| With the improvement of economy and living standard, public interests regarding the microcomponents of food with possiblely beneficial effects on health maintenance and disease prevention are increasing. High consumption of dietary saturated fatty acid could increase the risk of coronary heart disease in humans, while monounsaturated fatty acid and polyunsaturated fatty acid could have cholesterol-lowering effects. Conjugated linoleic acid (CLA) was reported to have potentially positive health effects. Food products from ruminants are major dietary sources of CLA for humans, and thus optimization of the FA composition, especially CLA content in milk, has become an important part of nutritional research in ruminants. Dietary lipids undergo extensive hydrolysis and biohydrogenation in the rumen, and the fatty acids formed were absorbed and transported to mammary gland where de novo fatty acid synthesis and desaturation were carried out in mammary tissues which would affect milk fatty acid profile. At the same time, people’s interests regarding the use of plant-derived essential oil have increased due to the abandoned use of growth-promoting antibiotics in animal feeds. Sutides have demonstrated that garlic has a wide spectrum of antibacterial activity and blood lipid-lowering effect which may influence ruminal biohydrogenation and milk fatty acid composition. Therefore, the aim of this study was to investigate the effects of garlic oil as ruminal modifer on ruminal fermentation, biohydrogenation, and milk fatty acid profile and lipogenesis-related gene expression in mammary gland of goats.1Effects of garlic oil on in vitro fermentation of substrates with different forage to concentrate ratios by microorganism from rumen of goatsDifferent levels of garlic oil (0,30,300, and3000mg/L of culture fluid) were incubated for24h in diluted ruminal fluid with substrates with different ratios of forage to concentrate (10:0,7:3,5:5and3:7) to investigate their effects on rumen microbial fermentation by random block experimental design. Results showed that the24-h cumulative gas production was reduced (P<0.05) with the increasing level of garlic oil. The dynamic changes of gas production per3hours suggested garlic oil altered the mode of in vitro fermentation. Compared with the control, the high level of garlic oil (3000mg/L) increased pH (P≤0.05), while the levels of30and300mg/L had no significant effects on pH (P>0.05). The magnitude of concentrations of NH3-N and MCP followed the order control>300mg/L>30mg/L>3000mg/L and30mg/L> control>3000mg/L>300mg/L, respectively. Compared with the control, garlic oil supplementation reduced total VFAs concentration (P≤0.05), whereas there were no significant differences (P>0.05) between30and300mg/L. The levels of30and300mg/L reduced the proportion of acetate and ratio of acetate to propionate (P≤0.05), and increased the proportions of propionate and butyrate (P≤0.05). Compared with other substrates, the effects of garlic oil (30and300mg/L) on high concentrate substrates had minor depression on24-h cumulative gas production and total VFAs concentration, whereas had more evident effect on reducing NH3-N concentration, acetate proportion and ratio of acetate to propionate, as well as increasing propionate proportion. In conclusion, garlic oil inhibited in vitro ruminal fermentation in a dose-dependent manner accompanied by the effects of alleviating the process of fermentation. The moderate levels (such as30and300mg/L) of garlic oil had better manipulation on rumen microbial fermentation of high concentrate-substrate.2Effects of ruminal infusion of garlic oil on ruminal fermentation dynamics, fatty acid profile and biohydrogenation bacterial population of goats2.1Effects of ruminal infusion of garlic oil on dry matter intake and blood parameters of goatsThe effects of garlic oil on dry matter intake and blood parameters of goats were investigated by garlic oil infusion (0.8g/d) via ruminal fistulas in a cross-over design with two30-d periods. Results showed that garlic oil reduced DM intake (P≤0.05). And there was interaction between treatment and day for DM intake (P≤0.05). Garlic oil reduced DM intake on d3and6(P<0.001and P=0.011, respectively), but had no significant effect (P>0.05) on that of other days. Garlic oil reduced serum HDL-C, LDL-C, cholesterol concentrations (P≤0.01) and lipase activity (P=0.048), and tended to increase triglycerides concentration (0.05<P≤0.1), while had no effects on glucose and NEFA (P>0.1). Overall, garlic oil infusion via ruminal fistulas affected DM intake, and the effect diminished over time. Garlic oil had lipid-lowering effect and may reduce the hydrolysis of glycerides. 2.2Effects of ruminal infusion of garlic oil on ruminal fermentation dynamics of goatsThe effects of garlic oil on ruminal fermentation dynamics were investigated through analyzing features in ruminal content collected at different time on d28,29and30of experimental period from goats treated by garlic oil infusion (0.8g/d) via ruminal fistulas in a cross-over design. Garlic oil increased (P≤0.01) ruminal NH3-N and MCP concentrations, but had no effects (P>0.1) on pH, total VFAs concentration, individual VFA proportion and ratio of acetate to propionate in ruminal content sampled before morning feeding (0h). During ruminal fermentation, the effects of garlic oil on the average of parameters at different time were similar with the effects at0h with the exception of reducing pH (P≤0.05) and total VFAs concentration (0.05<P≤0.1). But there was interaction between treatment and sampling time for total VFAs concentration, propionate proportion and ratio of acetate to propionate (P≤0.05). The time-course analysis showed total VFAs concentration and propionate proportion reached maximum at2h after morning feeding in the control, whereas at6h in the garlic oil treatment. Moreover, acetate proportion and the ratio of acetate to propionate in garlic oil treatment showed a modest fluctuation after morning feeding compared with the control. In conclusion, garlic oil infusion manipulated ruminal fermentation and alleviated the process of fermentation.2.3Effects of ruminal infusion of garlic oil on