Effect of breed factor on urea level and blood biochemical parameters in dairy cattle

Dairy cattle breeding has achieved great success due to the targeted improvement of dairy and combined breeds in different climatic and agroecological zones of the world. The level of urea and other biochemical parameters of cows' blood indicates the peculiarities of carbohydrate and protein balance, its impact on reproductive functions, health, feed efficiency, and methane emissions. The aim of the study was to determine the effect of the breed factor on urea levels and other biochemical parameters of blood in cows of different breeds. The research was conducted on cows of three contrasting breeds. The first breed is a combined (cross-border) Simmental, the last two are local – Ukrainian Red and White dairy (created by crossbreeding Simmental with Ayrshire, Montbéliard, Holstein) and Ukrainian Black and White dairy (created by crossing local Black and White with Holstein). The experiment was conducted under standard conditions when feeding cows “without restrictions” with the analysis of productive indicators and blood biochemical parameters. The most significant factor influencing the productive and biochemical parameters was the breed factor, which accounted for 14.6% and 51.2%, respectively, in terms of fat content in milk and milk yield in terms of total energy value. A significant influence of the breed was noted in blood biochemical parameters such as total bilirubin 24.7%, urea 33.2%, creatinine 49.8%, alanine aminotransferase 10.4%, aspartate aminotransferase 46.3%, albumin 35.1% and total protein 13.2%. A significant correlation between the concentrations of urea and creatinine, creatinine and aspartate aminotransferase, and albumin in the blood plasma of the studied animal groups was established. A preliminary conclusion was made about the presence of a significant genetic component of influence on the level of urea, blood biochemical parameters and productivity traits. The analysis of the manifestation of such traits in different breeds can be taken into account in selection programmes and the creation of appropriate feeding conditions, taking into account the peculiarities of protein nutrition