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Lactating Holstein cows (n = 141) were synchronized to receive their first timed artificial insemination (TAI). Blood and milk samples were collected 25 and 32 d after TAI, and pregnancy status was determined 32 d after TAI using transrectal ultrasonography. Cows diagnosed pregnant with singletons (n = 48) continued the experiment in which blood and milk samples were collected and pregnancy status was assessed weekly using transrectal ultrasonography from 39 to 102 d after TAI. Plasma and milk samples were assayed for pregnancy-associated glycoprotein (PAG) levels using commercial ELISA kits. Compared to ultrasonography, accuracy was 92% for the plasma PAG ELISA test and 89% for the milk PAG ELISA test 32 d after TAI. Plasma and milk PAG levels for pregnant cows increased from 25 d to an early peak 32 d after TAI. Plasma and milk PAG levels then decreased from 32 d after TAI to a nadir from 53 to 60 d after TAI for the plasma PAG assay and from 46 to 67 d after TAI for the milk PAG assay followed by an increase from 74 to 102 d after TAI. Overall, plasma PAG levels were approximately 2-fold greater compared with milk PAG levels, and primiparous cows had greater PAG levels in plasma and milk compared with multiparous cows. The incidence of pregnancy loss from 32 to 102 d after TAI based on ultrasonography was 13% for cows diagnosed with singleton pregnancies, and plasma and milk PAG levels decreased to nonpregnant levels within 7 to 14 d after pregnancy loss. Both plasma and milk PAG levels were negatively correlated with milk production for both primiparous and multiparous cows. We conclude that stage of gestation, parity, pregnancy loss, and milk production were associated with plasma and milk PAG levels after TAI similarly. Based on plasma and milk PAG profiles, the optimal time to conduct a first pregnancy diagnosis is around 32 d after AI, coinciding with an early peak in PAG levels. Because of the occurrence of pregnancy loss, all pregnant cows should be retested 74 d after AI or later when plasma and milk PAG levels in pregnant cows have rebounded from their nadir., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Two experiments were conducted to evaluate an accelerometer system (Heatime; SCR Engineers Ltd., Netanya, Israel) to manage reproduction in lactating dairy cows. In experiment 1, lactating Holstein cows (n=112) were fitted with an accelerometer system and were treated with GnRH followed 7d later by PGF(2α) to synchronize estrus. A total of 89 cows that had a follicle >10mm in diameter and a functional corpus luteum at the PGF(2α) injection that regressed by 48 h after induction of luteolysis were included in the analysis. Overall, 71% of cows were detected in estrus by the accelerometer system and 95% of cows showing estrus ovulated within 7d after induction of luteolysis. Of the cows not detected in estrus by the accelerometer system, 35% ovulated within 7d after induction of luteolysis. Duration of estrus activity (mean ± SD) was 16.1±4.7 h and was neither affected by parity nor milk production. Intervals (means ± SD) from induction of luteolysis, onset of activity, peak raw activity, and peak weighted activity to ovulation was 82.2±9.5, 28.7±8.1, 20.4±7.8, and 16.4±7.4 h, respectively, and the interval from AI to ovulation was 7.9±8.7 h, but ranged from -12 to 26 h. In experiment 2, cows were assigned randomly to receive an intramuscular injection of GnRH at artificial insemination (AI) after detection of estrus by the accelerometer system or receive no treatment (control). Nine hundred seventy-nine AI services from 461 cows were analyzed. Treatment with GnRH at AI did not affect fertility at 35 or 65 d after AI, and no interaction was detected between treatment and season or treatment and AI number. Overall, two-thirds of the cows that were considered properly synchronized were inseminated based on the accelerometer system and ovulated after AI. The remaining cows either were not inseminated because they were not detected in estrus or would not have had a chance to conceive to AI because they failed to ovulate after estrus. Furthermore, mean time of AI in relation to ovulation determined by the accelerometer system was acceptable for most of the cows that displayed estrus; however, variability in the duration of estrus and timing of AI in relation to ovulation could lead to poor fertility in some cows. For lactating dairy cows detected in estrus by the accelerometer system, treatment with GnRH at the time of AI without reference to the onset of estrus did not increase fertility., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

An observational study was conducted on 1,498 cows in 3 large Italian dairy farms. The objective of the study was to evaluate the prognostic value of early lactation fat-to-protein ratio in milk. In all 3 herds, an intensive herd health monitoring program was being practiced that included weekly visits and extensive data collection on health, reproduction, production, and culling. A milk sample was collected from all cows at approximately 7 d postpartum and the ratio of fat-to-protein percentage in this milk sample was measured. Animals with a fat-to-protein ratio in early lactation greater than 2.0 showed an increase in postpartum diseases such as retained placenta, left-displaced abomasums, metritis and clinical endometritis. We also observed a decrease in early lactation milk production but this was limited to cows in lactation 2 and higher when the fat-to-protein ratio was greater than 2.0 in the early postpartum milk sample. Finally, an increased risk of being culled from the herd was observed, with the risk of culling increasing with increasing fat-to-protein ratio in the early lactation milk sample. No effect of fat-to-protein ratio was found on the incidence of clinical mastitis in the 3 herds. From this study, we conclude that analyses of milk components in early postpartum (6-9 days in milk), particularly the ratio of fat-to-protein percentage, is a valuable indicator of lipo-mobilization and the negative energy balance status in postpartum cows. Because a single milk sample is sufficient to provide valuable information, we suggest that this is a valuable addition to herd health programs on dairy farms., (Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)