CO-Synch Protocol Research Articles

Evaluation of estrus detection by cervical monitoring and pregnancy rates in ovsynch and co-synch treated Anatolian buffalo heifers

The aim of this study was to assess the relationship between the occurrence and intensity of estrous expression and the success of artificial insemination in Ovsynch and Co-synch treated Anatolian buffalo heifers, employing a novel approach utilizing smartphone-based endoscopic inspection of the cervix uteri. Twenty-seven Anatolian buffalo heifers (n=27) were utilized for the study. In the Ovsynch synchronization protocol (n=15), GnRH (buserelin acetate, 12 μg) was administered on day 0, PGF2α (cloprostenol, 500 μg) on day 7, and GnRH (buserelin acetate, 12 μg) on day 9, with artificial insemination conducted 16-20 hours after the second GnRH application. For the Co-synch protocol (n=12), GnRH (buserelin acetate, 12 μg) was administered on day 0, PGF2α (cloprostenol, 500 μg) on day 7, and GnRH (buserelin acetate, 12 μg) along with artificial insemination on day 10. At the time of artificial insemination, estrous expression was categorized as intense, moderate, weak, or negative. Pregnancies were confirmed between 40 to 70 days after artificial insemination using either pregnancy-related glycoprotein or ultrasonography examinations.Intense, moderate, weak, and negative estrus intensities were observed at rates of 20%, 20%, 26.7%, and 33.3%, respectively, in the Ovsynch group and 41.7%, 58.3%, 0%, and 0%, respectively, in the Co-synch group (P

Reproductive outcomes in Holstein heifers synchronized with timed-AI protocols that provide for a lengthened proestrus.

This study compared reproductive outcomes among two protocols for synchronization of ovulation that provide for a lengthened proestrus with the conventional oestradiol-based protocol currently used for timed-AI (TAI). Holstein heifers (13-15 months) at one location were assigned randomly to one of three TAI protocols. Heifers (n = 150) in the 7-day oestradiol benzoate (EB) group received a progesterone device (Cue-Mate) and 2 mg EB on Day 0; 500 μg of cloprostenol (PGF) and Cue-Mate removal on Day 7; 1 mg of EB on Day 8 and TAI on Day 9 (54 h after Cue-Mate removal). Heifers (n = 150) in the 5-day CO-Synch (CO) group received a Cue-Mate and 100 μg of gonadotropin-releasing hormone (GnRH) on Day 2; Cue-Mate removal and PGF (twice, 12 h apart) on Day 7; and GnRH along with TAI on Day 10 (72 h after Cue-Mate removal). Heifers (n = 150) in the J-Synch (JS) group received a Cue-Mate and 2 mg of EB on Day 1; PGF and Cue-Mate removal on Day 7; GnRH and TAI on Day 10 (72 h after Cue-Mate removal). Heifers were inseminated by one technician with frozen-thawed conventional semen from one of four commercially available sires. Plasma progesterone (P4) concentrations (ng/mL) were determined at Cue-Mate removal and TAI. Ovarian ultrasonography was done in a subset of 217 heifers at the initiation of protocols, at Cue-Mate removal; TAI; and 7 days after TAI. Approximately, 28 and 50 days after TAI pregnancy status was determined by ultrasonography. Mean (±SEM) plasma P4 concentration at Cue-Mate removal was greater (p < .01) in CO (6.02 ± 0.2) and JS (6.51 ± 0.2) compared to EB heifers (4.53 ± 0.2). Mean (±SEM) plasma P4 concentration at TAI was lowest in the JS (0.28 ± 0.05), intermediate in CO (0.46 ± 0.02), and greatest in EB heifers (0.66 ± 0.05, p < .01). The diameter of the ovulatory follicle (mean ± SEM) was the smallest in the JS group compared to that in the CO and EB groups (15.8 ± 0.5; 13.9 ± 0.5; and 12.7 ± 0.5 mm for EB, CO and JS, respectively). More (p < .01) heifers in the JS group had their oestrous cycle synchronized (50.0, 78.8 and 82.4% for EB, CO and JS groups), and were pregnant at 28 (40.3, 51.3 and 63.3% for EB, CO and JS groups) and 50 days after TAI (32.6, 46.0 and 60.0% for EB, CO and JS groups). In summary, heifers subjected to the J-Synch TAI protocol had lower P4 at TAI, and better overall response to hormonal treatments, which resulted in increased P/AI at 28 and 50 days after TAI compared to those heifers subjected to either a 7-day EB protocol or a 5-day CO-synch protocol.

