The potential use of long-chain alcohols and fatty acids as diet composition markers: factors influencing faecal recovery rates and diet composition estimates in sheep

The limitations of the alkane technique in estimating the diet components of herbivores call for the introduction of new diet composition markers. Recently, long-chain alcohols (alcohols) and long-chain fatty acids (acids) have received the most attention and show great potential, when combined with alkanes, to estimate composition of complex diets. In the current study, faecal recoveries of alcohols and acids were determined in sheep in four different live weight groups fed three herbage species, either Leymus chinensis, L. dasystachys or Elymus sibiricum. Analysis of variance (ANOVA) was used to examine the effects of herbage species and live weight of sheep on faecal recoveries of individual alcohols and acids. Further, an indoor experiment with six sheep fed a diet of equal proportions, on dry matter (DM) basis, of three herbages was performed, allowing to assess the accuracy of alcohols and/or acids in combination with alkanes, to estimate diet composition. A one-sample t-test was carried out to test the accuracy of these estimates. Results of the first experiment indicated that the faecal recoveries of alcohols and acids were significantly affected by herbage species (P < 0.05). While the effects were significant or near significant for the faecal recoveries of some alcohols (C24-ol, C30-ol and C26-ol) (P 0.05), no effect of live weight on faecal recoveries of acids was observed (P > 0.05). Therefore, adjustments based on diet-specific faecal recoveries might improve diet composition estimates. This was illustrated by the results of the second experiment. The diet composition estimated from alcohols or all combinations of alcohols with other marker types, after diet-specific correction of faecal recoveries, did not significantly differ from the actual composition (P > 0.05). However, using acids as additional markers resulted in poorer diet composition estimates. This study confirmed the utility of alcohols, combined with alkanes, as markers to estimate composition of complex diets. Although corrections based on mean faecal recoveries, average over animals and diets, resulted in some accuracy loss, results were still satisfactory and better than without recovery correction.     

Evaluation of long-chain alcohols as diet composition markers in goats grazing heathland areas

An experiment was conducted to assess the potential of long-chain alcohols (LCOH), in alternative or combined with alkanes and long-chain fatty acids (LCFA), as faecal markers to estimate the diet composition of goats grazing heathland vegetation with associated improved pastures. A total of seven diets were offered across the grazing season. The diets were composed of mixtures of herb species (Lolium perenne and Trifolium repens) and woody species (Erica spp., Calluna vulgaris and Ulex gallii) in an attempt to simulate diet selection of goats on these complex vegetation areas. The diet composition was estimated using LCOH markers alone or combined with alkanes, LCFA and alkanes+LCFA, by least square optimization procedures. The data showed large differences between plant species in their LCOH profile. Generally, plant species showed higher LCOH concentrations than those of alkanes and lower than LCFA markers. Faecal recovery of LCOH was incomplete and increased in a linear manner (P < 0.001) with the carbon-chain length, and was influenced by diet composition and its digestibility. The diet composition estimates based on LCOH alone were more accurate (P < 0.05) than those using alkanes or LCFA alone. Results showed that the combination of LCOH with alkanes, LCFA and alkanes+LCFA resulted in more accurate (P < 0.05) estimates of diet composition, indicating that LCOH provided different discriminatory information to that of alkanes and LCFA, helping in the discrimination of the plant species used in this experiment. Results indicate that correction of faecal LCOH concentrations to incomplete faecal recovery is necessary to obtain more accurate estimates of diet composition. Nevertheless, it seemed that the use of a less accurate recovery correction on LCOH markers had a lower impact on the accuracy of estimates than that of alkanes and LCFA.     

Using the alkanes and long-chain alcohols of plant cuticular wax to estimate diet composition and the intakes of mixed forages in sheep consuming a known amount of alkane-labelled supplement

