First-service Conception Research Articles

Effect of Heat Stress on Subsequent Estrous Cycles Induced by PGF2α in Cross-Bred Holstein Dairy Cows.

This study aimed to determine the effect of heat stress (HS) on reproductive parameters (calving to first service (CTFS) and the first-service conception rate (FSCR)) and general physiological responses (rectal temperature (RT) and respiratory rate (RR)) in tropical cross-bred Holstein dairy cows raised in Ratchaburi province, Thailand. HS was determined using the temperature-humidity index (THI), calculated from temperature and humidity inside the barns, and was classified as moderate HS (THI: 80.67 ± 0.79) and mild HS (THI: 77.81 ± 1.09) in this study. Cows with detected corpus luteum were defined as cyclic cows and were injected with PGF2α at the beginning of the experimental period. Reproductive and physiological parameters were recorded. Cows showed significantly lower RT and RR in the mild HS group (38.47 ± 0.21 °C and 41.04 ± 4.55 bpm, respectively) than in the moderate HS group (38.87 ± 0.15 °C and 51.17 ± 10.52 bpm). The percentage of cows that ovulated after being induced by PGF2α and showed estrus signs was higher in the mild than the moderate HS groups (54.55% vs. 18.18%). Furthermore, the FSCR of cows under mild HS tended to be higher than that in the moderate HS group (42.11% and 15%, respectively) (p = 0.06), while the average CTFS interval was significantly shorter under mild HS than moderate HS (69.47 ± 18.18 and 84.60 ± 27.68 days, respectively). These results indicate that moderate HS impairs reproductive performance in crossbred Holstein cows, compared to mild HS conditions.

Prevalence, Risk Factors, and Relationship between Reproductive Performance and the Presence of Antibodies against Coxiellosis in Dairy Farm Milk Tanks in the Northwest of Spain

Q fever is a zoonotic disease that has been associated with reproductive problems in animals. As there is little epidemiological data regarding the distribution and risk factors of this disorder in cattle, the objective of this study was to evaluate the prevalence of Coxiella burnetii among dairy herds in the northwest of Spain, and to determine the on-farm risk factors associated with the disease and its effects on reproductive performance. Bulk tank milk (BTM) samples were collected from 262 commercial dairy herds from A Coruña, Lugo, and Pontevedra provinces. Data about location, mean age, and herd management features were obtained. A commercial indirect ELISA kit was used to determine the presence of antibodies against C. burnetii in BTM samples. The relationship between seropositivity to C. burnetii and the risk factors was checked using a Pearson’s χ2 test and a classification tree analysis. In addition, a one-way ANOVA test and the Mann–Whitney U test were used to check the impact of seropositivity to C. burnetii on reproductive performance. A total of 60.1% of the farms tested positive for coxiellosis, the herd size, the external purchase of livestock, and the geographical area were identified as the main risk factors. Conception rate and first-service conception rate were significantly lower (p < 0.05) in positive farms (37.1 and 32.9%) compared to negative farms (39.8 and 36.1%). Similarly, positive farms had significant higher incidence of endometritis (13.7% vs. 11.2%, p < 0.05). Consequently, a high seropositivity and slightly negative effects of coxiellosis on reproductive performance were observed, which intensifies the need for further research, including the identification an active infection in positive herds and the characterization of the genotype.

Ovarian and Energy Status in Lame Dairy Cows at Puerperium and Their Responsiveness in Protocols for the Synchronization of Ovulation.