Efficacy of omitting initial GnRH in once-used CIDR co-synch protocol for the treatment of anestrus in buffaloes during low breeding season

Progesterone-based hormonal protocols are effective to treat anestrus in buffaloes. However, most of those protocols are costly, thus, requiring a cost-effective protocol that minimizes handling frequencies. This study, therefore, evaluated the effectiveness of the ‘once-used CIDR co-synch protocol’ with or without initial GnRH for treating anestrus in buffaloes during low breeding season. Anestrous buffaloes (n=29) were divided into two Treatment groups. As a part of the ‘once-used CIDR co-synch protocol,’ the first group (T1, n=18) received an initial GnRH on a random day (day 0) while the second group (T2, n=11) did not receive it. On day 0, the once-used CIDR device was inserted intravaginally in both groups, with GnRH administered in T1 but omitted in T2. On day 7, during CIDR removal, each buffalo received PGF2α, and on day 10, GnRH was given, and fixed-timed artificial insemination (FTAI) was done. Ovarian status was assessed on d0 and on 8 to 9-day post-FTAI using transrectal ultrasonography. Plasma progesterone concentrations on 8 to 9-day post-FTAI were determined using ELISA. No significant differences in estrus expression, ovulation and pregnancy rates were observed between two Treatment groups, with overall rates of 93%, 69%, and 34.5%, respectively. However, the overall pregnancy outcome (from FTAI plus natural breeding of buffaloes that returned to estrus) up to 2 months post-FTAI was 48.3%. Parity affected the ovulation among treated buffaloes, with higher (P=0.04) ovulation rate in buffaloes ≤4th parity (79.2%) compared to &gt;4th parity (20%). There were no differences in CL size and plasma progesterone concentrations during 8 to 9-day post-FTAI between two treatment groups. In conclusion, omitting the initial GnRH in ‘once-used CIDR Co-synch protocol’ proved equally effective as the protocol with initial GnRH for the treatment of anestrus in buffaloes during the low breeding season.

Effectiveness of Once Used versus New CIDR in CIDR Co-synch Protocol for Resuming Reproductive Function in Anestrous Buffaloes During Low Breeding Season

Effectiveness of Once Used versus New CIDR in CIDR Co-synch Protocol for Resuming Reproductive Function in Anestrous Buffaloes During Low Breeding Season

Methods of artificial regulation of estrous cycle of Aberdeen Angus breeding stock

The research aim is to study the efficiency of using the OvSynch and Co-Synch schemes with subsequent resynchronization on beef cows and heifers of the Aberdeen Angus breed. The hormonal state of animals and the biochemical blood serum parameters were chosen as factors determining reproductive function. The purpose is to study the efficiency of applying the OvSynch and Co-Synch synchronization protocols on cows and heifers of the Aberdeen Angus breed depending on the hormonal state of the inseminated animals and the biochemical blood serum parameters. The rate of fertilization in cows inseminated according to the OvSynch protocol was determined to be 5.0 to 8.5 % higher during the first stage of insemination and 5.5 % higher during the second stage of insemination. In the group of heifers, the best fertilization results were obtained while using the Co-Synch protocol (59.3 %). Giving cows a second injection of GnRH, on day 9 of the OvSynch protocol, 16 hours before insemination, provided an average rate of fertilization of 52.3 %, which is 3.4 % higher compared to the 14-hour interval between GnRH injection and insemination. The concentration of steroid and gonadotropic hormones, including cortisol, estradiol, FSH and LH, in experimental animals during insemination corresponded to the estrus phase. The results of biochemical blood tests indicate a number of metabolic inconsistencies in the animal body. Changes in the biochemical blood serum parameters in animals that did not become pregnant followed the same patterns as in those that became pregnant. However, the level of increase or decrease in parameters was less pronounced. The results obtained can be used in arranging artificial insemination in breeding and commercial agricultural organizations engaged in beef cattle breeding, as well as in teaching process of zootechnical and veterinary disciplines in agricultural higher educational institutions of the Republic of Belarus.

