In vitro ruminal biohydrogenation of eicosapentaenoic (EPA), docosapentaenoic (DPA), and docosahexaenoic acid (DHA) in cows and ewes: Intermediate metabolites and pathways

A great deal of uncertainty still exists about intermediate metabolites and pathways explaining the biohydrogenation (BH) of 20- and 22-carbon polyunsaturated fatty acids (PUFA). Therefore, this study was conducted to provide further insight into the ruminal metabolism of 20:5 n-3 (EPA), 22:5 n-3 (DPA), and 22:6 n-3 (DHA), the main n-3 PUFA present in the marine lipids used in dairy ruminant feeding, and to examine potential differences between bovine and ovine. To meet this aim, we investigated the 20- and 22-carbon metabolites accumulated during in vitro incubation of EPA, DPA, and DHA with rumen inocula from cows and ewes. The PUFA were added at a dose of 2% incubated dry matter and digesta samples were analyzed after 24 h of incubation using complementary gas-liquid chromatography of fatty acid methyl esters and gas chromatography-mass spectrometry of 4,4-dimethyloxazoline derivatives. Results suggested that the main BH pathway of EPA and DPA would proceed via the reduction of the double bond closest to the carboxyl group (cis-5 in EPA and cis-7 in DPA); curiously, this mechanism seemed of much lower importance for DHA. Thus, DPA would not be a major intermediate product of DHA and their BH might actually follow separate pathways, with the accumulation of numerous unique metabolites in each case. A principal component analysis supported this hypothesis, with a clear separation between PUFA treatments in the score and loading plots. Within EPA and DPA groups, cow and ewe samples loaded separately from each other but not distant. No conjugated 20:5, 22:5, or 22:6 isomer compatible with the initial product of EPA, DPA, or DHA metabolism, respectively, was identified in the ruminal digesta, although this would not unequivocally exclude their transient formation. In this regard, results from DPA incubations provided the first indication that the metabolism of this very long chain PUFA may involve the formation of conjugated double bond structures. The BH of EPA, DPA, and DHA resulted in the appearance of several tentative trans-10–containing metabolites, showing a general trend to be more abundant in the digesta of ewes than in that of cows. This finding was speculated to have some relationship with the susceptibility of dairy sheep to marine lipid-induced milk fat depression. Differences in the relative proportion of intermediate products would also suggest an influence of ruminant species on BH kinetics, with a process that would likely be slower and less complete in cows than in ewes.     

In vitro and in vivo analysis of fatty acid effects on metabolism of 17β-estradiol and progesterone in dairy cows

Some studies have reported improved reproductive performance with dietary fat supplementation. This study examined effects of fatty acids with different lengths, or desaturation, or both, on metabolism of estradiol (E2) and progesterone (P4) in bovine liver slice incubations (experiments 1 and 2) and in vivo (experiment 3). In experiment 1, effects of fatty acids C16:0 (palmitic acid), C16:1 (palmitoleic acid), C18:1 (oleic acid), and C18:3 (linolenic acid) were evaluated at 30, 100, and 300 μM on P4 and E2 metabolism in vitro. In experiment 2, stearic acid (C18:0) and C18:3 were evaluated in the same incubation conditions. In experiment 1, all of the fatty acids had some significant inhibitory effect on metabolism of P4, E2, or both (300 μM C16:0 on E2; 100 μM C16:1 on E2; 300 μM C16:1 on both P4 and E2; 300 μM C18:1 on P4; and 100 and 300 μM C18:3 on both P4 and E2). In experiment 2, C18:3 (100 and 300 μM) but not C18:0 decreased P4 and E2 metabolism. Overall, the most profound increase (∼60%) in half-life of P4 and E2 was observed with incubations of 300 μM C18:3 in both in vitro experiments. Based on these in vitro results, in experiment 3 linseed oil (rich in C18:3) was supplemented into the abomasum and acute effects on metabolism of E2 and P4 were evaluated. Cows (n = 4) had endogenous E2 and P4 minimized (corpus luteum regressed, follicles aspirated) before receiving continuous intravenous infusion of E2 and P4 to analyze metabolic clearance rate for these hormones during abomasal infusion of saline (control) or 70 mL of linseed oil every 4 h for 28 h. Linseed oil infusion increased C18:3 in plasma by 46%; however, metabolic clearance rate for E2 and P4 were similar for control cows compared with linseed-treated cows. Thus, in vitro experiments indicated that E2 and P4 metabolism can be inhibited by high concentrations of C18:3. Nevertheless, in vivo, linseed oil did not acutely inhibit E2 and P4 metabolism, perhaps because insufficient C18:3 concentrations (increased to ∼8 μM) were achieved. Further research is needed to determine the mechanism(s) of fatty acid inhibition of P4 and E2 metabolism and to discover practical methods to mimic this effect in vivo.     

