Recently, it has been demonstrated that administration of equine chorionic gonadotropin (eCG) in the postpartum period in dairy cows can enhance follicle growth, reduce the interval from calving to first ovulation and increase plasma estradiol concentrations, and, thus, could enhance reproductive performance in a dairy herd when administered on day 6 postpartum. The aim of this study was to investigate the effects of a single dose of eCG between days 9 and 15 postpartum on parameters of reproductive performance in dairy cows. German Holstein cows (n = 1937; primiparous cows: n = 748; pluriparous cows: n = 1189) in a commercial dairy farm were randomly assigned to three experimental groups. Animals within the group eCG received a single dose of 600 IU eCG intramuscularly (i.m.) between days 9 and 15 postpartum followed by an i.m. administration of 500 μg cloprostenol after 14 days. Those of treatment group PG received cloprostenol only between days 23 and 29 postpartum. Cows of the control group remained untreated. Starting on day 49 postpartum, cows were subjected to a Presynch-Ovsynch protocol and inseminated artificially. The impact of application time (days postpartum) of eCG on the intervals calving to first service and calving to conception was statistically not significant. Outcomes of reproductive performance (i.e. first service conception rate, proportion of pregnant cows until 100 and 150 days in milk [DIM], number of inseminations until 150 DIM, calving to first service interval and calving to conception interval) did not differ significantly between treatment group eCG and group PG compared to control group. Regarding postpartum eCG administration, significant interactions between treatment and parity, season, milk yield, and early puerperal disorders, respectively, could not be shown. In conclusion, an eCG treatment of dairy cows between days 9 and 15 postpartum to increase reproductive performance cannot be recommended under the given circumstances.

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ABSTRACT:In dairy cows, immunosuppression occurs frequently during the periparturient period and is characterised by transient neutropenia and impaired polymorphonuclear neutrophil function. As a consequence, postpartum cows are more susceptible to production-related diseases such as mastitis, retained foetal membranes and metritis. Recently, it has been shown that a double injection with recombinant bovine granulocyte colonystimulating factor covalently bound to polyethylene glycol (PEG rbG-CSF) increased polymorphonuclear neutrophil number and the exocytosis of myeloperoxidase by stimulating polymorphonuclear neutrophil, which also played a role in innate uterine immune defence. The aim of this randomised clinical study was to investigate the effects of two periparturient PEG rbG-CSF injections (IMR; Imrestor TM , Elanco Animal Health, Bad Homburg/Germany) on the incidence of acute puerperal metritis, number of antibiotic doses required for treatment of acute puerperal metritis as well as parameters of milking performance (i.e., milk yield, milk fat, milk protein, and somatic cell count on the first dairy herd improvement test day) in primiparous cows within a dairy herd with an elevated incidence of acute puerperal metritis. In total, 169 heavily pregnant heifers were randomly assigned to the treatment group (IMR: n = 82) who received 15 mg PEG rbG-CSF subcutaneously 10 ± 3 days before the anticipated calving date and within 24 hours after calving, or to the untreated control group (Co: n = 87). In total, data from 157 animals (IMR: n = 75, Co: n = 82) were analysed. Administration of PEG rbG-CSF reduced the incidence of acute puerperal metritis in primiparous cows significantly (IMR: 22.7%, Co: 43.9%, P = 0.003; relative reduction: 48.3%). Moreover, the number of antibiotic doses per calving required for treatment of acute puerperal metritis was significantly lower in the pegbovigastrim group (IMR: 0.32 ± 0.66, Co: 0.59 ± 0.75, P = 0.005). No significant differences regarding incidence of clinical mastitis, milk production or milk composition were observed. These results suggest that further research should be performed to identify herd-and animal-specific factors that can be predictors of the beneficial effects of pegbovigrastim in preventing uterine diseases.Keywords: cattle; postpartum; uterine diseases; prevention; bovine granulocyte colony-stimulating factor; G-CSF List of abbreviations APM = acute puerperal metritis, DIM = days in milk, G-CSF = granulocyte colony-stimulating factor, MPO = myeloperoxidase, PMN = polymorphonuclear neutrophilIn cattle, acute puerperal metritis (APM) occurs within 21 days post partum and is defined by an abnormally enlarged uterus, a fetid, watery, red-brown uterine discharge, a rectal temperature > 39.5 °C and signs of systemic illness (e.g., dullness and decreased milk yield) (Sheldon et al. 2006). The

In this field study, the application of two different mastitis vaccines was not an appropriate tool to improve the considered parameters of udder health sustainably.

An increased conception rate was only achieved for the first service of high-yield dairy cows (lactation number ≥ 2) by gonadorelin treatment at day 0. Presumably, the higher incidence of delayed ovulations in this group was treated successfully by gona- dorelin administration.