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The objectives were to examine the effect of an automated premilking stimulation (APS) by means of a high pulsation frequency (300 cycles/min) without a reduction of the vacuum in the pulsation chamber or claw piece on (1) milking performance, (2) teat tissue condition, and (3) udder health in dairy cows. In a randomized controlled field study, Holstein cows (n = 427) from 1 commercial dairy farm with a milking schedule of 3 times per day were assigned to treatment and control groups over a 90-d period. Treatments consisted of a maximum of 80 s (APS80) or 99 s (APS99) of mechanical stimulation at a pulsation rate of 300 pulses per minute and a ratio of 25:75 (no reduction of the pulsation chamber or milking vacuum). Cows in the control group (CON) received traditional premilking stimulation by means of manual forestripping for 8 s. Milking characteristics were documented with on-farm milk meters. Short- and long-term changes in teat tissue condition induced by machine milking were assessed visually on a weekly basis. Composite milk samples were analyzed once per month to determine somatic cell count. Generalized linear mixed models were used to study the effect of the treatment on the outcome variables. We observed no meaningful differences in milk yield or milking unit-on time. Least squares means and their 95% confidence intervals (95% CI) for cows in the APS80, APS99, and CON groups were 13.5 (13.1-14.0), 13.2 (12.8-13.7), and 13.2 (12.8-13.7) kg for milk yield and 222 (213-231), 219 (210-228), and 223 (214-232) s for milking unit-on time, respectively. The effect of treatment on bimodality was modified by milk yield such that the odds of bimodality increased in the treatment groups with increasing milk yield. Compared with cows in the CON group, the odds ratios (95% CI) of bimodality were 1.08 (0.62-1.89) in the APS80 group and 0.89 (0.55-1.42) in the APS99 group at a milk yield of 11 kg and 2.0 (1.24-3.22) in the APS80 group and 2.08 (1.29-3.35) in the APS99 group at a milk yield of 16 kg. We observed differences in short- and long-term changes in teat tissue condition between the treatment and control groups. Compared with cows in the CON group, the odds (95% CI) of short-term changes were 1.87 (1.35-2.58) for the APS80 group and 1.49 (1.08-2.07) for the APS99 group, and the odds of long-term changes were 1.52 (1.24-1.85) for cows in the APS80 group and 1.59 (1.31-1.94) for cows in the APS99 group. The least squares means (95% CI) for somatic cell counts (log 10 -transformed) were 4.74 (4.68-4.81) for the APS80 group, 4.77 (4.71-4.83) for the APS99 group, and 4.79 (4.73-4.86) for the CON group. We conclude that the APS system tested here had no negative effects on milk yield or milking unit-on time. However, differences in bimodality and teat tissue condition suggest that the APS system did not provide sufficient stimulation to facilitate a gentle milk harvest and adversely affects teat tissue condition., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

In this study, we developed a machine learning framework to detect clinical mastitis (CM) at the current milking (i.e., the same milking) and predict CM at the next milking (i.e., one milking before CM occurrence) at the quarter level. Time series quarter-level milking data were extracted from an automated milking system (AMS). For both CM detection and prediction, the best classification performance was obtained from the decision tree-based ensemble models. Moreover, applying models on a data set containing data from the current milking and past 9 milkings before the current milking showed the best accuracy for detecting CM; modeling with a data set containing data from the current milking and past 7 milkings before the current milking yielded the best results for predicting CM. The models combined with oversampling methods resulted in specificity of 95 and 93% for CM detection and prediction, respectively, with the same sensitivity (82%) for both scenarios; when lowering specificity to 80 to 83%, undersampling techniques facilitated models to increase sensitivity to 95%. We propose a feasible machine learning framework to identify CM in a timely manner using imbalanced data from an AMS, which could provide useful information for farmers to manage the negative effects of CM., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Delayed milk ejection, manifested most often as bimodal milk flow, occurs when the cisternal milk fraction is removed before the alveolar