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Commercially available intravaginal progesterone (P4) devices differ in shape, surface area and P4 load, which may affect the resulting pregnancy per AI (P/AI) following timed-AI (TAI). The objective of this study was to compare two intravaginal P4 devices on estrus rate, follicular dynamics and P/AI in beef cattle subjected to shortened-TAI protocols. In Expt. 1, nulliparous heifers were randomly assigned to a P4-releasing intravaginal device (PRID-Delta, 1.55 g P4) or a controlled internal drug release (CIDR, 1.38 g P4) at the initiation of a J-synch protocol. Heifers that displayed estrus 72 h following device removal were TAI, or if not in estrus given GnRH at 72 h and TAI at 90 h. In Expt. 2, nulliparous heifers and non-suckling cows were randomly assigned to either PRID or CIDR groups and either 1 or 2 mg of estradiol benzoate (EB) at initiation of a J-synch protocol. All cattle were TAI concurrent with GnRH 72 h after device removal. In Expt. 3, nulliparous heifers and suckling cows were randomly assigned to either PRID or CIDR groups and initiated a 5-d Cosynch protocol, with TAI concurrent with GnRH 72 h following device removal. In each experiment, cattle received estrus detection patches at device removal, which were then scored from 0 to 3 based on color change between initial application and TAI; 0 = unchanged, 1 = ≤50% change, 2 = >50% change, 3 = missing. Estrus was defined to have occurred when the patch was scored 2 or 3. Transrectal ultrasonography was used to determine cyclicity, diagnose pregnancy in all experiments, and the size of the ovulatory follicle in Expt. 3. In Expt. 1, the estrus rate was greater (72.0% vs. 61.0%; P = 0.04) in the PRID compared to the CIDR group. In Expt. 2, a parity by EB dose interaction (P = 0.02) was attributed to an increased estrus rate (52.8% vs. 41.4%; P = 0.05) in heifers given 1 vs. 2 mg EB. In Expt. 3, there was no difference in the ovulatory follicle diameter at device removal (P = 0.22) or TAI (P = 0.28) between P4 groups. Treatment with a PRID tended (P = 0.10) to increase the P/AI in cows compared to a CIDR (73.5% vs. 61.0%). In all experiments combined, the overall P/AI tended to increase (55.2% vs. 51.0%; P = 0.08) and P/AI in cattle exhibiting estrus increased (64.4% vs. 59.7%; P = 0.02) in cattle given a PRID compared to those given a CIDR, respectively. In summary, the type of intravaginal P4 device affected estrus response and P/AI following TAI in beef cows.

The objective was to optimize fertility in a modified 5-d CO-Synch protocol by altering the timing of GnRH administration and AI. Holstein heifers (14-16 mo) received a controlled internal drug releasing device (CIDR) on d 0 and on d 5, CIDR were removed, prostaglandin F2α was administered and estrus detection patches were applied. Estrus was detected at 36, 48, 56 and 72 h after CIDR removal. In Experiment 1, control heifers (n = 195) received GnRH concurrent with timed-AI (TAI) 72 h after CIDR removal, regardless of expression of estrus. Treatment heifers expressing estrus at 36 or 48 h were AI at 56 h (n = 101) and the remaining heifers were randomly assigned to one of two groups: GnRH administration at 56 h and TAI at 72 h (GnRH56, n = 147) or GnRH administered concurrently with TAI at 72 h (GnRH72, n = 148). In Experiment 2, heifers expressing estrus at 36 or 48 h following CIDR removal were AI at 56 h (n = 118) and the remaining heifers were either TAI at 72 h (TAI72, n = 102) or 80 h (TAI80, n = 102), with only heifers not displaying estrus by TAI given GnRH concurrent with AI. All heifers were inseminated with sex-sorted semen and pregnancy diagnosis was performed at 28 d following TAI. In Experiment 1, estrus rate (P = 0.81) and pregnancy per AI (P/AI; P = 0.34) did not differ among control, GnRH56 and GnRH72 groups, so GnRH56 and GnRH72 groups were combined into one split-TAI (STAI) group. The P/AI was greater in heifers displaying estrus by 48 h compared to those not displaying estrus and receiving GnRH in both groups (69.5 vs. 31.3%; P 0.01) and there was a tendency for P/AI to increase in STAI heifers displaying estrus compared to control heifers displaying estrus (73.3 vs. 62.1%; P = 0.10). In Experiment 2, the estrus rate was increased in TAI80 compared to TAI72 heifers (81.4 vs. 62.7%, P 0.01); however, there was no difference in P/AI (P = 0.74). Heifers displaying estrus in the TAI72 group had a greater P/AI than heifers not displaying estrus in either group (P 0.01) and tended to have a greater P/AI than heifers in estrus in the TAI80 group (87.5 vs. 69.9%, P = 0.07). Across both experiments, P/AI was increased in heifers that displayed estrus before AI compared with heifers that did not and performing a STAI tended to increase P/AI in heifers that displayed estrus before AI. Other attempts made to optimize P/AI in the modified 5-d CO-Synch protocol by altering the timing of GnRH administration and/or AI were unsuccessful.

To understand the mechanisms underlying the inverse relationship between anogenital distance (AGD) and fertility in dairy cattle, we determined if embryo yield and quality differed between cattle of short- and long-AGD (Study 1), and whether anti-Müllerian hormone (AMH), antral follicle count (AFC) and superovulation responses differed by AGD group (Study 2). In Study 1, records of embryo yield and quality in Holstein heifers (n = 43) and cows (n = 14) from two commercial dairy herds were analyzed, retrospectively. Short- and long-AGD groups were based on the median AGD cut-points of 113 and 134 mm, for heifers and cows, respectively. The mean numbers of total (7.4 vs. 9.0; 9.4 vs.12.9), fertilized ova (5.6 vs. 6.2; 6.6 vs. 6.9), and viable embryos (4.4 vs. 4.8; 5.9 vs. 5.3) per heifer and cow did not differ between cattle of short vs. long AGD. Short-AGD cows, however, had greater proportions of fertilized ova (69.7 vs. 53.3%; P = 0.07) and viable embryos (62.1 vs. 41.1%; P = 0.03) than long-AGD cows. The odds of short-AGD cows yielding fertilized ova and viable embryos were 2.0 and 4.0 times greater, respectively, than the odds of long-AGD cows. In Study 2, lactating cows (n = 24) of a research herd had their AGD categorized as in Study 1, and AFC, AMH, and superovulation responses (i.e., no. of preovulatory follicles [≥ 10 mm] and CL) were determined. Mean AFC (27 ± 4.5 vs. 21 ± 4.0) and CL (9 ± 1.6 vs. 7 ± 1.4) per cow did not differ between short- and long-AGD groups. Serum AMH concentration (pg/mL) was lesser in short-AGD cows compared with long-AGD cows (114 ± 30.4 vs. 200 ± 26.8; P = 0.05), but the no. of preovulatory follicles was greater (15 ± 1.9 vs. 8 ± 1.7; P = 0.01) in short-AGD than in long-AGD cows. The overall proportion of follicles ≥10 mm was also greater in short-AGD cows than in long-AGD cows (56 vs 44%; P = 0.03). Preovulatory follicle number was affected by a parity x AGD group interaction (P = 0.04), with multiparous short-AGD cows accounting for the largest number of follicles. No associations were found among AGD, AFC and AMH. The associations between AFC and superovulation responses (follicles: r = 0.67, and CL: 0.58; P 0.01) were moderate but AMH was not associated with superovulation responses. In summary, whereas AGD-associated differences in the yield and quality of embryos were not evident in heifers, the proportions of fertilized ova and viable embryos were greater in short-AGD than in long-AGD cows. In addition, the proportion of preovulatory follicles, an indicator of superovulatory response, was greater in short-AGD cows than in long-AGD cows.