The purpose of this study was to assess the ovarian and energy status of multiparous lame dairy cows at the end of puerperium and investigate their responsiveness to estrous synchronization treatment regimens. Initial lameness scoring was performed at 28 ± 5 and 37 ± 5 d post partum, followed by lesion documentation and treatment. Cows were blocked by lameness severity and were randomly allocated to an estrous synchronization treatment regimen with seven days of progesterone supplementation (group LP, n = 26) or with an administration of PGF2α twice, 14 d apart (group LC, n = 26). Non-lame cows served as controls (group C, n = 27) and the same treatment regimen was imposed as that for group LC. Twelve days after estrous presynchronization, an Ovsynch treatment regimen and timed AI were imposed. Ultrasonography of the ovaries and blood sampling for progesterone were used to assess cyclicity status, whereas β-hydroxybutyrate (BHBA) and non-esterified fatty acids (NEFA) were used to assess energy status. Lame cows were to a greater proportion non-cycling (36.5% vs. 11.1%; p = 0.02), had greater overall NEFA concentrations (0.32 ± 0.02 vs. 0.26 ± 0.02 mEq/L; p = 0.02) and a greater incidence of elevated NEFA concentrations (53.9% vs. 29.6%, p = 0.04) compared to control cows. However, no interaction between energy and lameness status was evident regarding non-cycling cows. The percentage of cows responding to the presynchronization, synchronization and ovulating did not differ between groups LP, LC, and C. The first-service conception rate (FSCR) tended to be greater for group C (37.0%) compared to group LP (16.0%; p = 0.08). Long-term reproductive performance did not differ between lame and control cows, although culling rates did (21.2% vs. 0%, respectivly; p = 0.01). The severity of lameness had an effect on culling rates (30.6% vs. 0% for cows with marked vs. moderate lameness; p = 0.01), whereas the type of lesion largely explained poor reproductive performance (FSCR 13.9% vs. 40.0% for cows with claw horn disruptions vs. infectious lesions; p = 0.04). Conclusively, cows that were lame during puerperium are at a greater risk of not cycling irrespective of energy status. Treatment regimens for the synchronization of ovulation seem to be efficient at resuming ovarian cyclicity. Marked lameness was detrimental to survivability, whereas cows with claw horn lesions had compromised reproductive capacity.

Effects of a single transdermal administration of flunixin meglumine in early postpartum Holstein Friesian dairy cows: Part 2. Milk yield, culling risk, and reproductive performance.

This study was conducted to assess the effects of a single transdermal administration of flunixin meglumine (FM) in early postpartum Holstein Friesian dairy cows on milk yield, culling risk, and reproductive performance. We hypothesized that FM treatment would reduce systemic inflammation, leading to higher milk yield, reduced culling risk, and better reproductive performance in the subsequent lactation. Holstein Friesian dairy cows [n = 500, 153 primiparous (PRIM), 347 multiparous (MULT)] from 3 farms in northeast Germany were enrolled in a prospective, randomized controlled clinical trial. Farms at risk for cows with excessive postpartum inflammation were identified in a preliminary trial by measuring serum haptoglobin concentrations in their fresh lactating cows. Only cows that had a eutocic birth and delivered a singleton calf alive, with no signs of milk fever or retained fetal membranes and rectal temperature ≤40°C at first clinical examination, were included within 24 to 36 h postpartum. Treatment included a single transdermal administration of either FM (3.33 mg/kg) or a placebo as control (CON). Milk production, milk solids, urea, and somatic cell count were recorded monthly for 8 mo after calving. Culling risk, first-service conception risk, and days open were retrieved from the farms' herd management software. Separate models for PRIM and MULT cows were built for most parameters because of significant effects of parity and parity × treatment interaction. Energy-corrected milk yield from 8 monthly Dairy Herd Improvement-equivalent tests was slightly greater in PRIM cows treated with FM (29.51 and 30.73 ± 1.35 kg, CON vs. FM), whereas it was reduced in treated MULT cows (38.23 and 37.47 ± 1.17 kg, CON vs. FM) compared with CON. Milk fat and protein yields were greater in FM-treated PRIM cows and lower in treated MULT cows compared with CON. Milk urea and somatic cell count were not affected by treatment. No differences in culling risk, first-service conception risk, or days open were observed. We conclude that a single transdermal administration of FM in early postpartum dairy cows on farms at risk for excessive postpartum inflammation slightly increased milk, milk fat, and milk protein yields in PRIM cows and decreased these variables in MULT cows. Neither culling risk nor fertility was affected by treatment in this study.

Ultrasonography assisted estrus detection improves the submission rate in prostaglandin treated sub-estrus Murrah buffaloes

Sub-estrus is a condition in buffalo in which the ovarian picture and uterine changes suggest the presence of estrus and cyclicity, despite the absence of behavioural symptoms. The current study describes the effects of ultrasonography (USG)-aided estrus detection on submission and conception rate in sub-estrus Murrah buffaloes after a single shot of prostaglandin (PG) treatment. The study included 67 sub-estrus buffaloes between 2020 and 2021. The teaser bull was used to detect estrus, and the diameter of the pre-ovulatory follicle (POF) and corpus luteum (CL) was measured using transrectal USG. A single PG treatment induced behavioural estrus in 43.28% buffaloes (Gr. 1), while estrus were detected in 35.8% of sub-estrus buffaloes using sonographic examination (Gr. 2) that were otherwise remained undetected. The overall submission rate was 79.1 percent. The first-service conception rate was higher in Gr. 1 (55.2 vs. 33.3%), compared to Gr. 2. The CL diameter at pre-treatment was significantly larger in Gr. 1 buffaloes than in Gr.2 buffaloes. However, the POF diameter was comparable during induced estrus. Furthermore, the time elapsed between induction and breeding in both groups was comparable. Furthermore, the CL size at pre-treatment, POF size at estrus, and time elapsed to breeding had no effect on conception. Thus, the use of USG improves the submission rate in PG administered sub-estrus buffaloes, resulting in a 45.3% overall first service conception rate. However, breeding time must be optimised in order to improve the conception rate and efficient reproductive management in sub-estrus buffaloes in the field.

