Preparation and characterization of lysozyme loaded liposomal dry powder inhalation using non-ionic surfactants.

Delivering protein drugs through dry powder inhalation (DPI) remains a significant challenge. Liposomes offer a promising solution, providing protection for proteins from external environment and controlled release capabilities. Furthermore, the use of non-ionic surfactants plays a crucial role in protecting the activity of proteins because of how the surfactants positioning themselves at the liquid-gas interface during the spray-drying process. In this study, lysozyme-loaded liposomal DPI formulations were prepared using various non-ionic surfactants, including polysorbate 80, poloxamer 188, poloxamer 407, and sucrose stearate. Lysozyme solution and 1,2-distearoyl-sn-glycero-3-phosphatidylcholine liposomes were subjected through high-pressure homogenization to form lysozyme-loaded liposomes. Formulations of homogenized lysozyme liposomes were spray-dried and further characterized. The particle size of reconstituted liposomal lysozyme DPI was from 129.5 to 816.9 nm. The formulations showed encapsulation efficiency up to 32.5% with zeta potential value of around - 30 mV, and spherical structures were observed. The aerosol dispersion performance of the dry powder inhalers was evaluated with emitted doses reaching up to 103% and fine particle fractions up to 28.4%. Significantly higher lysozyme activity was confirmed in formulation with drug to PS 80 ratio of 1: 0.5 w/w (92.1%) compared to that of formulation containing no surfactant (59.8%). The formulation stood out as the only formulation that maintained protein activity while demonstrating good aerosol performance.

Impact of postpartum time period associated body condition score on reproductive performance in dairy cows.

This study was designed to identify the time period at which the body condition score (BCS) most critically affects the reproductive performance after calving in dairy cows. Data were collected from 4865 lactation records (1821 from primiparous and 3044 from multiparous cows) on 28 dairy farms, including the BCS (at calving, and month 1 and the first artificial insemination [AI] after calving), the presence of peri- or postpartum disorders, reproductive data, and the weather. The data on the extent of BCS loss from calving to the first AI was divided into two periods, namely, between calving and month 1 after calving (period 1), and between month 1 and the first AI after calving (period 2). Cows with BCS of 3.0, 3.25 and ≥ 3.5 at the first AI after calving were more likely (P < 0.05-0.01) to be pregnant at 30 (odds ratio [OR]: 1.36, 1.64, and 1.90) and 45 (OR: 1.39, 1.75, and 1.99) days post-AI and more likely (P < 0.05-0.01) to be pregnant within 180 days after calving (hazard ratio [HR]: 1.18, 1.43, and 1.58) than cows with BCS of ≤2.75. In addition, cows who suffered a BCS loss of ≥0.5 units during period 1 tended to be less likely (HR: 0.79, P < 0.1) to be pregnant within 180 days after calving than cows without a BCS loss. Cows with BCS of 3.0, 3.25, and ≥3.5 at calving were less likely (P < 0.1-0.05) to lose their pregnancy (OR: 0.37, 0.33, and 0.16) than cows with BCS of ≤2.75. These results indicate that the linearly higher BCS (3.0, 3.25, and ≥3.5) at the first AI is positively associated with the probability of pregnancy per AI after the first AI and the likelihood of pregnancy within 180 days after calving, whereas a higher BCS loss of ≥0.5 units during period 1 was adversely associated with the likelihood of pregnancy within 180 days after calving.

Efficacy of a modified Double-Ovsynch protocol for the enhancement of reproductive performance in Hanwoo cattle.

