Research articleThe prevalence of subclinical endometritis and intrauterine infections in repeat breeder cows
Introduction
Good fertility of dairy cows is the key to economically successful dairy farming. It is generally accepted that uterine disorders in the postpartum period have a negative impact on reproductive performance. In the past decades, the knowledge of the pathophysiology of clinical disorders, e.g., metritis, endometritis, and subclinical endometritis (SE) has increased significantly [1], [2], [3]. Short- and long-term effects of these diseases on fertility have been described [4], [5]. After the postpartum period, repeat breeding is considered one of the most important reproductive disorders in cattle [6]. Repeat breeder cows (RBCs) are defined as cows with regular cycles of 17 to 25 days and with three or more artificial inseminations (AIs) without conception [7], [8]. Recently reported mean prevalence of repeat breeding ranges from 10% to 14% in dairy cows [6], [9]. Although several causes of repeat breeding have been described, e.g., inadequate estrus detection [10], prolonged estrus, delayed LH peak, and late postovulatory rise in plasma progesterone [11], [12], [13], infections [14], and genetic factors [11], the particular reason often remains speculative. With a new diagnostic technique in endometrial cytology, more information can be obtained about these cows. The cytobrush technique has been established as a diagnostic method to detect SE in cows with no signs of clinical endometritis [15], [16]. The proportion of polymorphonuclear neutrophils (PMN) in the total number of endometrial cells is indicative for SE. Different thresholds of PMN for defining SE have been used, ranging from ≥5% [17] to greater than 18% [15]. Some studies have reported the negative impact of SE diagnosed in the postpartum period on fertility [4], whereas others did not confirm these results [17].
In RBCs, one study reported a prevalence of 52.7% SE, and it has been hypothesized that SE is one of the main reasons for cows to become a repeat breeder [18]. Information about intrauterine pathogens in RBCs is rare. It has been assumed that bacteriologic findings are coincidental and not responsible for the failure of cows to conceive [19].
Beside an affected endometrium as a possible reason for failure to conceive, RBCs may also be associated with impaired function of the ovaries [11], [12], [13]. The different aspects of anestrus cows have been described by [20]. Although RBCs are defined as cyclic cows [8], ovarian activity of these cows at the time of insemination is often unknown.
Therefore, the objectives of this study were to describe the prevalence of SE and the presence of common uterine pathogens in the RBC to assess whether RBCs are affected by SE, uterine pathogens or both. Such information would be valuable for discussing prevention and treatment strategies for RBC.
Section snippets
Animals, examinations, and recorded data
This study was approved by the institutional ethics committee and the national authority according to §8 of Law for Animal Experiments, Tierversuchsgesetz-TVG (BMWF-68.205/0137-II/3b/2011).
During the study period from October 2011 to February 2012, RBCs from 40 commercial dairy farms in Austria were enrolled. Herd size ranged from 20 to 218 cows and average 305-day milk production was 5875 to 11,900 kg. Cows were housed in free stalls (n = 38) and tie stalls (n = 2). Rations on all farms were
Descriptive statistics
A total of 121 cows met the inclusion criteria for RBC and were enrolled in this study. Study population consisted of 77.7% dual-purpose Austrian Simmental cows, 9.8% Holstein Friesian, 8.0% Brown Swiss, and 4.5% others. Mean milk production of RBCs that finished a 305-day lactation (n = 60) was 8259 kg (range, 4456–13,495 kg). The distribution of parity was 6.1% heifers, 14.1% primiparous, and 79.8% multiparous cows. Average days from parturition to the first AI were 76 (range, 23–397), and
Discussion
The objectives of this study were to describe the prevalence of SE and intrauterine infection in RBCs. Although several studies reported a prevalence of SE at the end of the postpartum period ranging from 14% to 52% [4], [17], [31], only little information exists about SE later in lactation or in the RBC. Salasel et al. [18] reported a proportion of 53% SE in the RBC. Although study design and the number of cows were similar, these findings did not match the results from our present study. The
Acknowledgments
The authors of the study like to acknowledge the support of the practitioners, the regional Dairy Herd Improvement Service (Landeskontrollverband), and the cooperation with the farm manager. In addition, they would like to acknowledge the financial support of the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva (MINCYT) and the Austrian Bundesministerium für Wissenschaft und Forschung (BMWF) 2010 to 2012.
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