The inverse association between anogenital distance (AGD; the distance from the center of the anus to the base of the clitoris) and fertility, its moderate heritability, and high variability reported in dairy cattle make AGD a promising candidate for further exploration as a reproductive phenotype. In addition to heritability, repeatability (i.e., consistency in measurements taken at different time points) is important for a reproductive phenotype to be considered useful in genetic selection. Therefore, our primary objective was to determine the repeatability of AGD from birth to breeding age (≈16 mo) in Holstein heifer calves, and during different stages of the estrous cycle, gestation, and lactation in Holstein cows. We also determined the associations among AGD, height (at the hip), and body weight (BW) at birth. In calves (n = 48), we recorded BW (kg) and height (cm) at birth and measured AGD (mm) at approximately 0, 2, 6, 9, 12, and 16 mo of age. In cows, AGD was measured at different stages of the estrous cycle (proestrus, estrus, metestrus and diestrus; n = 20), gestation (30, 90, 180, and 270 d; n = 78), and lactation (30-300 d in milk in 30-d increments; n = 30). Calf height and BW at birth had a weak positive association with AGD at birth. The AGD increased linearly from birth to breeding age, but there was no association between the AGD at birth and at breeding age in heifers. Although any 2 consecutive AGD measurements were correlated, 6 mo was the earliest age at which AGD was moderately correlated (r = 0.41) with that of breeding-age heifers. The AGD was neither influenced by the different stages of estrous cycle nor lactation and remained highly repeatable (r ≥ 0.95). Although AGD measurements at 30, 90, and 180 d of gestation (126.9, 126.7, and 127.7 mm, respectively) were strongly correlated (r ≥ 0.97) with each other, AGD at 270 d of gestation (142.8 mm) differed from AGD at all earlier stages of gestation. In summary, AGD measured at birth did not reflect AGD at breeding age in heifers, but AGD measurements in cows had high repeatability at all stages of the estrous cycle, gestation, and lactation, except at 270 d of gestation. Therefore, AGD could be measured reliably at any of the aforesaid physiological states in cows due to its high repeatability, except during late gestation. The earliest gestational stage when pregnancy-associated increase in AGD occurred, however, could not be definitively established in the present study.

The objective was to compare pregnancy per AI (P/AI) between two shortened timed-AI (TAI) protocols in beef cattle. This study also determined whether administration of eCG in heifers and timing of AI in cows would affect P/AI. Cattle were submitted at random to either a modified 5-d Co-synch protocol (Day 0 = progesterone releasing device (CIDR); Day 5 = CIDR removal and 500 μg of cloprostenol (PGF); Day 8 = 100 μg GnRH concurrent with AI) or J-synch protocol (Day 0 = CIDR insertion and 2 mg of estradiol benzoate i.m.; Day 6 = CIDR removal and 500 μg PGF; Day 9 = 100 μg GnRH concurrent with AI). In Experiment 1, 1135 heifers (13-15 mo of age) received an estrus detection patch (Estrotect™) on Day 5 and 579 were selected at random to receive 300 IU of equine chorionic gonadotropin (eCG) at the time of CIDR removal. Patches were scored from 0 to 3 based on color change between initial application and AI; 0 = unchanged, 1 = ≤ 50% change, 2 =50% change, 3 = missing. Estrus was defined to have occurred when the patch was scored 2 or 3. In Experiment 2, 399 cyclic, non-lactating beef cows from 1 location were submitted to either the modified 5-d Co-synch or J-synch protocol and within each protocol cows were TAI at either 66 ± 1 (n = 199) or 72 ± 1 h (n = 200) following CIDR removal. Transrectal ultrasonography was used in both experiments to determine presence of a corpus luteum (CL) on Day 0, and to diagnose pregnancy 35 d after TAI. In Experiment 1, eCG increased estrus rate only in heifers without a CL on day 0 that were submitted to the modified 5-d Co-synch protocol (41.9 vs. 69.6%). Heifers submitted to the J-synch protocol had greater (P = 0.03) P/AI compared with those in the modified 5-d Co-synch (48.7 vs. 41.1%) and heifers that expressed estrus before AI had increased (P 0.0001) P/AI compared to those that did not (53.6 vs. 36.5%). Administration of eCG and presence of a CL tended to affect P/AI (P = 0.13). In Experiment 2, cows submitted to the J-synch protocol tended (P = 0.07) to have greater P/AI compared to those in the modified 5-d Co-synch (74.1 vs. 66.5%). There was no association between P/AI and timing of AI. In summary, the J-synch protocol resulted in greater P/AI than the modified 5-day Co-synch protocol in heifers and cows. Administration of eCG increased estrus rate in heifers without a CL at the start of the protocol and tended to improve P/AI in all heifers. Timing of AI (66 vs. 72 h) had no effect on P/AI in cows subjected to either TAI protocol.

Objectives were to (1) identify factors associated with postpartum body condition (BCS) maintenance/gain, (2) determine the optimum pre-calving BCS predictive of postpartum BCS maintenance/gain, and (3) evaluate the relationship between postpartum BCS change categories, serum analytes and performance in dairy cows. The BCS were determined in 271 primiparous and 640 multiparous cows from 11 dairy herds in Alberta, Canada at (mean ± SD) 9.0 ± 2.3 d pre-calving and at 34.6 ± 4.0 d post-calving, using a 5-point scale with 0.25 increments. Cows were grouped into BCS change categories according to BCS change between post- and pre-calving as follows: lost ≥ 0.75 units (extreme loss; EL; n = 343), lost either 0.25 or 0.50 units (moderate loss; ML; n = 390), no change in BCS (maintained; M; n = 104), or gained ≥ 0.25 units (gained; G; n = 74). In a subset of 178 cows, the concentrations of glucose, beta-hydroxybutyrate, non-esterified fatty acids, urea, cholesterol, haptoglobin and aspartate aminotransferase were measured in serum at 9.0 ± 2.3 d pre-calving and at 8.2 ± 3.7 d post-calving. The proportion of cows grouped into EL, ML, M and G categories were 38, 43, 11 and 8%, respectively. Pre-calving BCS, season of calving and sickness were identified as factors associated with BCS maintenance/gain. The optimum pre-calving BCS predictive of postpartum BCS maintenance/gain was 3.25 for primiparous cows and 3.00 for multiparous cows. Mean serum concentration of beta-hydroxybutyrate, urea, cholesterol and haptoglobin did not differ among BCS change categories. However, G cows tended to have greater mean serum concentration of glucose compared with ML cows, and mean serum concentration of aspartate aminotransferase tended to be greater for EL cows compared with other BCS change categories. Mean serum concentration of non-esterified fatty acids was greater post-calving for EL cows compared with other BCS change categories. Milk yield by 25 and 90 days in milk (DIM) did not differ among BCS change categories; however, peak and 305-d mature equivalent milk yields were greater for EL compared with G cows. Overall, EL cows had reduced fertility compared with other BCS change categories, including a smaller proportion of cows with a corpus luteum by 35 DIM, reduced pregnancy to first AI and pregnancy by 150 DIM, and reduced hazard ratio of pregnancy risk up to 250 DIM. In summary, EL cows had reduced fertility compared with other BCS change categories and increased milk yield compared with G cows. Ensuring cows calve at an appropriate BCS to promote BCS maintenance, or only moderate loss, will improve fertility without sacrificing milk yield.