In a feeding trial with 24 sheep, we used the alkanes, long-chain alcohols (LCOH) or both of these plant wax markers, to estimate the diet composition of animals offered diets comprising alkane-labelled cottonseed meal (CSM) together with up to four forages. The diets used were: Diet 1 subterranean clover (Trifolium subterraneum); Diet 2 subterranean clover + phalaris (Phalaris aquatica); Diet 3 subterranean clover, phalaris + annual ryegrass (Lolium rigidum); and Diet 4 subterranean clover, phalaris, annual ryegrass + wheat straw (Triticum aestivum). Estimates of diet composition were made following correction of faecal alkane or LCOH concentrations for incomplete faecal recovery, using recovery estimates derived from individual animals, mean recoveries for a given dietary treatment or grand mean recoveries. Estimated dietary proportions of CSM and known intakes of CSM were used to estimate forage intake. The LCOH concentrations of the diet components were much higher than their alkane concentrations, especially for phalaris. Multivariate analyses showed that the discriminatory information provided by the LCOH was additional to that provided by the alkanes, and that a combination of (LCOH + alkanes) discriminated better between diet components than either class of marker alone. Faecal recoveries of LCOH increased with increasing carbon-chain length; there were no differences in recovery attributable to diet. The most accurate estimates of diet composition were obtained with the combination of (LCOH + alkanes). Estimates of diet composition based on LCOH alone were not as good as alkanes alone, due to the high correlation between the LCOH profiles of phalaris and ryegrass. Total grass content of the diet was very accurately estimated using LCOH. Diet composition estimates provided estimates of whole-diet digestibility, which did not differ from the measured values. Trends in the accuracy of forage intake estimates reflected those found with diet composition and almost two-thirds of estimates based on (LCOH + alkanes) had lower error than those found with alkanes alone. The results confirm that supplements labelled with plant wax components can be used to estimate forage intake, and also show that the LCOH are useful markers for estimating diet composition. Intakes were also computed using a combination of natural LCOH concentrations in the diet and the daily dose rate of even-chain alkanes administered by intra-ruminal device. Differences between intakes so estimated and the measured intakes were closely related to the difference in faecal recovery between the LCOH/alkane pair used to estimate intake, by an amount close to that expected on theoretical grounds. It is concluded that the use of plant wax LCOH, especially in combination with alkanes, will result in improved estimates of diet composition and intake in grazing animals.     

Faecal alkane recoveries from multi-component diets and effects on estimates of diet composition in sheep

In a feeding trial with sheep, four animals each were fed one of the three roughages (perennial ryegrass (PR), meadow fescue (MF) and red clover (RC)) or one of the four different mixtures (g/day 250 : 250 : 250, 375 : 75 : 300, 525 : 187.5 : 37.5 and 75 : 525 : 150, respectively) of those three roughages, both with and without the inclusion of 100 g of beeswax-labelled barley. Further, four sheep received a pure lucerne diet to enlarge available data on single species faecal recoveries. All sheep except those fed single-component diets and the 250 : 250 : 250 roughage mix were administered intra-ruminal alkane controlled-release devices (CRD). The aim of the study was to investigate the effect of diet composition on faecal alkane recoveries, and to assess the accuracy of the alkane-based estimate of diet composition and intake based either upon a general set of faecal recoveries across diets or upon dietary recoveries and dietary samples more specifically attributable to individual dietary treatments. For each roughage component independently, the accuracy of diet composition estimates was assessed using linear regression across all diets. The estimates of the proportion of barley were analysed further using mean differences and mean prediction errors. Faecal alkane recovery increased with increasing chain length and was affected by diet composition. RC had a significantly higher faecal recovery for alkanes C25, C27, C29 and C31 than at least one of the other single-roughage diets. When considering mixed diets consisting of PR, MF, RC and barley, the composition of the roughage component significantly affected faecal recovery of all alkanes except C30 and C33. The inclusion of beeswax-labelled barley caused a decrease in faecal recovery of alkanes up to C29. This effect was attributable to the beeswax rather than the barley itself. By contrast, the decrease of faecal recovery of synthetic dosed alkanes from the CRD in diets containing barley, compared with the corresponding diets without barley, was attributable to the supplement itself. It was concluded that synthetic dosed alkanes behaved differently during gut transit from natural alkanes. The proportions of individual dietary components were estimated well over a wide range of proportions. Generally, the more information available, the more accurate the estimates achieved. However, a general set of faecal alkane recoveries and bulked samples of dietary components yielded estimates of diet composition sufficiently accurate for a large number of studies, especially in situations where groups of animals are of concern and not the individual animal.     