14 Effect of Pulmonary Arterial Pressure and Precipitation Interaction on Reproductive Performance in Angus Heifers in South Central Wyoming

Abstract Variable precipitation in the western United States impacts forage availability, potentially influencing fertility. Furthermore, producers located above 1,500 meters contend with high altitude disease (HAD) due to reduced atmospheric oxygen, potentially resulting in right sided heart failure. Pulmonary arterial pressure (PAP) score is an indicator trait of HAD. The physiological stress of elevated PAP score could compound environmental stress, such as variable precipitation. Thus, the objective of this study was to investigate the interaction of precipitation and PAP score on beef heifer fertility. Data for this study were sourced from the Colorado State University Beef Improvement Center (CSU-BIC; 1993-2019; n = 3,834; 2,150 to 2,411 m elevation) near Saratoga, Wyoming. Records included identification, birth year, yearling year, yearling weight (YW), PAP, first service conception (FSC), overall heifer pregnancy (HPG) and sire. Precipitation data were sourced from the National Oceanic and Atmospheric Administration. Three classifications were created: cumulative precipitation from birth to breeding, precipitation from heifer birth to weaning, and precipitation from heifer weaning to breeding. Initial models contained sources of variation of precipitation classification, PAP, YW and a PAP by precipitation classification interaction for the response of HPG and FSC. Logistical regression was executed followed by analysis of variance. Yearling weight was a predictor of FSC (P < 0.01) while weaning to breeding precipitation was a predictor for HPG (P < 0.05). In general, the PAP by precipitation interaction was not detected; however, PAP by weaning to breeding precipitation tended to predict HPG (P < 0.10). A favorable, positive relationship was detected between YW and FSC (bi=0.00120 to 00120 to 0.00124; P < 0.01). A favorable, positive relationship also existed between weaning to breeding precipitation and HPG (bi=0.2528, P < 0.05). Those results suggested that increased precipitation during the development period from weaning to breeding was advantageous to HPG. The results also provided evidence to suggest that precipitation and PAP may interact to influence breeding success. Thus, we conclude that increased precipitation during the weaning to breeding period appears advantageous to overall breeding success of Angus heifers in a high-altitude production system.

Possible causes and treatment strategies for the estrus and ovulation disorders in dairy cows

The reproductive performance of dairy cows has declined, along with an increase in their milk yield. First-service conception rates in lactating dairy cows are often lower than 50%. The precise detection of estrus is an important factor in the reproductive management of dairy cows for successful fertilization and pregnancy. However, estrus expression has been decreasing in modern dairy cows, affecting the detection rate of estrus. In addition to estrus, a high incidence of ovulation disorders affects the fertility of dairy cows. To address these problems, it is necessary to understand the changes in the endocrine functions that underlie estrus and ovulation disorders, and to develop effective treatment strategies. Recent studies have revealed that neurokinin B and neurokinin 3 receptor signaling play important roles in the regulation of the secretion of gonadotropin-releasing and luteinizing hormones, suggesting a potential clinical avenue for the stimulation of gonadal function. In this review, I have discussed the problems in estrus and ovulation disorders in modern dairy cows as well as the possible applications of neurokinin 3 receptor agonists in the treatment of these disorders.

Effect of an integrated veterinary herd health program on fertility performance and incidence of reproductive disorders in five dairy herds.