Ruminal biohydrogenation and abomasal flow of fatty acids in lactating cows fed diets supplemented with soybean oil,whole soybeans,or calcium salts of fatty acids

Ruminants have a unique metabolism and digestion of unsaturated fatty acids (UFA). Unlike monogastric animals, the fatty acid (FA) profile ingested by ruminants is not the same as that reaching the small intestine. The objective of this study was to evaluate whole raw soybeans (WS) in diets as a replacer for calcium salts of fatty acids (CSFA) in terms of UFA profile in the abomasal digesta of early- to mid-lactation cows. Eight Holstein cows (80 ± 20 d in milk, 22.9 ± 0.69 kg/d of milk yield, and 580 ± 20 kg of body weight; mean ± standard deviation) with ruminal and abomasal cannulas were used in a 4 × 4 Latin square experiment with 22-d periods. The experiment evaluated different fat sources rich in linoleic acid on ruminal kinetics, ruminal fermentation, FA abomasal flow, and milk FA profile of cows assigned to treatment sequences containing a control (CON), with no fat source; soybean oil, added at 2.68% of diet dry matter (DM); WS, addition of WS at 14.3% of diet DM; and CSFA, addition of CSFA at 2.68% of diet DM. Dietary fat supplementation had no effect on nutrient intake and digestibility, with the exception of ether extract. Cows fed fat sources tended to have lower milk fat concentration than those fed CON. In general, diets containing fat sources tended to decrease ruminal neutral detergent fiber digestibility in relation to CON. Cows fed WS had lower ruminal digestibility of DM and higher abomasal flow of DM in comparison to cows fed CSFA. As expected, diets containing fat supplements increased FA abomasal flow of C18:0 and total FA. Cows fed WS tended to present a higher concentration of UFA in milk when compared with those fed CSFA. This study suggests that under some circumstances, abomasal flow of UFA in early lactation cows can be increased by supplementing their diet with fat supplements rich in linoleic acid, regardless of rumen protection, with small effects on ruminal DM digestibility.     

Effect of ruminal pulse dose of polyunsaturated fatty acids on ruminal microbial populations and duodenal flow and milk profiles of fatty acids

The objective of this study was to examine the effect of ruminal pulse dose of free linoleic acid (LA) and free docosahexaenoic acid (DHA) on microbial populations in the rumen, duodenal fatty acid (FA) flow, milk composition, and milk FA profiles of Chinese Holstein dairy cows. Four rumen- and duodenal-fistulated Chinese Holstein cows in mid lactation (138.5 ± 10 d in milk) were randomly assigned to 3 treatment groups and 1 control group in a 4 × 4 Latin square design over 4 periods (3 wk per period). Diets contained either no LA or 2.7% LA and either no DHA or 0.5% DHA in a 2 × 2 factorial arrangement of treatments. Ruminal pulse dose with DHA increased counts of Megasphaera elsdenii, decreased Fibrobacter succinogenes, but did not affect Butyrivibrio fibrisolvens or Ruminococcus flavefaciens. The pulse dose of LA at 2.7% dry matter had no effect on the population sizes of the 3 major cellulolytic bacterial species or M. elsdenii, and no interaction was observed between LA and DHA. The pulse dose of LA or DHA, either alone or in combination, increased the duodenal flow of vaccenic acid (VA). The milk VA and cis-9,trans-11 conjugated linoleic acid (CLA) contents also increased in response to the fatty acid pulse dose, and the pulse dose of both LA and DHA together had the most profound stimulatory effect. This study indicated that ruminal pulse dose of LA or DHA could be used to increase duodenal flow of VA and the milk contents of potentially health-promoting FA, such as VA and cis-9,trans-11 CLA. These results might be useful in formulating dietary interventions to improve milk cis-9,trans-11 CLA contents.     

