preprints.org > biology > agricultural sciences & agronomy > doi: 10.20944/preprints202112.0125.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 28 November 2021 / Approved: 8 December 2021 / Online: 8 December 2021 (14:08:31 CET)

The trials were performed on 20 multiparous cows of Holstein breed (39.7 ± 0.75 kg of milk) at the end of the first phase of lactation this different milk fat (4.1-2.8%). The aim of the research was to study the characteristics of nutrition, metabolism and biosynthesis of milk components in highly productive dairy cows with normal and low milk fat levels and the timing of their productive use. Study the characteristics of fermentation of scar formation substrates and their use in energy metabolism and biosynthesis of the milk components. Found that low fat milk is not associated with a lack of formation of acetate in the rumen (6.1 vs. 6.6 mmol/dl in the contents of the rumen, р>0.05) and the non change in the hormonal profile, but depends on the reduction of fatty acids synthesis de novo in mammary gland, regulated by conjugated higher fatty acids. The result is a reduction in the need of cows in the exchange energy (reduction of heat transfer by 6.2 MJ), a shorter service period (109.5 vs.139 days) and the prolongation of their productive use (the number of lactations correlated back with the level of fat in milk (r=-0.68, p<0.05, n=1300).

cows; milk fat; ruminal fluid; milk fatty acids; energy balance

BIOLOGY, Agricultural Sciences & Agronomy