Changes in fatty acid composition of milk from lactating dairy cows during transition to and from pasture

The management of the transition from hay- to pasture-based diets affects milk fatty acid kinetics

“…The concentrations of trans10 + trans11-C18:1 and cis9trans11-CLA increased progressively for both rapid and progressive transition after diet change, becoming stable 2 weeks later than the herbage intake peak. The prolonged increase in vaccenic and rumenic acids and their later stabilisation that we observed in ordinary farming conditions are consistent with the findings of Khanal et al (2008) for cows that had just starting grazing and by Roy et al (2006) for cows fed on hay and supplemented with linseed oil in a controlled trial. These authors explained this prolonged increase as the result of a high stability of the rumen environment in forage-rich diets, which may account for a lack of increase in the milk fat of trans10-C18:1, replacing trans11-C18:1, as the predominant trans-C18:1 isomers leaving the rumen.…”

“…The decrease in SFA and increase in MUFA and PUFA observed in both rapid and progressive transition milks are in line with reference data obtained in controlled conditions (Kelly et al 1998;Khanal et al 2008). Since changes did not occur in the daily concentrate supplementation, the changes in the milk FA profile during transition from hay to pasture could be related to the higher PUFA content in fresh grass (Elgersma et al 2006) in comparison to hay.…”

“…All the cows showed similar trends in milk FA kinetics, but with different FA concen-trations before and after diet change. The individual variability was broader when cows were grazing than when they were fed with hay and concentrates, confirming literature data (Kelly et al 1998;Khanal et al 2008). Differences in cow fresh herbage intake and in cow grazing selection of plant species, or plant parts richer or poorer in PUFA may explain the broader variability of the milk FA profile of pasture-fed cows (Coppa et al 2011b;Khanal et al 2008), especially on highly biodiverse upland pastures.…”

“…Elgersma et al (2004) reported rapid changes in milk fat composition when the diet of cows was switched abruptly from temporary grassland exploitation to a silage (maize and ryegrass)-based diet; the FA profile remained stable for 2 days after the diet change. Similar results were obtained by Biondi et al (2008) in a study of ewes and by Khanal et al (2008) in a study of cows after an abrupt diet transition from, respectively, a vetch hay (Vicia sativa) and concentrate ration to a vetch and oat pasture diet, and an abrupt transition from a total mixed ration (TMR) to a perennial ryegrass pasture diet and vice versa. CLA and PUFA concentration changes in milk were studied by Kelly et al (1998) and by La Terra et al (2010) on cows transferred gradually from a TMR to pasture feeding in controlled and on farm conditions, respectively; however, FA kinetics were not investigated in these studies.…”

Mapping and fine-mapping of genetic factors affecting bovine milk composition

“…The high herd correlation for C12:0 might be because on a herd the same type of concentrate is fed to cows in both winter and summer. C18:2cis-9,12 is one of the major PUFA found in maize silage (Chilliard et al, 2001, Khanal et al, 2008. The high herd correlation for this FA suggest that herds that feed maize silage do this in winter as well as in summer.…”