milk reaches the gland cistern. It is thought to be a consequence of not meeting cows' physiological needs, due to insufficient premilking teat stimulation, inadequate timing of milking unit attachment, or both. It has been associated with decreased milking efficiency, reduced milk yield, and impaired teat and udder health. Traditionally, portable electronic milk meters have been used to assess the presence of delayed milk ejection in dairy cows. By contrast, incremental milk flow rates from on-farm milk meters and their suitability as a measure to assess delayed milk ejection have not been studied by rigorous methods. The objectives were (1) to describe a protocol for identification of cows with chronically delayed milk ejection (CDME) and (2) to investigate risk factors for CDME using incremental milk flow rates obtained from automated on-farm milk meters. In a retrospective case control study, milk flow data from a 4,300-cow dairy with a thrice-daily milking schedule were obtained over a 1-wk period. Incremental milk flow rates (0-15 s, 15-30 s, 30-60 s, and 60-120 s) were used to identify cows with delayed milk ejection. Cases of CDME were defined as presence of delayed milk ejection at all 21 milking observations. Cows that had no delayed milk ejection at any of the same 21 milking observations were included as controls. A total of 171 cases and 393 controls were included in the study based on these criteria. A logistic regression model was used to evaluate associations of the following risk factors with CDME: parity (1, 2, ≥3), stage of lactation (<100, 101-200, >200 DIM), presence of a nonlactating quarter, milk somatic cell count, average daily milk production, and health and management events. Parity and CDME were associated such that compared with cows in their third or greater lactation, the odds (95% confidence intervals, 95% CI) of CDME were 1.27 (0.71-2.25) for cows in their first and 4.77 (2.47-9.22) for animals in their second lactation. The odds of CDME increased with increasing stage of lactation, with an odds ratio of 0.20 (0.11-0.36) for early and 0.28 (0.15-0.52) for mid-lactation animals, respectively, compared with late lactation cows. A 1-kg increase in average daily milk production was associated with decreased odds of CDME [odds ratio (95% CI): 0.89 (0.87-0.92)]. A lameness event during the study period increased the odds of CDME [odds ratio (95% CI): 8.04 (1.20-53.83)], as did a vaccination event 1 wk before the study period [odds ratio (95% CI): 4.07 (0.99-16.71)]. This study confirmed associations between CDME and previously reported risk factors and identified several previously less rigorously investigated health and management events that could be associated with CDME. Incremental milk flow rates from individual cows serve as an automated tool to evaluate milk flow dynamics. This information could be used to improve individual premilking udder preparation to meet the animal's physiological requirements, improve teat and udder health, and enhance parlor efficiency., (© 2022, The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Determining the species of mycoplasma isolated from culture-positive milk samples is important for understanding the clinical significance of their detection. Between August 2016 and December 2019, 214,518 milk samples from 2,757 dairy herds were submitted to Quality Milk Production Services (QMPS) at Cornell University for mycoplasma culture. From these samples, 3,728 collected from 204 herds were culture positive. Based on the request of herd managers, owners, or veterinarians, 889 isolates from 98 herds were subjected to molecular identification by PCR and amplicon sequencing. The largest proportion of the identified isolates were from New York State (78.1%), while the others came from the eastern United States (17.8%), Texas (2.0%), and New Mexico (2.1%). As expected, Mycoplasma spp. were the most common (855 isolates, 96.2%) and Acholeplasma spp. accounted for the remainder (34 isolates, 3.8%). Mycoplasma bovis was the most prevalent Mycoplasma species (75.1%), followed by M. bovigenitalium (6.5%), M. canadense (5.9%), M. alkalescens (5%), M. arginini (1.7%), M. californicum (0.1%), and M. primatum (0.1%). A portion of the isolates were confirmed as Mycoplasma spp. other than M. bovis but were not identified at the species level (16 isolates, 1.8%) because further information was not requested by the manager, owner, or veterinarian. Mycoplasma bovis was the only species identified in 59 of the 98 herds. However, more