The objective of this study was to compare the economic performance of an ear tag automated activity monitor system (AAM) versus a timed-AI (TAI) protocol in Holstein heifers. In total, 340 heifers were enrolled onto the study at 13.5 mo of age and randomly assigned to receive either an AAM (n = 170) or TAI (n = 170) protocol before breeding eligibility (D 0). Heifers in the AAM group were fitted with an ear tag AAM and bred based on high activity alert from the system. Heifers in the TAI group received a progesterone releasing intravaginal device on D −8, followed by device removal and prostaglandin on D −3 and gonadotropin-releasing hormone with TAI on D 0. In both treatments, the majority of heifers received sex-sorted semen for the first AI and conventional semen for subsequent AIs, with three opportunities to become pregnant. All heifers were diagnosed for pregnancy approximately 25 d post AI using transrectal ultrasonography, with confirmation at 30 and 45 d. Non-pregnant heifers in the TAI group, were resynchronized using the same TAI protocol. A partial budget was used to compare the costs and benefits of switching from a TAI to an AAM protocol in heifers, including protocol, labour, and rearing costs for each treatment, as well as estimated calf and milk value. Sensitivity analyses were also conducted to determine the effect of pregnancy per AI (P/AI), outsourcing AI, AAM tag cost and herd size on the net outcome. There was no difference in overall P/AI or days to pregnancy between treatments. However, number of AI was greater in the TAI than the AAM group. For the first AI, the P/AI was less in the TAI compared to the AAM group; however, the interval to first AI was less in TAI. There was minimal difference in performance for the second and third AI. There was a net gain of $11.97 per heifer when switching from a TAI to AAM protocol, due to the increased P/AI to the first AI and reduced cost of hormones. Several variables in the sensitivity analyses affected the net outcome. Considering only the first AI, switching to an AAM collar and a larger herd size all increased the net gain. Considering a greater P/AI to the first AI in the TAI group, outsourcing AI, using more AAM ear tags, and smaller herd sizes resulted in a net loss when switching from TAI to AAM. The AAM system resulted in exceptional P/AI and may be an economically viable alternative to improve heifer reproductive efficiency in herds with suboptimal P/AI to TAI.

Anogenital distance (AGD) has been defined in dairy cows as the distance from the center of the anus to the base of the clitoris. Initial reports on nulliparous Holstein heifers and first- and second-parity Holstein cows have found inverse relationships between AGD and measures of fertility. Our primary objective was to determine the relationship between AGD and measures of fertility in a larger population of North American Holstein cows to validate our previous finding that AGD is inversely related to fertility. Secondary objectives were to determine the associations between AGD and parity, and milk yield. Using digital calipers, we measured AGD in 4,709 Holstein cows [mean ± standard deviation (SD); parity 2.3 ± 1.4; days in milk (DIM) 154 ± 94; 305-d mature equivalent (ME) milk yield 13,759 ± 2,188 kg] from 18 herds in Western Canada and 1 herd in the USA. Anogenital distance (mm) was normally distributed with a mean (±SD) of 132 ± 12, ranging from 95 to 177, and a median of 133. Anogenital distance was linearly but inversely associated with pregnancy to first artificial insemination (P/AI1). For every 1-mm increase in AGD, the estimated probability of P/AI1 decreased by 0.8%. The optimum AGD cut-point that predicted probability of P/AI1 with sensitivity and specificity of 45 and 55%, respectively, was 129 mm. Consequently, data were categorized into either short (≤129) or long (129) AGD groups across parities, and associations between AGD, parity (first, second, and third+), and fertility measures were determined. Rates of P/AI1 were greater (36 vs. 30%) in short- than in long-AGD cows; short-AGD cows required fewer AI per conception (2.3 vs. 2.4) and had fewer days open (137 vs. 142), and a greater proportion of short-AGD cows (67 vs. 64%) was pregnant by 150 DIM compared with long-AGD cows. The rates of pregnancy up to 150 (hazard ratio of 0.91) and 250 DIM (hazard ratio of 0.93) were smaller in long- than in short-AGD cows. Anogenital distance had a weak positive association with both parity (r = 0.22) and 305-d ME milk yield (r = 0.04). Results indicate an inverse relationship between AGD and measures of fertility in lactating cows, validating our earlier report. We infer that although selecting cows for short AGD is expected to have an adverse effect on milk yield, the anticipated gain in fertility will outweigh the small decline in milk yield, strengthening the potential of AGD as a novel reproductive phenotype for use in future breeding programs to improve fertility.

Anogenital distance (AGD), defined as the distance from the center of the anus to the base of the clitoris, in lactating dairy cows of first and second parity, has been reported to be inversely related to fertility and moderately heritable. Thus, AGD may be a useful reproductive phenotype for future genetic selection to improve fertility. The objectives of this study were to (1) characterize AGD in nulliparous dairy heifers; and (2) determine if the inverse relationship between AGD and fertility, found in lactating dairy cows, is also evident in nulliparous heifers. We measured AGD in 1,692 Holstein heifers from 16 herds in Western Canada (Alberta and British Columbia) and one herd in the United States (Washington State). Data were analyzed using MEANS, UNIVARIATE, LOGISTIC, ROC, GLIMMIX, and LIFETEST procedures of SAS (SAS Institute Inc.). Mean (±standard deviation) age at AGD measurement was 13.9 ± 1.5 mo, and AGD was normally distributed with a mean of 107.3 ± 10.5 mm, ranging from 69 to 142 mm. With every 1-mm increase in AGD, the predicted probability of pregnancy was reduced by 1.9%. Receiver operating characteristic curve analysis was used to determine the optimum threshold AGD that predicted the probability of pregnancy. Based on the optimum threshold AGD, data from heifers were categorized into short (≤110 mm) and long (>110 mm) AGD groups, and associations between AGD groups and fertility measures were determined. Heifers with short AGD required fewer services per conception (1.5 vs. 1.7) than heifers with long AGD. Consequently, heifers with short AGD conceived earlier (448.4 vs. 454.3 d) and had greater pregnancy to first AI than those with long AGD (58.3 vs. 49.6%). Moreover, heifers with long AGD had reduced hazard (hazard ratio of 0.59) for pregnancy up to 450 d of life compared with those with short AGD. In summary, AGD was normally distributed and highly variable in the population. In addition, an inverse relationship between AGD and fertility measures in nulliparous heifers was evident, confirming an earlier report of a similar relationship in lactating dairy cows. These findings strengthen the potential for AGD to be used as a fertility trait and management tool in future selection programs.

Our objectives were to characterize parameters of luteal activity based on milk progesterone concentration (P4c) data from before and after artificial insemination (AI) and to evaluate their potential association with fertility in Holstein cows. Records of AI events (n = 4,353) and of milk P4c (n = 158,961) obtained through an in-line milk analysis system (Herd Navigator, DeLaval International, Tumba, Sweden) from 1,891 lactations of 1,423 Holstein cows were evaluated. Milk P4c (ng/mL) were measured every 2.2 ± 1.9 d (mean ± standard deviation) between 23.6 ± 7.3 and 185.3 ± 56.7 d in milk. Variations in milk P4c of consecutive records were used to determine onset of luteal phase (increase in P4c from5.0 to ≥5.0 ng/mL), luteal phase length (period, in days, of P4c ≥5.0 ng/mL), cessation of luteal phase (decline from ≥5.0 to5.0 ng/mL, designated as P4c-decline), and pregnancy (AI followed by a luteal phase that remained uninterrupted until 50 d post-AI). The length of the luteal phase preceding AI, the highest P4c (P4c peak) during the luteal phase preceding AI, the lowest P4c preceding AI (P4c pre-AI) that followed a P4c-decline, and the interval between P4c-decline and AI were evaluated, as well as the interval between AI and onset of luteal phase, and P4c at early diestrus (4.5 ± 0.6 d post-AI), mid diestrus (10.0 ± 0.6 d post-AI), and late diestrus (14.1 ± 0.6 d post-AI). Data were analyzed using logistic regressions, and comparisons made based on quartiles and cut-points established by receiver operating characteristic curve analysis. Overall probability of pregnancy was 32.0%. Parameters associated with reduced probability of pregnancy (represented as percentage points decrease in the probability of pregnancy) were (1) luteal phase length14.4 d (7.6% decrease), (2) P4c peak ≤24.7 ng/mL (4.5% decrease), (3) P4c pre-AI0.5 ng/mL (5.5% decrease), (4) interval between P4c-decline and AI of1.6 d (4.0% decrease), (5) interval between AI and onset of luteal phase of7 or11 d (9.3 and 12.1% decrease, respectively), and (6) P4c at early diestrus ≤0.7 or3.5 ng/mL (15.2 and 6.7% decrease, respectively), (7) P4c at mid diestrus ≤12.4 ng/mL (12.5% decrease), and (8) P4c at late diestrus ≤22.7 ng/mL (9.7% decrease). The parameters of luteal activity associated with reduced probability of pregnancy established here could be used as benchmarks while developing recommendations to improve reproductive performance in herds using in-line milk progesterone monitoring.

