Milk fatty acid composition of dairy cows fed greenwhole-plant buckwheat, phacelia or chicory in theirvegetative and reproductive stage

Summary

tThe hypothesis was tested that the phenological stage of dicotyledonous forages influencesmilk fatty acid (FA) composition of dairy cows. For this purpose buckwheat (Fagopyrum escu-lentum) and phacelia (Phacelia tanacetifolia; both in their first year of cultivation) as well aschicory (Cychorium intybus; second year) were cultivated in mixture with ryegrass (Loliummultiflorum). After 35 days of growth, feeding the green forages to 3 × 6 late lactating dairycows at ad libitum access started. The realized dietary dry matter proportions of the testplants were (vegetative and reproductive stage): buckwheat, 0.60 and 0.55; chicory, 0.70and 0.69; phacelia, 0.51 and 0.48. Experimental feeding lasted for 23, 17 and 26 days withbuckwheat, chicory and phacelia, respectively. The complete diets additionally contained2 kg of concentrate and 1 kg of barley straw per day per animal. Milk and feed sampleswere analyzed from every second day. Feedstuffs were analyzed for proximate contents,FA and fractions of phenolic compounds. In milk samples solids and FA were measured.Contents of FA and of phenol fractions decreased during advancing development stage inall test plants except total extractable phenols and total tannins in phacelia. This decreasewas particularly pronounced for a-linolenic acid (ALA) and linoleic acid (LA) in buckwheat.Phenological stage had no influence on milk yield and gross composition, but ALA and LAproportions of milk fat declined with time in all groups. Proportions of ALA (14.2 g/kg FA)and total poly-unsaturated FA in milk fat were highest with phacelia. Levels of conjugatedlinoleic acid (CLA) in milk fat were not affected by treatment or phenological stage. Vaccenicacid in milk fat was slightly elevated when feeding buckwheat and phacelia in the repro-ductive stage whereas it decreased with ongoing development in the chicory group. Nosystematic influence of phenological stage on the relative recovery of feed FA in milk fatoccurred. The study did not confirm the hypothesis that the recovery rate of ALA wouldincrease with maturing of the forages. In terms of generating a desired milk FA profile,phacelia and chicory seem however to be generally promising.