The study was carried out in 5 dairy herds of Polish Holstein-Friesian cows. The average milk yield was about 9000 kg per year. For each herd, the following fertility parameters were calculated at the start of the program and 4 years later: first- service conception rate, services per conception, length of inter-calving period and culling rate due to infertility. The incidence of silent heat, ovarian cysts, ovarian afunction, retained placenta and clinical endometritis was also recorded. Four years after implementation of the program, the average first-service conception rate increased from 43.2% to 51.2%. In three herds the differences were statistically significant (p⟨0.05). There was also a decrease in the number of services per pregnancy and in the culling rate due to infertility. Fertility performance was maintained in two herds. The average incidence of silent heat decreased from 38.1% to 29.7% and the difference was statistically significant (p⟨0.05) in three herds. There was no significant reduction in incidence of other reproductive disorders during the 4 years except for clinical endometritis in one herd. The average milk yield increased from 9300 kg to 9530 kg milk per cow per year. In conclusion, the results indicate that the implementation of the integrated veterinary herd health program improved or maintained fertility performance despite an increase in milk yield.

Improvement of First-Service Conception Rate in Dairy Cows after the Injection of Pregnant Mare Serum Gonadotropin Six Days Postpartum

BACKGROUND: Early resumption of ovarian activity after parturition could positively influence the fertility of dairy cows. Ovulation of the first postpartum follicular wave and formation of corpus luteum that secretes progesterone can sub-stantially benefit the resumption of ovarian cyclicity in cows. In this regard, the presence of a dominant follicle in the ovary before day 10 postpartum could enhance ovulation rate in the first postpartum follicular wave. Pregnant mare serum gon-adotropin (PMSG) is one of the hormones with the potential to improve the growth of follicles. OBJECTIVES: Accordingly, the present study was conducted to evaluate the effect of PMSG injection six days after parturition on reproductive parameters in dairy cows. METHODS: The subjects were randomly assigned to the two groups of control (N=74) and treatment (N=79). Cows in the control group received no treatment, while animals in the treatment group received 500 IU PMSG on day six postpartum. In both experimental groups, cows were subjected to Presynch-Ovsynch protocol 30-35 days postpartum. The subjects that experienced estrus during the Presynch-Ovsynch protocol were inseminated. On the other hand, the cows that were not in estrus during this period were subjected to fixed-time insemination at the end of the Presynch-Ovsynch protocol. Pregnancy was diagnosed 45 days after artificial insemination using the rectal examination. RESULTS: In the control group, 66.22% of cows were inseminated based on estrus detection and 33.78% of cows were inseminated at fixed times. In the intervention group, 68.35% of cows were inseminated based on estrus detection and 31.65% of cows were inseminated at fixed times. The first-service conception rate (FSCR) was 27.03% and 48.1% in the control and treatment groups, respectively (p =0.01). CONCLUSIONS: The present study showed that the injection of 500 IU PMSG six days after parturition could enhance FSCR in dairy cows.

PSI-32 Effect of pulmonary arterial pressure on reproductive performance in Angus heifers located in south central Wyoming

Abstract Pulmonary hypertension (i.e., high altitude disease) occurs in locations above 1,600 m in elevation and causes heart failure and death. Pulmonary arterial pressure scoring is an effective indicator of pulmonary hypertension and high-altitude disease. The objective of this study was to look at the effect of pulmonary arterial pressure (PAP) scoring on reproductive performance in Angus heifers. First service conception (FSC), pregnancy rate, and pulmonary arterial pressure scores were obtained from the Colorado State University Beef Improvement Center for 2,503 Angus heifers between 1995 and 2016. All spring-calving females were exposed to estrous synchronization and one-round of artificial insemination. After a 10-d holding period heifers were exposed to natural service sires for 60 days. First service conception and pregnancy rate traits were determined using ultrasonography via rectal palpation at 30 and 60 days post artificial insemination. Pulmonary arterial pressure scores were collected at ~12 mos of age. Data were analyzed with ANOVA as a completely randomized block design, blocking by birth year. Fixed effect was pulmonary arterial pressure group [high (>42mm Hg) vs. low (<42 mmHg)]. Logistic regression was used to further investigate fertility traits with PAP scores. Nodifferences were detected among pulmonary arterial pressure group for first service conception (P > 0.05); however, high pulmonary arterial pressure heifers had lower pregnancy rates compared to low PAP heifers (0.86 vs. 0.91 ± 0.01; P = 0.03). Logistic regression supported these findings, identifying PAP score as a significant predictor of breeding season pregnancy rate (P < 0.05), indicating an inverse relationship between PAP score and pregnancy rate. Cumulatively, results show an unfavorable relationship between heifers with high pulmonary arterial pressure scores and overall pregnancy rate.