Occurrence of Postpartum Anestrus and Estrus Behaviour in Hormonal Treated Buffaloes of Jabalpur

The present study was conducted during June to December, 2022 at the Department of Veterinary Gynaecology and Obstetrics, College of Veterinary Science and Animal Husbandry, Nanaji Deshmukh Veterinary Science University, Jabalpur, Madhya Pradesh, India to study the occurrence of postpartum anestrus and compare the intensity of estrus in anestrus and estrus induced buffaloes of Jabalpur (M.P.). A total of 120 postpartum buffaloes (5–10 years of age) reared under field conditions in the Jabalpur district of Madhya Pradesh were surveyed. The buffaloes with a history of not showing signs of estrus for 60 days or more postpartum were considered as open animals for the study of the occurrence of postpartum anestrus. Gynaeco-clinical examination was also carried out to know the status of ovaries (presence of follicle or corpus luteum). These animals were randomly divided into four groups (three treatments and one control group) and each group had 06 anestrus buffaloes. Group I, II and III were treated with CIDR plus Ovsynch, CIDR plus Cosynch and eCG plus Cosynch protocols, respectively, while the control group (Group IV) animals were not given any treatment. The results revealed that the occurrence of postpartum anestrus in buffaloes was 69.10%. The percentage of postpartum buffaloes with 60–90 days, 90–150 days and more than 150 days postpartum were recorded to be 25.30, 45.78 and 28.91%, respectively. Irrespective of treatment groups, the overall estrus intensity ranged from 58–92 with a mean estrus intensity score of 70.58±2.89. Estrus intensity scoring is a good tool to describe the intensity of estrus which has a positive relationship with fertility.

PSII-10 Effect of Equine Chorionic Gonadotrophin-Like Glycoprotein Treatment on Fertility in Angus Cows Subjected to a 7-Day Co-Synch Protocol

Abstract This study evaluated the effect of administering a glycoprotein with equine chorionic gonadotropin like activity produced by recombinant DNA technology (eCG-like) associated with a 7-d Co-Synch protocol on estrus rate (ER) and pregnancy per timed AI (P/TAI). A total of 1,344 suckled Angus cows (primiparous, n = 381; multiparous, n = 963) from 11 herds were scanned at initiation of synchronization protocol by transrectal ultrasonography and the presence of corpus luteum (CL) and uterine tone was used to classify them by cycling. On day -10, cows received 100 μg GnRH analogue and a progesterone intravaginal device (IVD; 1.0g progesterone) for 7 days. At IVD removal, cows were administered 500 μg of cloprostenol and randomly assigned to receive 400 IU of eCG-like glycoprotein (Syntex S.A., Argentina, PCT/EP2019/073277; eCG-like, n = 665) or to remain as untreated (Control, n = 679). Also on day -3, paint was applied on the sacrum to the tail head of each cow. Finally, 100 μg GnRH analog were injected concurrently with TAI on Day 0 (66h after IVD removal) and the ER was evaluated by the degree of paint loss. Pregnancy to TAI was determined on day 30 by transrectal ultrasonography when an embryo and fluid were detected in the uterus. Body condition score (BCS; scale = 1-9) was evaluated on days -10 and 30. Optimal BCS was considered ≥ 5 and BCS balance between days -10 and 30 was classified as negative (lost BCS) or positive (maintained or gained BCS). The associations among treatment, parity, cyclicity at initiation of protocol, optimal BCS on day -10, and their interactions and ER and P/TAI were analyzed by GLIMMIX (SAS 9.3). Estrus expression and BCS balance were also included as effects in the model of pregnancy per TAI. The effect of herd was included as a random effect. The model specifications included an option to retrieve the mean, SEM, and an adjustment for multiple comparisons (Tukey-Kramer). The percentage of acyclic cows was 31.3%. The ER in cyclic cows was 64.9% and the eCG-like treatment increased ER only in anestrus cows (55.8 vs. 44.3%; Treatment x cyclicity interaction; P = 0.03). The percentage of cows with negative BCS balance was 27.2%. The P/TAI in cows with positive BCS balance was 48.4% and the eCG-like treatment increased P/TAI only in cows with negative BCS balance (44.7% vs. 30.5%; Treatment x BCS balance interaction; P = 0.01). In conclusion, the addition of a recombinant eCG-like glycoprotein to a 7-day Co-Synch protocol increased estrus expression in anestrus Angus cows and P/TAI in those with negative body condition score balance. However, this addition did not influence the estrus expression in cycling cows or on P/TAI in those with positive BCS balance.