than 1 Mycoplasma sp. was identified in 29 herds, suggesting that herd infection with 2 or more mycoplasmas is not uncommon. Moreover, a Mycoplasma sp. other than M. bovis was the only species identified in 8 herds. From the subset of 889 mycoplasma culture-positive isolates from 98 herds, we determined that over a third of the herds had either more than 1 Mycoplasma sp. or a Mycoplasma sp. other than M. bovis detected in their milk samples. In conclusion, we observed that M. bovis is the most common pathogenic Mycoplasma species found in mastitic milk, but other Mycoplasma species are not uncommon. Our results suggest that it is critical to test milk samples for mycoplasmas using diagnostic tests able to identify both the genus and the species., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

The objectives were to study the effect of 2 different premilking stimulation regimens, with and without manual forestripping, on teat tissue condition and milking characteristics in dairy cows. In a randomized controlled crossover study, 130 Holstein cows milked 3 times daily were assigned to treatment and control groups. Premilking udder preparation for the treatment group consisted of: (1) predipping with 1% iodine, (2) sequential forestripping of 3 streams of milk per quarter, (3) wiping of teats, and (4) attachment of the milking unit. Premilking udder preparation for the control group was identical except that the forestripping step was omitted. The mean tactile stimulation durations were 16 s and 7 s for the treatment and control group, respectively. The time spent from first tactile stimulus (either forestripping or wiping of teats) to milking unit attachment was kept consistent at 90 s for both groups. The study lasted for 14 d with 2 periods, each consisting of a 2-d adjustment time followed by 5 d of data collection. Machine milking-induced short-term changes to the teat tissue were assessed by palpation and visually. The following milking characteristics were assessed with electronic on-farm milk meters: milk yield (MY), milking unit-on time (MUOT), 2-min MY (2MIN), and time spent in low milk flow rate (LMF). Generalized linear mixed models were used to describe the effect of treatment on the outcome variables. The odds of machine milking-induced short-term changes to the teat tissue were lower for cows that received forestripping compared with cows that were not forestripped (odds ratio = 0.31; 95% confidence interval = 0.22-0.42). Least squares means (95% confidence interval) for cows that were forestripped and animals that were not forestripped, respectively, were 12.7 (12.2-13.2) and 12.7 (12.2-13.2) kg for MY and 6.1 (5.8-6.4) and 5.6 (5.3-5.9) kg for 2MIN. There was an interaction between treatment and MY for LMF. Time spent in LMF for cows that were forestripped and received no forestripping, respectively, were 18 (17-20) and 24 (23-26) s for a MY level of 10 kg; and 13 (12-14) and 15 (14-16) s for a MY level of 15 kg. The effect of treatment on MUOT was modified by parity. Milking unit-on times for animals in first, second and third or greater lactation, respectively, were 230 (219-243), 249 (236-262), and 260 (249-272) s for cows that were forestripped, and 245 (232-258), 252 (239-266), and 268 (257-281) s for cows that received no forestripping. In this study, cows that were forestripped had shorter MUOT, higher 2MIN, lower LMF, and lower odds of exhibiting changes to the teat tissue after machine milking. We conclude that wiping of teats during premilking udder preparation alone and omitting forestripping of teats without compensating for the loss in stimulation time may not provide sufficient tactile stimulation to elicit the cows' maximum physiological milk-ejection capacity. This can aggravate the adverse effects of vacuum-induced forces on teat tissue during machine milking, diminish animal well-being, and possibly affect udder health., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objectives were to study the effect of 2 different automatic cluster remover settings on (1) milking characteristics, (2) milk component yields, (3) teat tissue condition, and (4) udder health. In a randomized controlled field trial, Holstein cows (n = 689) from 1 commercial dairy farm with a thrice-daily milking schedule were allocated to 2 treatment groups. Treatment consisted of a cluster remover take-off milk flow threshold of 1.2 (ACR1.2) or 0.8 kg/min (ACR0.8) for 57 d. Milking characteristics (milk yield; and milking unit-on time, MUOT) were obtained with electronic