Blood urea nitrogen may serve as a predictive indicator of retained placenta in dairy cows

https://doi.org/10.1016/j.anireprosci.2020.106481Get rights and content

Highlights

  • Screening of serum biochemical indicator to predict the occurrence of RP in cows.

  • Determined the critical threshold of serum BUN by ROC curve analysis.

  • High levels of BUN may cause difficulties in separation of maternal-fetal placentas.

  • BUN may serve as a predictive indicator of RP in dairy cows.

Abstract

Retained placentae (RP) results in significant economic losses to dairy farmers. In Experiment 1, to screen biochemical indicators of RP, 21 cows with RP and 21 cows with no retained placenta (NRP) were selected as a control group, and blood was collected at -7 d, 0 h (parturition) and 12 h. Serum biochemical indicators were ascertained. Results indicate serum concentrations of phosphorus (P) and blood urea nitrogen (BUN) in cows of the RP group were markedly greater than in cows of the NRP group at -7 d (P < 0.01). In Experiment 2, to evaluate predictive indicators for RP, 34 cows with RP and 34 cows with NRP were selected, and there was blood sampling at -15 d, -10 d, -7 d, -4 d, and -1 d. Serum P, BUN, and total protein (TP) were evaluated. Associations of values among the three indicators and occurrence of RP were analyzed using binary logistic regression. Results indicate there was a negative correlation between only the values for BUN and RP (P = 0.016). In Experiment 3, to test hypothesis that relatively greater concentrations of BUN effects immune function in placental tissues, four cows were selected, placentae were collected at 0 and 12 h, and hematoxylin-eosin (HE) staining was performed. Results indicated that the extent of inflammatory cell infiltration and vascular proliferation were less at the 12 than 0-hour timepoint. Taken together, BUN at -7 d may serve as a predictive indicator of RP in cows.

Introduction

Retained placentae (RP) in cows can be defined as occurrences in which the fetal placenta is not expelled within 12 h of parturition (Liu et al., 2011). Generally, there are two types of RP: when there is lack of or partial expulsion of the placenta. The RP condition is one of the most common occurrences postpartum in modern dairy farming and production enterprises, with an incidence rate of about 10% to 30%, with prevelances as great as 50% in the summer (Fourichon et al., 2000). Various diseases can be induced by RP, such as pyometra, metritis, mastitis, and laminitis, resulting in large economic losses in dairy farming, particularly affecting milk production and reproductive performance (Heinonen et al., 1989). Because of the extended days non-pregnant, the culling rate increases and milk production decreases. These and the cost of veterinary treatment and drugs have resulted in the total economic cost of RP for each primiparous cow to be $150.41 ± $51.43 (US) per year and that for each multiparous cow to be $ 313.49 ± $ 64.66 (US) per year (Liang et al., 2017). If appropriate prevention and control measures, therefore, are used in the early perinatal period, and as a result the occurrence risk of RP would be reduced. It, therefore, is of practical significance to implement procedures to reduce RP and improve the production performance of dairy cows.

The perinatal period of cows is a phase before and after 3 weeks of calving, which can be divided into two stages: prenatal and postpartum. Although it is very short, it is the most important stage of the production cycle for cows (Stoldt et al., 2015). Various diseases, such as fatty liver, ketosis, retained placenta, and abomasum displacement frequently occur after parturition due to physiological processes related to pregnancy, parturition, and lactation during the perinatal period, and the nutritional metabolism and immune system are affected by the negative energy balance and hormonal imbalances (Stoldt et al., 2015; Mormède et al., 2007; Ospina et al., 2013; Rhoads et al., 2010). In addition, reproductive performance is also affected by negative energy balance and metabolic disorders and result in greater than typical durations of postpartum anestrus, delayed ovulation from the time of parturition to the time of initiation of onset of estrous cycles after calving, and decreased pregnancy rates (Crowe, 2008). Nutrition management of dairy cows, therefore, is not only important to the health of calves, but also has a prominent effect on postpartum disease frequency and reproductive performance of cows during the perinatal period. In addition, results from a previous study (Barton et al., 1996) indicate the postpartum reproductive performance of cows is less when there are relatively greater than optimal concentrations of serum blood urea nitrogen (BUN), in which there is an increased incidence of non-viable sperm, ova, and embryos or lesser concentration of progesterone due to less actions of luteinizing hormone at the ovary as a result of relatively greater than optimal concentrations of serum BUN. The BUN in the serum is derived from the breakdown of proteins and fats.

The detection of blood biochemical indicators is a common method for predicting and assessing diseases. The purpose of the present study, therefore, was to screen and identify the biochemical predictive indicators of RP in Holstein dairy cows during the early perinatal period, and to determine if there are associations between this indicator before calving and the frequency of RP occurrence in cows. Such a predictive marker would provide a practical technique and theoretical basis for improving the reproductive performance of postpartum cows and consequently would be beneficial from an economic perspective.

Section snippets

Materials and methods

All procedures were approved by the Ethics Committee in Animal Experimentation of Heilongjiang Bayi Agricultural University (IACUC Issue No. 20180307-007) and were executed in accordance with the Guide for Care and Use of Laboratory Animals (National Research Council, 2011). All the experiments were performed on a commercial farm in Heilongjiang Province of China. All cows were managed at a sport field, and feed was provided ad libitum three times a day. The cows were fed grass silage, hay, and

Experiment 1

The ingredients and nutrient composition of total mixed ration (TMR) for dairy cows during prepartum or postpartum period are included in Table 1. The dry matter intake per cow was 12.82 kg/day and 13.20 kg/day during the prepartum or postpartum period, respectively. Overall average daily milk yield was 27.89 ± 0.12 kg 7 days after parturition.

The concentrations of calcium (Ca), phosphorus (P), magnesium (Mg), glucose (GLU), total cholesterol (TC), total protein (TP), albumin (ALB), blood urea

Discussion

To explore a potential serum biochemical indicator that can predict the occurrence of RP of dairy cows in the early perinatal period, there was an initial assessment of serum concentrations of Ca, P, Mg, GLU, TC, TP, ALB, BUN, AST and GGT in the cows of the RP and NRP groups at - 7 d, 0 h (parturition) and 12 h, and screening of the serum P, BUN and TP using statistical analysis at - 7 d. The serum P, BUN and TP at - 7 d may be the candidate indicators for prediction of RP in dairy cows. These

Conclusion

Early prediction of disease occurrence risk is important for maintaining health, milk production and reproductive performance of dairy cows. The results of the present study indicate the serum BUN at 7 days before parturition may serve as a predictive indicator of retained placenta in dairy cows. The predictive critical threshold is 10.25 mg/dL. When the BUN concentrations are greater than 10.25 mg/dL at 7 days before parturition, therefore, there is a lesser inflammatory cell infiltration in

Declaration of Competing Interest

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Blood urea nitrogen may serve as a predictive indicator of retained placenta in dairy cows”.

Acknowledgments

This research was supported by the Key Scientific Research Program of the General Bureau of State Farms of Heilongjiang Proviance (grant numbers: HKKY190302, HKKYZD190306 and HKKYZD190705) and finish school, introduction of talent research start-up fund (grant number XYB2013-06) of Heilongjiang Bayi Agricultural University and graduate innovation research project of Heilongjiang Bayi Agricultural University (grant number YJSCX2017-Y31), the Postdoctoral Scientific Research Foundation of

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