PSIII-18 Effect of Industrial Hemp Supplementation on the Salivary Melatonin Concentrations of Angus Cattle at Different Phase of Reproductive Cycle

Abstract Melatonin is an indoleamine, a neurotransmitter and neurohormone mainly produced in pineal gland but also in the ovary. It has an important role in reproduction, antioxidant, immune system and circadian behavior. Industrial hemp is increasingly being included in animal feeds and it is therefore important to evaluate the effect of industrial hemp supplementation on the profiles of melatonin following different phases of reproductive cycle. Twenty apparently healthy Angus heifers, aged 19 months with average body weight of 363 kg and body condition score of 6.5 were randomly divided into two groups of ten heifers each in a completely randomized design. Group 1 (n = 10) were supplemented with grounded industrial hemp at 20/200mg of the concentrate, and group 2 (n = 10) no industrial hemp supplementation. Hay and water were provided ad libitum. The animals were acclimatized for 1 week after which they were synchronized using the 7-day CO-Synch protocols. Salivary samples were collected at preestrus, during estrus and at post estrus. Melatonin in the saliva was assayed with a competitive ELISA kit. The salivary melatonin concentrations were greater (P &amp;gt; 0.05 in the treated groups at estrus (25.29 ± 1.48 pg/mL), pro-estrus (23.98 ± 2.3 pg/mL) and post-estrus (20.31 ± 3.0 pg/mL) compared with the untreated groups at pre-estrus (18.9 ± 1.5 pg/mL), estrus (20.4 ± 2.22 pg/mL) and post estrus (17.22 ± 2.6 pg/mL).The profiles of the salivary melatonin were greater (P &amp;gt; 0.05) at estrus phase in the hemp treated groups compared with the pre-estrus and post estrus phase of the treated groups; however, numerical but non-significant increases were observed in the untreated group at estrus phase compared with the pre-estrus and post estrus phases. It was concluded that industrial hemp supplementation could improve melatonin concentrations and hence improve reproductive, antioxidant and immune function of the cattle.

PSIV-19 The Identification of Possible Microrna Biomarkers of Successful Pregnancy in Timed Embryo Transfer Recipients

