Relationships Between Milk Urea and Production, Nutrition, and Fertility Traits in Israeli Dairy Herds

Abstract

The objectives of this study were to identify and evaluate production and environmental factors that influence milk urea (MU) in Israeli dairy herds, to analyze the relationships between MU concentration and nutritional variables, and to examine a possible association between MU and pregnancy rate (PR). Production and environmental data were obtained from the Israeli Dairy Herd Improvement (DHI) Center (n = 1,279,600). Programmed total mixed rations (feeds and quantities) on milk-test day were collected from 42 dairy herds. Data on 36,073 cows that were inseminated close to milk-test day and pregnancy diagnosis results were obtained from the DHI data bank. Highly significant positive relationships were found between MU concentration and milk yield and fat percentage; relationships between MU and milk total protein percentage and somatic cell count were negative. Milk urea levels were higher during the summer months and were higher for adult cows. These levels increased as lactation progressed. Milk urea was positively associated with dietary levels of crude protein, ruminal digestible protein, and neutral detergent fiber contents; it was negatively associated with ration energy and nonstructural carbohydrate contents. Significant influences of specific feeds on MU were detected. A significant negative association was found between MU level and PR. Least squares means for PR for cows in the lowest and highest MU quartiles were 38.4 and 36.1%, respectively. Increasing levels of MU were negatively related to reproductive performance of dairy cows, but the risk of nonpregnancy caused by high levels of MU was lower than reported in previous studies.

Modeling milk urea of Walloon dairy cows in management perspectives

“…Moreover, the new crop maize silage included in the ration in the fall could be a reason for the high herd deviant percentage. This assumption is supported by Hojman et al (2004), who studied the relationship between groups of rations fed to milking cows and test-day mean herd MUN concentrations. They found a significant relationship for the feed group "summer crop harvested as silage," which included maize and sorghum.…”

“…These studies have shown that MU is related mostly to the dietary CP (Broderick and Clayton, 1997;Hojman et al, 2004;Nousiainen et al, 2004) or to the surplus of nitrogen that is available in the rumen for microbial growth compared with the available energy (RDP balance, or OEB in the Dutch and Belgian standard; Hof et al, 1997;Schepers and Meijer, 1998;Frand et al, 2003). Moreover, MU concentrations are related to individual production traits, such as test-day production of milk, fat, or protein.…”

Genetic relationship between milk urea nitrogen and reproductive performance in Holstein dairy cows

“…Hypotheses suggest that a high urea concentration impairs reproduction through an indirect effect on the energy status (Broderic and Clayton, 1997). Hojman et al (2004) reported increase in the levels of MU was negatively related to reproductive performance of dairy cows. An excessive intake of degradable protein and a relative shortage of energy to synthesize bacterial proteins will result in the accumulation of excessive ammonia in the rumen, which is absorbed through the ruminal wall and converted into urea in the liver.…”

Genetic and environmental determinants of the urea level in cow's milk

“…Many authors (Aguilar et al, 2012;Biswajit et al, 2011;Geerts et al, 2004;Hojman et al, 2004;Oltner et al, 1985) are of the opinion that, for dairy cows, the level of urea in cow's milk (MU, milk urea) may be the indicator of whether the energy balance and protein ratio are proper. In general, in properly balanced feed, the MU ratio is at 15-30 mg dL −1 .…”