To study the influence of different levels of Bacillus subtilis on growth performance, nutrition metabolism and intestinal microflora of 1 to 42 d Arbor Acres (AA) broilers, a total of 800 one-day-old healthy broilers were randomly divided into 5 groups with 4 replicates per group and 40 broilers per replicate. Broilers were fed a basic diet (group 1) which acted as the control group, and 4 other groups (2 to 5) were fed the basal diet with B. subtilis added at concentrations of 100, 150, 200 and 250 mg/kg, respectively for 42 days. The results showed as follow: the average daily gain (ADG) of group 4 was significantly higher than (P < 0.05) that of group 1, and the average daily feed intake (ADFI) of group 5 was the highest but the differences between groups were not significant (P > 0.05). The feed to gain ratio (F/G) of all the experimental groups was lower than that of the control and the difference was significant in group 4 (P < 0.05). In addition, supplementation of B. subtilis increased the apparent metabolism of crude protein (P > 0.05), crude fat (P > 0.05), dry matter (P > 0.05) and organic matter (P < 0.05). B. subtilis decreased the Escherichia coli and Salmonella populations in the cecum. This shows that adding B. subtilis to the broiler diet can improve the growth performance, increase feed efficiency, regulate serum index and reduce harmful bacteria in the intestinal tract. Based on our study, it could be recommended that addition of B. subtilis at 200 mg/kg could improve the growth performance of broilers.

This study was conducted to determine the effects of saturated long-chain fatty acids (LCFA) on cell proliferation and triacylglycerol (TAG) content, as well as mRNA expression of αs1-casein (CSN1S1) and genes associated with lipid and protein synthesis in bovine mammary epithelial cells (BMECs). Primary cells were isolated from the mammary glands of Holstein dairy cows, and were passaged twice. Then cells were cultured with different levels of palmitate or stearate (0, 200, 300, 400, 500, and 600 μM) for 48 h and fetal bovine serum in the culture solution was replaced with fatty acid-free BSA (1 g/L). The results showed that cell proliferation tended to be increased quadratically with increasing addition of stearate. Treatments with palmitate or stearate induced an increase in TAG contents at 0 to 600 μM in a concentration-dependent manner, and the addition of 600 μM was less effective in improving TAG accumulation. The expression of acetyl-coenzyme A carboxylase alpha, fatty acid synthase and fatty acid-binding protein 3 was inhibited when palmitate or stearate were added in culture medium, whereas cluster of differentiation 36 and CSN1S1 mRNA abundance was increased in a concentration-dependent manner. The mRNA expressions of peroxisome proliferator-activated receptor gamma, mammalian target of rapamycin and signal transducer and activator of transcription 5 with palmitate or stearate had no significant differences relative to the control. These results implied that certain concentrations of saturated LCFA could stimulate cell proliferation and the accumulation of TAG, whereas a reduction may occur with the addition of an overdose of saturated LCFA. Saturated LCFA could up-regulate CSN1S1 mRNA abundance, but further studies are necessary to elucidate the mechanism for regulating milk fat and protein synthesis.

Acetate is a short-chain fatty acid (SFA) that is the major substrate for de novo fatty acid synthesis. The mammalian target of rapamycin/eukaryotic initiation factor 4E (mTOR/eIF4E) signaling pathway is involved in fat synthesis. However, the effect and mechanism of acetate on fatty acid synthesis by the mTOR/eIF4E signaling pathway is unclear in bovine mammary epithelial cells (BMECs). The objectives of this study were to investigate the effect of acetate on cell viability, triacylglycerol (TG), and mRNA expression of the genes related to lipid synthesis. The mechanism of acetate regulation milk fat synthesis through the mTOR/eIF4E signaling pathway was assessed by blocking the mTOR signaling pathway and silencing eIF4E in BMECs. Third-passage BMECs were allocated to 6 treatments including 0, 4, 6, 8, 10, and 12 mM acetate to evaluate the effect of acetate on lipid synthesis; the optimum concentration in the first study was selected for the subsequent study. Subsequently, cells were randomly allocated to 4 treatments, 1 control group and 3 treated groups, consisting of acetate (6 mM), rapamycin (100 nM), and acetate + rapamycin to test the role of mTOR signaling pathway response to acetate in milk lipid synthesis. Finally, eIF4E was silenced by small interfering RNA (siRNA) to detect the role of eIF4E in milk lipid synthesis. Treatments included control, eIF4E siRNA, acetate (6 mM), and acetate+ eIF4E siRNA. Results showed that acetate increased TG accumulation and the relative expression of fatty acid synthase (FASN), acetyl-coenzyme A carboxylase α (ACACA), fatty acid-binding protein 3 (FABP3), sterol regulatory element binding protein 1 (SREBP1), peroxisome proliferator-activated receptor gamma (PPARG), mTOR, eIF4E, P70 ribosomal protein S6 kinase-1 (S6K1), and 4E-binding protein-1 (4EBP1) in a dose-dependent manner. Rapamycin effectively inhibited the positive effect of acetate on the relative expression of mTOR, eIF4E, S6K1, 4EBP1, FASN, ACACA, FABP3, stearoyl-CoA desaturase (SCD1), SREBP1, and PPARG. The upregulation of acetate on the relative expressions of FASN, ACACA, SCD1, and SREBP1 was suppressed when eIF4E was knocked down. It suggested that acetate regulated milk fat synthesis through mTOR/eIF4E signaling pathway in BMECs.