Abstract The objective of the current study was to look for potential microRNA (miRNA) biomarkers indicative of a successful pregnancy in timed embryo transfer (ET) recipients. Commercial beef cows were synchronized using a 7-day CIDR co-synch protocol and GnRH injection given 66 hours following CIDR removal. At 6.5 days post GnRH administration, cows (n = 78) had a frozen thawed embryo delivered into the uterine horn ipsilateral to the corpus luteum detected by rectal palpation. A blood sample was collected by coccygeal venipuncture and serum isolated and frozen at -80°C 24 days post embryo transfer. At 38 days post embryo transfer pregnancy was determined by rectal ultrasound by a trained individual and confirmed by Biopryn assay. A total of 42 recipients were determined to be pregnant and 36 were determined to be non-pregnant. Of the 42 pregnant recipients, 10 did not calve and 32 delivered a calf at full term. Day 24 post ET serum samples from pregnant cows that calved normally (n = 4), pregnant cows that did not calve (n = 4), and pregnant cows that had an abnormal pregnancy at time of ultrasound and did not calve (n = 4) were selected for further analysis. These samples had RNA extracted with the microRNA fraction enriched and were then subjected to RNA sequencing (LC Sciences). Differential miRNA abundance was determined using ANOVA adjusted for false discovery rate using the Benjamini-Hochberg method with significance set at P &amp;lt; 0.05. A total of 747 miRNAs were detected and annotated to the bovine genome. A total of 36 miRNA showed differential abundance (P &amp;lt; 0.05) between groups of recipients. Of them, bta-mir-185-p3_1ss21CT, bta-miR-224_R-1, bta-mir-125b-1-p3, bta-miR-363_L+1, and bta-miR-494_R+1 had increased (P &amp;lt; 0.01) abundance in animals that calved to ET compared with cattle that did not calve to ET. MicroRNA PC-5p-120366_31 and PC-5p-89234_47 had increased abundance (P &amp;lt; 0.01) in recipients that had an abnormal appearing pregnancy compared with the other two recipient groups. MicroRNA bta-mir-1306-p3 had increased abundance (P &amp;lt; 0.01) in the two groups of recipients that had normal appearing pregnancies compared with the groups whose pregnancies were abnormal at time of ultrasound. These microRNAs could be used as biomarkers for an insufficient pregnancy that will not go to full term and therefore could be used to increase the efficiency of large scale ET.

Effect of delayed timing of artificial insemination with sex-sorted semen on pregnancy per artificial insemination in synchronized dairy heifers managed in a seasonal-calving pasture-based system

The objective of this study was to evaluate the timing of artificial insemination (AI) with frozen-thawed sex-sorted semen on pregnancy per AI (P/AI) in dairy heifers. A 6-d progesterone Co-Synch protocol was used for ovulation synchronization of dairy heifers, with timed AI (TAI) coincident with (TAI-0) or 8 h (TAI-8) after the second injection of GnRH, corresponding to either 48 h or 56 h after removal of the progesterone-releasing intravaginal device. Pregnancy diagnosis was conducted by transrectal ultrasound scanning of the uterus 34 d after TAI (n = 816 records available for analysis). Generalized linear mixed models were used to examine the effects of treatment on P/AI. Treatment (n = 2), herd (n = 11), and treatment × herd were included as categorical fixed effects. Heifer body weight and Economic Breeding Index values for milk production, fertility, calving performance, beef carcass, cow maintenance, cow management, and health were included as continuous fixed effects. Heifer ID was included as a random effect. Pregnancy per AI was greater for TAI-8 heifers (59%) compared with TAI-0 heifers (50%). Pregnancy per AI ranged from 38% to 75% between herds but there was no treatment × herd interaction. The fertility subindex (positive) and the cow management subindex (negative) were the only continuous animal variables associated with P/AI. Delaying the timing of AI with frozen-thawed sex-sorted semen by 8 h in dairy heifers enrolled on a 6-d progesterone Co-Synch protocol improved P/AI.

Comparative Efficacy of Medroxyprogesterone Acetate (Progestin) Sponges with Co-Synch Protocol for Estrus Synchronization in Holstein Friesian Cattle

The study involved forty non-pregnant, first-parity Holstein Friesian cows housed under semi-intensive management conditions. They were divided into four groups: Group A received a 7-day CIDR followed by a PGF2α injection, Group B received a 12-day CIDR followed by a PGF2α injection, Group C underwent a 10-day Co-Synch protocol, and Group D served as the control. Estrus symptoms were weak in all groups, while strong signs of standing heat were observed. Group B showed the highest estrus response, earliest onset of estrus, longest duration, and highest conception rate, resulting in positive pregnancies. In contrast, Group D had no pregnancies. These findings suggest that the extended CIDR treatment in Group B led to improved reproductive outcomes, indicating its potential as an effective method for estrus synchronization in Holstein Friesian cattle.