on-farm milk meters. Composite milk samples were collected and analyzed for fat, protein, lactose, and somatic cell count. Machine-milking-induced short- and long-term changes to the teat tissue condition were assessed visually. General linear mixed models demonstrated differences in MUOT, whereas no meaningful differences in milk yield were detected. Milk yield (least squares means, 95% confidence interval) was 11.3 (10.9-11.8) and 11.3 (10.8-11.8) kg in groups ACR1.2 and ACR0.8, respectively. The effect of treatment on MUOT was modified by parity. Milking unit-on time in first-, second-, and ≥third-lactation cows, respectively, was 260.7 (252.0-269.4), 257.8 (247.4-268.1), and 260.2 (252.6-267.9) s in group ACR1.2; and 273.7 (264.9-282.5), 279.1 (269.4-288.8), and 295.7 (287.9-303.6) s in group ACR0.8. We detected no meaningful differences in milk component yields or linear somatic cell score. Least squares means in groups ACR1.2 and ACR0.8, respectively, were milk fat yield, 0.42 (0.40-0.44) and 0.42 (0.40-0.44) kg; milk protein yield, 0.36 (0.35-0.37) and 0.37 (0.36-0.37) kg; milk lactose yield, 0.61 (0.60-0.63) and 0.63 (0.61-0.64) kg, and linear somatic cell score, 1.9 (1.8-2.0) and 1.9 (1.8-2.0). A generalized linear mixed model revealed an effect of treatment on machine-milking-induced short-term changes. The odds of short-term changes to the teat tissue were lower for cows in group ACR1.2 [odds ratio (95% confidence interval) = 0.78 (0.63-0.96)]. No meaningful differences were detected in machine-milking-induced long-term changes between treatment groups. Increasing cluster remover take-off milk flow threshold from 0.8 to 1.2 kg/min decreased individual milking duration and alleviated machine-milking-induced short-term changes to the teat tissue without adversely affecting milking performance or somatic cell count. Future studies are warranted to investigate the effect on milk production and udder health over a whole lactation period., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The purpose was to evaluate 2 intramammary treatments for mild-to-moderate cases of clinical mastitis in a noninferiority comparison. Noninferiority trials are intended to show whether a given treatment, hetacillin potassium, has at least comparable efficacy as the reference treatment, ceftiofur hydrochloride. Treatments can be deemed inferior to the reference treatment by an amount less than the margin of noninferiority, or inconclusive if the confidence interval crosses the margin of noninferiority. Cows with clinical mastitis from 6 farms were considered for enrollment. Using a randomized design, cows with mild or moderate mastitis in 1 quarter were assigned to on-label treatment with either ceftiofur or hetacillin. A total of 596 cows met the criteria needed for continued enrollment. Treatment distribution resulted in 309 cows in the ceftiofur group and 287 cows in the hetacillin group. Mixed regression analysis was performed for the following outcomes: bacteriological cure, pathogen cure, clinical cure, postevent milk production and linear score, and survival to d 30 and 60. Cox proportional hazards analysis was used to describe treatment effect on survival and mastitis risks. Bacteriological cure, defined as absence of causative organism in samples retrieved at d 14 and 21 postmastitis, was similar between groups. No significant statistical differences were found in cure risk, and noninferiority of hetacillin relative to ceftiofur for bacteriological cure was conclusive (hetacillin=67%, ceftiofur=72%). Absence of a pathogen on both follow-up samples designated a cow as a pathogen cure. Pathogen cure was similar between treatment groups and noninferiority of hetacillin relative to ceftiofur was shown (hetacillin=35%, ceftiofur=32%). Clinical cure (hetacillin=68%, ceftiofur=64%), postevent milk production (hetacillin=37.0kg, ceftiofur=38.2kg), and linear scores (hetacillin=3.4, ceftiofur=3.1) were also not statistically different between treatment groups. Noninferiority of hetacillin relative to ceftiofur was shown for survival to d 30 and survival to d 60, whereas hetacillin was more likely to have a clinical cure than ceftiofur by d 4. No differences were seen between groups when Cox proportional hazards were performed, neither for exit from the herd in the 60 d following the event nor in the risk for a subsequent mastitis event. These findings can be used to develop farm-specific protocols for clinical mastitis treatment., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to