PHYTOMILK

Pasture and silage botanical composition - effect on milk quality

Two feeding experiments will be carried out at the Animal Production Centre, University of Life Science, Norway (APC-UMB) and one at Röbäcksdalen, SLU, Umeå.

Grazing experiment APC-UMB

A continuous grazing trial will be carried out during the grazing season 2008, with the first 2 weeks as pre-experimental period where the cows graze the same pasture. Two groups of 8 cows (Norwegian Red Cattle) each, in mid lactation, will be formed on the basis of their performance before the grazing season, calving date and lactation number. After the 2-week adaptation to grazing, three 4-week experimental periods will follow; early (May), mid (June/July) and late (August) summer, during which each group will graze one of the two organic pasture management treatments; botanical diverse long term pasture and clover-rich short term pasture. The long term pasture has a relatively high botanical diversity and high proportion of other herbs than red clover (Steinshamn et al., 2001), whilst the short term managed pasture will be dominated by red clover sown with timothy (Phleum pratense L.) and Meadow fescue (Festuca pratensis Huds.). The cows will receive small and equal amounts of concentrate, a mineral additive but no vitamin supplements. The groups will as far as possible receive the same herbage allowance, by adjusting the area, so that the cows will have the same energy intake.

Cow grazing botanical diverse pasture including dandelion and cow grazing red clover-grass in Ås 2008. Photos: Steffen Adler

Silage feeding experiment (APC-UMB and SLU-Umeå)

Two silage feeding experiments will be carried out during 14 weeks of the housing period 2008/ 2009, with the first 2 weeks as a transition period where all cows receive the same forage. The number of cows, stage of lactation and allocation to treatments will be similar to and carried out in the same way as in the grazing experiment. The experiment will be conducted using a change-over design with three 4-week periods. Two weeks for adaptation to the experimental feed and two weeks for measurement and sampling. The silage will be fed ad libitum with a small and equal amount of concentrate supplementation. The cows will receive no vitamin supplements but a mineral additive. In the experiment conducted at APC-UMB, the treatments will be round bale silage prepared from two contrasting organically managed grasslands; DS) Grassland with high proportion of non red clover herbs like Taraxacum officinale and white clover and RC) short term rotational ley with high proportion of sown species rich in red clover. In the experiment at SLU-Umeå the treatments will be silage from short term rotational leys with high proportion of red clover and grass mixture (RC), and birdsfoot trefoil and grass mixture (BG). The same varieties will be used in RC at the two sites to investigate effects of site on milk quality.

Progress of work

The grazing experiment at APC-UMB was carried out summer 2008 as planned. However, we had to do some minor changes in the experimental plan. The RC pasture was very much dominated by an annual weed (Capsella bursa-pastoris L.) in spring, and we therefore decided to add an extra measurement period: period 1 week 20-21, period 2 week 24-26, period 3 week 31-33 and period 4 week 34-36. Measurement was taken in all four periods, but due to budget limitations we decided to analyze chemically the herbage and milk samples collected in period 2, 3 and 4. Most analyzes have been carried out and is completed. PhD-student Steffen Adler stayed for 14 days with Søren Krogh Jensen at Foulum and carried out much of the chemical analysis of fatty acid and vitamins. A MSc-student used milk samples from the experiment to examine the treatments effect on lipid oxidation, both chemically and with fluorescence spectroscopy, after exposure to light. This work has been done in co-operation with Annette Veberg Dahl at Nofima Food.

The harvesting and preservation of the silages for the silage feeding experiment at APC-UMB was carried out according to the plan. The DS sward had much lower proportion of other herbs than clover than anticipated, but the proportion of white clover was satisfactory. Red clover established poorly in half of the RC sward, but satisfactory in the other half. We decided to add an extra experimental factor; Vitamin E supplement (without and with natural vitamin E). The experimental design has been changes accordingly, and the experiment will be run according to a 3-period changeover design (4 incomplete Latin squares). We have also reduced the experimental periods from 4 to 3 weeks due to lower yields than expected (poor clover content of half of the RC sward).The experiment will be carried out in accordance with the planned time schedule.

The harvesting and preservation of the silages for the silage feeding experiment at SLU, Umeå was also carried out according to the plan. Red clover and birdsfoot trefoil grow poorly in the spring growth, but in the second and the third period the proportions were normal. We decided to use higher proportion of second and third cut in the ration in the feeding experiment. The experimental design will be run according to a 3-period change over design as planned. We had a base line period before the experiment started. We have reduced the experimental periods from 4 to 3 weeks due to lower yield than expected (it was not possible to harvest the whole experimental field because of outwintering of the red clover in the lower parts of the field). The feeding experiment started with a baseline period in the beginning of December 2008, and will be finished in the end of February 2009. Plant samples were collected from the experimental field during the season to investigate the growth and changes in quality.