ruminal fatty acid profile, total bacterial community and biohydrogenation bacterial pupolation of goatsThe effects of garlic oil on ruminal fatty acid profile, total bacterial community and biohydrogenation bacterial population of goats were investigated by ruminal infustion of garlic oil (0.8g/d) in a cross-over design in30day period. Garlic oil reduced ruminal C15, C16and SFA proportions (P≤0.01), increased the proportions of C18, TV A, c9t11CLA, t10c12CLA and PUFA (P≤0.05). and tended to increase MUFA proportion (0.05<P≤0.1). Garlic oil reduced TVA/(c9/11CLA+TV A)(P=0.021) and C18:0/(TVA+C18:0)(P=0.055). PCR/DGGE profile showed that garlic oil infusion did not affect ruminal bacterial community. Real-time PCR showed that garlic oil tended to reduce B. proteoclasticus population and the ratio B. proteoclasticus/Butyrivibrio (0.05<P≤0.1), while had no effect on the Butyrivibrio group bacterial population(P>0.1). In conclusion, garlic oil altered ruminal fatty acid profile and the process of ruminal biohydrogenation through depressing the growth of B. proteoclasticus without effect on Butyrivibrio group bacterial population. 2.4Effects of ruminal infusion of garlic oil on diversity of Butyrivibrio group bacteria using sequence analysis of16S rRNA gene clone from rumen of goatsBased on Butyrivibrio-specific selection by primers B395f/B812r from full-length16S rRNA gene clones, Butyrivibrio group bacterial clone library from rumen of goats was constructed. The16S rRNA gene clone library showed that the Butyrivibrio group represented about12.98%(37of total285clones) and10.95%(38of total347clones) of ruminal bacteria in the control (accession numbers HQ326588-HQ326624) and garlic oil treatment (accession numbers JN008400-JN008437), respectively. Based on sequence analysis with the RDP library, the clones in both libraries were classified to the genus Pseudobutyrivibrio, Butyrivibrio and others within the family Lachnospiraceae. Some clones classified to the genus Ruminococcus and others within the family Ruminococcaceae were found in the treatment library. Results of sequence blast showed that the dominant clones were affiliated with Lachnospiraceae bacterium (control and treatment,32.43%and21.05%), followed by Pseudobutyrivibrio ruminis (control and treatment,21.62%and15.79%). The clones affiliated with the species Ruminococcus flavefaciens in the treatment library represented10.53%. No clones affiliated with the species Ruminococcus flavefaciens were found in the control. The Shannon indexes of the control and treatment library were2.47and2.91, respectively. Overall, Butyrivibrio group bacteria represented about12.98%in rumen of goats, classified to the genus Pseudobutyrivibrio, Butyrivibrio and others within the family Lachnospiraceae. Garlic oil infusion reduced the proportion, but increased the genetic diversity of Butyrivibrio group bacteria in rumen of goats.3Effects of garlic oil supplementation on milk fatty acid profile and lipogenesis-related gene expression in mammary gland of dairy goats3.1Effects of garlic oil supplementation on dry matter intake, blood parameters and milk composition of dairy goatsThe effects of garlic oil supplementation on dry matter intake, blood parameters and milk composition were investigated. Twenty four early-lactation Saanen dairy goats of China were paired and randomly allocated to four treatments with six goats each, and were offered corn silage ad libitum and0.79kg/d DM concentrate supplemented with different levels of garlic oil (0,0.57,1.14,1.71g/kg DM concentrate) for30d. Results showed that the concentrate intake was not affected, but the high level of garlic oil supplementation (1.35g/d) reduced corn silage intake (P≤0.05). Garlic oil supplementation had no significant effects on blood parameters (P>0.05), but tended to reduce serum LDL-C and NEFA concentrations (0.05<P≤0.1). Garlic oil supplementation had no effects on milk composition (P>0.1) with the exception of tending to increase lactose content (0.05<P≤0.1). Overall, the high level of garlic oil reduced DM intake, whereas garlic oil supplementation had minor effects on milk composition of dairy goats.3.2Effects of garlic oil supplementation on milk fatty acid profile and lipogenesis-related gene expression in mammary gland of dairy goatsThe effects of garlic oil supplementation on milk fatty acid profile and lipogenesis-related genes (ACC, FAS, LPL, SCD, SREBP1and PPARy) expression in mammary gland were investigated. Twenty four early-lactation Saanen dairy goats of China were paired and randomly allocated to four treatments with six goats each, and were offered corn silage ad libitum and0.79kg/d DM concentrate supplemented with different levels of garlic oil (0,0.57,1.14and1.71g/kg DM concentrate) for30d. Results showed that garlic oil supplementation altered milk fatty acid profile with more evident effects during d14-21. Compared with the control, garlic oil supplementation reduced the proportions of C14:0, C16:0and SFA (P≤0.05). and increased C18:0, C18:l, C18:3, c9t11CLA, MUFA and PUFA proportions and the ratio c9tl1CLA/(c9t11CLA+t11C18:1)(P≤0.05) in milk of dairy goats after27d. The proportions of TVA and t10c12CLA in milk increased with the increasing level of garlic oil in concentrate, but the differences were not significant (P>0.05). Real-time PCR analysis showed that there were no significant effects of garlic oil on lipogenesis-related genes mRNA abundance. Correlation analysis showed that there was a positive correlation (P≤0.01) between SREBP1and FAS mRNA abundance. And the mRNA abundance of SCD positively correlated with those of LPL (P≤0.05) and SREBP1(0.05<P≤0.1) genes suggesting there were modulation effects among these genes. The results demonstrated that garlic oil supplementation altered milk fatty acid profile, but did not significantly change mRNA abundance of lipogenesis-related genes. Thus, the effects of garlic oil on milk fatty acid profile in dairy goats may not be related to these lipogenesis-related genes expression, and may be related to the manipulation on ruminal fatty acid profile and/or enzyme activities of genes in mammary gland. |
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