亚麻籽在反刍动物中的应用

亚麻籽是反刍动物营养物质的一个重要来源,含有丰富的蛋白质、能量及必需脂肪酸。饲喂亚麻籽日粮可以提高肌肉中#-3必需脂肪酸的水平,从而改善肉质,优化人们饮食结构。文章介绍了亚麻籽的营养价值,以及通过在日粮中添加亚麻籽,对反刍动物消化吸收和肌肉性能的影响。     

Two in vitro assays to evaluate resistance in Linum usitatissimum to Fusarium wilt disease

Two types of in vitro seedling tests were developed to evaluate resistance in flax (Linum usitatissimum) against Fusarium oxysporum f.sp. lini. In the first test a solid medium was used. The second test was based on a liquid medium. Disease severity was assessed after three weeks, using the observed reduction of plant length as a scale. Both methods proved to be useful for screening for resistance, for evaluating race specificity of resistance and for studying symptomatology. The solid medium method proved to be the more accurate for the screening, but the liquid medium method was much less time- and labour-consuming. The results of the tests were significantly correlated with observations under field conditions.     

Gene expression of fatty acid-binding proteins, fatty acid transport proteins (cd36 and FATP) and β-oxidation-related genes in Atlantic salmon (Salmo salar L.) fed fish oil or vegetable oil

Relative gene expression pattern of fatty acid transport proteins (FATP and cd36), intracellular fatty acid-binding proteins (FABP3, FABP10 and FABP11), β-oxidation-related genes [carnitine palmitoyl transferase II (CPTII), peroxisome proliferator-activated receptor β (PPARβ), acyl-CoA oxidase (AOX), long-chain fatty acyl-CoA synthetase (FACS), acyl-CoA dehydrogenase (dehydrogenase)] and uncoupling protein 2 (UCP2) was assessed by RT-qPCR in Atlantic salmon muscle (red and white), liver, heart, myosepta and visceral fat. FABP11, a FABP isoform not previously described in Atlantic salmon, was highly expressed in visceral fat and myosepta and at the lower level in red muscle, white muscle, myosepta and heart. Furthermore, Atlantic salmon were fed either a diet containing fish oil (FO) or a complete replacement of FO with a vegetable oil blend (55% rapeseed oil, 30% palm oil and 15% linseed oil; VO) for the production cycle (27 months from start of feeding and until ∼4.5 kg mean weight). The expression of genes related to β-oxidation, fatty acid uptake and transport in the white muscle indicate ( n  = 3) significant down-regulation in VO fed Atlantic salmon and correlated with previously reported white muscle triacylglycerol stores and β-oxidation. FABP11 in visceral fat and myosepta was also down-regulated in VO fed fish.     

Effects of different forms and origins of oilseeds on dynamics of ruminal biohydrogenation of long‐chain fatty acids in vitro

Dietary unsaturated fatty acids (FA) are intensively hydrogenated in the rumen, resulting in reduced amount of poly‐unsaturated fatty acids (PUFA) and accumulation of several biohydrogenation (BH) products. In this study, BH of PUFA originating from different oilseeds (linseed, soya beans, sunflower seed and rapeseed) present in crushed oilseeds or their free oils were assessed in vitro. The assay substrates were incubated in buffered rumen fluid for 0, 6, 12 and 24 h. After incubation, the FA pattern of the incubated samples was analysed using gas chromatography. Biohydrogenation is defined as disappearance of double bonds (DB) calculated from the contents of unsaturated FA. After 24‐h incubation, the DB contents of all oilseeds were reduced (p < 0.001) by 40–60%. The reduction was higher (p < 0.001) for the crushed form compared with the oil form. In addition, linseed and sunflower seed known as oilseeds with high contents of linolenic acid C18:3 c9,12,15 (LNA) and linoleic acid C18:2 c9,12 (LA), respectively, showed a higher (p < 0.001) accumulation of the BH intermediates conjugated linoleic acid (CLA, isomer C18:2 c9t11) and vaccenic acid (C18:1 t11) for the crushed form, when compared with the oil. These results suggest an inherent effect of the physical form of the assay oilseeds on in vitro BH. Changes in FA pattern during BH in vitro can be attributed to both source and physical form of the assay oilseeds. However, further investigations are warranted to ensure whether the observed in vitro effects on ruminal BH can be confirmed in vivo.     

Influence of partial substitution of dietary fish oil by vegetable oils on the metabolism of [1-14C] 18:3n-3 in isolated hepatocytes of European sea bass (Dicentrarchus labrax L.)