compare the reproductive performance of lactating dairy cows using a treatment (TRT) program for second and subsequent artificial insemination (AI) services aimed at (1) increasing AI upon estrus detection based on increased physical activity (AIAct) and (2) increasing fertility of timed AI (TAI) services for cows not AIAct through presynchronization of the estrous cycle and improved physiological milieu before TAI. Cows in the control (CON) group were managed with a program that combined AIAct and TAI after the Ovsynch protocol. After nonpregnancy diagnosis (NPD) by transrectal ultrasonography at 31 ± 3 d after AI, cows received the following treatments: (1) CON (n=634), AIAct any time after a previous AI and resynchronization with the Ovsynch-56 protocol (GnRH-7d-PGF2α-56 h-GnRH-16 h-TAI) 1d after NPD, or (2) TRT (n = 616): cows with a corpus luteum (CL) ≥ 20 mm (TRT-CL) received a PGF2α injection 1d after NPD, whereas cows with no CL or a CL < 20 mm (TRT-NoCL) received a GnRH injection 3d after NPD. Cows in TRT-CL and TRT-NoCL not AIAct were enrolled in a 5-d Ovsynch + progesterone protocol (GnRH + controlled internal drug release-5d-PGF2α + controlled internal drug release removal-24 h-PGF2α -32 h-GnRH-16 h-TAI) 9 and 7d after the PGF2α or GnRH injection, respectively, to receive TAI. The hazard of pregnancy up to 270 DIM was similar for cows in the CON and TRT group (hazard ratio = 1.07, 95% CI = 0.95 to 1.21), but it was affected by parity (primiparous greater than multiparous cows). Median days to pregnancy for the CON and TRT group were 111 and 110 d, respectively. When evaluated after 104 DIM (first time point at which cows were affected by the treatments), the hazard of pregnancy was similar for the CON and TRT group (hazard ratio = 1.15, 95% CI = 0.95 to 1.39). Based on this analysis, median days to pregnancy for the CON and TRT group were 161 and 178 d, respectively. Thus, in spite of increasing the proportion of cows AIAct (29 and 10% for TRT and CON), median days to insemination after NPD were greater for cows in the TRT (17 d) than the CON (10 d) group, which coupled with similar fertility to AIAct, and TAI failed to improve overall reproductive performance. A low proportion of cows with a CL at NPD (65.2%) and a poor response to PGF2α may explain the poor estrus detection efficiency in the TRT group. We concluded that, when compared with a typical estrus detection and TAI program for cows failing to conceive to previous AI services, a program aimed at increasing the proportion of cows AIAct after NPD and fertility of TAI services increased the proportion of cows AIAct but failed to reduce days to pregnancy during lactation because of greater days to AI after NPD., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Prestimulation administered to a cow before attachment of the milking unit has historically been performed manually. Development of innovative milking technology has allowed manual stimulation to be replaced by mechanical forms of stimulation. Holstein cows (n=30) were enrolled in a crossover design to determine the effect of manual stimulation (forestripping and drying) and high-vibration pulsation on oxytocin profiles, milk yield, milk flow rates, incidence of delayed milk ejection causing bimodal milk flow curves, and residual milk in Holstein cows milked 3 times daily (3×). All cows were subjected to all treatments. Cows received manual (forestripping and drying) or mechanical (high-vibration pulsation) stimulation along with lag times of 0, 30, or 90 s for 21 consecutive milkings. Forestripping involved the manual removal of 2 streams of milk from each teat and drying of the teats. High-vibration pulsation involved increasing the pulsation cycles from 60 to 300 pulses/min and reducing the vacuum in the pulsation chamber to 20 kPa. The 5 treatments were (1) immediate attachment of the milking machine under normal pulsation (T0); (2) dip plus forestrip and drying with 30-s lag time (FD30); (3) dip plus forestrip and drying with 90-s lag time (FD90); (4) high-vibration pulsation for 30 s (HV30); and (5) high-vibration pulsation for 90 s (HV90). Milk yield per milking averaged 14.0 kg and was significantly different among treatments; however, the maximum difference detected among treatments was 0.8 kg/milking. Milking unit on-time, which represents the time when the milking unit is under normal pulsation and harvesting milk (excluding the high-vibration pulsation time of 30 or 90 s), was shortest (245 s) for cows subjected to 90 s of high-vibration