OBJECTIVE: We aimed to evaluate the efficacy of a modified Double-Ovsynch protocol vs artificial insemination following estrus detection (AIED) for the enhancement of reproductive performance in Hanwoo cattle. METHODS: Four hundred twelve Hanwoo cows were allocated to two treatment groups. The first group of cows were administered gonadotropin releasing hormone (GnRH) on Day 36 (±0.6), prostaglandin F2α (PGF2α) on Day 46 (8 to 12 days later), and GnRH on Day 49, which was followed by Ovsynch, consisting of an injection of GnRH on Day 56, PGF2α on Day 63, and GnRH 56 h and timed AI (TAI) 16 h later (modified Double-Ovsynch group, n = 203). The second group of cows underwent AIED (AIED group, n = 209) and were designated as controls. RESULTS: The pregnancy per AI 60 days after the first AI was higher in the modified Double- Ovsynch (68.5%) than in the AIED (56.5%) group, resulting in a higher probability of pregnancy per AI (odds ratio: 1.68, p<0.05). Moreover, cows in the modified Double- Ovsynch group were more likely (hazard ratio: 1.28, p<0.05) to be pregnant by 150 days after calving than cows in the AIED group, and this difference was associated with a lower mean number of AIs per conception (1.27 vs 1.39, p<0.05) and a shorter median interval between calving and pregnancy (72 vs 78 days, p<0.1). CONCLUSION: The modified Double-Ovsynch protocol, adjusted according to the herd visit schedule, can be readily used to increase the pregnancy per AI following the first AI and to shorten the interval between calving and pregnancy in beef herds.

Factors affecting reproductive outcomes in lactating dairy cows that undergo presynchronization-Ovsynch and successive resynchronization programs.

This study was designed to identify the factors affecting reproductive outcomes in lactating dairy cows undergoing Presynchronization-Ovsynch and successive resynchronization programs. Data were collected from 1,458 cows on 11 dairy farms, regarding nutrition, health, reproduction, and specifically reproductive programs used for the first timed artificial insemination (TAI; Modified Presynch-Ovsynch or Modified Double-Ovsynch) and for re-inseminations (Ovsynch or PreGnRH-Ovsynch); as well as the weather. Body condition score (BCS) and timing of TAI affected (P < 0.01) the probability of pregnancy per AI after first TAI. Cows with a BCS ≥3.25 were more likely (P < 0.01) to be pregnant at 31 (odds ratio [OR]: 1.85) and 49 (OR: 1.93) days after the first TAI than cows with BCS ≤2.75. Cows inseminated during months of heat stress (June to September) were less likely (P < 0.01) to be pregnant at 31 (OR: 0.74) and 49 (OR: 0.68) days after first TAI than those inseminated during months of no heat stress (October to May). Cows that had a pre- or postpartum disorder were more likely to lose their pregnancy (OR: 2.17, P < 0.01) than those that did not. Cows inseminated ≥76 days after calving (OR: 1.67, P < 0.1) or during the months of heat stress (OR: 2.02, P < 0.05) were also more likely to lose pregnancy than cows inseminated ≤75 days after calving or during the months of no heat stress. Following successive resynchronizations, cows with a third (OR: 1.32, P < 0.1) or fourth (OR: 1.68, P < 0.05) TAI were more likely to be pregnant than those with a second TAI. Cows with BCS ≥3.25 at the beginning of resynchronization were more likely (OR: 1.49, P < 0.05) to be pregnant than cows with BCS ≤2.75. Finally, the likelihood of being pregnant by 210 days postpartum was positively associated with a favorable BCS, but negatively associated with the presence of a pre- or postpartum disorder and a larger number of days to first TAI following calving (≥76 vs. ≤75 days). In conclusion, high BCS has beneficial effects during the entire reproductive period, whereas TAI during heat stress, the presence of a pre- or postpartum disorder, a larger number of days to first TAI following calving, and TAI number (second or ≥ fifth) adversely affects the outcomes associated with pregnancy during the early or later breeding periods in lactating dairy cows undergoing Presynchronization-Ovsynch and successive resynchronization programs.

Selective use of a modified pre-synchronization-Ovsynch and resynchronization reproductive strategy in dairy herds: A field application study.

