First-service Conception Rate Research Articles

Conception rates of cows inseminated with frozen semen of Rural Development Academy, Bogura, Bangladesh

Background: The first service conception rate (FSCR) is an important parameter for any artificial insemination (AI) programme. The present study was conducted to determine the FSCR and its influencing factors in cows inseminated with frozen semen produced by Rural Development Academy, Bogura. Methods: Data were collected from 372 cows at 39 villages under Sherpur Upazilla of Bogura district on breed, age, body condition score (BCS), parity, milk yield, suckling, AI season and the interval between oestrus to AI using a questionnaire. Results: The overall FSCR of cows was 66.4% and the service per conception was 1.53. The FSCR was higher (74.1%) in local cows compared to the Holstein-Friesian (HF) cross counterpart (64.2%). The FSCR was higher (70.4%) in 24-47 months old cows compared to 84-98 months old counterpart (61.5%). The highest FSCR (81.6%) was observed in cows with 3.0 to 3.5 BCS and the lowest (25.7%) was observed in cows with 2.5 BCS. The highest FSCR (68.3%) was observed in the 0 (zero) parity (heifers) group of cows and the lowest (62.5%) was observed in the 4-7 parity counterpart. The highest FSCR (72.4%) was observed in cows yielded daily >15-22 L milk and the lowest (62.1%) was observed in cows yielded ≤5 L milk. The highest FSCR (72.7%) was observed in suckling restricted cows and the lowest (60.9%) was observed in cows that had several times suckling daily. The highest FSCR (72.1%) was observed in cows received inseminations in Rainy (July-October) season and the lowest (58.4%) was observed in cows received inseminations in Winter (November-February). The highest FSCR (67.1%) was observed in cows received inseminations between 12-18 hrs of detection of oestrus and the lowest (59.1%) was observed in cows received insemination between 8-11 hrs of detection of oestrus. However, the difference in FSCR in cows with different BCS groups was significant (p<0.01). Conclusion: The current FSCR in cows can be considered to be satisfactory. The BCS of cows significantly influences the FSCR in cows.

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.

A randomized study on the effect of an extended voluntary waiting period in primiparous dairy cows on fertility, health, and culling during first and second lactation

When the voluntary waiting period (VWP), defined as the days between calving and when the cow is eligible to receive the first insemination, is extended, high-yielding dairy cows may have better opportunities to regain energy balance before first insemination. This study investigated the effect of an extended (145-215 days in milk [DIM], n = 280) or conventional (25-95 DIM, n = 251) VWP treatment on fertility, disease incidence, and culling rate in cows during their first lactation. The cows were also followed through a second lactation without intervention regarding VWP, during which the farmers could decide when they wished to start the inseminations. This was done in a randomized-controlled study on 16 high-yielding commercial herds in southern Sweden, containing a total of 531 primiparous cows of the Holstein and Red Dairy Cattle breeds. Data from the Swedish national dairy herd recording scheme collected between August 2018 and September 2021 were used in the analysis, including records on breed, calvings, estrus intensity, inseminations, disease, somatic cell count, culling date, and culling reason. During first lactation, more cows receiving the extended VWP treatment showed strong estrus intensity (score 4-5, 55% vs. 48%) and fewer showed moderate estrus intensity (score 3, 35% vs. 43%) at first insemination, compared with cows receiving the conventional VWP treatment. First service conception rate (FSCR) was higher (67% vs. 51%) and number of inseminations per conception (NINS) was lower (1.6 vs. 2.0) during the first lactation for cows receiving the extended compared with the conventional VWP treatment. For disease incidence rate or culling rate expressed as number of events per cow-time in the study, we found no differences between the cows receiving the 2 VWP treatments in any lactation. Calving to first service interval during second lactation was longer (86 vs. 74 d) for cows with extended compared with conventional VWP. In conclusion, primiparous cows with extended VWP showed improved reproductive functions, in the form of higher estrus intensity, greater FSCR, and lower NINS, during the first lactation. However, we observed no apparent effect on these fertility measures during the following lactation (without VWP intervention) and no differences in disease prevalence or culling between cows receiving the 2 different VWP treatments in either lactation. Compliance with the planned VWP treatment was lower for cows with planned extended compared with planned conventional VWP treatment. We studied the "intention-to-treat" effect (i.e., the results for all cows randomized to each treatment regardless of whether the planned VWP was achieved or not) to identify any bias arising due to degree of compliance. However, we found no difference in culling rate between cows randomized to an extended VWP compared with those randomized to a conventional VWP. These findings can be used to support management decisions on VWP length in high-yielding dairy herds.

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.