The objectives of this study were to evaluate the performance of the SCR eSense ear tag automated activity monitor (AAM) to detect estrus behavior in Holstein heifers and to determine the optimal time from estrus alert to artificial insemination (AI) using sex-sorted or conventional semen. In total, 281 heifers were fitted with the AAM once eligible for breeding (13.5 m of age). For the first AI, estrus was synchronized using 500 μg of cloprostenol (PGF), given 14 d apart, and heifers were given estrus detection patches (Estrotect™) after the second PGF. Heifers were inseminated at randomly attributed times after high activity alert from the AAM system or if the estrus patch had ≥ 50% colour change. Most heifers received sex-sorted semen for the first AI and conventional semen for subsequent inseminations. Pregnancy diagnosis was performed at 30 d post AI and heifers had four opportunities to become pregnant. In a subset of heifers (n = 149), ovaries were scanned every 12 h from the time of AI until ovulation (OV). The system recorded a heat index (measure of estrus strength), maximum activity change, maximum rumination change and duration of high activity. The sensitivity was 91.0%, with a false positive and false negative rate of 8.0%, and the positive predictive value to detect true estrus events was 83.5%. Pregnancy per AI to first AI was 67.6% and 97.9% of heifers become pregnant after four inseminations. Most false positive estrus events had a heat index45 and a rumination change -20, while false negative events had a rumination change ≥ -20. Odds of pregnancy was not associated with any estrus characteristics measured by the system. However, pre-ovulatory follicle diameter had a weak correlation (r 0.25) with all estrus characteristics. The average (range) interval of onset of high activity, peak activity and end of high activity to OV was 28 h (16-46 h), 22 h (10-40 h) and 16 h (0-36 h), respectively. For conventional semen, each hour increase in interval from activity onset or peak activity to AI reduced the predicted probability of pregnancy by 3.8 and 4.2%, respectively. For sex-sorted semen, the relationship between activity onset or peak activity to AI and predicted probability of pregnancy was quadratic, but not significant. Overall, the SCR eSense ear tag AAM performed well and strategies to identify false positive and false negative estrus events, along with optimization of timing of AI, should further improve performance in Holstein heifers.

peer-reviewed The objectives of this study were to (1) evaluate factors associated with variation in circulating anti-Müllerian hormone (AMH) concentrations, (2) establish an optimum AMH threshold predictive of pregnancy to first artificial insemination (P/AI), (3) examine the relationship between AMH and fertility (P/AI, pregnancy loss between 30 and 60 d after artificial insemination, and pregnancy risk up to 250 d postpartum), and (4) identify quantitative trait loci associated with phenotypic variation of AMH concentrations in dairy cows. Serum AMH concentrations (pg/mL) were determined at 7 ± 2.4 d postpartum in 647 lactating Holstein cows (213 primiparous, 434 multiparous) from 1 research and 6 commercial dairy herds in Alberta, Canada. Of these, 589 cows were genotyped on the 26K Bovine BeadChip (Neogen Inc., Lincoln, NE) and subsequently imputed to the Illumina Bovine High Density BeadChip (Illumina, San Diego, CA) for genome-wide association analysis for variation in serum AMH concentrations. Factors associated with variation in serum AMH concentrations and the relationship between categories of AMH and aforementioned fertility outcomes were evaluated only in a subset of 460 cows that had a complete data set available. The overall mean (±standard error of the mean), median, minimum, and maximum AMH concentrations were 191.1 ± 6.3, 151.7, 13.9, and 1,879.0 pg/mL, respectively. The AMH concentrations were not associated with herd, precalving body condition score, postpartum week, and season of sampling; the lactation number, however, had a quadratic relationship with serum AMH concentrations (116.2, 204.9 204.5, and 157.9 pg/mL for first, second, third, and ≥fourth lactation, respectively). The optimum AMH threshold predictive of P/AI could not be established because the receiver operating characteristic curve analysis model was nonsignificant. Categories of AMH [low (285.0 pg/mL; n = 92) based on lowest 20%, intermediate 60%, and highest 20% serum AMH) had no associations with P/AI (34, 43, and 40%), pregnancy loss between 30 and 60 d after artificial insemination (20, 12, and 8%), or pregnancy risk up to 250 d postpartum. One candidate gene associated with AMH production [AMH gene on Bos taurus autosome (BTA) 7] and 4 candidate genes related to embryo development (SCAI and PPP6C genes on BTA11 and FGF18 and EEF2K genes on BTA20 and BTA25, respectively) were in linkage disequilibrium with single nucleotide polymorphisms associated with phenotypic variation in serum AMH in dairy cows.

The objective of this study was to evaluate the use of a cow-side device (FreeStyle Precision Neo™) to diagnose ketosis and hypoglycemia based on measures of blood β-hydroxybutyrate (BHBA) and glucose. Eleven commercial dairy farms were visited and blood samples were taken from Holstein cows between 2 and 14days in milk, yielding 441 samples for BHBA analysis and 308 samples for glucose analysis. Concentrations of BHBA and glucose were measured in two ways, 1) using the cow-side device with whole blood immediately after sampling and 2) serum samples analyzed with a standard laboratory assay (Animal Health Laboratory, University of Guelph, Canada). The accuracy of the device was determined by comparing the results to the laboratory method as well as the ability to diagnose ketosis (BHBA ≥1.2mmol/L) and hypoglycemia (glucose

The objectives were to evaluate differences in circulating prepartum metabolites, minerals, cytokines and hormones based on postpartum disease category and determine critical circulating concentrations of prepartum analytes associated with postpartum disease in 229 cattle from 11 commercial dairies in Alberta, Canada. Blood was collected at 8.8 ± 2.1 d prepartum and analyzed for a wide array of analytes. Cattle were categorized as healthy (n = 76) or as having inflammatory (INF; n = 28), metabolic (MET; n = 34) or inflammatory and metabolic (INFMET; n = 91) postpartum diseases. The prepartum circulating concentrations of Cu were lesser (0.84 vs. 0.90 μg/mL; P = 0.02) and concentrations of Mo (19.1 vs. 16.5 ng/mL; P = 0.04) and NEFA (0.27 vs. 0.18 mmol/L; P = 0.01) were greater in INFMET cattle compared with healthy cattle. The critical threshold for Cu, Mo and NEFA prepartum concentration that predicted INFMET was ≤ 0.81 μg/mL (sensitivity 45.5% and specificity 74.3%), ≥ 9.91 ng/mL (sensitivity 70.0% and specificity 52.7%) and ≥ 0.19 mmol/L (sensitivity 62.2% and specificity 79.7%), respectively. Regardless of differences in the prepartum circulating concentrations of Cu, Mo and NEFA among healthy cattle and those with postpartum disease, the use of these analytes to predict the incidence of postpartum diseases was limited.