We aimed to evaluate whether a modified pre-synchronization-Ovsynch (MPO) and resynchronization method, adjusted for the timing of biweekly reproductive consulting visits, could be implemented successfully under field conditions in dairy herds. Forty-five days after calving (calving: Day 0), 1,182 cows were assigned randomly to Ovsynch, MPO or control groups. (1) Cows were administered GnRH on Day 65, PGF2α on Day 72 and GnRH 56 hr later, followed by timed artificial insemination (TAI) 16 hr later (Ovsynch, n = 380). (2) Cows with a CL were administered PGF2α (n = 204) and cows without were administered GnRH (n = 199) on Day 45. Then, each cow was administered PGF2α on Day 55 (9 to 12 days later), GnRH on Day 58 and underwent Ovsynch 7 days later (selective MPO [sMPO] n = 403). (3) The remaining cows underwent AI when oestrus was detected (EDAI, n = 399). The probabilities of pregnancy per AI 30 and 45 days after the first AI were higher in the sMPO group (odds ratios 1.99 and 1.92, p < .0001) than in the EDAI group. In addition, the probability of pregnancy by 105 days postpartum tended to be higher (p < .1) in the sMPO group than in the EDAI and Ovsynch groups, which shortened the mean interval from calving to pregnancy in the sMPO group (3.4 and 4.2 days, respectively) than in the EDAI and Ovsynch groups. In the sMPO group, the interval between the first and second treatments during pre-synchronization did not affect the probability of pregnancy per AI after the first AI. The probability of pregnancy per AI after the second AI did not differ between the Ovsynch, sMPO and EDAI groups. In conclusion, the sMPO programme, adjusted for the timing of biweekly reproductive consulting visits, followed by resynchronization, could be successfully adopted in field conditions, and is associated with good reproductive performance in dairy herds.

Reproductive performance following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program in Korean dairy herds.

We aimed to compare the reproductive performance of dairy cattle following a modified Presynch-Ovsynch, Double-Ovsynch, or conventional reproductive management program (CRMP). On Day 30 (±5) after calving (calving = Day 0), 960 lactating cows were assigned randomly to one of two presynchronization treatments, before the synchronization of ovulation (Ovsynch) or CRMP without presynchronization. Cows were administered prostaglandin F2α (PGF2α) on Days 38 (±5) and 52, and gonadotropin-releasing hormone (GnRH) on Day 55 (Presynch-G-Ovsynch group, n = 333); or GnRH on Day 45 (±5), PGF2α on Day 52, and GnRH again on Day 55 (Double-Ovsynch group, n = 307). Thereafter, each cow underwent Ovsynch 7 days later: GnRH on Day 62, PGF2α on Day 69, and GnRH again 56 h later, followed by timed artificial insemination (AI) 16 h later. The remaining cows underwent AI when estrus was detected or Ovsynch (CRMP group, n = 320). In a subset of cows (each n = 40) in the two presynchronization groups, blood collections and ovarian ultrasonography were performed on Days 30 (±4), 52, 62, and 69, and uterine cytology on Days 30 (±4) and 52. The probabilities of pregnancy per AI 32 and 60 days after the first AI were higher in the Presynch-G-Ovsynch (odds ratio [OR]: 1.89 and 1.81, P < 0.01) and Double-Ovsynch (OR: 1.63 and 1.60, P < 0.05) groups than in the CRMP group. The likelihood of pregnancy by 210 days postpartum was higher (P < 0.05) in Presynch-G-Ovsynch (hazard ratio [HR]: 1.29) and Double-Ovsynch (HR: 1.31) groups than in the CRMP group, whereas the least square mean number of inseminations per conception was lower (P < 0.05) in Presynch-G-Ovsynch (1.8) and Double-Ovsynch (1.8) groups than in the CRMP group (2.1). The percentages of cows with serum progesterone concentrations ≥1.0 ng/mL or with a corpus luteum (CL) did not differ between the groups (P > 0.1) on Days 30, 62, and 69, but were lower (P < 0.05) on Day 52 in the Presynch-G-Ovsynch than in the Double-Ovsynch groups. However, the diameter of the dominant follicles, the proportion of neutrophils in uterine cytological samples, and the prevalence of an accessory CL on Day 69 did not differ (P > 0.1) between the two groups. In conclusion, both the Presynch-G-Ovsynch and Double-Ovsynch programs improved reproductive performance vs. CRMP in smallholder Korean dairy herds, and there were no differences in the ovarian endocrine and structural dynamics, or uterine health, between the two programs involving presynchronization.

