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BackgroundPregnancy rates with cooled equine semen can be unsatisfactory and show great variation. Information about first cycle pregnancy rates and pregnancy rates per cycle are often lacking from publicly available records. This retrospective cohort study was performed to evaluate the fertility of the Norwegian Coldblooded trotter. The aim of the study was to compare the breeding results after insemination with fresh, extended with those of cooled, shipped semen among Norwegian Coldblooded trotter mares. First cycle pregnancy rate was the main parameter used to measure fertility. Stud-books were collected from four studs from the years 2006–2010. Statistical analyses were done in Stata using Chi square test and multivariable analyses where different models were compared based on Akaike’s information criterion.ResultsFirst cycle pregnancy rate, seasonal pregnancy rate and foaling rate all showed significant differences (P < 0.0001) when comparing mares inseminated at stud with mares inseminated with cooled, shipped semen, favoring artificial insemination (AI) at stud. First cycle pregnancy rate was 55.1 % for mares inseminated at stud with fresh extended semen and 42.2 % for mares inseminated with cooled shipped semen. The overall pregnancy rate per cycle was 84.4 % for AI at stud and 66.9 % for cooled, shipped semen. The parameters stud, mare age, number of inseminations within an estrus cycle and individual stallion were also investigated for influence on fertility.ConclusionsFew retrospective studies include the parameter of first cycle pregnancy rates. Our study does not differ dramatically when comparing seasonal pregnancy rates and foaling rates with similar studies. Fertility parameters for the Norwegian Coldblooded trotter do not differ significantly from most other studies of Coldblooded mares and other mare breeds around the world. But the difference in fertility parameters between AI at stud to AI with cooled semen between our study and others, indicates that higher pregnancy rates in Norwegian Coldblooded trotter may be possible.

Background The timing of artificial insemination is critical to achieve acceptable results in cattle production systems. Over the past 60 years the length and expression of oestrus in dairy cattle has altered. Recent studies have indicated the optimal timing for insemination after the commencement of oestrus may now be earlier than traditional recommendations in beef cattle, as is the case in dairy cattle. The aim of the current study was to evaluate the effect of time from onset of oestrus [as determined by an automated activity monitoring system (AAMS)] to artificial insemination (AI) on pregnancy outcome in Norwegian beef cattle. Five commercial beef suckler herds participated in a cohort study by providing data on the time of AAMS alarm and time of AI. Blood sampling on the day of AI was performed and serum progesterone concentration measured. Pregnancy detection was performed by transrectal ultrasonography and aging of the fetus performed when necessary. A mixed logistic regression model was fitted to study the effect of time from AAMS alarm to AI on pregnancy outcome. Time categories used in the model were < 12 h, 12–24 h, and > 24 h. Results AI periods (n = 229) with serum progesterone concentration < 1 ng/mL were available for analysis. Overall pregnancy risk per AI for the whole study period was 65.5%, with an inter-herd variation from 10 to 91%. Median time elapsed from AAMS alarm to AI was 17.75 h. Herd affected pregnancy outcome (P = 0.001), while breed and parity status (heifer/cow) did not. The time category closer to AAMS alarm 0–12 h showed a numerically lower pregnancy risk as compared to the baseline group which had AI 12–24 h after onset of oestrus. Conclusion This study found no evidence to support a change in the recommended timing of AI in beef suckler cows.