PSI-37 Post-weaning feed efficiency did not influence female fertility traits of commercial or Lowline Angus heifers

Abstract Feed costs represent ~50% of beef production costs making selection for improved efficiency without affecting female reproduction critical to the cow/calf sector. Objectives were to determine the relationship between post-weaning feed efficiency and female fertility in commercial (n = 19) and half-blood Lowline-influenced Angus heifers (n = 20). Yearling heifers were delivered to the CSU, Chico Farm cattle feeding unit 45-d post weaning and randomly assigned to one of three 7 x 18 m pens, equipped with GrowSafe feeding units. Heifers were given ad libitum access to water and a forage-based diet targeting 0.68 kg gain/d (TDN: 54%, CP: 14%, and NDF: 39.7%, on a DM basis) for 72-d. Feed efficiency measures included dry matter intake (DMI), feed conversion ratio (FCR) and residual feed intake (RFI). Heifer RFI was calculated as the difference between predicted DMI and actual DMI during the trial. Feed efficiency groups were identified as: 1) low RFI (0.5 SD above the RFI mean), 2) marginal RFI (+/- 0.5 SD about the RFI mean), and 3) high RFI (0.5 SD above the RFI mean). Serial weights were taken every 14-d to calculate average daily gain (ADG) and metabolic midweight (MMWT). Heifers were synchronized using a 14-d CIDR-PG protocol. Heifers received PG injection 16-d post-CIDR removal and were equipped with an estrous detection patch. Estrous behavior was observed morning and evening for 90-h. Heifers were artificially inseminated (AI) 12-h post-standing estrus and injected with 2 mL GnRH. Pregnancy determination via rectal palpation occurred 6-mos after initial AI. Reproductive measures included: first service conception (FSC), pregnancy rate (PR), and response to estrous synchronization (RES). Reproductive traits were analyzed using the GLM procedures of SPSS with a binary logistic response. Breed type and feed efficiency group were independent variables. Relationships among reproductive measures and performance were analyzed using logistic regression of SPSS, fitting the independent variables of ADG, DMI, and RFI. Traits FSC, PR, and RES did not differ among breed types or feed efficiency groups (P > 0.05) and DMI, ADG and RFI were not predictors of FSC, PR, nor RES (P > 0.05). Cumulatively, results indicate there is no relationship between feed efficiency and reproductive performance. Producers can select for low RFI to decrease feed costs without compromising reproductive performance.

Effects of Extruded Linseed and Soybean Dietary Supplementation on Lactation Performance, First-Service Conception Rate, and Mastitis Incidence in Holstein Dairy Cows.

Simple SummaryNatural and processed fat supplements directly affect milk yield and composition in cows. Oilseed extrusion is a heat-treatment process used for seeds fed to ruminants to prevent rumen biohydrogenation of unsaturated fatty acids. This process increases postruminal fat absorption when compared with the effects of feeding whole oilseeds. Hence, we investigated the effects of feeding a mixture of extruded linseed and soybean on lactation performance, first service conception rate, and mastitis incidence in Holstein dairy cows. We found that supplementing dairy cow feed with a mixture of extruded linseed and soybean at a rate of 100 g/kg feed increased milk yield and both monounsaturated and polyunsaturated fatty acid content. However, incidences of clinical mastitis and first-service conception rates were not affected by extruded linseed and soybean supplementation.This study quantifies the effects of extruded linseed and soybean (ELS) dietary supplementation on milk yield, composition, and fatty acid profiles, as well as first-service conception rate in Holstein dairy cows. Seventy-eight open Holstein dairy cows were divided into two groups: (1) a control, which received a basal diet; and (2) a test group, which received a basal diet supplemented with the ELS (650 g/kg of extruded linseed and 150 g/kg of extruded soybean) at a rate of 100 g/kg. In the ELS group, milk yield per day and solid not fat (SNF) yield increased by 3.26% and 0.88%, respectively, in relation to the control. Percentage milk fat decreased significantly by 1.4% in the ELS group when compared with the control. The ELS supplement resulted in a decrease in saturated fatty acids (SFAs) and an increase in monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) in milk. In conclusion, the supplementation of dairy cow feed with 100 g/kg of ELS increases milk yield and milk unsaturated fatty acids (especially MUFAs and PUFAs). ELS supplementation also causes a decrease in percentage fat and SFA levels but does not affect the first-service conception rate or the incidence rate of mastitis.