Effects of chitosan and whole raw soybeans on ruminal fermentation and bacterial populations,and milk fatty acid profile in dairy cows

The objective of this study was to evaluate whether providing chitosan (CHI) to cows fed diets supplemented with whole raw soybeans (WRS) would affect the nutrient intake and digestibility, ruminal fermentation and bacterial populations, microbial protein synthesis, N utilization, blood metabolites, and milk yield and composition of dairy cows. Twenty-four multiparous Holstein cows (141 ± 37.1 d in milk, 38.8 ± 6.42 kg/d of milk yield; mean ± SD) were enrolled to a 4 × 4 Latin square design experiment with 23-d periods. Cows were blocked within Latin squares according to milk yield, days in milk, body weight, and rumen cannula (n = 8). A 2 × 2 factorial treatment arrangement was randomly assigned to cows within blocks. Treatments were composed of diets with 2 inclusion rates of WRS (0 or 14% diet dry matter) and 2 doses of CHI (0 or 4 g/kg of dry matter, Polymar Ciência e Nutrição, Fortaleza, Brazil). In general, CHI+WRS negatively affected nutrient intake and digestibility of cows, decreasing milk yield and solids production. The CHI increased ruminal pH and decreased acetate to propionate ratio, and WRS reduced NH₃-N concentration and acetate to propionate in the rumen. The CHI reduced the relative bacterial population of Butyrivibrio group, whereas WRS decreased the relative bacterial population of Butyrivibrio group, and Fibrobacter succinogenes, and increased the relative bacterial population of Streptococcus bovis. No interaction effects between CHI and WRS were observed on ruminal fermentation and bacterial populations. The CHI+WRS decreased N intake, microbial N synthesis, and N secreted in milk of cows. The WRS increased N excreted in feces and consequently decreased the N excreted in urine. The CHI had no effects on blood metabolites, but WRS decreased blood concentrations of glucose and increased blood cholesterol concentration. The CHI and WRS improved efficiency of milk yield of cows in terms of fat-corrected milk, energy-corrected milk, and net energy of lactation. The CHI increased milk concentration [g/100 g of fatty acids (FA)] of 18:1 trans-11, 18:2 cis-9,cis-12, 18:3 cis-9,cis-12,cis-15, 18:1 cis-9,trans-11, total monounsaturated FA, and total polyunsaturated FA. The WRS increased total monounsaturated FA, polyunsaturated FA, and 18:0 to unsaturated FA ratio in milk of cows. Evidence indicates that supplementing diets with unsaturated fat sources along with CHI negatively affects nutrient intake and digestibility of cows, resulting in less milk production. Diet supplementation with CHI or WRS can improve feed efficiency and increases unsaturated FA concentration in milk of dairy cows.     

Effects of pH and concentrations of linoleic and linolenic acids on extent and intermediates of ruminal biohydrogenation in vitro

Three experiments were conducted by in vitro incubations in ruminal fluid to investigate the effects of pH and amounts of linoleic and linolenic acids on the extent of their biohydrogenation, the proportions of conjugated linoleic acid (CLA) and trans-C18:1 as intermediates, and the ratio trans-10:trans-11 intermediates. The effects of pH and amount of linoleic acid were investigated in kinetic studies, and effects of the amount of linolenic acid were studied with 6-h incubations. With identical initial amounts of linoleic acid, its disappearance declined when the mean pH during incubation was under 6.0 compared with a mean pH over 6.5, and when the amount of linolenic acid increased from 10 to 180 mg/160-ml flask, suggesting an inhibition of the isomerization step of the biohydrogenation. Low pH decreased the ratio of trans-10:trans-11 intermediates. With initial amounts of linoleic acid increasing from 100 to 300 mg, the percentage of linoleic acid disappearance declined, but the amount that disappeared increased, without modification of the trans-10:trans-11 ratio, suggesting a maximal capacity of isomerization rather than an inhibition. Moreover, increasing initial linoleic acid resulted in high amounts of trans-C18:1 and an increase of C18:0 that was a linear function of time, suggesting a maximal capacity for the second reduction step of biohydrogenation. High amounts of initial linolenic acid did not affect the amounts of CLA, trans-C18:1, or the ratio trans-10:trans-11. Based on these experiments, a ruminal pH near neutrality with high amount of dietary linoleic acid should modulate the reactions of biohydrogenation in a way that supports CLA and trans-11C18:1 in the rumen.     