peer-reviewed The objectives of this study were to (1) characterize the distribution and variability of plasma anti-Müllerian hormone (AMH) concentration; (2) evaluate factors associated with phenotypic variation in plasma AMH; (3) examine the associations between categories of plasma AMH and reproductive outcomes [pregnancy to first artificial insemination (P/AI), and pregnancy rates within 21, 42, and 84 d after the mating start date (MSD)]; (4) estimate pedigree and genomic heritability for plasma AMH; and (5) identify and validate SNP associated with phenotypic variation in plasma AMH. Plasma AMH concentration (pg/mL) was determined from a blood sample collected (mean ± standard deviation) 10 ± 2 d after first insemination at detected estrus (IDE) in 2,628 first- and second-parity Irish dairy cows. Overall, plasma AMH had a positively skewed distribution with mean (± standard deviation), median, minimum, and maximum concentrations of 326 ± 231, 268, 15, and 2,863 pg/mL, respectively. Plasma AMH was greatest for Jersey, followed by Holstein × Jersey, Holstein × Norwegian Red, and Holstein cows (410, 332, 284, and 257 pg/mL, respectively). Second-parity cows had greater plasma AMH than first-parity cows (333 vs. 301 pg/mL, respectively). Samples collected at 7 and 8 d after first IDE had lesser plasma AMH than those collected on d 9, 10, 11, 12, and 13 after first IDE (291 and 297 vs. 317, 319, 331, 337, and 320 pg/mL). Plasma AMH was not associated with either body condition score at first IDE or the interval from calving to MSD. Cows were categorized into low (≤150 pg/mL; n = 526; lowest 20%), intermediate (>150 to ≤461 pg/mL; n = 1,576; intermediate 60%), and high AMH (>461 pg/mL; n = 526; highest 20%) groups based on plasma AMH, and associations with reproductive outcomes were tested. Cows with high and intermediate plasma AMH had 1.42- and 1.51-times-greater odds of becoming pregnant within 84 d after the MSD than those with low plasma AMH (90.3 and 90.8 vs. 86.8%, respectively); however, P/AI and pregnancy rate within 21 and 42 d after the MSD did not differ among AMH categories. Plasma AMH was moderately heritable (pedigree heritability of 0.40 ± 0.06 and genomic heritability of 0.45 ± 0.05), and 68 SNP across Bos taurus autosomes 7 and 11 were associated with phenotypic variation in plasma AMH. Out of 68 SNP, 42 were located in a single quantitative trait locus on Bos taurus autosome 11 that harbored 6 previously identified candidate genes (NR5A1, HSPA5, CRB2, DENND1A, NDUFA8, and PTGS) linked to fertility-related phenotypes in dairy cows.

The objectives of this study were to (1) characterize the variability for sire's predicted transmitting ability (PTA) for daughter's pregnancy rate (DPR) and cow conception rate (CCR), (2) determine the relationships among sire's PTA for DPR, sire's PTA for CCR, daughter's parity, and daughter's 305-d mature-equivalent (ME) milk production, and (3) evaluate the associations among sire's PTA for DPR and CCR and daughter's reproductive performance [pregnancy to first artificial insemination (P/AI), pregnancy by 150 d in milk (PR150) and pregnancy loss (PL) after first AI] in Canadian Holstein cows. The data were obtained from 822 lactating Holstein cows from 10 commercial dairy herds located in Alberta. Overall mean (range) for sire's PTA for DPR and CCR was -0.09 (-9.6 to 8.2) and -0.05 (-9.9 to 7.4), respectively. Sire's PTA for DPR was strongly and positively associated with sire's PTA for CCR (r = 0.89; P 0.01). Sire's PTA for DPR and CCR were weakly and negatively associated with parity (r = -0.15 and -0.17, respectively; P 0.01); however, the amount of phenotypic variation in sire's PTA for DPR and CCR explainable by parity was small (coefficient of determination; R

peer-reviewed The objectives of this study were to determine (1) factors associated with serum concentration of insulin-like growth factor-1 (IGF-1); (2) the relationship between serum IGF-1 concentration during the first week postpartum and ovarian cyclicity status by 35 d postpartum (DPP); (3) an optimum serum IGF-1 concentration threshold predictive of pregnancy to first artificial insemination (P/AI), including its diagnostic values; (4) the associations among categories of serum IGF-1 concentration and reproductive outcomes (P/AI and pregnancy risk up to 150 and 250 DPP); and (5) single nucleotide polymorphisms (SNP) associated with phenotypic variation in serum IGF-1 concentration in dairy cows. Serum IGF-1 concentration was determined at 7 (±2.4; ±standard error of the mean) DPP in 647 lactating Holstein cows (213 primiparous, 434 multiparous) from 7 herds in Alberta, Canada. The overall mean, median, minimum, and maximum serum IGF-1 concentrations during the first week postpartum were 37.8 (±1.23), 31.0, 20.0, and 225.0 ng/mL, respectively. Herd, age, parity, precalving body condition score, and season of blood sampling were all identified as factors associated with serum IGF-1 concentrations. Although serum IGF-1 concentration during the first week postpartum had no association with ovarian cyclicity status by 35 DPP in primiparous cows, it was greater in cyclic than in acyclic multiparous cows (32.2 vs. 27.4 ng/mL, respectively). The optimum serum IGF-1 thresholds predictive of P/AI were 85.0 ng/mL (sensitivity = 31.9%; specificity = 89.1%) and 31.0 ng/mL (sensitivity = 45.5%; specificity = 66.9%) for primiparous and multiparous cows, respectively. When cows were grouped into either high or low IGF-1 categories (greater or less than or equal to 85.0 ng/mL for primiparous cows and greater or less than or equal to 31.0 ng/mL for multiparous cows, respectively), primiparous cows with high IGF-1 had 4.43 times greater odds of P/AI and a tendency for higher pregnancy risk up to 150 DPP than those with low IGF-1, but not up to 250 DPP. Likewise, multiparous cows with high IGF-1 had 1.61 times greater odds of P/AI than those with low IGF-1. Pregnancy risk up to 150 and 250 DPP, however, did not differ between IGF-1 categories in multiparous cows. Moreover, 37 SNP across 10 Bos taurus autosomes were associated with variation in serum IGF-1 concentration, and 4 previously identified candidate genes related to fertility that were in linkage disequilibrium with some of these SNP were also identified.

The objectives were to evaluate the effect of different categories of endometritis on follicular growth and ovulation, reproductive performance, dry matter intake (DMI), and milk yield (MY) in dairy cows. Lactating Holstein cows (n = 126) were examined for endometritis on 25 ± 1 day postpartum (DPP) using vaginoscopy, transrectal ultrasonography, and endometrial cytology to determine the presence and type of vaginal discharge, uterine fluid, and proportion of polymorphonuclear (PMN) cells, respectively. Cows that had mucopurulent vaginal discharge and/or presence of uterine fluid, no mucopurulent vaginal discharge or uterine fluid but 8% or more PMN, and mucopurulent vaginal discharge and/or uterine fluid and 8% or more of PMN were defined as having clinical (CLIN; n = 45), cytological (CYTO; n = 15), and clinical and cytological (CLINCYTO; n = 30) endometritis, respectively. Cows that had none of the above pathological conditions were classified as unaffected (UNAF; n = 36). The diameter of the largest follicle at first examination, intervals from calving to first dominant (diameter = 10 mm) follicle, preovulatory size (diameter = 16 mm) follicle, ovulation, presence of follicular cyst, and proportion of ovular cows at 35 and 65 DPP were recorded as the measures of follicular growth and ovulation. None of the ovarian follicular parameters analyzed was affected by categories of endometritis. The first service conception rate tended (P = 0.06) to differ among categories of endometritis; cows that had CLIN and CLINCYTO endometritis were four times less likely to conceive to the first insemination compared to UNAF cows. Cows that had CLIN (hazard ratio: 0.52) and CLINCYTO (hazard ratio: 0.40) endometritis had decreased likelihood of pregnancy at 150 DPP compared to UNAF cows. Similarly, cows diagnosed as having CLINCYTO endometritis had decreased likelihood (hazard ratio: 0.48) of pregnancy at 250 DPP compared to UNAF cows. The DMI and MY up to 5 weeks postpartum were not affected by categories of endometritis. In summary, categories of endometritis as determined at 25 DPP did not affect follicular growth and ovulation, DMI, or MY. However, the combined (CLINCYTO endometritis) category had a negative impact on first service conception rate and subsequent services.