Targeted reproductive management for lactating Holstein cows: Reducing the reliance on exogenous reproductive hormones

Adoption of automated monitoring devices (AMD) affords the opportunity to tailor reproductive management according to the cow's needs. We hypothesized that a targeted reproductive management (TRM) would reduce the use of reproductive hormones while increasing the percentage of cows pregnant 305 d in milk (DIM). Holstein cows from 2 herds (n = 1,930) were fitted with an AMD at 251.0 ± 0.4 d of gestation. Early-postpartum estrus characteristics (EPEC; intense estrus = heat index ≥70; 0 = minimum, 100 = maximum) of multiparous cows were evaluated at 40 (herd 1) or 41 (herd 2) DIM and EPEC of primiparous cows were evaluated at 54 (herd 1) or 55 (herd 2) DIM. Control cows received the first artificial insemination at fixed time (TAI; primiparous, herd 1 = 82 and herd 2 = 83 DIM; multiparous, herd 1 = 68 and herd 2 = 69 DIM) following the Double-Ovsynch (DOV) protocol. Cows enrolled in the TRM treatment were managed as follows: (1) cows with at least one intense estrus were inseminated upon AMD detected estrus for 42 d and, if not inseminated, were enrolled in the DOV protocol; and (2) cows without an intense estrus were enrolled in the DOV protocol at the same time as cows in the control treatment. Control cows were re-inseminated based on visual or patch aided detection of estrus, whereas TRM cows were re-inseminated as described for control cows with the aid of the AMD. Cows received a GnRH injection 27 ± 3 d after insemination and, if diagnosed as nonpregnant, completed the 5-d Cosynch protocol and received TAI 35 ± 3 d after insemination. Among cows in the TRM treatment, 55.8 and 42.9% of primiparous and multiparous cows, respectively, received the first insemination in spontaneous estrus. The interaction between treatment and parity affected pregnancy 67 d after the first AI (primiparous: control = 37.6%, TRM = 27.4%; multiparous: control = 41.0%, TRM = 44.7%). The TRM treatment increased re-insemination in estrus (control = 48.3%, TRM = 70.5%). Pregnancy 67 d after re-inseminations tended to be affected by the interaction between treatment and EPEC (no intense estrus: control = 25.3%, TRM = 32.0%; intense estrus: control = 32.9%, TRM = 32.2%). The interaction between treatment and EPEC affected pregnancy by 305 DIM (no intense estrus: control = 80.8%, TRM = 88.2%; intense estrus: control = 87.1%, TRM = 86.1%). Treatment did not affect the number of reproductive hormone treatments among cows that had not had an intense estrus (control = 10.5 ± 0.3, TRM = 9.1 ± 0.2 treatments/cow), but cows in the TRM treatment that had an intense estrus received fewer reproductive hormone treatments than cows in the control treatment (2.0 ± 0.1 vs. 9.6 ± 0.2 treatments/cow). Selecting multiparous cows for first AI in estrus based on EPEC reduced the use of reproductive hormones without impairing the likelihood of pregnancy to first AI. The use of AMD for re-insemination expedited the establishment of pregnancy among cows that did not display an intense estrus early postpartum.

A single dose of FSH or hCG during a split-time AI program did not enhance follicular growth or pregnancy per artificial insemination in beef heifers

ABSTRACT The objective of this study was to evaluate the effect of a low dose of hCG or FSH on follicle growth and pregnancy per artificial insemination (AI) in crossbreed beef heifers subjected to a split-time AI program. All heifers (n = 386) were subjected to a 7-d Co-synch protocol and an intravaginal controlled internal drug release (CIDR) device (GnRH and CIDR insertion; 7 days later PGF2α, CIDR removal, and application of a tail head estrus detection patch; 36 hours later AI of heifers detected in estrus, 24 hours later timed AI of remaining heifers). At CIDR removal, heifers were randomly assigned to receive either 150 IU of hCG, 20 mg of FSH, or remained as untreated controls. The diameter of the preovulatory follicle and the pregnancy per AI did not differ among treatments. A smaller (P = 0.035) proportion of heifers in the hCG group were detected in estrus compared with control. Additionally, the incidence of premature ovulation was greater (P < 0.01) among heifers treated with hCG compared with control. In conclusion, using a low dosage of hCG or FSH at the time of device removal did not affect pre-ovulatory follicle growth or the proportion of pregnant heifers.

