PHYTOMILK

Silage botanical composition – effect on rumen FA hydrogenation and milk FA composition

The experiment will be carried out during the housing period 2009/2010 at the Depatment of Animal and Aquacultural Sciences, Norwegain University of Life Sciences

Four types of silages ensiled in round bales will be prepared from the first cut in 2009:

• Lolium perenne (LP
• Phleum pratense (GS)
• Red clover-grass mixture (RC);
• Non red clover herb-grass mixture (DS)

The LP and GS are included as control treatments The RC and DS silages will be the same as the silage used in Task 2, and the varieties used in the GS and RC treatments will be the same as the one used in the field trials in Task 4 and 5. The silages will be offered ad libitum with small and equal amount of concentrate supplementation. The experimental diets will be fed to 4 cannulated dairy cows in a Latin square design with 4 periods of 24 days (14 days adaptation to the diet and 10-day measurement period for milk sampling and collection of faeces, rumen and duodenal fluid. Markers will be used in order to estimate digesta flow at the duodenum. Faecal output will be measured on days 15 to 20, and duodenal digesta will be collected every 4 h on days 21 and 22. Samples of rumen fluid will be taken every 2h over a 24-h period on day 23. Silage will be sampled daily during the measurement period. Sub- samples of silage, digesta and faeces will be stored frozen for chemical analysis. Rumen fluid will be analysed for pH, ammonia and volatile fatty acids. Digesta flow and apparent digestibility of fatty acids in the rumen will be calculated after mathematical reconstitution of true digesta, and the biohydrogenation of C:18 PUFAs will be estimated by simple difference between feed and duodenal flow.

Report from the work:

The establishment of the LP and GS sward was good. However, the DS sward had much less proportion of unsown herbs than anticipated (see report from WP1). We therefore decided to postpone the experiment from winter 2009 to autumn 2009. We will harvest the experimental grassland and make the round bales summer 2009. We will the use the DS grassland from the pasture experiment (WP1) to prepare the DS silage.