Abstract
The objective of this study was to reveal the effect of milk urea levels on the fertility of dairy cows, taking into account their age, herd production level, number of cows, season of first insemination, which were analyzed using data from the SYMLEK national system. The study included data on milk urea levels in 88,745 test-day yields of 55,685 Holstein?Friesian cows, which were milked up to 30 days before first insemination, during the period preceding 180 days of first and second lactation. The GLM procedure of the SAS package was used in the statistical calculations. Considering the observed significant relationships and tendencies, a milk urea level higher than 300 mg/L was found to negatively affect reproductive efficiency in dairy cows, although the effects of the urea level could be masked by the more profound impact of environmental factors. Regardless of the factors, an increased milk urea level was paralleled by decreased cow fertility, with statistically significant differences occurring only for the interactions with herd production level and with herd size. The unfavorable effect of the increase in the level of urea in milk (from ≤150 to >300 mg/L) on cow fertility was particularly evident in the highest producing herds (>9000 kg milk).
Highlights
From a zootechnical and economic point of view, recording the urea content of test-day milk is a quick, inexpensive, convenient, noninvasive, and above all useful method, as it informs the farmer about the efficiency of protein utilization and provides a basis for proper ration formulation (1,2,3)
Analysis of fertility parameters indicates that the cows were characterized by intermediate fertility (CI – 426 days, service period (SP) – 54.8 days, services per conception (SPC) – 2.20, success at first insemination – 44%) (Table 1)
Using a study group of cows kept under South African conditions, Muller et al (11) showed that during a period of less than 20 years (1986– 2004), calving interval (CI) increased by 26 days
Summary
From a zootechnical and economic point of view, recording the urea content of test-day milk is a quick, inexpensive, convenient, noninvasive, and above all useful method, as it informs the farmer about the efficiency of protein utilization and provides a basis for proper ration formulation (1,2,3). Some authors (2,7,8) indicate that urea levels around 200 mg/L or lower may be responsible for poor reproductive performance in dairy cows. Decreased or increased milk urea levels indicate that the diet is improperly balanced for protein and energy available for ruminal microbes (4,6,8). The inadequate amount of energy available for rumen microorganisms which accompanies the excessive amount of protein increases the urea level in the body, which has both indirect and direct negative effects on reproductive function. Excess urea in the organism has Skrzypek et al (6) demonstrated the effect of urea concentration on reproductive parameters to be nonlinear, and showed that urea concentrations of [201–250] mg/L (services per conception was 1.85) are most favorable in terms of reproduction, whereas exceeding 300 mg urea per liter of milk caused a significant decrease in conception rate (SPC was 2.52).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
