Changes in milk urea around insemination are negatively associated with conception success in dairy cows

Abstract

Dietary protein levels are a risk factor for poor reproductive performance. Conception is particularly impaired in cases of high blood or milk urea. The objective of this study was to investigate the association between conception and low milk urea or changes in milk urea around artificial insemination (AI). Data were obtained from the French Milk Control Program for a 4-yr period (2009)(2010)(2011)(2012). Milk urea values between 250 and 450 mg/ kg (4.3 and 7.7 mM) were considered intermediate (I), and values ≤150 mg/kg (2.6 mM) were considered low (L). Milk urea values before and after each AI were allocated into 4 classes representing the dynamics of milk urea (before-after; I-I, I-L, L-I, and L-L). Subclinical ketosis was defined using milk fat and protein contents before AI as proxies. A logistic regression with a Poisson correction and herd as a random variable was then performed on data from Holstein or all breeds of cows. The success of conception was decreased [relative risk (95% confidence interval) = 0.96 (0.94-0.99)] in lowurea cows compared with intermediate-urea cows after AI; no significant association was found for urea levels before AI. When combining data on urea before and after AI, I-L urea cows exhibited a 5 to 9% decrease in conception compared with I-I urea cows, and L-I urea cows showed no difference in conception success compared with I-I urea cows. A decreased conception success for L-L urea cows compared with I-I urea cows was observed for the analysis with cows of all breeds. This work revealed that a decrease in urea from intermediate (before AI) to low (after AI) is a risk factor for conception failure. Surveys of variation in milk urea in dairy cows close to breeding are highly recommended. Key words: dairy cow, milk urea, conception INTRODUCTIONEfficient nutritional management of dairy cattle at calving is one of the most important factors in sustainable dairy farming. It has important effects on the health and reproductive performance of dairy cows. Farmers adopt various nutritional strategies to meet high production requirements while minimizing feed costs and maximizing economic returns. Cows in the early postpartum period experience negative energy balance when their energy requirements exceed their dietary intake (Bauman and Currie, 1980;Bell, 1995). Negative energy balance remains a major challenge for the dairy industry, and extensive literature is available on its physiology, strategic management, and effects on health and performance (Beam and Butler, 1999;Wathes et al., 2003;Raboisson et al., 2014). Protein supply presents a major dietary challenge for postpartum and lactating cows. High-protein diets are widely used during early lactation to stimulate high milk production. However, such diets may be deleterious for reproductive performance, especially when rumendegradable or rumen-undegradable protein exceeds the cow's requirements (Butler, 1998). In contrast, diets with low levels of proteins are often provided to beef cows, which may be fed only hay or grazed ...

Changes in milk characteristics and fatty acid profile during the estrous cycle in dairy cows

“…In dairy goats, the stress associated with estrus has been related to variation in milk urea content and correlated with feeding and metabolism changes, in spite of a nonsignificant association with cycle stage (Moroni et al, 2007). Conclusions regarding the variation of milk urea around the insemination day have not been consistent in previous studies, but extremely high or low values of milk urea have been associated as a risk factor for conception failure in Holstein cows (Melendez et al, 2000;Albaaj et al, 2017). The SCS increased gradually from the diestrus-HP to the proestrus phase and then gradually decreased during the estrus, metestrus, and initial diestrus-IP phases.…”

Effects of Propylene Glycol on Negative Energy Balance of Postpartum Dairy Cows

“…The NEB of dairy cows in early lactation will also increase the mobilization of protein, which will increase the metabolic residues of ammonia and urea. Ammonia is believed to play a role in starting before ovulation, whereas urea mainly interferes negatively after fertilization [28]. The first ovulation of a dairy cow is retarded by decreasing the luteinizing hormone (LH) pulsatility because of the low blood glucose [29].…”

Effects of Milk Urea Nitrogen (MUN) and Climatological Factors on Reproduction Efficiency of Holstein Friesian and Jersey Cows in the Subtropics

“…These findings agree with a previous study on conception rates in dairy cows [ 7 ], which showed lower conception rates for cows with higher concentrations of MUN. In a more recent study, it was emphasized that a high MUN concentration had a particularly negative effect on reproductive success if the MUN concentration was high on the day of insemination [ 17 ]. A decrease in the rumen degradable protein (RDP) fraction was shown to improve the rumen microbiome and decreased MUN, which improved the reproduction of cows [ 5 ].…”

“…Conception rates of first service dairy cows are negatively associated with milk production and MUN [ 7 ]. High concentrations of MUN at the time of insemination is a contributing factor to higher risk pregnancy failures [ 17 ].…”