Susceptibility to milk fat depression in dairy sheep and goats: Individual variation in ruminal fermentation and biohydrogenation

Small ruminants are susceptible to milk fat depression (MFD) induced by marine lipid supplementation. However, as observed in dairy cows, there is wide individual variation in the response to MFD-inducing diets, which may be due to individual differences in ruminal processes. Therefore, we compared the ruminal responses of goats and sheep with varying degrees of MFD extent to improve our understanding of this complex syndrome. Our specific aims were to attempt to elucidate whether pre-existing variations in ruminal fermentation and biohydrogenation determine a higher tolerance or susceptibility to MFD, and whether the severity of MFD depends exclusively on the response to the diet. The trial was conducted with 25 does and 23 ewes fed a basal diet without lipid supplementation for 3 wk (control period). Then, 2% fish oil (FO) was added to the same diet for 5 additional weeks (MFD period). Based on the extent of the elicited MFD (i.e., the percentage variation between milk fat concentrations recorded at the end of the control and MFD periods), the 5 most responsive (RESPON+) and the 5 least responsive (RESPON?) animals were selected within each species. On the last day of each period, ruminal fluid samples were collected to examine fermentation parameters and fatty acid profiles. In general, the individual degree of MFD in sheep and goats did not seem to be predetermined by traits related to ruminal fermentation and biohydrogenation, including fatty acids that may serve as biomarkers of microorganisms. Regarding differences in the response to FO, the results suggest no link between MFD susceptibility and concentration of biohydrogenation intermediates such as trans-10-containing C18, C20, and C22 metabolites. The explanation for individual responses based on a shortage of ruminal acetate and 18:0 for mammary uptake also seems to be dismissed, based on the lack of variation in these compounds between RESPON+ and RESPON?. However, the concentration of unsaturated fatty acids provided by FO (e.g., cis-9 16:1, cis-11 18:1, and 20:5n-3) was higher in the rumen of RESPON+ than RESPON? ewes and does. Thus, although further research is needed, the extent of biohydrogenation of these fatty acids might be associated with tolerance or susceptibility to MFD.     

Effects of lauric and myristic acids on ruminal fermentation, production, and milk fatty acid composition in lactating dairy cows

The objectives of this experiment were to investigate the effects of lauric (LA) and myristic (MA) acids on ruminal fermentation, production, and milk fatty acid (FA) profile in lactating dairy cows and to identify the FA responsible for the methanogen-suppressing effect of coconut oil. The experiment was conducted as a replicated 3 × 3 Latin square. Six ruminally cannulated cows (95 ± 26.4 DIM) were subjected to the following treatments: 240 g/cow per day each of stearic acid (SA, control), LA, or MA. Experimental periods were 28 d and cows were refaunated between periods. Lauric acid reduced protozoal counts in the rumen by 96%, as well as acetate, total VFA, and microbial N outflow from the rumen, compared with SA and MA. Ruminal methane production was not affected by treatment. Dry matter intake was reduced 35% by LA compared with SA and MA, which resulted in decreased milk yield. Milk fat content also was depressed by LA compared with SA and MA. Treatment had no effect on milk protein content. All treatments increased milk concentration of the respective treatment FA. Concentration of C12:0 was more than doubled by LA, and C14:0 was increased (45%) by MA compared with SA. Concentration of milk FA < C16 was 20% lower for LA than MA. Concentrations of trans 18:1 FA (except trans 12) and CLA isomers were increased by LA compared with SA and MA. Overall, the concentrations of saturated FA in milk fat were reduced, and that of > C16 FA and MUFA were increased, by LA compared with the other treatments. In this study, LA had profound effects on ruminal fermentation, mediated through inhibited microbial populations, and decreased DMI, milk yield, and milk fat content. Despite the significant decrease in protozoal counts, however, LA had no effect on ruminal methane production. Thus, the antimethanogenic effect of coconut oil, observed in related studies, is likely due to total FA application level, the additive effect of LA and MA, or a combination of both. Both LA and MA modified milk FA profile significantly.     

