Nitrogen supplementation of corn silages. 2. Assessing rumen function using fatty acid profiles of bovine milk.

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dc.contributor.author Cabrita, A. R. J.
dc.contributor.author Dewhurst, Richard J.
dc.contributor.author Fonseca, A. J. M.
dc.contributor.author Gomes, E.
dc.date.accessioned 2010-03-01T09:50:35Z
dc.date.available 2010-03-01T09:50:35Z
dc.date.issued 2003
dc.identifier.citation Cabrita , A R J , Dewhurst , R J , Fonseca , A J M & Gomes , E 2003 , ' Nitrogen supplementation of corn silages. 2. Assessing rumen function using fatty acid profiles of bovine milk. ' Journal of Dairy Science , vol 86 , no. 12 , pp. 4020-4032 . en
dc.identifier.issn 0022-0302
dc.identifier.other PURE: 135617
dc.identifier.other dspace: 2160/4124
dc.identifier.uri http://hdl.handle.net/2160/4124
dc.description Sponsorship: Ministe´rio da Cieˆncia e Tecnologia of Portugal en
dc.description.abstract The effects of N supplementation strategies on milk fatty acid profiles of dairy cows and their use as a noninvasive technique to diagnose rumen function, and to guide protein feeding decisions on-farm were evaluated in three experiments. Each experiment was designed according to three 3 × 3 Latin squares with 9 Holstein cows receiving total mixed rations based on corn silage. Experiment 1 was designed to study effects of diets with different ratios of effective rumendegradable protein (ERDP; g) to fermentable metabolizable energy (FME; j) providing, respectively, a large deficiency, a slight deficiency, and a slight excess in relation to the target level of 11 g of ERDP/MJ FME for lactating cows. Experiment 2 evaluated effects of different proportions of quickly and slowly rumen-degradable protein achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea for U0, U5, and U10, respectively). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in rumen by offering the protein-rich concentrate once or twice per day before the meal (corn silage, ryegrass hay, and energy-rich concentrate), or included in the total mixed ration. Milk fatty acid profiles were significantly affected by dietaryNand carbohydrate supply. Principal component factor analysis provided a reasonable description of the data, clearly discriminating between fatty acids that are synthesized by different metabolic pathways. Several sources/pathways were distinguished: de novo synthesis in the mammary gland (short- and medium-chain fatty acids), 9-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (longchain fatty acids), and de novo synthesis by the rumen microbial populations (odd-chain fatty acids). Discriminant canonical analysis showed that milk odd-chain fatty acids had a higher ability to discriminate between diets than even-chain fatty acids. The anteiso C15:0 increased in line with increasing sugar supply, and C17:0 appears to be a marker of protein deficiency. Additionally, iso C17:0 and anteiso C17:0 were associated with the NDF and CP contents of diets. The results suggests that milk odd-chain fatty acids have the potential to be used as a noninvasive technique to assess rumen function in terms of microbial populations, substrates and interactions. en
dc.format.extent 13 en
dc.language.iso eng
dc.relation.ispartof Journal of Dairy Science en
dc.subject corn silage en
dc.subject dairy cows en
dc.subject nitrogen supplementation en
dc.subject rumen synchrony en
dc.title Nitrogen supplementation of corn silages. 2. Assessing rumen function using fatty acid profiles of bovine milk. en
dc.type Text en
dc.type.publicationtype Article (Journal) en
dc.identifier.doi http://dx.doi.org/10.3168/jds.S0022-0302(03)74013-2
dc.contributor.institution Institute of Biological, Environmental and Rural Sciences en
dc.description.status Peer reviewed en


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