pulsation (HV90) and ranged from 256 to 261 s for all other treatments. Milk harvest may have begun during high-vibration pulsation; however, only 0.13 and 0.32 kg of milk was harvested during high-vibration pulsation for HV30 and HV90, respectively. The incidence of bimodal milk curves was lowest for FD90 (7%) and highest for T0 (21%). The somatic cell count was <72×10(3) cells/mL for all treatments. Residual milk obtained by giving 10 IU of oxytocin in the jugular vein followed by 2 min of milking unit attachment represented 12 to 14% of the total milk and did not differ among treatments. Endogenous oxytocin profiles peaked between 12.4 and 18.3 pg/mL for all treatments, and the peak occurred sooner in manually stimulated cows; however, we detected no difference in oxytocin concentration beyond 2 min after milking unit attachment. High-vibration pulsation elicited a similar oxytocin release when taking the start time of stimulation from manual stimulation or high vibration into consideration. Forestripping for visual observation of milk combined with the use of high-vibration stimulation may reduce variation in the milking routine. A predetermined lag time with minimal variation may be achieved via the time spent in high-vibration stimulation instead of a lag period dictated by milking personnel., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Some strains of sporeforming bacteria (e.g., Bacillus spp. and Paenibacillus spp.) can survive pasteurization and subsequently grow at refrigeration temperatures, causing pasteurized fluid milk spoilage. To identify farm management practices associated with different levels of sporeformers in raw milk, a bulk tank sample was obtained from and a management and herd health questionnaire was administered to 99 New York State dairy farms. Milk samples were spore pasteurized [80°C (176°F) for 12 min] and subsequently analyzed for most-probable number and for sporeformer counts on the initial day of spore pasteurization (SP), and after refrigerated storage (6°C) at 7, 14, and 21 d after SP. Management practices were analyzed for association with sporeformer counts and bulk tank somatic cell counts. Sixty-two farms had high sporeformer growth (≥3 log cfu/mL at any day after SP), with an average sporeformer count of 5.20 ± 1.41 mean log10 cfu/mL at 21 d after SP. Thirty-seven farms had low sporeformer numbers (<3 log cfu/mL for all days after SP), with an average sporeformer count of 0.75 ± 0.94 mean log10 cfu/mL at 21 d after SP. Farms with >25% of cows with dirty udders in the milking parlor were 3.15 times more likely to be in the high category than farms with ≤10% of milking cows with dirty udders. Farms with <200 cows were 3.61 times more likely to be in the high category than farms with ≥200 cows. Management practices significantly associated with increased bulk tank somatic cell count were a lack of use of the California mastitis test at freshening and >25% of cows with dirty udders observed in the milking parlor. Changes in management practices associated with cow cleanliness may directly ensure longer shelf life and higher quality of pasteurized fluid milk., (Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Premilking udder preparation (including forestripping and duration of lag time-the time between first tactile stimulation and attachment of milking unit) might influence milking measures such as milking unit on-time, incidence of bimodality, and milk flow rates in Holstein cows milked 3 times daily. Holstein cows (n=786) from an 1,800-cow commercial dairy herd were enrolled under a restricted randomized design to determine the effect of 9 different premilking routines. Lag times were 0, 60, 90, 120, and 240s and included forestripping or no forestripping for a total of 9 treatments (no forestripping for 0 lag time); the study was conducted from February to November 2008. All cow-treatment combinations were compared with the control: predipping plus forestripping and drying with 90s of lag time. Cows were initially assigned to 1 of 3 treatments for a period of 7d and upon completion of the first 7-d period were reassigned to a different treatment until all treatments had been completed. From one treatment period to the next, cows had to switch stimulation method with no restriction on lag time. Cows did not receive all treatments during the duration of the trial. Early- to mid-lactation cows (EML; 17-167 DIM) and late-lactation cows (LL; 174-428 DIM) were housed in 2 different pens. Milk yield was significantly different