Omega-3多不饱和脂肪酸在高脂血症中的作用机制研究进展

高脂血症是一种代谢紊乱疾病,直接引起或导致一些严重危害人体健康的疾病,如动脉粥样硬化、冠心病等。Omega-3多不饱和脂肪酸能够显著降低大鼠及人体血清中总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL)、极低密度脂蛋白(VLDL)的含量,同时增加高密度脂蛋白(HDL)的含量,其作用机制主要为增加外源性胆固醇代谢,减少内源性胆固醇合成,抑制肝脏胆固醇转运相关基因的表达,抑制肝脏载脂蛋白的产生,在高脂血症及其相关代谢性疾病的防治中发挥重要作用。基于国内外研究Omega-3多不饱和脂肪酸对血脂水平的调节作用,对Omega-3多不饱和脂肪酸在高脂血症中的作用机制进行综述,以期为深入研究Omega-3多不饱和脂肪酸对于血脂和脂质代谢调节的相关机制和后续相关药物的研发提供参考。     

Temperature and duration of heating of sunflower oil affect ruminal biohydrogenation of linoleic acid in vitro

Sunflower oil heated at 110 or 150°C for 1, 3, or 6 h was incubated with ruminal content in order to investigate the effects of temperature and duration of heating of oil on the ruminal biohydrogenation of linoleic acid in vitro. When increased, these 2 parameters acted together to decrease the disappearance of linoleic acid in the media by inhibiting the isomerization of linoleic acid, which led to a decrease in conjugated linoleic acids and trans-C18:1 production. Nevertheless, trans-10 isomer production increased with heating temperature, suggesting an activation of Δ⁹-isomerization, whereas trans-11 isomer production decreased, traducing an inhibition of Δ¹²-isomerization. The amount of peroxides generated during heating was correlated with the proportions of biohydrogenation intermediates so that they might explain, at least in part, the observed effects. The effects of heating temperature and duration on ruminal bacteria community was assessed using capillary electrophoresis single-strand conformation polymorphism. Ruminal bacterial population significantly differed according to heating temperature, but was not affected by heating duration. Heating of fat affected ruminal biohydrogenation, at least in part because of oxidative products generated during heating, by altering enzymatic reactions and bacterial population.     

Effect of feeding oilseed supplements to dairy cows on ruminal and milk fatty acid composition

The objective of this study was to compare the effects of oilseed‐based supplements, rapeseed and linseed, against a barley‐based control, on the fatty acid composition, and subsequent solid fat ratio, of the milk fat from dairy cows. In addition, as a means of understanding the digestive processes which influence the milk fat composition, ruminal extracts were collected from the cows and analysed for fatty acid composition. Four lactating dairy cows each fitted with a rumen fistula were provided with silage and one of four concentrate diets. The main constituent of the concentrate supplements was either rapeseed (ground or unground), linseed (unground) or a barley control. The diets were offered in accordance with a 4 × 4 Latin square arrangement. The oilseed‐supplemented concentrates provided the cows with 620–640 g fatty acids day^?1. Experimental treatments were provided to the cows for 2 weeks, after which ruminal extracts were collected over a 24 h period and a milk sample was taken. All extracts were analysed for fatty acid composition. The diets fed influenced the long‐chain fatty acid composition of the ruminal extracts and milk fat. The proportion of C18:1n‐9 in the ruminal extracts increased from 202–224 to 282–321 g kg^?1 of the total fatty acids when the cows were provided with the rapeseed‐based diets. The linseed‐based diet increased the C18:1n‐9 proportion of the ruminal extracts from 164 to 218 g kg^?1 of the total fatty acids. Both rapeseed‐based diets also resulted in a higher proportion of C18:0 in the ruminal extract, possibly owing to biohydrogenation of the dietary fatty acids. This proportion of C18:0 in the ruminal extract was lowest immediately after feeding, increasing to a maximum 4–6 h later. Both rapeseed‐based concentrates increased the proportion of C18:1n‐9 in the milk fat to approximately 300 g kg^?1 of the total fatty acids as compared with 214 g kg^?1 for the control. The proportion of C18:1n‐9 in the milk fat from the cows offered the linseed‐based concentrate was 246 g kg^?1 of the total fatty acids. There were also significant decreases in the proportions of C16:0 in the milk fat from the cows offered all oilseed‐based concentrates. There was no difference between the fatty acid compositions of the milk fats from the cows fed the ground or unground rapeseed‐based supplements. The oilseed‐based supplements also resulted in significant decreases in the solid fat content of the milk fat at temperatures ranging from 0 to 35 °C, which would be indicative of a softer, more spreadable butter. © 2002 Society of Chemical Industry     