Application of long-chain alcohols as faecal markers to estimate diet composition of horses and cattle fed with herbaceous and woody species

Utilization of long-chain alcohols (LCOH) as diet composition markers in horses and cattle was assessed in a study conducted with 12 mature crossbreed mares (385±47 kg BW) and six adult non-lactating cows (499±36 kg BW) of Asturiana de los Valles breed. The LCOH data were combined with alkane and long-chain fatty acid (LCFA) data to test the applicability of combining these markers to estimate diet composition. Animals were randomly divided into groups of three animals and received a daily total amount of 1.0 kg dry matter/100 kg BW of diets composed of different proportions of ryegrass (Lolium perenne) and woody species (Ulex gallii and heather). Diet composition was estimated from even-chain LCOH (C₂₀-OH to C₃₀-OH) combined or not with alkane (C₂₅-C₃₁ and C₃₃) and/or LCFA (C₂₂-FA to C₂₈-FA, C₃₀-FA, C₃₂-FA and C₃₄-FA) concentrations in diet components and faeces by least-squares procedures, using marker faecal concentrations uncorrected for incomplete faecal recovery (FR0) or corrected using mean recoveries across diets within animal species (FR1). Results showed large differences between plant species in their LCOH profiles, and that these markers offered additional discriminatory information to that provided by alkanes and LCFA. The LCOH markers were incompletely recovered in the faeces of both animal species. In cattle, LCOH FR tended to increase with carbon-chain length in a linear manner in both diets (P<0.001), whereas in horses overall data showed a curvilinear relationship between these variables. Combination of LCOH, LCFA and alkanes resulted in more accurate diet estimates. Correction of faecal LCOH concentrations to incomplete FR led to more accurate diet composition estimates in both animal species. Results obtained in this study suggest the usefulness of LCOH markers combined with alkanes and LCFA to estimate diet composition of horses and cattle grazing mixed grassy–woody plant communities.     

The potential application of plant wax markers from alfalfa for estimating the total feed intake of sheep

Estimating the feed intake of grazing herbivores is critical for determining their nutrition, overall productivity and utilization of grassland resources. A 17-day indoor feeding experiment was conducted to evaluate the potential use of Medicago sativa as a natural supplement for estimating the total feed intake of sheep. A total of 16 sheep were randomly assigned to four diets (four sheep per diet) containing a known amount of M. sativa together with up to seven forages common to typical steppes. The diets were: diet 1, M. sativa + Leymus chinensis + Puccinellia distans; diet 2, species in diet 1 + Phragmites australis; diet 3, species in diet 2 + Chenopodium album + Elymus sibiricus; and diet 4, species in diet 3 + Artemisia scoparia + Artemisia tanacetifolia. After faecal marker concentrations were corrected by individual sheep recovery, treatment mean recovery or overall recovery, the proportions of M. sativa and other dietary forages were estimated from a combination of alkanes and long-chain alcohols using a least-square procedure. Total intake was the ratio of the known intake of M. sativa to its estimated dietary proportion. Each dietary component intake was obtained using total intake and the corresponding dietary proportions. The estimated values were compared with actual values to assess the estimation accuracy. The results showed that M. sativa exhibited a distinguishable marker pattern in comparison to the other dietary forage species. The accuracy of the dietary composition estimates was significantly (P < 0.001) affected by both diet diversity and the faecal recovery method. The proportion of M. sativa and total intake across all diets could be accurately estimated using the individual sheep or the treatment mean recovery methods. The largest differences between the estimated and observed total intake were 2.6 g and 19.2 g, respectively, representing only 0.4% and 2.6% of the total intake. However, they were significantly (P < 0.05) biased for most diets when using the overall recovery method. Due to the difficulty in obtaining individual sheep recovery under field conditions, treatment mean recovery is recommended. This study suggests that M. sativa, a natural roughage instead of a labelled concentrate, can be utilized as a dietary supplement to accurately estimate the total feed intake of sheep indoors and further indicates that it has potential to be used in steppe grassland of northern China, where the marker patterns of M. sativa differ markedly from commonly occurring plant species.     

