Effects of milking time and week of lactation on the variability in milk yield and milk composition in early lactation dairy cows

ŠTOLCOVÁ, Magdaléna, ŘEHÁK, Dalibor and BARTOŇ, Luděk. Effects of milking time and week of lactation on the variability in milk yield and milk composition in early lactation dairy cows. Mlékařské listy, 2021, vol. 32(6), p. 33-39. ISSN 1212-950X.
Year2021
CathegoryPublication in specialized journals
Internal link21125.pdf
Abstract

The effect of milking time and lactation week on the variability in milk yields and milk contents was investigated in 71 Holstein dairy cows during the first five weeks of lactation. A total of 568 milk samples from morning and afternoon milkings were used. The amount of milk gradually increased during the first five weeks of lactation and a higher milk yield was observed during the morning milking. On the contrary, the fat content decreased with advancing lactation. A significantly higher milk fat content was observed in the milk from the afternoon milking. In addition to the basic components, the differences in milk fatty acid (FA) composition were also determined. The content of short-chain FA (SCFA) and palmitic acid (C16:0) increased significantly with advancing lactation, while the content of long-chain FA (LCFA), stearic acid (C18:0), and octadecenoic acid (C18:1) gradually decreased as the lactation advanced. The content of SCFA, medium-chain FA, and C16:0 was higher in the milk samples from the morning milking, while the content of LCFA, monounsaturated FA, and C18:1 was higher in the samples from the afternoon milking. The progression of milk FA contents is mainly related to the metabolic load in early lactation. The causes of different milk FA contents between morning and afternoon milking samples have not been completely explained yet and will probably be related to circadian rhythms. However, these differences can play an important role in assessing the relationships between direct energy balance indicators and some of milk components.