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The aim of this study was to determine the relationship between observed estrous-related behavior, activity clusters (AC; detected by automatic activity monitor), endocrine profiles, and ovulation time. Twenty-one cows in estrus (after 2 cloprostenol treatments, 11 d apart) and 12 nonsynchronized cows, to establish Heatime (SCR Engineers Ltd., Netanya, Israel) herd baseline activity, were enrolled. Cows had Heatime monitors applied 3 wk before the trial to establish their own baseline activity level. Cows in standing estrus had ultrasonography and phlebotomy carried out every 4 h to determine dominant follicle size, endocrine profiles, and ovulation time. After ovulation, these procedures were repeated once on d 3 to 6. Heatime alerted estrus in 90% of cows, and incorrectly alerted 17% of AC. The mean±SEM duration for standing estrus was 9±1 and 13±1 h for estrous-related behavior. Estrous-related behavior began after the start of the proestrous estradiol-17β (E2) increase (59±6.5 h). Cows with longer durations of raised proestrous E2 had longer intervals from its onset to the start of standing estrus and AC. The AC duration increased with longer durations of estrous-related behavior. Higher peak E2 occurred with longer standing estrus and estrous-related behavior. As E2 concentration decreased after the peak, 90% of cows still had estrous-related behavior. Duration of estrous-related behavior increased with higher average E2 concentration during the last 8 h before the start of the LH surge. During this surge 90% of cows had all of their standing estrus. As yields increased, so did the magnitude of the preovulatory FSH surges. Higher surges occurred with shorter standing estrus and estrous-related behavior. Cows with shorter LH surges had longer standing estrus. Peak LH preceded the AC peak (6.6±0.8 h). Duration of overlap between the AC start and the LH surge end ranged between 0 and 14 h; 1 cow had none. No association was found between the AC characteristics with the E2, LH, or FSH profiles. In conclusion, the relationship between the timing of the E2 increase and estrous activity may be mediated by other factors (GnRH surge). Estrous-related behavior, but not endocrine profiles, was related to AC duration. Timing of standing estrus during the LH surge ensures that mating allows sperm maturation before ovulation. Based on the interval from the start of an AC to ovulation (27±1 h), the optimum time to artificial insemination is, on average, between 9 and 15 h after the AC start., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The aims of the present study were to investigate (1) the risk factors that influence the achievement of reproductive targets postpartum (pp) and (2) the key factors that influence pregnancy rate following first artificial insemination (AI) in dairy cows. Ninety-eight Holstein-Friesian pp cows were blood sampled from wk 1 to 4 pp for hematology and biochemistry. Reproductive tract health was assessed weekly by ultrasonography and vaginal mucus scoring. Body condition score (BCS), lameness score, and milk yield were assessed every 2 wk. Milk samples for progesterone assay were collected twice weekly and on d 4, 5, and 7 after AI. Risk factors associated with achieving reproductive targets depended on (1) increased metabolic activity of the liver (increased glutamate dehydrogenase at calving and increased γ-glutamyl transpeptidase in wk 4), (2) a competent immune system (increased neutrophils in wk 1; decreased α1-acid glycoprotein in wk 1, 2, and 3), (3) an endocrine system that was capable of responding by producing sufficient triiodothyronine in wk 2 and increased insulin-like growth factor I in wk 3 and 4, (4) a lower negative energy balance status (decreased nonesterified fatty acid concentration in wk 1; decreased β-hydroxybutyrate concentration in wk 2; BCS loss between calving and d 28 pp <0.5), (5) good reproductive tract health [normal uterine scan at d 45 pp; clear vaginal mucus discharge at first ovulation and at d 45 pp; resumed ovarian cyclicity by the end of the voluntary waiting period (≥ d 35 pp)], and (6) adequate diet (to ensure increased glutathione peroxidase in wk 2 and 3 and increased magnesium in wk 4). Risk factors that increased the odds of a successful first AI were previous ovulation(s) (odds ratio=3.17 per ovulation), BCS >2.5 at AI (odds ratio=3.01), and clear vaginal mucus (score=0) compared with purulent mucus (score >0) 4 d after first AI (odds ratio=2.99). In conclusion, this study identified key risk factors in the early pp period that give a higher probability of cows achieving their reproductive targets and of having a first-AI pregnancy., (Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The aim was to investigate 1) the relationship between the physical activity index created for each cow by activity monitoring systems and the identification of the preovulatory follicular phase, and 2) the influence of various production, health, and cow factors on the relationship between physical activity and estrous behavior. Eighty-nine spring calving cows, on pasture, were monitored during the breeding season using the neck-mounted estrous activity monitor Heatime (SCR Engineers Ltd., Netanya, Israel). Milk samples were collected twice weekly for progesterone assay to characterize resumption of reproductive activity. Reproductive tract health was assessed weekly by ultrasonography and vaginal mucus scoring. Body condition score and milk yield were assessed every 2 wk. Heatime identified 72% of preovulatory follicular phases from which 145 inseminations resulted in 69 conceptions; 32% of activity clusters were associated with high-progesterone states (i.e., false positives). By inclusion of a 6 to 8-h duration threshold and maintaining the borderline peak activity threshold, this was improved to 87.5% with 21.3% false positives. Mean (± standard error of the mean) peak activity and cluster duration (19.3±0.53 and 10.8±0.38, respectively) were highest for the second or subsequent preovulatory follicular phases followed, in descending order, by those during first preovulatory follicular phases (14.8±2.13 and 8.4±1.4, respectively) and high progesterone states (8.0±0.47 and 3.0±0.42, respectively). The odds of an activity cluster being in a preovulatory follicular phase rather than a high-progesterone phase improved by 29% for every 1-unit increase in peak activity and by 91% for every 2-h increase in duration. The probability of an activity cluster detecting a preovulatory follicular phase was improved if it was a second or subsequent follicular phase, if body condition score was 0.25 units higher, if milk yield was 10 kg lower, and uterine infection was absent. Conception rate was influenced by insemination on the same day (52%) or day after a cluster (34.3%); inseminations were carried out using the a.m.-p.m. rule. Advances in the development of more accurate automatic monitoring of the preovulatory follicular phase will aid the timing of insemination and, thus, improve conception rates., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)