Fertility and survival of Swedish Red and White × Holstein crossbred cows and purebred Holstein cows

Swedish Red and White × Holstein (S×H) cows were compared with pure Holstein (HOL) cows for fertility and survival traits in 2 commercial dairy farms in central-southern Córdoba province, Argentina, over 6 years (2008-2013). The following traits were evaluated: first service conception rate (FSCR), overall conception rate (CR), number of services per conception (SC), days open (DO), mortality rate, culling rate, survival to subsequent calvings, and length of productive life (LPL). The data set consisted of 506 lactations from 240 S×H crossbred cows and 1,331 lactations from 576 HOL cows. The FSCR and CR were analyzed using logistic regression, DO and LPL were analyzed using a Cox's proportional hazards regression model, and differences of proportions were calculated for mortality rate, culling rate, and survival to subsequent calvings. The S×H cows were superior to HOL cows in overall lactations for all the fertility traits (+10.5% FSCR, +7.7% CR, -0.5 SC, and 35 fewer DO). During the first lactation, S×H cows were superior to HOL cows for all fertility traits (+12.8% FSCR, +8.0% CR, -0.4 SC, and 34 fewer DO). In the second lactation, S×H cows exhibited lower SC (-0.5) and 21 fewer DO than HOL cows. In the third or greater lactations, S×H cows showed higher FSCR (+11.0%) and CR (+12.2%), lower SC (-0.8), and 44 fewer DO than pure HOL cows. In addition, S×H cows had a lower mortality rate (-4.7%) and a lower culling rate (-13.7%) than HOL cows. Due to the higher fertility and lower mortality and culling rates, the S×H cows had higher survival to the second (+9.2%), third (+16.9%), and fourth (+18.7%) calvings than HOL cows. Because of these results, S×H cows had longer LPL (+10.3 mo) than HOL cows. These results indicate that S×H cows had higher fertility and survival than HOL cows on commercial dairy farms in Argentina.

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.

Association of Electrical Resistance of Vaginal Mucus (ERVM) with Follicle Diameter and Conception Rate in Crossbred Dairy Cows

Background: Estrus detection by observing behavioral signs are time consuming and ineffective method that causes approximately 21 days loss with a significant financial consequence. This study highlights the value of electrical resistance of vaginal mucus (ERVM) during estrus and its association with genital changes, follicle diameter and first service conception rate (FSCR) in crossbred cows. Methods: A total of 400 cows were selected from different states of North-East, India, out of which 200 numbers of cows were examined to determine the ERVM value prior to artificial insemination (AI) by using Draminski estrus detector.The remaining 200 number of animals were examined for studying the association of ERVM with genital changes, follicle diameter and FSCR.The ERVM value obtained prior to AI was divided into three groups such as 150-200 (Group I), 201-250(Group II) and 251-290 (Group III) ohm, comprising 50 animals in each group. A control groups comprising 50 animals were kept in the study.The genital changes were recorded by transrectal palpation and follicle diameters were recorded by using transrectal ultrasonographic (USG) probe. Result: The mean ERVM value prior to AI was 196.26±1.25 ohm.The lowest ERVM value (150-200 and 201-250 ohm) was closely associated with free flowing vaginal discharge, open cervix, moderate tone of uterus and mature graffian follicle.The follicles diameters were differed significantly between groups. The FSCR was found to be higher when the cows were inseminated at ERVM value from 201-250 ohm. The result suggested that, ERVM value can be consider as a suitable tool for detection of proper time of AI in cows.

​Genital Changes, Haemato-biochemical Profile and Therapeutic Management of Endometritis in Crossbred Dairy Cows

Background: Reproductive performance is one of the major determinants for the economic improvement of a dairy farm. Endometritis and other uterine complications cause decrease the pregnancy rate. In this study, the genital changes and haemato-biochemical profile of crossbred dairy cows affected with endometritis was studied to evolve a suitable treatment protocol in order to improve reproductive efficiency. Methods: Crossbred cow affected with endometritis were selected based on mucopurulent vaginal discharge at estrus and tested positive for white side test. Animals were divided randomly into 8 groups with 24 animals in each group. Different therapeutic regimens fortified with supportive treatment were opted. The therapeutic regimens were supportive therapy having bypass fat, vitamins and minerals, Lugol’s iodine, Lugol’s iodine with supportive therapy, intrauterine (IU) antibiotic, IU antibiotic with supportive therapy, E. coli. LPS, E. coli. LPS with supportive therapy and control group respectively. Efficacy of each treatment regimen was based on first service conception rate (FSCR). Result: Of all the therapeutic regimens, fortification of Lugol’s iodine with supportive therapy resulted in higher FSCR (83.33%) indicating better applicability as a treatment tool for endometritis in crossbred cows.

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.