The objective of this study was to evaluate the effects of the different ratios of unsaturated fatty acids (UFAs) (oleic acid, linoleic acid, and linolenic acid) on the cell viability and triacylglycerol (TAG) content, as well as the mRNA expression of the genes related to lipid and protein synthesis in bovine mammary epithelial cells (BMECs). Primary cells were isolated from the mammary glands of Holstein dairy cows and were passaged twice. Afterward, the cells were randomly allocated to six treatments, five UFA-treated groups, and one control group. For all of the treatments, the the fetal bovine serum in the culture solution was replaced with fatty acid-free BSA (1 g/L), and the cells were treated with different ratios of oleic, linoleic, and linolenic acids (0.75:4:1, 1.5:10:1, 2:13.3:1, 3:20:1, and 4:26.7:1) for 48 h, which were group 1 to group 5. The control culture solution contained only fatty acid-free BSA without UFAs (0 μM). The results indicated that the cell viability was not affected by adding different ratios of UFAs, but the accumulation of TAG was significantly influenced by supplementing with different ratios of UFAs. Adding different ratios of UFAs suppressed the expression of ACACA and FASN but had the opposite effect on the abundances of FABP3 and CD36 mRNA. The expression levels of PPARG, SPEBF1, CSN1S1, and CSN3 mRNA in the BMECs were affected significantly after adding different ratios of UFAs. Our results suggested that groups 1, 2, and 3 (0.75:4:1, 1.5:10:1, and 2:13.3:1) had stronger auxo-action on fat synthesis in the BMECs, where group 3 (2:13.3:1) was the best, followed by group 4 (3:20:1). However, group 5 (4:26.7:1) was the worst. Genes related to protein synthesis in the BMECs were better promoted in groups 2 and 3, and group 3 had the strongest auxo-action, whereas the present study only partly examined the regulation of protein synthesis at the transcriptional level; more studies on translation level are needed in the future. Therefore, when combining fat and protein synthesis, group 3 could be obviously fat and protein synthesis in the BMECs concurrently. However, further studies are necessary to elucidate the mechanism for regulating fat and protein synthesis in the BMECs.

ABSTRACT:The objective of this study was to evaluate the effects of the different ratios of acetate and β-hydroxybutyrate (BHBA) on cell viability, triacylglycerol (TAG) content, and mRNA expression of the genes related to lipid and protein synthesis in bovine mammary epithelial cells (BMECs). Primary cells were isolated from the mammary glands of Holstein dairy cows and were passaged twice. Then, the cells were cultured with different ratios of acetate and BHBA (1 : 3, 1 : 2, 1 : 1, 2 : 1, 3 : 1, 4 : 1, and 1 : 1, Group 1 to Group 7, respectively) for 48 h, and the fetal bovine serum in the culture media was replaced with fatty acid-free bovine serum albumin (BSA) (1 g/l). The control culture media contained only fatty acid-free BSA without unsaturated fatty acids (0mM). Cell viability was not affected by adding different ratios of acetate and BHBA, but TAG accumulation was significantly influenced by supplementing the culture media with different ratios of acetate and BHBA. The expression levels of genes related to milk fat (FASN, ACACA, CD36, SCD, FABP3, LPL, PPARG, and SPEBF1) and milk protein-related genes (CSN1S1, CSN3, mTOR, 4E-BP1, S6KB1, STAT5, JAK2, and LEPTIN) were significantly affected by the addition of different ratios of acetate and BHBA to the BMECs. Our results suggested that Groups 3 and 4 (1 : 1 and 2 : 1) had a stronger acceleration of milk fat synthesis, and Group 4 (2 : 1) had the strongest effect. The expression of the CSN1S1 and LEPTIN mRNAs was more effectively promoted in Groups 3 and 4 (1 : 1 and 2 : 1), and Group 3 (1 : 1) had the strongest acceleration. Expressions of genes related to milk protein synthesis (mTOR, 4E-BP1, S6KB1, JAK2, and STAT5) were up-regulated using a ratio of acetate and BHBA of 2 : 1. Taken together, the 2 : 1 ratio of acetate and BHBA had the best effect for both the milk fat synthesis and milk protein synthesis genes. However, further studies are necessary to elucidate the mechanism for regulating milk fat and protein synthesis by different ratios of acetate and BHBA.Keywords: ratio of short chain fatty acids; milk fat precursor; dairy cow; milk fat; milk protein; gene expression List of abbreviations: BHBA = β-hydroxybutyrate, TAG = triacylglycerol, BMECs = bovine mammary epithelial cells, FBS = fetal bovine serum, UFA = unsaturated fatty acids, BSA = bovine serum albumin, FAs = milk fatty acids, GAPDH = glyceraldehyde 3-phosphate dehydrogenase, FASN = fatty acid synthase, ACACA = acetyl-CoA carboxylase, SCD = stearoyl-CoA desaturase, CD36 = cluster of differentiation 36, FABP3 = fatty acid-binding protein 3, LPL = lipoprotein lipase, PPARG = peroxisome proliferator-activated receptor γ, SREBF1 = sterol regulatory element binding transcription factor 1, CSN1S1 = αs1-casein, CSN3 = κ-casein, mTOR = mammalian target of rapamycin, 4EBP1 = eukaryotic translation initiation factor 4E, RPS6KB1 = ribosomal protein S6 kinase 1, STAT5 = signal transducer and activator of transcription 5, JAK2 = Janus kinase 2, LEPTIN = leptin, PBS = phosphate buffer saline, DMEM/F12 ...