The use of dosed and herbage n-alkanes as markers for the determination of digestive strategies of captive giraffes (Giraffa camelopardalis)

Selected aspects of digestion in captive giraffes were investigated in two trials with a type of marker that is new for digestive studies in non-domestic species. N-Alkanes were used as internal and external markers. In Trial 1, diet composition, intake, and digestibility were directly measured and estimated with the marker. Six giraffes were dosed once daily for 3 weeks with labeled pellets containing 3,800 ppm of each C₂₈, C₃₂, and C₃₆ alkanes at ˜100 mg/100 kg bodyweight. Intake of cabbage, browse, and a cattle pellet could accurately be estimated with the alkane method. For an oat/wheat mix and clover hay, however, there were large differences between directly measured intakes and those obtained using the alkane method, with the alkane method substantially underestimating. In Trial 2 mean retention times (MRTs) of fluid and particle phase were estimated. Three subadult giraffes were dosed once with cobalt-ethylenediamine tetraacetic acid (Co-EDTA) (260 mg) and alkanes C₂₉ (140 mg) and C₃₆ (370 mg). The average MRT for the fluid phase (Co-EDTA) was 31 hr and for the particle phase (alkanes) was 41 hr (C₃₆) and 43 h (C₂₉). This study showed that n-alkanes have potential as markers for investigating digestive strategies in non-domestic herbivores. Zoo Biol 17:295–309, 1998. © 1998 Wiley-Liss, Inc.     

Microalgae for use in tropical aquaculture I: Gross chemical and fatty acid composition of twelve species of microalgae from the Northern Territory,Australia

Twelve species of microalgae, isolated from north Australian marine, freshwater and hypersaline environments, were grown under controlled conditions of temperature, pH, photon flux density and salinity, and analysed for ash, total protein, water soluble carbohydrates, chlorophylla, total lipids, total fatty acids and fatty acid composition. Highest levels of the polyunsaturated fatty acid eicosapentaenoic acid [20:5(n-3)] were found in the marine diatoms.Nitzschia (frustulum) andN. closterium (23.1% and 15.2% of total fatty acids, respectively). None of the species studied had levels of docosahexaenoic acid [22:6(n-3)] greater than 1.1 % of total fatty acids. None of the chlorophyte species contained significant levels of either 20:5(n-3) or 22:6(n-3). The highest total fatty acid concentration of all species in the study was found in the freshwater chlorophyte speciesScenedesmus dimorphus (105 mg g^–1 dry wt). The hypersaline speciesDunaliella salina had the highest total lipid content (28.1% dry wt), followed byN. closterium, N. (frustulum) andNavicula sp. (24.2–27.8% dry wt).Chlamydomonas sp. had the highest protein content (66.9% dry wt).N. (frustulum) was highlighted as a possible useful source of lipids and polyunsaturated fatty acids in mixed microalgal diets for mariculture organisms used in tropical aquaculture.Author for correspondence     

The lipid composition of two species of serrasalmid fish in relation to dietary polyunsaturated fatty acids

The lipid composition of two species of Serrasalmid fish with different natural feeding habits were compared in relation to the polyunsaturated fatty acids (PUFA) supplied in their diets. Mylossoma aureum , a herbivorous piranha, was maintained on oatmeal flakes in which : 2(n-6) and : 3(n-3) were the only PUFA and accounted for 40–8 and 1.2%, respectively of dietary fatty acids. Serrasalmus nattereri , the carnivorous red piranha, was fed mosquito larvae containing .0-33.4% of their total fatty acids as : 2(n-6)+18 : 3(n-3) and 4.9-8.5% as 20 : 4(n-6)+20 : 5(n-3). The two species had similar lipid class compositions in liver, brain, viscera and carcass, except that lipids from M. aureum were generally richer in triacylglycerols. In both species, visceral and carcass lipid contained high levels of triacylglycerols whose principal PUFA was : 2(n-6). In M. aureum the major PUFA in liver total lipid and triacylglycerols was : 2(n-6) whilst the major PUFA in liver phospholipids were : 4(n-6) and : 5(n-6), with : 6(n-3) being a minor component. The level of : 6(n-3) in ethanolamine glycerophospholipids was significantly greater in brain than liver of M. aureum. Although absent from dietary lipid, : 6(n-3) was the major PUFA in phosphatidylcholine and ethanolamine glycerophospholipids from both the liver and brain of S, nattereri . In both species, the ratio of (n-6)/(n-3)PUFA was consistently lower in tissue lipids than in dietary lipids. The results are consistent with (i) the herbivorous M. aureum converting dietary C18 PUFA to their C20 and C22 homologues, (ii) the carnivorous S, nattereri forming : 6(n-3) from either 18:3(n-3) or 20: 5(n-3) and (iii) both species selectively desaturating and elongating (n-3) rather than (n-6) PUFA.     