鱼油提取、多不饱和脂肪酸富集及EPA和DHA的应用研究进展

文章对鱼油的提取工艺、多不饱和脂肪酸聚集方法、二十二碳六烯酸（DHA）和二十碳五烯酸（EPA）的保健功能进行了阐述,并对未来鱼油行业的发展进行了展望。     

Short communication: Diurnal profiles of conjugated linoleic acids and trans fatty acids in ruminal fluid from cows fed a high concentrate diet supplemented with fish oil, linseed oil, or sunflower oil

Trans-18:1 and 18:2 isomer composition in ruminal fluid during the daily feeding cycle was examined in 3 cows fed a high concentrate diet (35:65) with 5% (DM basis) sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) in a 3 x 3 Latin square with 3 4-wk periods. Grass hay and concentrate mixtures were fed at 0900, 1300, and 1700 h daily. Ruminal fluid was collected at 0900, 1100, 1300, 1500, 1700, 2000, and 0000 h. Feeding SO resulted in the greatest mean concentrations (% of total fatty acids) of trans10,cis12-18:2 and cis9,trans11-18:2. In particular, trans10,cis12-18:2 with SO was greater at 1500 (0.29%), 2000 (0.34%), and 0000 h (0.25%) relative to 0900 h (0.07%). Cis9,trans11-18:2 concentration increased from 0.47% at 0900 h to a peak of 2.06% at 1100 h; it remained greater than the percentage determined at 0900 h at 1300 (1.4%) through 0000 h (1.1%). Concentration of trans11,cis15-18:2 was greatest with LO, ranging from 3.3% (0900 h) to a peak of 11.4% at 2000 h. Mean trans10-18:1 concentration ranked by diet was SO > FO > LO. Peak trans10-18:1 with SO was observed at 1700 h (14.9%) compared with 0900 h (5.1%). Trans11-18:1 did not differ with diet or time. Stearic acid decreased over time with all diets reaching minimum concentrations at 1700 to 2000 h relative to 0900 h. Feeding FO, however, decreased mean 18:0 concentration 4-fold compared with LO or SO. The moderate effect on concentration of trans-18:1 coupled with accumulation of 18:2 intermediates and the decrease of 18:0 over time suggest that oils reduced the biohydrogenation of 18:2 isomers to trans-18:1.     

Milk saturated fatty acids,odd- and branched-chain fatty acids,and isomers of C18:1, C18:2, and C18:3n-3 according to their duodenal flows in dairy cows: A meta-analysis approach

We sought to establish predictive response models of milk fatty acid (FA) yields or concentrations from their respective duodenal flow, rumen digestive parameters, or diet characteristics in dairy cows, with a special focus on cis and trans isomers of C18:1, C18:2, odd- and branched FA, and mammary de novo synthesized FA. This meta-analysis was carried out using data from trials with nature of forage, percentage of concentrate, supplementation of diets with vegetable oils or seeds, and marine products' animal fats as experimental factors. The data set included 34 published papers representing 50 experiments with 142 treatments. Increasing duodenal C18 FA flow induced a quadratic increase in milk total C18 yield and a linear decrease in milk C4:0 to C14:0 concentration. Intra-experimental predictive response models of individual milk cis C18:1 isomers (Δ 11 to 15 position) from their respective duodenal flows had coefficients of determination (R²) ranging from 0.74 to 0.99, with root mean square error varying from 0.19 to 0.96 g/d, 0.02 to 0.10% of total FA, and 0.03 to 0.29% of C18 FA. Models predicting milk trans C18:1 isomer yields or concentrations had R² greater than 0.90 (except for trans-4 and trans-10 C18:1) with root mean square error varying from less than 0.1 to 5.2 g/d. Linear regressions for C18:2n-6, trans-10,cis-12 CLA, and trans-11,trans-13 CLA were calculated according to their respective duodenal flows. Quadratic models of milk C18:3n-3 yield or concentration from its duodenal flow had R² values above 0.97. Models of amounts desaturated from C18:0 into cis-9 C18:1 and trans-11 C18:1 into cis-9,trans-11 CLA indicated that the contribution of C18:0 and trans-11 C18:1 desaturation to respective cis-9 C18:1 and cis-9,trans-11 CLA yields in milk fat was 83.8% (±0.75) and 86.8% (±2.8). Furthermore, when cows were fed marine products, our results could indicate a lower mammary uptake of C18:0 and trans-11 C18:1 in proportion to their respective duodenal flow, with no associated change in mammary Δ⁹-desaturase activity. Yields or concentrations of C15:0, C17:0, iso-C15:0, iso-C17:0, anteiso-C15:0, and anteiso-C17:0 were dependent on their respective duodenal flow or concentration at duodenum, but synthesis of these FA from C3 units for linear-chain odd FA, and from C2 units for branched-chain FA was suggested, respectively. Several milk C18 FA concentrations were closely related to their duodenal concentrations with slopes of the linear models close to the bisector; this could reflect a priority for the use of these duodenal C18 FA by the mammary gland to favor their high concentration in plasma triglycerides and nonesterified FA, which are preferentially taken up by the mammary gland.     