The objectives were to (1) investigate factors associated with serum Ca concentration, and (2) examine its relationship with serum analytes, incidence of health disorders, and productive and reproductive outcomes in dairy cows. Serum concentrations of macro minerals, metabolites, liver enzymes, β-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), and haptoglobin were determined between 2 and 7 days in milk (DIM) in 398 Holstein cows from 11 dairy herds in Alberta, Canada. Cows were categorized into either Low- (≤2.10 mmol/L; n = 136) or High- (>2.10 mmol/L; n = 262) Ca groups. Concentrations of Ca were affected by herd, calf sex and number, and DIM at sample collection. Low-Ca cows had lower concentrations of Mg, Na, K, albumin, globulin, total protein and cholesterol, and greater concentrations of urea, aspartate aminotransferase, BHB, NEFA and haptoglobin than High-Ca cows. Low-Ca cows had greater incidence of health disorders compared to High-Ca cows, with the exception of mastitis and displaced abomasum. Low-Ca cows had lower milk yield only by 25 DIM compared to High-Ca cows, with no difference in later milk yield measurements. The proportion of cows cyclic at 35 DIM and pregnant to first artificial insemination tended to be lesser for Low-Ca cows compared to High-Ca cows, with no difference in the proportion of cows pregnant by 150 DIM. In summary, cows categorized as Low-Ca had lower serum concentrations of macro minerals, greater concentrations of markers for fat mobilization and inflammation, greater incidence of postpartum health disorders and poorer reproductive outcomes compared to those categorized as High-Ca.

peer-reviewed The evaluation of anogenital distance (AGD), the distance from the center of the anus to base of the clitoris, as a potential fertility trait for genetic selection in dairy cows has generated recent interest. The objectives of this cross-sectional observational study were to (1) characterize the distribution and variability of AGD, (2) determine factors associated with AGD, (3) estimate heritability for AGD, (4) identify single nucleotide polymorphisms (SNP) associated with phenotypic variation of AGD, and (5) validate the relationship between categories of AGD and fertility in Irish Holstein-Friesian cows. Anogenital distance was measured using digital calipers in 1,180 Holstein cows (mean ± standard deviation: 225 ± 79 d in milk) from 10 dairy herds located in Munster, Ireland. In addition, age (yr), weight (kg), height at hip (cm), and body condition score (BCS) at the time of AGD measurement were determined in a subset of 281 cows. Genotype information available from 908 cows was subsequently imputed to the Illumina Bovine High Density BeadChip (Illumina Inc., San Diego, CA) for genome-wide association analysis of phenotypic variation in AGD. Overall, AGD had a normal distribution and high variability (mean ± standard deviation; 119.2 ± 11.6 mm). Anogenital distance was weakly but positively associated with cow age, hip height, and body weight, and negatively associated with BCS; the phenotypic variation in AGD that was explainable by these variables was small (coefficient of determination; R2 = 0.09, 0.06, 0.10, and 0.02, respectively). The estimated heritability for AGD was 0.37 (standard error of mean ± 0.08). Six SNP of suggestive significance were identified on Bos taurus autosomes 6, 15, 20, and 26; however, none of these SNP was related to previously identified candidate genes for fertility. Cows were categorized into quartiles (Q1; 86 to 111 mm; n = 311, Q2; 112 to 120 mm; n = 330; Q3; 121 to 127 mm; n = 265, and Q4; 128 to 160 mm; n = 274) based on AGD and the association with reproductive outcomes examined (21-d submission rate, pregnancy to first AI, pregnancy rate within 21, 42 and 84-d after the farm mating start date, and number of times bred). None of the reproductive variables differed significantly between AGD categories. In summary, despite identification of high variability and moderate heritability for AGD in Irish Holstein-Friesian cows, reproductive outcomes did not differ between categories of AGD. This latter result differs from our previous finding of an inverse relationship between AGD and pregnancy outcomes in first- and second-parity Canadian Holstein cows, emphasizing the need to test and validate this new phenotype in diverse cow populations.

peer-reviewed The objective of the present study was to assess the effects on ovulation and reproductive performance of a single injection of either GnRH or hCG applied 9 days before the start of the seasonal breeding period in anovulatory anoestrus cows compared with a 7-day progesterone-Ovsynch protocol. The study was conducted on four grass-based seasonal calving dairy herds in Ireland. The total number of cows in the herds was 2112, of which 488 were diagnosed as anoestrus based on absence of behavioural oestrus during a 30 day period. Ovarian structures and the uterus were examined by transrectal ultrasound on all 488 presumptive anestrus cows 9 days before mating start date (MSD). The number of corpora lutea (CL), number of large follicles (≥10 mm) and uterine reproductive tract score were recorded. Only cows that had no CL, ultrasound reproductive tract score ≤2 and were ≥30 days in milk (DIM) were enrolled in the study (n = 214). Cows were blocked by parity, DIM and body condition score and randomly assigned to one of four treatments: i.m. injection of gonadotropin releasing hormone analogue [GnRH; (n = 57)], i.m. injection of human chorionic gonadotropin [hCG; (n = 48)], 7-day Progesterone-Ovsynch protocol [P4OV; (n = 60)] and Control (no hormonal intervention, n = 49). A second ultrasound examination was performed 7 days after treatment to determine ovulatory response. There was a treatment effect on ovulation rate (P

Flaxseed is a source of polyunsaturated fatty acids and could be used as a dietary ingredient to enhance reproductive performance of ruminants. The objectives of this study were to determine the effect of feeding diets with different levels of flaxseed on the nutrient intake, and quantity and quality of embryos in Boer goats. A total of 24 multiparous Boer goats were fed with a diet containing either 0, 4, 8 or 12% of flaxseed (n = 6 per group) and subjected to superovulation to determine the quantity and quality of embryos collected on 7 d after natural service. The nutrient intake was linearly associated with levels of flaxseed in the diet and, whereas while the fat (measured as ether extract) intake was positively associated, the non-fiber carbohydrate intake had a negative association with increasing levels of flaxseed in the diet. The quantity, quality and stage of embryonic development on 7 d after natural service were significantly different between levels of flaxseed in the diet. The number of viable embryos was greater in goats fed with a diet containing 4, 8, and 12% flaxseed (94, 84, and 87%, respectively) than those fed with a diet containing 0% flaxseed (65%). On the other hand, the number of degenerated embryos was greater for goats fed with a diet containing 0% flaxseed (35%) than those fed with a diet containing 4, 8, and 12% flaxseed (6, 16, and 13%, respectively). The proportion of grade 1 embryo collected was greater for goats fed with a diet containing 4 and 8% flaxseed (74 and 83%, respectively) than those fed with a diet containing 0 and 12% flaxseed (40 and 46%, respectively). In summary, our study demonstrated that feeding a diet with moderate levels of flaxseed could produce a greater number of better-quality embryos in Boer goats.

The objective of this study was to evaluate the progression of the uterine microbiota from calving until establishment of metritis. Uterine swabs ( n = 72) collected at 0, 2, and 6 ± 2 days postpartum (dpp) from 12 metritic and 12 healthy cows were used for metagenomic sequencing of the 16S rRNA gene on the Illumina MiSeq platform. A heat map showed that uterine microbiota was established at calving. The microbiota changed rapidly from 0 to 6 ± 2 dpp, with a decrease in the abundance of Proteobacteria and an increase in the abundance of Bacteroidetes and Fusobacteria , which were dominant in metritic cows. Uterine microbiota composition was shared; however, metritic and healthy cows could be discriminated using relative abundance of bacterial genera at 0, 2, and 6 ± 2 dpp. Bacteroides was the main genus associated with metritis because it was the only genus that showed significantly greater abundance in cows with metritis. As the abundance of Bacteroides organisms increased, the uterine discharge score, a measure of uterine health, worsened. Fusobacterium was also an important genus associated with metritis because Fusobacterium abundance increased as Bacteroides abundance increased and the uterine discharge score worsened as the abundance increased. The correlation with uterine discharge score and the correlation with Bacteroides or Fusobacterium showed that other bacteria, such as Helcoccocus , Filifactor , and Porphyromonas , were also associated with metritis. There were also bacteria associated with uterine health, such as “ Candidatus Blochmannia,” Escherichia , Sneathia , and Pedobacter .