Risk factors limiting first service conception rate in dairy cows and their economic impact.

OBJECTIVE: We determined the risk factors limiting first service conception (FSC) rate in dairy cows and their economic impact. METHODS: Data were collected from 790 lactations regarding cow parity, peri- and postpartum disorders, body condition score (BCS), reproductive performance, and expenses associated with reproductive management (treatment, culling, and others). Initially, we identified the risk factors limiting FSC rate in dairy cows. Various biological and environmental factors, such as herd, cow parity, BCS at 1 month postpartum and first artificial insemination (AI), resumption of cyclicity within 1 month of calving, year, AI season, insemination at detected estrus or timed AI, peri- and postpartum disorders, and calving to first AI interval, were evaluated. Next, we evaluated the economic impact of the success or failure of FSC by comparing the expense associated with reproductive management until conception between cows that did or did not conceive at their first service. RESULTS: Cows with BCS <3.0 had a lower probability of conceiving at first insemination (odds ratio [OR] = 0.64, p<0.05) than cows with BCS ≥3.0. Cows inseminated during summer were less likely to conceive (OR = 0.44, p<0.001) than cows inseminated during spring. Cows with peri- or postpartum disorders were less likely to conceive (OR = 0.55, p<0.001) than cows without disorders. Survival curves generated using MedCalc showed an 81 day extension in the mean interval between calving and conception in cows that failed to conceive over those that did conceive at first insemination. Cows failing conceive required additional expenditure on reproductive treatment ($55.40) and other management ($567.00) than cows that conceived at first insemination. CONCLUSION: Lower BCS, hot weather at first insemination, and peri- and postpartum disorders are risk factors limiting FSC, which result in an economic loss of $622.40 per dairy cow.

Associations between serum calcium concentration and postpartum health and reproductive performance in dairy cows.

In the present study, the aim was to evaluate the associations between serum calcium concentration after calving and serum metabolites, postpartum disorders, and reproductive performance in dairy cows. Blood samples were collected from 200 Holstein cows immediately and 1, 2, 4, 6, and 8 weeks after calving to measure serum metabolites and progesterone concentrations. Cows were divided into three groups on the basis of the mean serum calcium concentration after calving: a Low group (<7.9 mg/dL, n = 52), a Moderate group (7.9-9.6 mg/dL, n = 100), and a High group (≥9.7 mg/dL, n = 48). Total cholesterol (TCH) concentration was greater in the High group than in the Moderate group during the postpartum period (P < 0.01). The High group had greater albumin concentrations during the postpartum period (P < 0.01) and glucose concentrations after calving and 1 week postpartum (P < 0.05) than the Low and Moderate groups. The High group had a lesser incidence of retained placenta than the Low (P < 0.1) and Moderate (P < 0.01) groups, and a lesser incidence of clinical endometritis than the Moderate group (P < 0.05). The probability of resuming estrous cyclicity by 8 weeks postpartum was greater in the High group than in the Low group (hazard ratio = 3.71, P < 0.05). In conclusion, greater serum calcium concentration after calving is associated with greater serum TCH, albumin, and glucose concentrations, a lesser incidence of retained placenta, and clinical endometritis, and earlier resumption of estrous cyclicity in dairy cows.

Cytological endometritis in dairy cows: diagnostic threshold, risk factors, and impact on reproductive performance.