Heterosis of crossbred genotypes of muturu cows mated with white fulani bulls using modified co-synch protocol under natural grazing conditions

Heterosis is the improved performance of the offspring over the parents. The experiment was carried out to determine the heterosis of some anthropometric traits from crossing of Muturu cows with the White Fulani bulls using artificial insemination (AI). This experiment was carried out during the period of dry season and on-set of rainy season (November to February) between 2016 and 2019. Sixty adult Muturu cows were inseminated using semen from 15 different White Fulani bulls. Fifty-one crossbred calves were produced (32 females and 19 males). Data on different anthropometric traits were taken of the calves when they were a yearling. The data was compared with the parent’s data at yearlings by analyzing using T test in SPSS version 19 window. The results showed that all the traits were significantly (P&lt;0.05) different between the crossbred and the parents presenting direct and positive heterosis over and above the parents. Heterosis occurred in both the crossbred bull and heifer calves. Crossbred calves grow faster than their inbred parents.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; L’hétérosis est l’amélioration des performances de la progéniture par rapport aux parents. L’expérience a été réalisée pour déterminer l’hétérosis de certains traits anthropométriques du croisement des vaches Muturu avec les taureaux White Fulani par insémination artificielle (IA). Cette expérience a été réalisée pendant la période de saison sèche et au début de la saison des pluies (novembre à février) entre 2016 et 2019. Soixante vaches Muturu adultes ont été inséminées à partir de la semence de 15 taureaux White Fulani différents. Cinquante et un veaux croisés ont été produits (32 femelles et 19 mâles). Des données sur différents traits anthropométriques ont été prises sur les veaux lorsqu’ils étaient un an. Les données ont été comparées aux données des parents chez les yearlings en analysant à l’aide du T-test dans la fenêtre SPSS version 19. Les résultats ont montré que tous les caractères étaient significativement (P&lt;0,05) différents entre les croisés et les parents présentant une hétérosis directe et positive au-delà des parents. L’hétérosis s’est produite à la fois chez les taureaux croisés et les génisses. Les veaux croisés grandissent plus vite que leurs parents consanguins.

A high dose of initial GnRH increased ovulatory response and fertility in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol

The objectives of this study were to investigate the effect of presynchronization or dose of GnRH on ovulatory response to initial GnRH, estrus expression and reproductive outcomes in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol. Heifers were fitted with a collar-mounted automated activity monitoring system on Day −5 and were assigned randomly to one of three groups: 1) G100 (n = 111), a 5-d CO-Synch plus PRID protocol with administration of 100 μg of GnRH at the time of PRID insertion (Day 0), 500 μg of cloprostenol (PGF) at the time of PRID removal (Day 5) and again 24 h later (Day 6); 2) G200 (n = 112), same as G100 except 200 μg GnRH was administered on Day 0; 3) P10 (n = 111), PRID + PGF on Day −5 followed by a 5 d CO-Synch with administration of 100 μg of GnRH on Day 0, PGF at the time of PRID removal (Day 5) and again 24 h later (Day 6). Approximately 72 h after PRID removal (Day 8), all heifers were timed-inseminated (TAI) and concurrently 100 μg of GnRH was administered to those not exhibiting estrus. All inseminations were done by one technician using either sex-sorted (n = 265) or conventional (n = 69) frozen-thawed semen. Transrectal ultrasonography was done to determine ovarian cyclicity and normalcy of the reproductive tract, ovarian dynamics and pregnancy. All heifers were cyclic and ovulatory response to initial GnRH was greater (P < 0.01) in G200 (51.8%) and P10 (47.7%) compared to G100 (27.9%). Estrus expression rate tended to be greater (P = 0.08) in G100 (93.7%) compared to G200 (85.7%) and intermediate in P10 (89.2%). Expression of estrus was associated positively with P/AI at 45 d post-TAI (P < 0.01; 70.2 vs. 31.4% for heifers expressing or not expressing estrus). Heifers in the G200 group had greater P/AI at 30 (P < 0.01) and 45 (P = 0.01) d post-TAI (79.5 and 75.9%, respectively) compared to those in G100 (63.1 and 60.4%) or P10 (64.0 and 62.2%) groups. Pregnancy loss did not differ among treatment groups (overall 3.9%). Results indicate that increasing the dose of the initial GnRH from 100 to 200 μg resulted in increased ovulatory response and improved P/AI in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol. Although heifers presynchronized with a combination of PRID and PGF had an increased ovulatory response to the initial GnRH, P/AI did not differ from the standard progesterone based 5-d CO-Synch protocol.