peer-reviewed Anogenital distance (AGD) serves as a marker for prenatal androgenization, reproductive development, and fertility in humans and rodents. The primary objectives of this observational study in lactating dairy cows were to (1) characterize the distribution and variability of AGD, (2) determine the relationship among AGD and potential postnatal AGD determinants of age and height, and (3) evaluate the associations between AGD and pregnancy to first artificial insemination (P/AI) and cumulative pregnancy by 250 d in milk (DIM) within parity groups (first, second, and third+ parities). The secondary objective was to evaluate the association between AGD and testosterone concentrations. The AGD (mm), age (yr), and height at hip (cm) at the time of AGD determination, and aforesaid reproductive outcomes were determined in 921 Holstein cows (first, second, and third+ parity; n = 360, 256, and 305, respectively). Plasma concentrations of testosterone were determined in a subset of 93 cows. Overall, AGD had a normal distribution and high variability [mean (±standard deviation); 131.0 ± 12.2 mm], was weakly associated with cow age and height (coefficient of determination = 0.09 and 0.04, respectively), and had an inverse relationship with P/AI in first- and second-parity cows, but not in third+ parity cows. For every 1 mm increase in AGD, the odds of P/AI decreased by 3.4 and 2.4% for first- and second-parity cows, respectively. The optimal AGD threshold to predict probability of P/AI was 127.1 mm for both first- (sensitivity: 66.4; specificity: 56.6%) and second-parity cows (sensitivity: 46.0; specificity: 70.4%). Accordingly, first- and second-parity cows were categorized into either short or long AGD (≤ or >127.1 mm), and associations with reproductive outcomes were evaluated. First-parity cows with long AGD had lower P/AI (30.9 vs. 53.6%) and decreased likelihood (hazard ratio: 0.68) of pregnancy by 250 DIM than those with short AGD. Similarly, second-parity cows with long AGD had reduced P/AI (28.3 vs. 44.4%) and a tendency for decreased likelihood (hazard ratio: 0.76) of pregnancy by 250 DIM than in cows with short AGD. The association between AGD and testosterone was weak and nonsignificant. In summary, AGD in Holstein cows was normally distributed, highly variable, and weakly associated with age and height. Besides, AGD had an inverse relationship with P/AI and cumulative pregnancy by 250 DIM in first- and second-parity cows; however, such a relationship was not evident in older (third+ parity) cows. This project was financially supported in part by Growing Forward 2, a federal-provincial-territorial initiative (Research Opportunities and Innovation–Internal Initiatives Project # DA7642064). M. Gobikrushanth is a recipient of the Teagasc-University of Alberta Walsh Fellowship sponsored by Alberta Innovates Biosolutions.

The objectives of this retrospective study were to use in-line milk progesterone (mP4) data to investigate relationships of (1) commencement of luteal activity (CLA), and (2) luteal phase (LP) length and frequency preceding first postpartum AI, with parity and AI outcomes in Canadian Holstein cows. Starting 21 ± 1 days postpartum (DPP), levels of mP4 were assessed every 2.2 ± 2.0 d through an automated in-line milk analysis system (Herd Navigator™, DeLaval International, Tumba, Sweden) until ∼55 d after first or second AI in 748 Holstein cows from two herds. The CLA was defined as the DPP of the first of at least two consecutive samples with mP4 ≥5 ng/mL, and the period with elevated mP4 (≥5 ng/mL) was defined as the LP. Cows were categorized by CLA [earlier (≤) or later (>) than 28, 35, 42, 49, 56, and 63 DPP], and by the pattern of LP frequency preceding first AI as having or not: (1) one or more normal LP (LP length ≥7 and ≤19 d); (2) one or more abnormal LP (LP length 19 d, or interluteal period ≥12 d); and (3) two or more LP (either normal or abnormal). Outcomes of first or second AI were determined by the interval between AI and cessation of the ensuing LP as: non-pregnant (mP4-decline ≤30 d), presumed-pregnant (no mP4-decline until 55 d), or presumed-pregnancy loss (mP4-decline between 31 and ≤55 d). The odds of pregnancy per AI (P/AI) at 55 d and pregnancy loss were evaluated using generalized linear mixed models. Primiparous cows had lower odds of having CLA ≤28 DPP [Odds ratio (OR) = 0.58, P = 0.002] and one or more abnormal LP (OR = 0.73, P = 0.04) than multiparous cows. In multiparous cows, CLA ≤28 DPP decreased pregnancy loss (OR = 0.48, P = 0.05) and CLA ≤56 DPP increased P/AI (OR = 4.69, P < 0.01) compared to a later CLA. Primiparous and multiparous cows that had one or more normal LP before first AI had increased P/AI (OR = 3.85 and 3.45, respectively, P < 0.01) and reduced pregnancy loss (OR = 0.26 and 0.27, respectively, P < 0.01) than cows without a normal LP. Primiparous cows that had one or more abnormal LP had decreased P/AI (OR = 0.62, P = 0.04) and increased pregnancy loss (OR = 1.64, P = 0.04) compared to those without an abnormal LP. In summary, AI outcomes were improved in multiparous cows that had early CLA and in cows of both parity groups that had at least one normal LP before first AI. However, primiparous cows that had at least one abnormal LP had reduced AI outcomes. Relationships between early postpartum luteal activity and AI outcomes were inconsistent between primiparous and multiparous cows.

The objective of the current study was to evaluate the effect of GnRH early postpartum on induction of ovulation, uterine health, and fertility in dairy cows. Holstein cows without a corpus luteum (CL) at 17 ± 3 DIM were assigned randomly to receive i.m. GnRH (n = 245) at 17 ± 3 and 20 ± 3 DIM or remain as controls (n = 245). Ovaries were scanned by ultrasonography twice weekly totaling 4 examinations. Ovulation was characterized by the appearance of a CL ≥ 20 mm at any ultrasound or CL

The primary objective was to determine the variability and repeatability of GnRH-induced LH responses. The secondary objective was to evaluate the associations among plasma LH, FSH, estradiol (E2), and progesterone (P4) concentrations. One hundred lactating Holstein cows (35 primiparous, 65 multiparous) were initially subjected to a presynchronization protocol (d 0, PGF2α; d 3, GnRH) followed 7 d later by Ovsynch (d 10, GnRH; d 17, PGF2α; 56 h later, GnRH) and timed artificial insemination 16 h after the last GnRH. Blood samples were collected immediately before the GnRH injection of presynchronization and the second GnRH of Ovsynch to determine plasma concentrations of LH, FSH, and P4. A second blood sample was collected 2 h after each of the above GnRH injections to determine GnRH-induced LH and FSH concentrations. Plasma concentrations of E2 were also determined in samples collected immediately before the second GnRH of Ovsynch. Cows that (1) had higher LH concentrations at 0 h than at 2 h after GnRH, (2) showed an ongoing spontaneous LH surge, (3) did not respond to GnRH, and (4) had P4 ≥ 0.5 ng/mL at GnRH of presynchronization and the second GnRH of Ovsynch were excluded from the analysis. The variability (coefficient of variation) and repeatability [between animal variance/(within animal variance + between animal variance)] of GnRH-induced LH response were determined from samples collected 2 h after the GnRH of presynchronization and the second GnRH of Ovsynch. The associations among plasma LH, FSH, E2, and P4 were determined at the second GnRH of Ovsynch. Mean (±SEM) LH concentrations before GnRH were 0.5 ± 0.04 and 0.6 ± 0.03 ng/mL, whereas mean LH concentrations 2 h after GnRH were 9.8 ± 1.0 and 12.1 ± 0.8 ng/mL at GnRH of presynchronization and the second GnRH of Ovsynch, respectively. The variability of GnRH-induced LH was 76.1 and 52.1% at GnRH of presynchronization and the second GnRH of Ovsynch, respectively. The repeatability estimate for GnRH-induced LH concentration between GnRH of presynchronization and Ovsynch assessments was 0.10. Plasma concentrations of LH were positively associated with FSH and E2 (r = 0.61 and 0.30, respectively) and negatively associated with P4 (r = -0.46) at the second GnRH of Ovsynch. In summary, GnRH-induced LH responses were highly variable and unrepeatable, and LH concentrations were positively associated with FSH and E2 and negatively associated with P4.