10 Pregnancy rates following artificial insemination or embryo transfer in lactating Holstein cows

Excessive heat affects the fertility of high production lactating cows, and reduced pregnancy rates (PR) are observed during summer and early fall. Embryo production programs are used to produce more calves from high genetic merit animals, but could it also increase fertility by bypassing all the negative variables affecting the embryo development before Day 7 (oocyte development, ovulation, fertilization, early embryo development)? The data from AIs and embryo transfers (ET) between June 2017 and May 2019 were analysed. June, July, August, September, and October were called critical months (first-service AI conception rate dropped below 44%). The cows were located at Maddox Dairy in Riverdale, CA, USA, a Holstein herd that milks 3500 cows with a 305-day mature-equivalent milk production of 12 800 kg. First- and second-lactation cows were enrolled in a Presynch-Ovsynch oestrus-synchronization program and scheduled for the first AI at 86 days after calving or to receive an embryo 7 or 8 days after the expected heat. The embryos were produced invivo or invitro from Holstein donors and were transferred fresh or frozen. Blood was sampled on Day 30 after expected heat day (23 days after embryo transfer), and pregnancy was detected by the IDEXX PAG Bovine Pregnancy Test. Table 1 summarises the results, where ET PR% is the number of pregnant cows divided by the number of cows that received and embryo. All the cows synchronized for AI were bred, but only cows with the presence of a corpus luteum (CL) on ET day received an embryo. The presence of a CL was not detected in 28.7% (471/1642) of the cows (32.2% in the critical months and 25.7% in the others). Unfortunately, we could not detect the presence of a CL by ultrasonography every time we transferred embryos, so the nonovulation rate might be overestimated. The cows without a CL were considered open and used to calculate the adjusted PR (AdjPR%). Embryo transfer PR is superior to that of AI, especially during the critical months. Fresh invivo embryos have the most impact. When the cows without CLs are considered open, the difference between AI and ET is still evident for fresh invivo embryos. Besides producing animals with higher genetic merit, depending on the type of embryo used, ET can increase fertility in lactating Holstein cows, especially during the critical months. The other benefit of using ET is that cows that do not ovulate are synchronized right away, which is not the case for AI cows. Table 1.AI×embryo transfer in lactating Holstein cows1 from June 2017 to May 20192 Item Critical months (June to October) Other months (November to May) All year %PR n Adj PR% n %PR n Adj PR% n %PR n Adj PR% n Artificial insemination 41.2% 896 41.2% 896 47.7% 1767 47.7% 1767 45.5% 2663 2663 Fresh invivo embryo 62.7% 373 47.5% 493 69.5% 262 55.3% 329 65.5% 635 50.6% 822 Frozen invivo embryo 59.3% 221 44.8% 292 59.4% 256 47.3% 322 59.3% 477 46.1% 614 IVF fresh embryo 47.9% 167 36.2% 221 54.0% 363 43.0% 456 52.1% 530 40.8% 677 Total embryos 58.5% 761 44.2% 1006 60.2% 881 47.9% 1107 59.4% 1642 46.1% 2113 1Lactating Holstein cows, first and second lactation, first service, Presynch-Ovsynch, 85 DIM. 2PR%=the number of pregnant cows divided by the number of cows that received and embryo; AdjPR%=adjusted pregnancy rate.

PREVALENCE, DIAGNOSTICS AND TREATMENT OF OVARIAN FOLLICULAR CYSTS IN DAIRY COWS

Ovarian cysts are among the primary causes for poor reproduction efficiency and economic losses in dairy cattle farming. Material and metods: The studies were performed in 2015-2017 in three dairy cattle farms.In the experiment, 79 cows with follicular ovarian cysts were divided randomly into 3 groups. To the first group (n=33), a standard double Ovsynch was applied with 0.01 mg GnRH (Veterelin, Laboratorios Calier, Spain) on day 0, 150 µg PGF2α (D – Cloprosstenolsodium, Indupart, Vetpharma Animal Health, Spain) on day 7, 0.01 mg GnRH (Veterelin, Laboratorios Calier, Spain) on day 10, and after 7 days, Ovsynch (GnRH-PGF-GnRH). The cows from the second group (n=28) were submitted to double Ovsynch and additional progesterone treatment through placement of Controlled Internal Drug Release device (EAZI BREED CIDR Cattle insert, 1.38 g progesterone; Pfizer Animal Health, USA) for 7 days between the first GnRH at day 0 and prostaglandin on day 7. The control group comprised 18 untreated cows. Results: First-service conception rate in cows treated by double Ovsynch and vaginal inserts was higher 28.6% compared to that in standard double Ovsynch: 24.2%. Cumulative pregnancy percentage after applied treatments was 60.7% in double Ovsynch plus progesterone and 54.5% in standard double Ovsynch.

