Michael Herlihy

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The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows(More)
The objective of this study was to compare circulating progesterone (P4) profiles and pregnancies per AI (P/AI) in lactating dairy cows bred by timed artificial insemination (TAI) following Ovsynch-56 after 2 different presynchronization protocols: Double-Ovsynch (DO) or Presynch-Ovsynch (PS). Our main hypothesis was that DO would increase fertility in(More)
Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: 1)(More)
Lactating dairy cows (n=1,538) were enrolled in a randomized complete block design study to evaluate protocols to synchronize estrus and ovulation. Within each herd (n=8), cows were divided into 3 calving groups: early, mid, and late, based on days in milk (DIM) at mating start date (MSD). Early calving cows (n=1,244) were ≥42 DIM at MSD, mid-calving cows(More)
Our objectives were to (1) compare the effect on pregnancies per artificial insemination (P/AI) of presynchronization of the estrous cycle with human chorionic gonadotropin (hCG) 7d before resynchronization of ovulation (Resynch) initiated 25 d after timed artificial insemination (TAI) and compare the presynchronization treatment with the Double-Ovsynch(More)
Lactating Holstein cows (n=1,456) were randomized in a 2×2 factorial design to compare the main effects of day of initiation of resynchronization after artificial insemination (AI; 32 vs. 39 d) and presynchronization with GnRH 7d before initiation of resynchronization on fertility to timed AI (TAI). This design resulted in the following 4 resynchronization(More)
Lactating dairy cows (n=57) ≥45 d postpartum at first service were enrolled in a randomized complete block design study to evaluate treatments to synchronize estrus and ovulation. At 10 d before artificial insemination (AI), animals were randomly assigned to 1 of 3 treatments: (1) d -10 GnRH (GnRH1; 10 μg of buserelin, i.m.) and controlled internal drug(More)
Ovulation to the first GnRH injection of Ovsynch-type protocols is lower in cows with high progesterone (P4) concentrations compared with cows with low P4 concentrations, suggesting that P4 may suppress the release of LH from the anterior pituitary after GnRH treatment. The objectives of this study were to determine the effect of 1) circulating P4(More)
Fertility to timed AI (TAI) is profoundly affected by progesterone (P4) levels during hormonal synchronization protocols. Holstein-Friesian dairy cows managed in a seasonal-calving, pasture-based production system were randomly assigned to 2 treatments to manipulate P4 before TAI during growth of the preovulatory follicle. Cows in the first treatment (High(More)
Logistic regression was used to identify factors associated with fertility outcomes in cows treated with protocols to synchronize estrus and ovulation. Lactating dairy cows (n=1,538) were enrolled in a completely randomized block design study to evaluate synchronization treatments. Within each herd (n=8), cows were divided into 3 calving groups: early [≥ 42(More)