Comparison of methods for determining the fatty acid composition of photosynthetic tissues

The fatty acid (FA) composition of photosynthetic tissue differs from that in other plant or animal tissues. In leaves, the lipid fraction constitutes less than 10% of the dry weight and is mostly located in the chloroplasts. An extraction solvent should dissolve polar lipids readily, but should also overcome interactions between the lipids and the tissue matrix. A mixture of chloroform/methanol (C/M) is commonly used. However, less toxic alternative methods such as hexane/isopropanol (H/I) and ethanol (E) have been suggested. In this preliminary study we compared the effectiveness of these three methods which are used as standard extraction protocols for FA analysis of plant material at three different European Universities. C/M extraction gave the highest total FA content and H/I the lowest, suggesting that C/M is indeed the best general-purpose lipid extraction solvent. Significant differences were also observed for FA composition including the ratio of saturated to unsaturated FA indicating selectivity of the various solvents in extracting different individual FA. Further and more detailed investigations are required to confirm this hypothesi

Composition chimique, dégradabilité in sacco et produits de fermentation in vitro de la fétuque élevée (Festuca arundinacea

Objectifs : En vue d’une sélection pour une utilisation comme aliment pour bétail, vingt quatre écotypes de fétuque élevée (Festuca arundinacea) provenant du milieu naturel du nord de la Belgique ont été étudiés afin d’en déterminer la valeur nutritionnelle.Méthodologie et Résultats : La composition chimique, la dégradabilité in sacco et les incubations in vitro ont été réalisés. Un mouton adulte fistulé au niveau du rumen a été utilisé pour la détermination de la dégradabilité in sacco des écotypes et les incubations in vitro. La teneur moyenne en MAT (8,0% MS) des 24 écotypes étudiés est faible. Les écotypes de Festuca arundinacea présentent en moyenne une meilleure dégradabilité potentielle (a + b) (82,7%) que les fourrages tropicaux Pennisetum purpureum (64,9%) et Tripsacum laxum (66,8%) mais moindre que les fourrages tempérés (Lolium perenne : 90,5%). Festuca arundinacea a présenté une production élevée de propionate (234.7 Gmol/mmol AGV totaux).Conclusion : Les meilleurs de la collection de 24 écotypes de F. arundinacea ont été identifiés pour une utilisation comme aliment pour bétail. Les teneurs en MAT trouvées pour la fétuque élevée sont comparables à celles des fourrages tropicaux qui sont généralement plus pauvres en protéine que les fourrages tempérés ; ce qui représente un handicap pour leur ingestion volontaire. Ces résultats impliquent d’une part qu’il faut une supplémentation en azote pour les pâturages de Festuca arundinacea et d’autre part l’exploitation des pâturages à la fétuque élevée au stade avant frutification. Par ailleurs, la culture en association de fétuque élevée et légumineuses est également une solution envisageable. Une variabilité a été notée entre les écotypes de Festuca arundinacea qui en moyenne présentent une meilleure dégradabilité que les fourrages tropicaux, mais moindres que les fourrages tempérés. Cet avantage de la fétuque élevée sur les fourrages tropicaux se consolide par une production élevée d’acide propionique et faible d’acide acétique comparables à celles des fourrages tempérés ; ce qui est très intéressant car le propionate peut générer du glucose, un des facteurs limitant pour la production laitière.Mots clés: Festuca arundinacea, écotype, azote ammoniacal, dégradabilité in sacco, méthane, acides gras volatile

Dose and time response of ruminally infused algae on rumen fermentation characteristics, biohydrogenation and <i>Butyrivibrio</i> group bacteria in goats

Background: Micro-algae could inhibit the complete rumen BH of dietary 18-carbon unsaturated fatty acid (UFAs). This study aimed to examine dose and time responses of algae supplementation on rumen fermentation, biohydrogenation and Butyrivibrio group bacteria in goats. Methods: Six goats were used in a repeated 3 x 3 Latin square design, and offered a fixed diet. Algae were infused through rumen cannule with 0 (Control), 6.1 (L-Alg), or 18.3 g (H-Alg) per day. Rumen contents were sampled on d 0, 3, 7, 14 and 20. Results: H-Alg reduced total volatile fatty acid concentration and acetate molar proportion (P 0.10), while H-Alg reduced the total bacteria abundance (P < 0.05). However, this was induced by a significant difference between control and H-Alg on d 14 (-4.43 %). Afterwards, both treatments did not differ as increased variation in the H-Alg repetitions, with in some cases a return of the bacterial abundance to the basal level (d 0). Conclusions: Changes in rumen fermentation and 18-carbon UFAs metabolism in response to algae were related to the supplementation level, but there was no evidence of shift in ruminal biohydrogenation pathways towards t10-18:1. L-Alg mainly induced a transient effect on rumen biohydrogenation of 18-carbon UFAs, while H-Alg showed an acute inhibition and these effects were not associated with the known hydrogenating bacteria