11 Conception rate of high-producing dairy cows at first service using prostaglandin F2α and oestradiol benzoate

We have shown that a simplified oestrus synchronization protocol using prostaglandin F2α (PG) and oestradiol benzoate (EB) resulted in a satisfactory conception rate, similar to that obtained in high-producing dairy cows with natural oestrus (Yamaguchi et al. 2018 Reprod. Fertil. Dev. 30, 147 abstr). However, we found no significant effect of PG+EB protocols on the first-service conception rates (CR) of dairy cows. This study investigated the effect of the first-service CR by using PG+EB protocols in the high-producing dairy cows that had not exhibited oestrus expression after calving. Data concerning the first-service CR were obtained for 481 Holstein cows from 4 commercial dairy herds in Hokkaido and Ibaraki, Japan, from 2014 to 2017. The average number of parity, average interval between calving and the first service, and average milk yield (at 305 days) of the cows were 2.2±1.3, 89.7±26.1 days, and 10314±1994kg, respectively. We carried out the PG+EB protocols on cows not showing evident standing heat from Days 50 to 150 postpartum regardless of the presence of a corpus luteum in the ovary. The statuses of ovaries of cows were confirmed using ultrasonography before starting the treatment. Prostaglandin F2α (25 mg; Lutalyse, Pfizer, New York, NY, USA) was injected into cows with a >20mm cutoff for functional corpus luteum diameter at a random stage of oestrus, and EB (1 mg; Ovahormon®, Aska Animal Health Co., Tokyo, Japan) was injected 24h later, and AI was carried out 24 to 48h after EB injection. Cows with a natural oestrus service from Days 50 to 150 postpartum were used as control. All the cows were inseminated after the onset of standing heat or removal of the tail chalk. Pregnancy diagnoses were performed using ultrasonography 30 to 45 days after AI. The CR and intervals of partum to conception were analysed using a chi-square test and ANOVA. The first-service CR (i.e. the number of pregnant cows/total number of cows in the treatment group) of the natural oestrus (n=330) and PG+EB (n=151) groups were 42.7 and 41.1%, respectively, and there were no significant differences between these 2 groups (P=0.7). The average interval between calving and the first service of the PG+EB groups was significantly longer than that of the natural oestrus groups (86.4±1.5 days v. 96.9±1.9 days; P<0.01). The average days open of the natural oestrus and PG+EB groups were 88.5±3.2 days and 98.1±2.3 days, respectively (P<0.05). These results confirmed that the first-service CR in the PG+EB and natural oestrus groups of high-producing dairy cows were similar. We suggest that conducting PG+EB protocols was effective in the high-producing dairy cows that had not exhibited oestrus expression after calving. Moreover, using PG+EB protocols could prevent the further increase in the number of days open.

Association between milk urea nitrogen and first service conception in smallholder dairy farms under heat and humidity stress.

Aim:The study was to evaluate the relationship between the first service conception (FSC) and milk urea nitrogen (MUN) in smallholder dairy farms under heat and humidity stress.Materials and Methods:Dairy cows from 43 dairy farms giving birth between November 2014 and April 2015 (n=295) contributed to the study. All cows were sampled monthly to measure milk compositions, and we collected additional farm data from farmers through a questionnaire. The first service during the first 120 days of lactation was the outcome of interest in this study. Multivariable logistic regression determined significant associations with FSC.Results:The overall FSC was 22% and the mean MUN concentration was 11.55 mg/dl. The final FSC model included MUN concentration, the season of breeding, and protein energy ratio (PE ratio) in the diet. The odds of FSC were reduced by approximately 10% for each mg/dl higher MUN on the day of the milk sample that was nearest to the artificial insemination (AI) day. The odds of FSC were nearly 3 times higher when the first insemination occurred in winter compared to summer first services. Taking into account the nutritional factors, the odds of FSC were nearly 70% higher with an increase in PE ratio of 10 g of crude protein/Mcal from the mean of 35.90 g.Conclusion:This study of smallholder dairy farmers in the hot and humid climate of Thailand confirmed that season, nutritional management, and MUN concentration were associated with FSC. MUN appears to be a useful indicator to monitor the effects of diet on reproductive performance from this study.

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

ObjectiveWe determined the risk factors limiting first service conception (FSC) rate in dairy cows and their economic impact.MethodsData 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.ResultsCows 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.ConclusionLower 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.

Risk factors for clinical ketosis and association with milk production and reproduction variables in dairy cows in a hot environment.