The objectives were to determine (1) the repeatability of antral follicle counts (AFC) and anti-Mullerian hormone (AMH) concentrations at an unknown stage of follicular growth (FG) and at an expected day of follicular wave emergence (FWE) in dairy cows, and (2) the association between AFC and AMH at the above two stages. Transrectal ultrasound imaging of the ovaries and blood sample collection were performed on 91 lactating Holstein cows (33 primiparous, 58 multiparous) to determine AFC and serum concentrations of AMH at an unknown stage of FG (mean ± SEM; 14 ± 0.5 d postpartum) and an expected day of FWE (mean ± SEM; 73 ± 0.5 d postpartum, approximately 36 h after the 2nd GnRH of Ovsynch protocol). The AFC ranged from 10 to 53 (mean ± SEM; 26.1 ± 1.0) and 6 to 45 (mean ± SEM; 23.4 ± 1.0) at an unknown stage of FG and expected day of FWE, respectively (P = 0.02). Serum concentrations (pg/mL) of AMH ranged from 13.9 to 528.8 (mean ± SEM; 187.3 ± 13.1) and 38.2 to 774.1 (mean ± SEM; 218.7 ± 14.5) at an unknown stage of FG and expected day of FWE, respectively (P < 0.01). The repeatability estimates for AFC and serum AMH concentrations between an unknown stage of FG and the expected day of FWE were 0.37 and 0.73 (P < 0.01), respectively. The correlation between AFC and AMH was moderate at an unknown stage of FG (r = 0.54; P < 0.01) and at an expected day of FWE (r = 0.59; P < 0.01). In summary, both AFC and AMH were repeatable when measured at an unknown stage of FG and an expected day of FWE, but the repeatability was greater for AMH. Thus, if cows are tested at an unknown stage of FG, serum AMH may be a more reliable phenotype than AFC to test association with reproductive outcomes. Furthermore, AFC and AMH were moderately correlated at the two stages examined.

Postpartum uterine infections affect ovarian function and delay ovulation in cattle. As dietary fats can affect immune cell function, we investigated the influence of prepartum diets on postpartum uterine inflammatory status (UIS) as assessed 25 ± 1 days postpartum by endometrial cytology (normal: ≤8% polymorphonuclear cells (PMN) vs subclinical endometritis (SCE): >8% PMN) and associations between SCE, pro- and anti-inflammatory cytokine gene expression and ovarian function. During the last 5 weeks of gestation, dairy cows received a diet supplemented with 8% rolled sunflower (n = 10) or canola seed (n = 9) or no oilseed (n = 9). Ovaries were scanned until 35 days postpartum. Prepartum diets did not influence SCE, but a preovulatory-size follicle developed sooner (P ≤ 0.05), the interval to first ovulation was shorter and the proportion of cows ovulating within 35 days postpartum was greater in the sunflower seed group. Although mRNA expression of cytokines was not affected by diet, cows with SCE had higher (P ≤ 0.05) expression of interleukin-1β (IL1B), interleukin-8 (CXCL8), IL10 and tumour necrosis factor-α (TNF) than normal cows. The interval (mean ± s.e.m.) from calving to preovulatory-size follicle was shorter (P ≤ 0.05) in normal (13.2 ± 0.9 days) than SCE cows (18.7 ± 1.4 days). In summary, a prepartum diet supplemented with sunflower seed positively influenced postpartum ovarian function without affecting UIS or pro- and anti-inflammatory cytokine gene expression in endometrial cells.

Our objective was to evaluate the effects of dietary starch content, altered by partial substitution of dietary grain with wheat dried distillers grain with solubles (DDGS), on the interval from calving to first ovulation, concentrations of hormones and metabolites in plasma and follicular fluid, and granulosa cell gene expression in preovulatory follicles. Sixty lactating dairy cows were assigned to 1 of 2 diets from calving until 84d postpartum. Diets were formulated to contain either 17.3% rolled barley grain (29.2% starch) or 17.2% wheat DDGS (19.1% starch), with 43.0% barley silage and 21.6% rolled corn grain as the other major ingredients (dry matter basis). Transrectal ultrasonography was performed twice weekly to monitor ovarian dynamics from 7±2d postpartum until ovulation or until 56d in milk, whichever occurred earlier. Plasma concentrations of insulin and insulin-like growth factor-1 (IGF-1) were determined in all 60 cows, and that of glucose, fatty acids, and urea in a subset of 24 cows, representing those in which the first ovulation occurred spontaneously within 5 wk postpartum. Estradiol (proestrus) and progesterone (12d postovulation) in plasma were also measured. Concentrations of insulin, IGF-1, glucose, fatty acids, and urea were determined in follicular fluid (wk 9), and the expression of LH receptor, estrogen receptor β, cytochrome P450 aromatase, and plasma type glutathione peroxidase genes measured in granulosa cells obtained from the preovulatory follicles at wk 9 postpartum in the subset of 24 cows. Diets did not alter the interval from calving to first ovulation (32.3±2.5d), but a significantly lower proportion of cows on the DDGS diet (20%) ovulated multiple (≥2) follicles at the first ovulation than those on the barley grain diet (40%). The incidence of multiple ovulations tended to be lower at first insemination (10 vs. 21% for cows fed DDGS and barley grain diets, respectively). Mean plasma concentration of insulin was higher in cows fed the barley grain diet (2.5 vs 1.6 IU/mL), and a diet by time interaction was noted, with cows on the barley grain ration having higher insulin from wk 6 to 12 postpartum; however, mean plasma IGF-1 concentration did not differ between dietary groups. In the subsets, mean plasma concentrations of metabolites or estradiol and progesterone were not affected by diet, parity, or diet by parity interactions. Cows on the DDGS diet had lower concentrations of IGF-I (69 vs. 108 ng/mL) and higher fatty acids (222 vs. 149mEq/L) in the follicular fluid obtained from preovulatory follicles. Diet, parity, and diet by parity interactions did not affect the concentrations of insulin, glucose, urea, estradiol, and progesterone in follicular fluid. Diets did not alter the expression profiles of LHr, estrogen receptor β, CYP19, and GPx3 genes in granulosa cells. In summary, diets did not affect the interval from calving to first ovulation or granulosa cell gene expression. However, reducing dietary starch content by a partial replacement of dietary grain with wheat DDGS increased fatty acids in follicular fluid and reduced the concentrations of insulin in plasma, IGF-1 in follicular fluid, and the incidence of multiple ovulations.

The objective of this retrospective observational cohort study, combined with simulation, was to evaluate the effect of extending the voluntary waiting period (VWP) during the summer on profitability on a Florida dairy farm. Data from Holstein cows (n=1,416) that calved between June and September of 2007 and 2008 were used. Cows that calved between June 1 and July 21 (regular group; REG; n=719) were artificially inseminated (AI) for the first time upon estrus detection (ED) after the second PGF 2α of the Presynch protocol administered between 57 and 63d in milk (DIM), or underwent timed AI using the Ovsynch protocol (TAI) if not detected in estrus. Cows that calved between July 22 and September 18 (extended group; EXT; n=697) underwent AI for the first time after the first or second PGF 2α starting November 14 or November 21 or underwent TAI if not detected in estrus. For second and subsequent AI, all cows underwent AI upon ED or enrolled on TAI after nonpregnancy diagnosis. Following these schemes, average VWP in the REG group and EXT group were 60 and 83d, respectively. Overall profitability for both experimental and subsequent parities were calculated by subtracting the costs existing of feeding costs ($0.30/kg lactating cow diet; $0.25/kg dry cow diet), breeding costs ($2.65/dose PGF 2α ; $2.40/dose GnRH; $0.25/injection administration; $10/semen straw; $5/AI; $3/pregnancy diagnosis), and other costs ($3/d) from the daily revenues with milk sales ($0.44/kg of milk), cow sales ($1.76/kg of live weight), and calf sales ($140/calf). A herd budget simulation was used to predict future cash flow after culling or end of subsequent parity until 6yr after the start of the study to account for all cash flow consequences of extended VWP. Cows in the EXT group had greater first-service pregnancy per AI (PAI1) but still had greater days open and calving interval. Delaying breeding did not affect total cash flow because the EXT group had greater combined profitability for the experimental parity and subsequent parity but lesser future cash flow. Delayed breeding during the summer increased PAI1 but did not improve overall reproductive efficiency and did not affect overall profitability.