Effect of diet and dietary fatty acids on the transformation and incorporation of C18 fatty acids in double-muscled Belgian Blue young bulls

Three groups of double-muscled Belgian Blue young bulls were fed during different stages of production diets differing in the proportions of linolenic and linoleic acid by including linseed in the concentrate or giving grass silage as main linolenic acid suppliers. Samples of rumen and abomasal contents and of the longissimus thoracis, subcutaneous fat, and liver were taken to analyze the fatty acid pattern with emphasis on the individual trans (t) C18:1 fatty acids and cis-9,trans-11 conjugated linoleic acid (c9t11CLA). Trans C18:1 isomers represented up to 20 g/100 g of total fatty acids in rumen and abomasal contents, whereas the accumulation of c9t11CLA was limited. Total trans C18:1 content in subcutaneous fat and intramuscular fat of the longissimus thoracis comprised 8.4 and 5.2 g/100 g of total fatty acids, respectively, with t11C18:1 being the most abundant one. Compared to rumen contents, subcutaneous and intramuscular fat were enriched in c9t11CLA and contained fewer tC18:1 isomers, resulting in a higher c9t11CLA/t11C18:1 ratio (0.04, 0.22, and 0.22, respectively). This result suggests that the endogenous synthesis of c9t11CLA in adipose tissue by the Delta(9)-desaturase was more important than its ruminal production

Effects of in vitro and in vivo dietary supplementation with saponins on rumen fermentation with particular reference to volatile fatty acids, ammonia and methane

Résumé publié dans : Advance in Animal Biosciences, Janv. 2013; 4(2):577. doi:10.1017/S2040470013000125.International audienc

CD32+CD4+memory T cells are enriched for total HIV-1 DNA in tissues from humanized mice

CD32 has raised conflicting results as a putative marker of the HIV-1 reservoir. We measured CD32 expression in tissues from viremic and virally suppressed humanized mice treated relatively early or late after HIV-1 infection with combined antiretroviral therapy. CD32 was expressed in a small fraction of the memory CD4(+) T-cell subsets from different tissues in viremic and aviremic mice, regardless of treatment initiation time. CD32(+) memory CD4(+) T cells were enriched in cell associated (CA) HIV-1 DNA but not in CA HIV-1 RNA as compared to the CD32(-) CD4(+) fraction. Using multidimensional reduction analysis, several memory CD4(+)CD32(+) T-cell clusters were identified expressing HLA-DR, TIGIT, or PD-1. Importantly, although tissue-resident CD32(+)CD4(+) memory cells were enriched with translation-competent reservoirs, most of it was detected in memory CD32-CD4(+) T cells. Our findings support that CD32 labels highly activated/exhausted memory CD4(+) T-cell subsets that contain only a small proportion of the translation-competent reservoir

Prediction of first test day milk yield using historical records in dairy cows

The transition between two lactations remains one of the most critical periods during the productive life of dairy cows. In this study, we aimed to develop a model that predicts the milk yield of dairy cows from test day milk yield data collected in the previous lactation. In the past, data routinely collected in the context of herd improvement programmes on dairy farms have been used to provide insights in the health status of animals or for genetic evaluations. Typically, only data from the current lactation is used, comparing expected (i.e., unperturbed) with realised milk yields. This approach cannot be used to monitor the transition period due to the lack of unperturbed milk yields at the start of a lactation. For multiparous cows, an opportunity lies in the use of data from the previous lactation to predict the expected production of the next one. We developed a methodology to predict the first test day milk yield after calving using information from the previous lactation. To this end, three random forest models (nextMILKFULL, nextMILKPH, and nextMILKP) were trained with three different feature sets to forecast the milk yield on the first test day of the next lactation. To evaluate the added value of using a machine-learning approach against simple models based on contemporary animals or production in the previous lactation, we compared the nextMILK models with four benchmark models. The nextMILK models had an RMSE ranging from 6.08 to 6.24 kg of milk. In conclusion, the nextMILK models had a better prediction performance compared to the benchmark models. Application-wise, the proposed methodology could be part of a monitoring tool tailored towards the transition period. Future research should focus on validation of the developed methodology within such tool