We determined the threshold proportion of polymorphonuclear leukocytes (PMNs) for a diagnosis of cytological endometritis (CEM), the risk factors for this condition, and its impact on reproductive performance in dairy cows. Uterine cytology was performed on 407 Holstein cows 4 weeks postpartum to determine the proportions of endometrial cells and PMNs. A receiver operator characteristics curve was used to determine the threshold above which the PMN proportion affected the likelihood of cows conceiving by 200 days postpartum. The optimal threshold was ≥ 14% PMN (sensitivity, 31.3%; specificity, 81.7%; p ＜ 0.05). The farm identity, retained placenta (odds ratio [OR] = 1.87), and septicemic metritis (OR = 3.07) were risk factors for CEM (p ＜ 0.05). Cows with CEM were less likely to resume cyclicity (OR = 0.58) and to conceive by 200 days postpartum (hazard ratio = 0.58). Cows with CEM tended (p ＜ 0.1) to be less likely to become pregnant after their first insemination (OR = 0.65) and to require a greater number of inseminations per conception (2.3 vs. 2.2). In conclusion, a PMN threshold of 14% defined the presence of CEM at 4 weeks postpartum. The farm, retained placenta, and septicemic metritis were risk factors for CEM, which reduces subsequent reproductive performance.

Effect of two treatment protocols for ketosis on the resolution, postpartum health, milk yield, and reproductive outcomes of dairy cows.

We determined the effect of ketosis treatment with propylene glycol (PG) or PG plus l-carnitine and methionine (Metabolase®, Fatro, Bologna, Italy) on the resolution, postpartum health, milk yield, and reproductive performances of dairy cows. Blood from 475 Holstein cows was collected weekly until 4 weeks after calving to measure blood ß-hydroxybutyrate (BHBA) concentrations. Cows with blood BHBA concentration ≥1.2 mmol/L were diagnosed with ketosis and were enrolled. One hundred and fifty cows diagnosed with ketosis were randomly assigned to three treatment groups (Day 0): (1) PG (300 g, PO) for 3 days (PG group, n = 50), (2) PG (300 g, PO) plus l-carnitine (1.25 g) plus methionine (5 g, IV) for 3 days (PG + CM group, n = 50), and (3) no treatment (control group, n = 50). On Day 3, blood was collected to evaluate whether the ketosis had resolved. Cows in the PG and PG + CM groups with blood BHBA ≥1.2 mmol/L were retreated for an additional 2 days, and then blood BHBA concentration was evaluated on Days 5 and 10. Blood glucose and haptoglobin concentrations, rumen fill score (RFS), and body condition score (BCS) were measured on Days 0, 3, 5, and 10. Postpartum complications, milk yield during the first 2 months, and reproductive outcomes were evaluated. The probability of resolution from ketosis was higher (P < 0.05) in the PG + CM group than in the control group on Days 3, 5, and 10 (odds ratio: 2.6-6.3). Blood BHBA in the PG + CM group was lower (P < 0.05) than that of the control group on Days 3 and 5, whereas blood glucose in the PG + CM group was higher (P < 0.05) than that of the control group on Days 3 and 5. RFS in the PG and PG + CM groups was higher than that of the control group on Day 10 (P < 0.01), while BCS loss from Day 0-10 in the control group was higher than those of the PG and PG + CM groups (P < 0.05). Milk yields on the 30th and 60th days postpartum were higher in the PG + CM group than the control and PG groups (P < 0.05). Postpartum complications and intervals between calving and first postpartum insemination or pregnancy did not differ among the groups (P > 0.05). In conclusion, treatment of dairy cows with PG plus l-carnitine and methionine improved the chances of resolution of ketosis and increased milk yield, while affecting neither the incidence of postpartum complications nor reproductive performance.

Effects of gonadotropin-releasing hormone administration or a controlled internal drug-releasing insert after timed artificial insemination on pregnancy rates of dairy cows.

This study investigated the effects of gonadotrophin-releasing hormone (GnRH) administration (Experiment 1) and a controlled internal drug-releasing (CIDR) insert (Experiment 2) after timed artificial insemination (TAI) on the pregnancy rates of dairy cows. In Experiment 1, 569 dairy cows that underwent TAI (day 0) following short-term synchronization with prostaglandin F2α were randomly allocated into two groups: no further treatment (control, n = 307) or injection of 100 µg of gonadorelin on day 5 (GnRH, n = 262). In Experiment 2, 279 dairy cows that underwent TAI (day 0) following Ovsynch were randomly allocated into two groups: no further treatment (control, n = 140) or CIDR insert treatment from days 3.5 to 18 (CIDR, n = 139). The probability of pregnancy following TAI did not differ between the GnRH (34.4%) and control (31.6%, p > 0.05) groups. However, the probability of pregnancy following TAI was higher (odds ratio: 1.74, p < 0.05) in the CIDR group (51.1%) than in the control group (39.3%). Overall, CIDR insert treatment at days 3.5 to 18 increased pregnancy rates relative to non-treated controls, whereas a single GnRH administration on day 5 did not affect the pregnancy outcomes of dairy cows.