黄龙带水库甲藻水华的脂肪酸组成特征

浮游植物是水体颗粒物中最重要的组成,同时也是生态系统中物质和能量传递的重要物质基础。脂肪酸是浮游植物细胞内一种重要的生理构件,并具有重要和特殊的生理功能。由于不同浮游植物所含的颗粒脂肪酸不同,因此自然水体中的颗粒脂肪酸种类和数量的组成与变化反映了水体中浮游植物的群落结构及演替过程。在水体富营养化过程中,浮游植物的组成也随之变化,因此研究水体中颗粒脂肪酸的浓度和组成结构可以直接反映水体的富营养化水平和特征的生化指标,也能有利于掌握不同类型浮游植物水华的发生机制。2005年4月,在中国广东一座处于北回归线中营养型水平的水库-黄龙带水库中发生了二角多甲藻水华,本研究主要研究了此次水华过程中的浮游植物群落结构的变化、水体中颗粒物的脂肪酸组成和浓度的变化,探讨了热带亚热带地区二角多甲藻水华过程中浮游植物群落与脂肪酸组成特征、脂肪酸组成特征与水体营养状态之间的关系。结果表明:黄龙带水库为中富营养水平水库,此次共鉴定出藻类28种,二角多甲藻(Peridinium bipes Stein)是这次水华的优势种。其生物量变化为0～5138μg·L^-1。在水华高峰期二角多甲藻生物量占总生物量的80%以上,水华消退期占30%以下。硅藻生物量在水华高峰期有下降趋势,水华消失期有上升趋势;蓝藻的增长趋势更加明显,绿藻在整个过程中生物量较低,波动不大。水华过程中脂肪酸的种类丰富,浓度很高。共检测出脂肪酸21种,包括各种饱和脂肪酸(SFA),单不饱和脂肪酸(MUFA)和多不饱和脂肪酸(PUFA),含量变化为0～74.593μg·L^-1。在水华高峰期,偶碳数饱和脂肪酸占有非常明显的优势,而奇碳数脂肪酸相对浓度较少,总脂肪酸浓度为85.5～192.2μg·L^-1。与水华高峰期相比,水华消退期的总脂肪酸浓度仅有16.5～45.5μg·L^-1。水华消退期饱和脂肪酸的相对丰度要高于水华高峰期,而多不饱和脂肪酸的相对丰度则相反。C18:5和EPA、DHA等甲藻标志脂肪酸的检出频率和浓度较高,颗粒物脂肪酸特征较好地反映了甲藻水华过程浮游植物群落结构的变化;并为淡水甲藻脂肪酸的研究提供一些基础资料。     

Effects of forage composition and growing season on methane emission from sheep in the Inner Mongolia steppe of China

Understanding the effects of dietary composition on methane (CH₄) production of sheep can help us to understand grassland degradation resulting in an increase of CH₄ emission from ruminant livestock and its resulting significance affecting CH₄ source/sink in the grazing ecosystem. The objective of this study was to investigate the effect of forage composition in the diet of sheep in July and August on CH₄ production by sheep in the Inner Mongolia steppe. The four diet treatments were: (1) Leymus chinensis and Cleistogenes squarrosa (LC), (2) Leymus chinensis, Cleistogenes squarrosa and concentrate supplementation (LCC), (3) Artemisia frigida and Cleistogenes squarrosa (AC), and (4) Artemisia frigida, Cleistogenes squarrosa and concentrate supplementation (ACC). CH₄ production was significantly lower in July than in August (31.4 and 36.2 g per sheep-unit per day, respectively). The daily average CH₄ production per unit of digestive dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) increased by 10.9, 11.2 and 42.1% for the AC diet compared with the LC diet, respectively. Although concentrate supplementation in both the AC and LC diets increased total CH₄ production per sheep per day, it improved sheep productivity and decreased CH₄ production by 14.8, 12.5 and 14.8% per unit of DM, OM and NDF digested by the sheep, respectively. Our results suggested that in degraded grassland CH₄ emission from sheep was increased and concentrate supplementation increased diet use efficiency. Sheep-grazing ecosystem seems to be a source of CH₄ when the stocking rate is over 0.5 sheep-units ha⁻¹ during the growing season in the Inner Mongolia steppe. Shiping Wang and He Zhou contributed equally to this work.     