Sexual Behaviour and Seminal Attributes Associated with Fertility of Jaffarabadi Buffalo Bulls

Background: The selection of breeding bulls based on the association of sexual behaviour, seminal attributes and conception rate are more important and economical. However, information on association of sexual behaviour and seminal attributes with fertility in buffaloes particularly with reference to Jaffarabadi buffalo bulls is meager. Methods: The study was carried out to assess the association of sexual behaviour and seminal attributes with first service conception rate (FCR) of Jaffarabadi buffalo bulls. A total of 192 semen ejaculates were evaluated and cryo-preserved. First AI conception rate (FCR) was carried out on 800 Jaffarabadi female buffaloes inseminated with frozen-thawed semen and pregnancy was confirmed by per rectal palpation at 2 months post-insemination. Result: The results indicated that both sexual behaviour and seminal attributes were associated with fertility in Jaffarabadi buffalo bulls.

Short communication: Effect of subclinical mastitis on reproductive performance of Holstein dairy cows in the Northwest of Spain

Aim of study: To investigate the effect of subclinical mastitis (SCM) before and after first artificial insemination (AI), characterized by a somatic cell count (SCC) higher than 200×103 cell/mL, on reproductive performance including first service conception rate (FSCR) and pregnancy loss (PL) in Holstein dairy cows.
 Area of study: The central area of Lugo, Galicia, Spain.
 Material and methods: This retrospective study was conducted on herd database of a population of 80 commercial Holstein dairy cow farms. A total number of 2053 lactations were included in this study. A binary logistic regression was carried out to analyse all data.
 Main results: The results of this study indicated that cows that registered a SCC lower than 200×103 cell/mL within 30 days after first AI were more likely to conceive pregnancy than cows with a higher SCC (31.2% and 25.1% FSCR, respectively; OR=1.285, 95% CI=1.000-1.653). Additionally, an increased SCC neither 30 days before nor 30 days after first AI had a negative effect on prevalence of PL in dairy cows.
 Research highlights: These findings revealed that SCM within 30 days after first AI negatively affected FSCR, whilst 30 days before first AI did not affect it. Therefore, it could be suggested that preventing subclinical mastitis after first AI, during a critical period of 30 days, is important to maximize the reproductive performance of dairy cows.

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.

Impact of frequency of milking on milk yield and fertility of Holstein cows undergoing extended lactations due to failure to conceive

The objective of this observational study was to determine the effect of two (2x) compared to three (3x) times a day milking in Holstein cows undergoing lactations ≥600 d on milk production and reproductive performance. Two large adjacent commercial dairy herds with similar size, facilities, and management in a hot area of northern Mexico (25° N) were used. Cows in one herd (n= 214) were milked two times a day (2x), the other herd was milked three times a day (3x; n=245) and both groups were milked for at least 600 days. For cows in first lactation, total milk yield did not differ between 3x and 2x cows (19796 ± 3354 vs. 19269 ± 3652 kg; p > 0.10) in lactations with an average of 696 and 650 days in milk (DIM), respectively. Multiparous 3x cows produced more total milk days than 2x cows (20942 ± 3920 vs. 18910 ± 2632 kg; p < 0.01) with greater (p < 0.01) DIM for 3x (685 ± 117 days) than 2x (631 ± 88 days) cows. Lactation persistence was greater (p < 0.05) in 2x (62 ± 9%) than 3x (60 ± 10%) cows. Overall conception rate (CR) did not differ between 2x and 3x cows (53.3% vs. 49.8%) but 3x cows required one more service (p < 0.01) to get pregnant than 2x animals. Given that average milk yield throughout the complete lactation did not differ between 2x (29.8 ± 2.0 kg) and 3x (29.3 ± 2.9 kg) cows, it was concluded that two-times-a-day milking is equally effective as three-times-a-day milking to attain acceptable milk yield in lactations over 600 days. However, reproductive performance based on first-service CR and services per pregnancy was negatively affected by three-times-a-day milking.

Heparin binding proteins in seminal plasma of breeding buffalo bulls and their relation with semen freezability and in vivo fertility

The present study was conducted to determine the concentrations of heparin binding proteins (HBP) in seminal fluid of breeding buffalo bulls and establish their relationship with frozen-thawed semen characteristics and fertility. Both fresh and frozen semen were collected from same ejaculate of 30 breeding buffalo bulls. Based on HBP concentrations in seminal plasma obtained from affinity chromatography, all the bulls were divided into 2 groups, viz. high fertility bulls (HFB, ≥ 6.5 mg/ml; n=15) and low fertility bulls (LFB, < 6.5 mg/ml; n=15) for further comparisons. The frozen-thawed semen of same ejaculate was evaluated for per cent CASA-based sperm kinetics, viability, Hypo-osmotic swelling test (HOST), acrosome integrity, in vitro acrosome reaction and first service conception rate (FSCR). The overall HBP concentrations were significantly higher in seminal plasma (7.31±0.14 vs 5.33±0.19 mg/ml) and fresh (0.66±0.03 vs 0.59±0.02 mg/109 sperms) sperm extracts of HFB than LFB. The frozen-thawed semen characteristics, viz. total motility, per cent acrosome reaction and FSCR were also significantly higher in bulls with high fertility than in lower ones. No significant difference was observed in sperm viability, HOST and acrosome integrity in the 2 groups of bulls. Total 12 HBP bands in range of 11 to 135 kDa were recorded on SDS-PAGE. Higher levels of HBP in seminal plasma of HFB might be responsible for their better semen quality and fertility.

