Milk fatty acids profile and metabolic indicators in postpartum dairy cattle fed with soiling or alfalfa silage under confinement system

Abstract

The aim of this study was to determine differences between milk fatty acids (FA) profiles in postpartum dairy cows fed alfalfa soiling or alfalfa silage under confinement. Two groups of 20 cows each were selected randomly from a commercial dairy farm. Feed were analyzed for nutritional content using wet chemistry. Blood samples were taken on days 0, 7, 14 and 21 postpartum to determine beta-hydroxybutyrate (BHB) and non-esterified fatty acids (NEFA) concentrations. Individual milk samples were obtained on day 21 postpartum to determine the FA profile. Milk tank was also sampled on day 21. Analysis of variance for repeated measures was performed using SAS 9.2^®. In individual milk samples, silage group had higher concentrations (P < 0.05) of C14:1, C16:1 and C18:3 FA. Contrary, soiling group had a higher concentration of C18:1 FA. In milk bulk tank samples, silage group had higher concentration of C18:3 FA (P < 0.05). C10:0, C12:0, C14:0 and C18:1 FA had a direct association (P < 0.05) with parity and C14:1, C16:1 and C18:3 FA had a direct association with the use of alfalfa silage. Multiparous and silage group had the highest concentrations (P < 0.05) of polyunsaturated FA in milk. NEFA levels were lower (P < 0.05) at day 7 and BHB (P < 0.05) at days 7, 14 and 21 postpartum in soiling group. It is concluded that parity number and type of feeding system are related to content and profile of milk FA and energy-related blood metabolites.