Microalgae for use in tropical aquaculture II: Effect of salinity on growth,gross chemical composition and fatty acid composition of three species of marine microalgae

The influence of salinity on the growth, gross chemical composition and fatty acid composition of three species of marine microalgae,Isochrysis sp.,Nannochloropsis oculata andNitzschia (frustulum), was investigated. There was no significant change in growth rate ofIsochrysis sp. andN. (frustulum) over the experimental range of salinity (10–35 ppt), whileN. oculata had a significantly slower growth rate only at 35 ppt. The ash content of all three species increased with increasing salinity. Two species,Isochrysis sp. andN. oculata, showed significant linear increases in total lipid content with increasing salinity over the range 10 to 35 ppt.N. (frustulum) showed significant linear decrease in total lipids, with the highest percentage at low salinity within the range 10–15 ppt. Variation in salinity had only a slight effect on the total protein, the soluble carbohydrate and chlorophylla content of all species. All species responded to change in salinity by modifying their cellular fatty acid compositions. Significant positive correlations were observed between increase in salinity and increase in the percentage ofcis-9-hexadecenoic acid [16:1 (n-7)] over the entire experimental range inN. (frustulum) and between 25–35 ppt inN. oculata. There were curved relationships between salinity and percentage of hexadecanoic acid [16:0] inN. oculata andN. (frustulum), with maxima within the range 25–30 ppt for both species. A curved relationship was found between salinity and percentage of eicosapentaenoic acid [20–5(n-3)], forN. (frustulum), with lowest percentages of the fatty acid within the range 25–30 ppt. There was no consistent pattern in the percentages of other major fatty acids as functions of salinity. The Northern Territory isolateN. (frustulum) was unusual in having a substantial increase in total fatty acids with decreasing salinity (85 mg g^–1 dry wt at 10 ppt compared with 33 mg g^–1 at 35 ppt). The optimum salinities for the production of maximum amount of lipids and the essential fatty acids 20:5(n-3) and/or 22:6(n-3) were as follows:25 ppt forIsochrysis sp. [22:6(n-3)]; 20–30 ppt forN. oculata [20:5(n-3)]; 10–15 ppt forN. (frustulum) [20:5(n-3) and 22:6(n-3)].Author for correspondence     

Three species of Ulva (Ulvophyceae) from the Persian Gulf as potential sources of protein,essential amino acids and fatty acids

Three species of the cosmopolitan genus Ulva (U. paschima , U. chaugulii and U. ohnoi ) from the Persian Gulf were identified using morphological and molecular markers, and were analyzed for total lipids, fatty acids, proteins and amino acid profiles. Our results show that the studied Ulva species have high protein content (9?25% dry weight), contain essential fatty acids and nearly all essential amino acids. This suggests Ulva could have potential as a form of human nutrition and animal feed with a low carbon footprint.     

Comparison of fatty acid composition of bacterial and protozoal fractions in rumen fluid of sheep fed diet supplemented with sunflower, rapeseed and linseed oils

The objective of this study was to investigate effects of oil supplements on the composition of fatty acids (FA), especially of trans11-C18:1 (vaccenic acid, TVA) and cis9, trans11-C18:2 conjugated linoleic acid (c9,t11-CLA), in bacterial (BF) and protozoal (PF) fractions of rumen fluid of sheep that was fractionated centrifugation. Four sheep were fed a diet consisting of meadow hay (960 g dry matter (DM)/day) and of barley grain (240 g DM/day), with sunflower oil (SO), rapeseed oil (RO) or linseed oil (LO) as supplements (60 g/day) in a Latin square design. The oils were used as they are rich in linoleic acid (SO, 533 g/kg of FA), oleic acid (RO, 605 g/kg of FA) and α-linolenic acid (LO, 504 g/kg of FA). Compared to the control (i.e., without oils), oil supplements influenced the concentration of unsaturated (UFA) and saturated fatty acids (SFA). In both BF and PF, the main fatty acids were palmitic and stearic, but PF contained a higher proportion of TVA and c9,t11-CLA than BF. In PF, TVA concentrations, ranked by oil supplement, were SO > RO > LO > Control (174, 150, 118, 74 g/kg of FA, respectively) and the c9,t11-CLA concentrations were RO > SO > LO > Control (59, 51, 27 and 15 g/kg of FA, respectively). Concentrations of c9,t11-CLA in PF were two to three times higher than in BF with all the oil supplements versus the control. Oil treatments impacted the c9,t11-CLA concentration in the fractions, especially SO and RO. The protozoal fraction contained a higher proportion of TVA and c9,t11-CLA than did the bacterial fraction, and dietary addition of SO, RO and LO resulted in a higher incorporation of TVA into both bacterial and protozoal microbial fractions, which probably positively affected TVA flow from the rumen.     