Intrauterine therapy with ozone reduces subclinical endometritis and improves reproductive performance in postpartum dairy cows managed in pasture-based systems.

New postpartum strategies have been developed in dairy cows to ameliorate uterine health and reproductive performance, especially the first service conception rates. This study aimed to assess the effect of intrauterine therapy with ozone (IUTO) in early postpartum on subclinical endometritis prevalence and reproductive parameters in dairy cows under commercial farm conditions. For this purpose, eighty clinically healthy cows with a body condition score between 3.0 and 3.5, from four dairy farms, were randomly allocated into two groups: ozone therapy group (OG, n = 40), which were subjected to IUTO, and control group (CG, n = 40). Content of uterine polymorphonuclear (PMN) leukocytes and subclinical endometritis (SE) percentage were assessed at 35days after calving by uterine cytology. A second cytology was performed 72h after IUTO. Reproductive parameters such as interval calving to first service (IFS), number of services per conception (nSC), interval calving to conception (ICC) and first service conception rate (FSCR) were analysed. The second endometrial cytology demonstrated that IUTO reduced (P < 0.01) both PMN (3.7 ± 1.4 vs. 7.6 ± 1.1%) and SE (5.0 vs. 50.0%) percentages compared with CG. Likewise, after ozone treatment, both nSC (2.1 ± 0.3 vs. 3.1 ± 0.2; P < 0.01) and ICC (126.2 ± 9.7 vs. 149.0 ± 9.0; P = 0.0672) decreased, and FSCR increased (50.0 vs. 16.2%; P < 0.01) compared with CG. In conclusion, intrauterine ozone therapy applied at 35days after calving reduced subclinical endometritis prevalence and improved reproductive performance in postpartum dairy cows managed in a pasture-based system.

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.

155 Fertility of sexed semen in Holstein heifers and cows

Compared with conventional semen, use of sexed semen decreases the conception rate (CR); therefore, it is important to address the factors that lead to sperm damage. Recently, a novel sexed semen technology was developed for improving dairy cattle fertility (Betthauser et al. 2016 J. Dairy Sci. 99 (E-Suppl. 1), 534). However, there are few reports about the fertility of this novel sexed semen in dairy cattle in Japan. The objective of this study was to compare the CR of traditional sorting semen (S1: flow cytometry/cell sorting) and the novel sexed semen (S2: SexcelTM, ABS Global Inc.) in Holstein heifers and cows in Japan. The CR for the first insemination was obtained from 391 Holstein cows and 148 heifers (10.7-17.8 months old) from 14 dairy farms in Hokkaido from June 2017 to April 2019. Semen used for AI was collected from six bulls and packaged into 0.25-mL straws and frozen. Cows inseminated with conventional frozen semen (S3: unsexed semen in 0.5-mL straws) were used as controls. Calving data were collected from 123 cows and 69 heifers that had calved between January 2018 and May 2019. The diagnosis of pregnancy was confirmed using ultrasonography between 30 and 45 days after insemination. The CR and sex ratio were analysed using chi-square test. The average parity number was 1.9±1.1, and average days open was 84.9±20.4 days. The average interval between calving and the first service was 86.2±20.3 days. The average milk yield (at 305 days) was 12 195±1595 kg. All of the animals were inseminated after the onset of standing heat or removal of the tail chalk of natural heats and oestrus and ovulation synchronisation programmes on the farm. Conception rates of heifers of the first service of S1 (n=54) and S2 (n=94) were 68.5 and 70.2%, respectively. Conception rates of cows of the first service of S1 (n=32), S2 (n=173), and S3 (n=186) were 56.3, 57.8, and 53.8%, respectively. There were no significant differences in CR between these groups (P&amp;gt;0.4). The proportion of female calves produced using S1 (n=61) and S2 (n=57) was 91.8 and 93.0%, respectively, which was significantly more (P&amp;lt;0.01) compared with the 50.0% produced using S3 (n=74). There were no significant differences between S1 and S2 (P&amp;gt;0.8) in terms of the proportion of calves produced. The results of this study demonstrated that the traditional sorting and novel sexed semen (S1 and S2, respectively) did not differ in terms of the first-service CR and produced considerably more female calves than when the conventional semen (S3) was used. Furthermore, these findings indicate that the use of this novel sexed semen could achieve a sex ratio close to 90% female offspring.

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.