Performance and ruminal fermentation of dairy cows fed whole cottonseed with elevated concentrations of free fatty acids in the oil

Twenty-four lactating Holstein cows were used in an 8-wk completely randomized design trial to examine the effects of feeding whole cottonseed (WCS) with elevated concentrations of free fatty acids (FFA) in the oil on intake and performance. Treatments included WCS with normal concentrations of FFA (6.8%, control) and 2 sources of WCS with elevated FFA [HFFA1 (24.1%) or HFFA2 (22.3%)]. The 2 sources of WCS with elevated FFA differed in that HFFA2 were discolored from being initially stored with excess moisture, which led to heating and deterioration during storage, whereas HFFA1 were normal in appearance and the increase in FFA occurred without heating and visible damage to the WCS. Nutrient concentrations were similar among WCS treatments, which provided 14% of the total dietary dry matter. Dry matter intake tended to be higher for cows fed HFFA2 compared with control and HFFA1. Yield of milk and components was similar among treatments, but milk fat percentage was lower for HFFA1 and HFFA2 compared with control. In a concurrent 3 × 3 Latin square trial with 6 ruminally canulated Holstein cows, molar proportions of isobutyrate were higher for HFFA2 than control and HFFA1, but no differences were observed in acetate or propionate. Results of these trials indicate that feeding WCS with high concentrations of FFA decreases milk fat percentage but does not alter dry matter intake, milk yield, or concentrations of other components. The minor changes in ruminal fermentation that were observed do not account for the decrease in milk fat percentage.     

日粮添加不同来源脂肪酸对奶牛脂质代谢及激素水平的影响

研究日粮中添加不同来源脂肪酸对泌乳中期奶牛脂质代谢及激素水平的影响。选择36头泌乳中期中国荷斯坦奶牛,采用随机区组设计,按照产奶量、胎次及泌乳日龄将奶牛分为对照组、中短链脂肪酸(SMC-FA)组和长链脂肪酸(LCFA)组。对照组饲喂基础日粮,SMCFA组和LCFA组分别在基础日粮的基础上添加400g/d SMCFA和400 g/d LCFA,正试期为56 d。结果显示,LCFA组奶牛血清中非酯化脂肪酸的含量显著高于对照组(P<0.05),其余组间差异不显著(P>0.05);血清中胆固醇的含量在SMCFA和LCFA组均有增加的趋势,但未达到显著水平(P>0.05);胰岛素样生长因子的含量在SMCFA组显著降低(P<0.05),其余组间没有显著差异(P>0.05);添加LCFA或SMCFA对奶牛血清中三酰甘油、高密度脂蛋白、低密度脂蛋白、生长激素及胰岛素均没有显著影响(P>0.05)。结果表明日粮中添加SMCFA对泌乳中期奶牛脂质代谢有一定的负面影响。     

Increasing dietary levels of docosahexaenoic acid-rich microalgae: Ruminal fermentation,animal performance,and milk fatty acid profile of mid-lactating dairy cows