不同干扰方式对内蒙古典型草原植物种组成和功能群特征的影响

研究休牧、补播和自由放牧3种人为干扰方式对内蒙古典型草原群落植物种组成、功能群组成、群落物种多样性和地上生物量的影响.结果表明: 3种干扰方式对植物功能群结构及其多样性有显著影响,休牧方式下群落植物种数量、地上生物量、多样性指数和丰富度指数最大,分别为22种、171.32 g·m^-2、1.46和5.7,灌木半灌木和多年生禾草的重要值、物种所占比例、地上生物量、多样性指数、丰富度指数和均匀度指数显著高于其他干扰方式,多年生杂类草的重要值、物种所占比例、地上生物量、多样性指数和均匀度指数显著低于其他干扰方式,中生植物、C3和C4植物的地上生物量最大,分别为22.22、143.35和27.97 g·m^-2.补播方式下,中旱生植物地上生物量最大,为13.60 g·m^-2,旱生植物物种所占比例最小(48.5%),C4植物物种所占比例最大(28.8%).自由放牧方式下,一、二年生草本植物物种所占比例最大,达12.3%,中生植物和C4植物所占比例最小,分别为17.0%和20.9%.春季休牧措施有利于退化草原的恢复.     

The effects of selenium,vitamin E and their combination on the composition of fatty acids and proteins in Saccharomyces cerevisiae

The aim of our studies was to test the effect and role of vitamin E and selenium supplements on yeast cell. In this study, the effects of selenium (Se), vitamin E (Vit. E), and their combination (Se plus Vit. E) on the composition of fatty acids and proteins were examined in Saccharomyces cerevisiae strains WET136 and 522. S. cerevisiae cells were grown up in YEPD medium supplemented with Se, Vit. E or their combination. It was found that the level of stearic acid was increased in all supplemented groups (p<0·05; p<0·001). The content of saturated and unsaturated fatty acids was decreased (p<0·05; p<0·01; p<0·001) in Vit. E and Vit. E plus Se supplemented S. cerevisiae. On the other hand, Se alone caused an increase (p<0·001) in the saturated fatty acids but a decrease (p<0·05; p<0·001) in the unsaturated fatty acids. Total proteins in S. cerevisiae were significantly increased (p<0·001) by Vit. E supplement. There was no significant change observed in S. cerevisiae supplemented with Se. These findings indicate that membrane composition of S. cerevisiae is affected by both Vit. E and Se supplements. © 1997 John Wiley & Sons, Ltd.     

Lipid content and fatty acid composition of larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, as affected by larval diet

Eight fatty acids were found in the food, larvae and adults of the velvetbean caterpillar, Anticarsia gemmatalis, with C16:0, C18:0, C18:1, C18:2 and C18:3 accounting for over 90% of the total. Fatty acid composition of the larvae tended to reflect that of their food. The most striking differences were the high percentages of C18:1 and C18:2 and the low percentage of C18:3 in the artificial diet and artificial diet-reared larvae compared to the foliage of three species of legume food plants (soybean, Glycine max; pigeon pea, Cajanus cajan; and hairy indigo, Indigofera hirsuta) and foliage-reared larvae. Lipid content (%dw) declined during metamorphosis from mature larva to adult with diet-reared larvae and adults exhibiting significantly higher lipid contents than foliage-reared insects. Regardless of larval food, newly eclosed adults tended to exhibit a decrease in the % of C18:3, and increases in C16:0 and C18:1 compared to larvae. Larval diet clearly influenced the fatty acid composition of larvae and adults, but only the % of C18:2 did not change between food, larvae and adults.     