between dip + forestrip and dip+dry for 2 of the treatments for EML cows compared with dip + forestrip and 90 s of lag-time (DF90); however, this was not thought to be due to treatment because the significant lag times were very different (60 and 240 s) and neither was an extreme value. Milk yield did not differ with treatment for the LL cows. Milking unit on-time did not differ when comparing all treatments for EML with treatment DF90; however, an increase in milking unit on-time occurred when lag time was 60s or less for LL cows. The highest incidence of bimodal milk curves was when lag time = 0 and this was independent of stage of lactation; a lag time of 240 s had the second-highest incidence of bimodal milk curves for EML and LL cows. Milk harvested in the first 2 min was lower for lag times of 0 and 240 s when compared with DF90. Increasing the lag time for all cows appeared to improve overall milking time efficiency (although lag time had no effect on EML cows)., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Fertility of dairy cows has decreased for the past several decades. Measures of energy balance (EB; e.g., change in EB, EB nadir, cumulative negative EB, or duration of negative EB) are related to reproductive performance. Our research group has concluded that modification of diets fed during the dry or transition period are unlikely to have significant effects on postpartum EB and fertility. Rather, more radical alterations in dairy management are needed if energy status of postpartum cows is to be improved. We have examined the potential to alter EB by shortening or eliminating the dry period. In an initial study, the effects of a 56, 28, and 0 d dry period on ovarian dynamics and reproductive performance of dairy cows were examined. Postpartum EB was improved by reducing the dry period; however, only significantly for the 0 d dry period. Cows on the 0 d dry period did not experience negative EB. Improvements in EB were a reflection of lower milk production and greater feed intake. Consistent with the improvements in EB, time to first ovulation and first service, first service conception rate, services per conception, and days open were all improved by reduction of dry period length. Because small animal numbers were used in the study, a second study was conducted on a commercial dairy with many more animals to determine if results from the initial trial could be duplicated. A comparison was made between a 55 and 34 d dry period. Shortening the dry period resulted in fewer days to first ovulation, fewer days open, and a greater percentage of cows pregnant at 150 days in milk, although the improvements in the latter two variables were only significant for cows in their third or greater lactation. A current study is being performed in a large commercial dairy to examine the effects of eliminating the dry period on reproduction utilizing a large commercial dairy.

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results.

Holstein cows (n = 781) in a commercial dairy herd were used in a randomized design to evaluate 2 dry period (DP) management strategies on milk production, milk components, milk quality, colostrum quality, and incidence of metabolic disorders. Cows were randomly assigned to a traditional 55 d (T) or shortened 34 d (S) DP. Cows assigned to T were fed a low-energy diet until 34 d before expected calving at which time all cows were fed a moderate-energy transition diet until calving. Postpartum, cows assigned to T produced more milk and tended to produce more solids-corrected milk than cows on S. Treatment differences in milk and solids-corrected milk yield were accounted for by cows in their second lactation. Milk fat percentage did not differ between treatments, but milk protein percentage was greater for cows assigned to S. Colostrum quality measured as IgG concentration did not differ between management strategies. Somatic cell score and cases of mastitis were not affected by management strategy. There was a tendency for prepartum nonesterified fatty acid (NEFA) to be lower for cows assigned to T compared with S. However, postpartum, cows assigned to S had significantly lower NEFA concentrations than those assigned to T. The incidences of ketosis, retained placenta, displaced abomasum, and metritis did not differ between treatments. Postpartum energy balance, as indicated by plasma NEFA, may have been improved for cows assigned to S; there was no detectable effect on animal health.

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