Effects of days of regrowth and N fertilization on fatty acid composition of perennial ryegrass and CLA concentration in milk from stall-fed dairy cows.
Year: 2007
Type: book
Abstract: Grassland management could offer means to produce milk with naturally higher concentrations of unsaturated fatty acids (FA) such as conjugated linoleic acid (CLA). Regrowth stage and N fertilization affect the concentration of FA in grasses, which could affect milk FA. Four paddocks were split and received either 73 or 37 kg N ha -1 ; herbage was subsequently cut daily from 25 to 43 days of regrowth. Two groups of 18 cows were stall-fed during these 19 days with either high or low N fertilized grass. FA concentrations in the herbage and the CLA concentration in the milk were monitored. The high N fertilized plots had a higher herbage mass, but there was no difference in herbage N or FA concentration. There was a negative effect of days of regrowth on the FA concentration in grass, which was associated with a lower CLA concentration in the milk. In general there was no effect of N treatment on milk CLA concentration. Only during the last two days of the experiment, when there was a very large difference in herbage mass between the N treatments (2000 vs. 4000 kg DM ha -1 ), the CLA concentration was significantly (P < 0.05) higher in milk of cows fed grass from the low N treatment. This could be a result of the lower herbage yield and NDF content. The lack of effect of N fertilizer treatment on milk FA composition may be due to the fact that treatments surprisingly did not differ in grass N content. During the final days, effects were confounded with changes in other chemical composition variables. The negative effect of grass regrowth stage on herbage FA and milk CLA concentration confirmed our hypotheses.
Authors: H.J. Smit, K. Malda, J. Dijkstra, A. Elgersma
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W1770768594