藻华发生过程中胶州湾水体颗粒有机物脂肪酸的组成与动态

胶州湾在2005年夏季发生了中肋骨条藻(Skeletonema costatum ( Grev.) Cleve)藻华,该优势种占细胞总量的比例在两个研究站位(C3站及A5站)分别达到59%和86%.对藻华发生过程中(7月,8月及9月份)的颗粒有机物进行了采样分析,测定了脂肪酸、叶绿素(Chl-a)和颗粒有机碳(POC)的浓度,分析了藻华发生过程中浮游植物和脂肪酸的组成特征,并通过标志脂肪酸对藻华发生过程中颗粒有机物组成的动态变化进行了分析.总脂肪酸浓度同叶绿素和颗粒有机碳浓度一样,在藻华发生期达到最高,两个采样站位(C3站及A5站)分别为29.0μg·L-1及185.5μg·L-1,比藻华发生前和消退后高2～3倍及20倍.胶州湾悬浮颗粒脂肪酸主要包括16:0,14:0,18:0等直链饱和脂肪酸(SSFA),16:1ω7、16:1ω5+ω9、18:1ω9,18:1ω7等单不饱和脂肪酸(MUFA)及以 20:5ω3(DHA)和22:6ω3(EPA)为主的多不饱和脂肪酸(PUFA)和以i-15:0及ai-15:0为主的支链饱和脂肪酸(BSFA).藻华期与发生前相比,脂肪酸中的不饱和组分(MUFA,PUFA)所占比例在两个取样站位均有提高.随着藻华的消退,藻华区域中心的A5 站的SSFA及BSFA比例有大幅提高,而在非藻华中心区域的C3站,不饱和脂肪酸尤其是ω3系列多不饱和脂肪酸(DHA, EPA等)比例的上升非常显著.藻华发生时浮游植物在颗粒有机物中的比重提高.藻华消退后,A5站颗粒有机物中碎屑有机物及细菌所占比重提高,而C3站颗粒有机物中浮游植物的比重仍然很高.浮游植物大量死亡是A5站藻华消退的主要形式,而C3站藻华的消退则可能与浮游动物的摄食有关.     

Role of maternal tissue in the synthesis of polyunsaturated fatty acids in response to a lipid-deficient diet during pregnancy and lactation in rats

During pregnancy and lactation, metabolic adaptations involve changes in expression of desaturases and elongases (Elovl2 and Elovl5) in the mammary gland and liver for the synthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) such as arachidonic acid (AA) required for fetal and postnatal growth. Adipose tissue is a pool of LC-PUFAs. The response of adipose tissue for the synthesis of these fatty acids in a lipid-deficient diet of dams is unknown. The aim of this study was to explore the role of maternal tissue in the synthesis of LC-PUFAs in rats fed a low-lipid diet during pregnancy and lactation. Fatty acid composition (indicative of enzymatic activity) and gene expression of encoding enzymes for fatty acid synthesis were measured in liver, mammary gland and adipose tissue in rats fed a low-lipid diet. Gene expression of desaturases, elongases, fatty acid synthase (Fasn) and their regulator Srebf-1c was increased in the mammary gland, liver and adipose tissue of rats fed a low-lipid diet compared with rats from the adequate-lipid diet group throughout pregnancy and lactation. Genes with the highest (P < 0.05) expression in the mammary gland, liver and adipose tissue were Elovl5 (1333%), Fads2 (490%) and Fasn (6608%), respectively, in a low-lipid diet than in adequate-lipid diet. The percentage of AA in the mammary gland was similar between the low-lipid diet and adequate-lipid diet groups during the second stage of pregnancy and during lactation. The percentage of monounsaturated and saturated fatty acids was significantly (P < 0.05) increased throughout pregnancy and lactation in all tissues in rats fed a low-lipid diet than in rats fed an adequate-lipid diet. Results suggest that maternal metabolic adaptations used to compensate for lipid-deficient diet during pregnancy and lactation include increased expression of genes involved in LC-PUFAs synthesis in a stage- and tissue-specific manner and elevated lipogenic activity (saturated and monounsaturated fatty acid synthesis) of maternal tissues including adipose tissue.