This study aimed to evaluate the effects of increasing dietary levels of microalgae (ALG), rich in docosahexaenoic acid (DHA; All-G-Rich, Alltech, Nicholasville, KY), in isolipidic diets, on animal performance, nutrient digestibility, ruminal fermentation, milk fatty acid profile, energy balance, microbial protein synthesis, and blood serum metabolites in mid-lactating dairy cows. Twenty-four Holstein cows [130.3 ± 15.4 d in milk, and 30.8 ± 0.543 kg/d of milk yield (mean ± standard error)] were used in a 4 × 4 Latin square design experiment to evaluate the following treatments: control diet, without addition of ALG; and increasing levels of ALG [2, 4, and 6 g/kg of dry matter (DM)]. The ALG decreased DM intake and increased total-tract DM apparent digestibility. A tendency was observed for a quadratic effect on total-tract NDF digestibility by ALG inclusion, with peak value of the quadratic response at 4.13 g/kg of DM dose. Moreover, ALG increased ruminal pH and decreased acetate and total volatile fatty acid concentrations. Fat-corrected milk and energy-corrected milk were quadratically affected, and a tendency for a milk yield effect was observed when ALG levels increased, whereas maximal yields were observed with intermediate doses. Milk fat, protein, and lactose concentrations were diminished, whereas productive efficiency was improved by the increase of ALG levels. Saturated fatty acid proportions were decreased, whereas polyunsaturated fatty acid proportions were increased when ALG was fed. There was low DHA transfer into milk; however, ALG inclusion decreased C18:0, C18:1 cis-9, C18:2 cis-9,12, and C18:3 cis-9,12,15 proportions, and increased C18:2 cis-9,trans-11, C18:1 trans-9, and C18:1 trans-11 proportions. Gross energy intake was decreased, whereas no effect was observed on digestible, metabolizable, or net energy intake. The ALG inclusion quadratically affected the microbial protein synthesis, with maximal enhancement at 3.24 g/kg of DM dose, and also increased serum cholesterol concentration. Under the conditions of this experiment, the inclusion of ALG in diets for mid-lactating dairy cows decreased feed intake and increased nutrient digestibility, improving productive efficiency and modifying milk fatty acid profile. Estimated intermediate doses (1.22 to 2.90 g/kg of DM) of DHA-rich ALG may be beneficial to milk, fat-corrected milk, and energy-corrected milk yields, and is recommended for dairy cows.     

Short communication: Effects of diets containing supplemental fats on ruminal fermentation and milk odd- and branched-chain fatty acids in dairy cows

There is a growing interest in odd- and branched-chain fatty acids (OBCFA) in milk following reports that several branched-chain fatty acids (FA) have health promoting effects, and certain milk OBCFA could serve as a biomarker to assess ruminal function. Twenty-four Holstein cows were fed 3 low-forage diets containing 30 g/kg of dry matter of prilled palm fat (PPF), sun?ower oil (SO), or an equal mixture of both fats (experiment 1) or 3 diets containing 30 g/kg of dry matter of SO with a forage-to-concentrate ratio of 39:61, 44:56, or 48:52 (Experiment 2); diets were fed to investigate milk OBCFA composition and to explore the relationships between ruminal VFA and milk OBCFA using principal component analysis. Including SO in diets decreased yields of milk 13:0 anteiso, 15:0 anteiso, 15:0, 17:0, cis-9 15:1, and cis-9 17:1 compared with PPF. The molar proportion of ruminal propionate was the lowest and the yields of milk 14:0 iso and 16:0 iso were the greatest with the diet containing both fat supplements. Replacing concentrate with forages linearly increased ruminal acetate and yields of milk 13:0 iso, 14:0 iso, 15:0 iso, 16:0 iso, 17:0 iso, 13:0 anteiso, 15:0 anteiso, 15:0, 17:0, cis-9 15:1, and cis-9 17:1. The principal component analysis revealed that ruminal molar proportion of acetate related to concentrations of milk iso FA containing <17-carbon, whereas ruminal propionate related to milk 15:0, 17:0, cis-9 15:1, and cis-9 17:1, with the stronger correlations between milk OBCFA and ruminal acetate than propionate. No associations were found between ruminal molar proportion of butyrate and milk OBCFA concentrations. The results suggest that complete replacement of PPF with SO at 30 g/kg of dry matter in low-forage diets is not an effective strategy to enhance bioactive branched-chain FA in milk, rather this feeding practice lowers anteiso FA in milk; however, increasing forage proportion in diets containing SO enhances several iso and anteiso FA in milk. The milk OBCFA concentrations have stronger correlations with ruminal acetate molar proportion than with propionate or butyrate in cows fed diets containing supplemental fats.