Short communication: Greater intensity of estrous expression is associated with improved embryo viability from superovulated Holstein heifers

摘要

The aim of this study was to determine the associationbetween estrous expression, measured using abreeding indicator and an automated activity monitor(AAM), and the success of embryo collection after superovulation.Holstein heifers (n = 51; 10.5 to 14.5 mo,and 325.0 ± 21.1 kg of body weight) were superovulated(n = 69 events) for the collection of embryos using aprotocol based on sequential administration of FSH forfollicle superstimulation and GnRH to induce ovulation.Artificial insemination (AI) was performed twice,once at the moment of GnRH administration and again12 h later, using thawed, sexed semen. Ovaries werescanned via ultrasonography on the day of the first AIto count the total number of preovulatory follicles and7 d later for the total number of corpora lutea present.Embryos were collected 7 d post-AI, counted, andassessed for viability. A breeding indicator (Estrotect,Rockway Inc., Spring Valley, WI) and a collar-mountedAAM (CowScout Activity Monitoring System, GEA,Dusseldorf, Germany) were used to measure standingmounts and an algorithmic estimate of estrous expression,respectively. A score for the breeding indicatorwas given as follows: score 1 = 100% of the indicatorwas intact; score 2 = 50% of the indicator was rubbedoff; score 3 = greater than 50% of the indicator wasrubbed off. Estrous expression detected by the AAMwas quantified through the relative increase in physicalactivity and duration of time spent above a set threshold.Data were analyzed by ANOVA using the MIXEDprocedures of SAS (SAS Institute Inc., Cary, NC). Thenumber of follicles present at AI was not affected byestrous expression. The mean (± SD) ovulatory responsewas 67.5 ± 26.3%. We found an effect of estrousexpression as detected by the breeding indicator on theovulatory response (42.1 ± 8.0, vs. 78.2 ± 9.0, vs. 74.0± 4.9%, for scores 1, 2, and 3, respectively) but notfrom the AAM. Heifers that had a score of 3 (versusthose with scores of 1 and 2) on the breeding indicatorhad a greater number of embryos (4.1 ± 0.5, vs. 1.2 ±1.0, vs. 1.8 ± 1.0 embryos), and a greater percentageof these embryos were viable (43.1 ± 0.05, vs. 35.5 ±0.1, vs. 34.3 ± 0.1%). Similarly, heifers that showed agreater intensity of activity (as measured by the AAM)had a greater number of embryos collected (10.2 ± 1.2vs. 6.0 ± 1.3 embryos), and a greater percentage ofthose embryos were viable (53.1 ± 5.0 vs. 23.4 ± 5.1%).Longer-duration estrus episodes were associated witha higher percentage of viable embryos (51.2 ± 5.2 vs.25.3 ± 5.3%). In conclusion, stronger estrous intensitywas associated with a greater number of total embryoscollected and a greater percentage of viable embryos.These results suggest that monitoring the intensity ofestrus could be used to predict superovulatory responseas well as embryo quality in Holstein heifers.