and ammonia content did not change. CONCLUSION: It was concluded that observed changes could have been attributed to increased milk intake; no differences could be attributed to consumption of the different CLAs.

The effects of t10,c12 CLA isomer compared with c9,t11 CLA isomer on lipid metabolism and body composition in hamsters.

The objective of the present study was to examine the effects of two different isomers of conjugated linoleic acid (CLA), c9,t11 CLA and t10,c12 CLA, compared with linoleic acid (LA) used as control, on body composition, lipoprotein profile, hepatic lipids and fecal fat content in hamsters. Animals were assigned to the three diet groups (n=15) during 28 days. The diet was composed of 2% of the experimental fat, and throughout the experimental protocol, the hamsters experienced similar food intake. No significant differences were noted in body weight gain among the three diet groups. However, the t10,c12 CLA-fed animals showed higher low-density lipoprotein cholesterol (LDL-C) concentrations (0.9+/-0.1 mmol/L) than those who ingested either LA (0.6+/-0.1 mmol/L) or c9,t11 CLA isomer (0.7+/-0.1 mmol/L), although the t10,c12 CLA consumption decreased hepatic cholesterol and triglycerides and increased fecal fat content compared with the other two groups. Under the present experimental conditions, the dietary c9,t11 CLA isomer showed no positive beneficial effect on plasma lipids. Furthermore, the t10,c12 CLA isomer induced undesirable higher LDL-C, although it reduced hepatic lipids and fat digestibility in hamsters.