Relationships among ketosis, serum metabolites, body condition, and reproductive outcomes in dairy cows.

We determined the relationships among ketosis, serum metabolites, body condition, and reproductive disorders and performance in dairy cows. Blood samples from 213 dairy cows were collected at 4 and 2 weeks prepartum, just after calving, and at 1, 2, 4, 6, and 8 weeks postpartum to measure serum ß-hydroxybutyrate, nonesterified fatty acids (NEFAs), glucose, total cholesterol, urea nitrogen, aspartate aminotransferase, γ-glutamyltransferase, and progesterone concentrations. Cows were grouped on the basis of the ß-hydroxybutyrate concentration at 1 and/or 2 weeks postpartum into two groups: the ketotic group (≥1200 µmol/L, n = 59) and the nonketotic group (<1200 µmol/L, n = 154). The body condition score (BCS) was assessed simultaneously with blood collection. Clinical endometritis was diagnosed by observation of vaginal discharges (>50% pus), and subclinical endometritis was diagnosed by evaluation of uterine cytology (>18% neutrophils) at 4 weeks postpartum. Ovarian cysts were diagnosed by ultrasonography, and resumption of postpartum cyclicity was evaluated by progesterone concentrations (≥1 ng/mL) at 4, 6, and 8 weeks postpartum. In the ketotic group, NEFA levels were higher (P ≤ 0.0005), whereas glucose (P < 0.05-0.0005) and urea nitrogen levels (P < 0.05-0.01) were lower than those in the nonketotic group during the postpartum period. Aspartate aminotransferase levels were higher (P < 0.01) in the ketotic group than those in the nonketotic group at 2 weeks postpartum. The BCS of the ketotic group was higher than the nonketotic group during the prepartum (P < 0.001) and postpartum (P < 0.05-0.001) periods. The probabilities of clinical endometritis (odds ratio = 2.55) and ovarian cysts (odds ratio = 2.80) were higher (P < 0.05) in the ketotic group than those in the nonketotic group. The hazards of resumption of postpartum cyclicity by 8 weeks postpartum (hazard ratio = 0.67) and pregnancy by 360 days postpartum (hazard ratio = 0.68) were lower (P < 0.05) in the ketotic group. In conclusion, a higher BCS during prepartum and postpartum period and increased NEFA and aspartate aminotransferase levels, along with decreased glucose and urea nitrogen levels during postpartum, were associated with ketosis, increased reproductive disorders, and decreased reproductive performance in dairy cows.

Inflammatory cytokine concentrations in uterine flush and serum samples from dairy cows with clinical or subclinical endometritis.

The objective of this study was to compare the concentrations of inflammatory cytokines in uterine flush and serum from healthy postpartum dairy cows and cows with clinical or subclinical endometritis. Clinical endometritis was diagnosed by observation of vaginal discharges (>50% pus) and subclinical endometritis was diagnosed by evaluation of uterine cytology (neutrophils >18%) at 4 weeks postpartum. Uterine flush was obtained from 48 cows at 4, 6, and 8 weeks postpartum for evaluation of tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6, IL-8, and IL-10 concentrations. Serum samples were obtained from 34 cows just after calving and at 1, 2, 4, 6, and 8 weeks postpartum for evaluation of TNF-α, IL-1ß, and IL-6 concentrations. Concentrations of TNF-α, IL-6, and IL-10 were greater (P < 0.05) in cows with clinical endometritis than in cows with subclinical endometritis and healthy controls, whereas concentrations of IL-8 in both cows with clinical and subclinical endometritis were greater (P < 0.005) than in controls. Overall, IL-6 and IL-10 concentrations decreased during the postpartum period. IL-1ß concentrations in cows with clinical endometritis decreased (P < 0.0005) during the postpartum, whereas concentrations in cows with subclinical endometritis and controls did not change significantly with time; at 4 weeks postpartum, concentrations were greater (P < 0.0001) in cows with clinical endometritis. There were no significant effects of group, sampling time, or interaction on serum cytokine concentrations. In conclusion, cows with endometritis have greater inflammatory cytokine concentrations in uterine flush than healthy cows, but no differences were observed in serum.

