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

• Type: Article in International Scientific Journal
• Date: 2003

Authors

A. Cabrita (Author) FCUP; Antonio J M Fonseca (Author) ICBAS; Dewhurst, RJ (Author) Other; Gomes, E (Author) Other

Journal

Title: Journal of Dairy Science

Vol. 86 No. 10

Pages: 4020-4032

ISSN: 0022-0302

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 40 Citations

Scopus - 41 Citations

Scientific classification

CORDIS: Natural sciences > Agrarian Sciences > Zootechnics

FOS: Agrarian Sciences > Animal and Dairy science

Other information

Authenticus ID: P-000-E9T

Abstract (EN): 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 x 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 rumen-degradable 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 dietary N and 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), Delta(9)-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (long-chain 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 C-15:0 increased in line with increasing sugar supply, and C-17:0 appears to be a marker of protein deficiency. Additionally, iso C-17:0 and anteiso C-17:0 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13