The static or declining supply of fish oil from industrial fisheries demands the search of alternatives, such as plant (vegetable) oils, for diets in expanding marine aquaculture. Vegetable oils are rich in C₁₈ polyunsaturated fatty acids but devoid of the n-3 highly unsaturated fatty acids in fish oils. Previous studies, primarily with salmonids, have shown that including vegetable oils in their diets increased hepatocyte fatty acid desaturation. In the present study, we have investigated the effects of dietary partial substitution of fish oil (FO) with rapeseed oil (RO), linseed oil (LO) and olive oil (OO) on the desaturation /elongation and, -oxidation capacities of [1-¹⁴C]18:3n-3 in isolated hepatocytes from European sea bass (Dicentrarchus labrax L.), in a simultaneous combined assay. Fish were fed during 34 weeks with diets containing 100% FO, or RO, LO and OO, each included at 60% with the balance being met by FO, with no detrimental effect upon growth or survival. The highest total desaturation rates were found in hepatocytes of fish fed FO diet (0.52±0.08 pmol/h/mg protein) and OO diet (0.43±0.09 pmol/h/mg protein), which represented 3.2% and 2.7% of total [1-¹⁴C]18:3n-3 incorporated, respectively. In contrast, lowest desaturation rates were presented by hepatocytes of fish fed LO and RO diets (0.23±0.06 and 0.14±0.05 pmol/h/mg protein, respectively) represented 1.4% and 0.9% of total [1-¹⁴C]18:3n-3 incorporated, respectively. The rates of [1-¹⁴C]18:3n-3 β-oxidized were between 11-fold and 35-fold higher than desaturation. However, no significant differences were observed among β-oxidation activities in hepatocytes of fish fed any of the diets. The present study demonstrated that the European sea bass, as a carnivorous marine fish, presented a ‘marine’ fish pattern in the metabolism of 18:3n-3 to 20:5n-3 and 22:6n-3. This species appeared to have all the enzymic activities necessary to produce 22:6n-3 but presented only extremely low rates of fatty acid bioconversion. Furthermore, nutritional regulation of hepatocyte fatty acid desaturation was minimal, and dietary vegetable oils did not increase desaturase activities, and in RO and LO treatments the activity was significantly lower. This revised version was published online in July 2006 with corrections to the Cover Date.     

Present status of genetics of rust resistance in flax

Summary Present knowledge of host genes conferring resistance to rust in flax and their genetics are reviewed. There are at least 34 genes conferring resistance to rust occurring in seven groups, namely, K, L, M, N, P, D and Q. Expression of these host genes is affected by temperature, genetic background and by the inhibitor gene present in certain rust strains. Recombination analysis indicates that genes within each of the M and N groups are probably closely linked and that of the L group are genetically complex. When testcross progeny between two genes of the L group were screened, susceptible and modified recombinants were recovered. Some of these susceptible recombinants yielded rare resistant revertants in their progeny. Mechanism of such reversion is not defined but appears to follow a definite pattern. It is also indicated that some of the recombinants represent new specificity. A molecular approach of cloning host genes in flax is described.     

Importance of sepals in fruit and seed development in linseed (Linum usitatissimum L.)

Summary The green sepals in linseed (Linum usitatissimum L.) persist till almost the time of fruit ripening. Since the plant retains very few leaves and the fruits are better exposed to receive sunlight, the green sepals may be important in fruit and seed development. Influence of the removal of 0, 1, 3 and 5 sepals on the day of anthesis, 7, 15 and 25 days after anthesis on fruit and seed development was examined. Excision of all the fine sepals on the day of anthesis stopped fruit and seed development in the varieties M 10 and NP (RR) 45 but in Mukta the reduction was about 55%. Removal of three sepals also decreased fruit growth in Mukta and NP (RR) 45. The effect of removal of sepals was more pronounced on the number of seeds per fruit than on seed weight. Sepals fixed ¹⁴CO₂ and translocated ¹⁴C to seeds. However, the ¹⁴CO₂ fixation was maximum at early stages of fruit development, whereas a higher percentage of the fixed ¹⁴C was translocated at later stages of growth. It is suggested that the sepal size in linseed could be a useful selection criterion.     

Comparison of pedigree selection and single seed descent for oil yield in linseed (Linum usitatissimum L.)

Summary Four populations of linseed derived from five parents were advanced from the F₂ to the F₆ generation by SSD and to the F₅ by pedigree selection. These populations were used to compare the efficiency of the two methods in order to provide superior genotypes with respect to grain yield and oil content, i.e. oil yield. The results showed minimum differences between pedigree and SSD lines for grain yield, where in only one cross the SSD lines were significantly superior to the pedigree lines. Since pedigree selection was carried out for both, seed yield and oil content, a positive response to selection was expected. However, early selection for yield, a character with low heritability, was not successful. On the contrary, significant differences for oil content were detected between the two groups of lines in three of the four crosses studied. In these cases the pedigree lines were superior to the SSD lines. These results demonstrate that strict selection in early generations for oil content, a character with comparatively high heritability, is feasible and successful in linseed. However, selection for seed yield should be postponed to later inbred generations. Consequently, in breeding for maximum oil yield of linseed a two-step selection procedure is recommended.Abbreviations PS pedigree selection - SSD single seed descent - TGW thousand grain weight     

亚麻胶的研究

亚麻种子的种皮占种子干重的４５％左右，且种皮的５５％是胶质，约占干种子的２５％左右，这种胶属酸性粘胶，简称亚麻胶。该胶可用水、碱、酸提取，提取量与水解温度和时间有关，胶的酯化度和甲氧基含量与提取温度有关。