Effects of palmitic and stearic acids supplementation on milk yield, composition and milk lipolysis in dairy cows
When facing the fact that high yielding dairy cows has an increasing energy requirements, the practice of adding lipid supplements such as concentrates rich in palm oil and/or palm oil industry by-products become more common. Palm oil containing high levels of C16:0 causes high levels of free fatty acids (FFA) which are linked to larger milk fat globules (MFG) which affect the reaction of lipolysis resulting in rancid flavour and processing problems. Instead of using palm oil, rapeseed oil rich in C18:1 C18:2 can be used. In order to evaluate the effect of added C18:0 and C16:0 on milk lipolysis, 30 Swedish Red lactating dairy cows including 15 multiparous (MP) and 15 primiparous (PP) cows were randomly divided in three groups resulting in 3 10 cow-groups (5 PP and 5 MP cows per group) and fed one out of three concentrate mixtures: control (C), a standard concentrate mixture with no fat added; palmitate (P) as C plus the addition of palmitate methyl ester (10 % in DM basis); and stearate (St) as C plus the addition of stearate methyl ester (10 % in DM basis). Milk yield was registered, and milk samples were collected and analysed for milk composition, FFA content and size of MFG. In addition, feed intake and in vivo digestibility were estimated. Results from the experiment showed no treatment effect on feed intake or in vivo digestibility. Changes in milk yield and composition were more evident in MP than in PP cows. The inclusion of C16:0 and C18:0 caused an increase in milk yield and milk fat content and yield, with changes being greater for cows supplemented with C18:0. The high fat treatments resulted in higher levels of FFA in milk associated with an increased size of the milk fat globules. While the results of the present study would support the concept that C16:0 may be replaced by C18:0 in treatment for dairy cows without any detrimental effect on milk yield and composition, further conclusions cannot be drawn without the data on FA profile in milk.