The aims of the present study were to investigate (1) the risk factors that influence the occurrence of clinical ketosis (CK; blood β-hydroxybutyrate > 3.0mmol/L) and (2) to determine the influence of subclinical ketosis (SCK; 1.2 ≤ β-hydroxybutyrate ≤ 2.9mmol/L) and CK on reproductive performance and milk yield in high-yielding Holstein cows in a hot environment. Cows (n = 345) were blood sampled from 6 to 15days postpartum for β-hydroxybutyrate (BHB) determination with a hand-held meter. Cows calving in spring had 3.7 increased odds of having CK (20.7% incidence) than cows calving in summer (3.9% incidence) and autumn (9.4% incidence). Temperature-humidity index < 83 was associated with 1.6 times higher risk for CK compared with cows calving in warmer days. First-service conception rate was 12 and 16 percentage point higher (P < 0.05) in nonketotic cows compared with cows with SCK and CK, respectively. Actual 305-day milk yields for healthy, SCK, and CK cows were 9991 ± 1411, 10,123 ± 1442, and 10,386 ± 1435kg (mean ± SD), respectively, with no difference (P > 0.05) between groups. In conclusion, this study documented that ketosis was seasonal with lower incidence of this metabolic disease during hot seasons and with increased ambient temperature at calving. Also, 305-day milk yield of Holstein cows was not related to blood BHB content early in lactation in this hot environment. However, elevated circulating BHB was negatively associated with conception rate at first service and fetal losses.

Reproductive performance of cows after fixed-time artificial insemination with ovulation synchronisation and re-synchrony in southern Australian dairy herds.

To describe reproductive performance of lactating dairy cows after fixed-time artificial insemination (FTAI) with ovulation synchronisation and re-synchrony in Australian dairy herds, and to compare reproductive outcomes with those of conventional mating programs. The study was conducted in two seasonally calving dairy herds in which lactating dairy cows (n = 675) were enrolled into three treatment groups: group 1, oestrus detection and AI for 34 days followed by a natural service period; group 2, FTAI on day 1 followed by re-synchrony of all cows prior to ultrasound pregnancy diagnosis at day 31 and FTAI of cows diagnosed not pregnant at day 34, then a natural service period; group 3, FTAI on day 1 followed by oestrus detection and AI for 34 days, then a natural service period. First-service conception rate (FSCR), 6-week in-calf (6WIC) rate and proportions pregnant at the end of mating were compared using logistic regression with farm fitted as a fixed effect. Times from mating start date to conception were described using survival analysis with Kaplan-Meier failure functions. FSCRs (45.3%, 49.1% and 45.6% for groups 1, 2 and 3, respectively) and proportions pregnant at the end of mating (77.6%, 76.0% and 76.8% for groups 1, 2 and 3, respectively) were similar for all groups. The 6WIC rate in group 2 was similar to that in group 3 (70.4% vs. 67.2%; P = 0.486), but tended to be higher than in group 1 (70.4% vs. 62.0%, P = 0.066). The median days to pregnancy for cows that conceived was 1 day in groups 2 and 3 and 10 days in group 1. Mating plans that use FTAI with ovulation synchronisation and re-synchrony during the AI period can achieve comparable reproductive performance to conventional mating programs in seasonally calving dairy herds.

Impaired reproduction in Japanese Black cattle under cold environmental conditions

Environmental factors such as the temperature-humidity index (THI) are known to affect reproductive parameters in cattle. Therefore, here, we examined whether there was any correlation between the THI and the reproductive performance of Japanese Black cattle by analysing the first-service conception rates of 178,492 artificially inseminated cows across 9,833 herds in south-western Japan over a 3-year period. The daily mean (±SD) THI over the study period was 63.6±11.3 (range: 41.4-81.5). The calving to first artificial insemination (AI) interval was significantly negatively correlated with THI in the month of AI (r=-.75, p<.001), whereas conception rate to first AI (CRFA) showed a cyclical change that did not correspond with that of THI, resulting in a time lag between CRFA and THI in the month of AI. Furthermore, there was a stronger correlation between CRFA and THI between 3 and 2months before AI (r=.76 vs. .83, p<.001) than in the month of AI (r=.34, p=.04). Therefore, this extensive field study showed that a decrease in THI was associated with declined reproductive performance in Japanese Black cattle and that the impact of the cold environment on the conception rate is attributable to a carryover effect from the cold season before AI rather than conditions at the time of AI.