Synchronization using PGF(2α) and estradiol with or without GnRH for timed artificial insemination in dairy cows.

This study examined the use of PGF(2α) and estradiol benzoate (EB) either with or without GnRH to synchronize estrus in dairy cows for timed artificial insemination (TAI) under field conditions. First, Holstein dairy cows with a corpus luteum (CL) received 500 µg cloprostenol and were then randomly allocated to three groups: no further treatment (control, n=236); treatment with 1 mg EB 56 h after cloprostenol (EB group, n=339); or treatment with 1 mg EB 56 h after cloprostenol followed by treatment with 100 µg gonadorelin 24 h later (EB + GnRH group, n=216). All cows received TAI 80 h after the cloprostenol injection. In a second experiment, Holstein dairy cows with a CL received 500 µg cloprostenol and were then randomly allocated to two groups: treatment with 2 mg EB 36 h later (EB group, n=284) or treatment with 2 mg EB 36 h after cloprostenol followed by 100 µg gonadorelin 24 h later (EB + GnRH group, n=229). All cows received TAI 24 h after the EB injection. Logistic analyses revealed that the odds ratio for the probability of pregnancy when 1 mg EB was administered 56 h following cloprostenol was 1.9 and 2.0 times (P<0.001) higher in the EB (39.5%) and EB + GnRH groups (40.7%), respectively, compared with the control group (25.8%). However, pregnancy rates in cows receiving 2 mg EB 24 h following cloprostenol showed no difference compared with cows treated with EB only (32.4%) or with EB + GnRH (35.8%). These results indicate that a synchronization protocol comprising PGF(2α) and EB could be used for TAI in dairy herds under field conditions.

Field investigation of whether corpus luteum formation during weeks 3-5 postpartum is related to subsequent reproductive performance of dairy cows.

This study analyzed the effect of corpus luteum (CL) formation during weeks 3-5 postpartum on the subsequent reproductive performance of dairy cows. Factors contributing to CL formation during the postpartum period were also determined. Data were collected from 1524 Holstein dairy cows on 18 farms using a single ultrasonographic examination to determine the presence or absence of a CL during weeks 3-5 postpartum. The dates of calving, AI, conception and cow parity were also collected. Data were acquired for a subset of 475 cows on five farms related to peripartum reproductive events and the body condition score (BCS) during weeks 3-5 postpartum. The hazard of first postpartum insemination by 150 days in milk (DIM) was higher for cows with a CL compared with herd mates without a CL during week 3 (hazard ratio [HR]: 1.40, P=0.007), week 4 (HR: 1.28, P=0.004) and week 5 postpartum (HR: 1.43, P<0.0001). Furthermore, the pregnancy hazard was also higher by 210 DIM for cows with a CL compared with cows without a CL during week 3 (HR: 1.56, P=0.0009), week 4 (HR: 1.28, P=0.006) and week 5 postpartum (HR: 1.20, P=0.04). Cows calved during autumn were more likely to have a CL than cows calved during spring (odds ratio [OR] =2.32, P=0.003). Primiparous cows were less likely to have a CL than multiparous cows (OR=0.63, P=0.03). Cows with a BCS < 3.00 were less likely to have a CL than cows with a BCS ≥ 3.00 (OR=0.51, P=0.0013). In conclusion, CL formation during weeks 3-5 postpartum was related to subsequent improved reproductive performance when compared with herd mates without a CL.