Estrous activity and pregnancy outcomes in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol with or without administration of initial GnRH.

The objectives of this study were to investigate whether estrous activity and its impact on pregnancy outcomes would differ in heifers subjected to a 5d CO-Synch plus progesterone releasing intravaginal device (PRID) protocol with or without an initial GnRH treatment. Holstein Heifers (n=308) were fitted with a collar-mounted automated activity monitoring system approximately 1 week prior to the initiation of the synchronization protocol (Day-7). Heifers were assigned randomly to a 5d CO-Synch plus PRID protocol either with (GnRH; n=154) or without (NGnRH; n=154) an initial administration of 100μg of GnRH at the time of PRID insertion (Day 0). Heifers received a single administration of 500μg of cloprostenol (PGF) at the time of PRID removal (Day 5) and again 24h later (Day 6). Approximately 72h after PRID removal (Day 8), heifers were timed-inseminated (TAI) and concurrently 100μg of GnRH was administered to those not exhibiting estrus. All inseminations were done by one of two technicians using either sex-sorted (n=252) or conventional (n=56) frozen-thawed semen. Transrectal ultrasonography was done on Day 0 to determine ovarian cyclicity and normalcy of the reproductive tract and 30 and 45d post-TAI to determine and confirm pregnancy, respectively. The percentage of heifers determined to be in estrus following PRID removal was greater in the GnRH than in the NGnRH group (94 vs. 82%, respectively; P<0.01). The mean interval from PRID removal to the onset of estrus was shorter for GnRH- than NGnRH-treated heifers (50.8 vs. 59.2h, respectively; P<0.01). Pregnancy per AI (P/AI) at 30d post-TAI tended to be greater for GnRH than NGnRH heifers (68 vs. 59%, respectively; P=0.1). However, P/AI at 45d post-TAI (65 vs. 57%, respectively) and pregnancy loss between 30 and 45d post-TAI (6 vs. 4.5%, respectively) did not differ. The association between the interval from PRID removal to the onset of estrus and P/AI at 30d post-TAI was linearly negative for GnRH heifers; for every 1h increase in the interval from PRID removal to the onset of estrus, the predicted probability of P/AI at 30d post-TAI tended (P=0.08) to be reduced by 2.7%. The association between the interval from PRID removal to the onset of estrus and P/AI at 30d post-TAI was not significant for NGnRH heifers. In addition, the interval from TAI to subsequent estrus, in non-pregnant heifers, was approximately 3d longer for the GnRH than the NGnRH group (20.7 vs. 17.5d, respectively). In summary, the initial GnRH treatment in a 5d CO-Synch plus PRID protocol increased estrus expression and reduced the interval from PRID removal to the onset of estrus in Holstein heifers and tended to increase P/AI at 30d, but did not affect P/AI at 45d post-TAI.

Correction to: PSXII-20 Ovarian dynamics and fertility in beef cows administered a 5-day or 6-day CO-Synch protocol for timed artificial insemination

Correction to: PSXII-20 Ovarian dynamics and fertility in beef cows administered a 5-day or 6-day CO-Synch protocol for timed artificial insemination

Greater numbers of antral follicles in the ovary are associated with increased concentrations of glucose in uterine luminal fluid of beef heifers

Increased antral follicles are associated with greater fertility and a uterine environment that is more supportive of early embryonic development in beef heifers. Glucose is a primary energy source for embryos, and glucose concentrations are elevated in uterine luminal fluid (ULF) of pregnant heifers. We hypothesized that ULF glucose concentrations and endometrial transcript abundance for glucose transporters on d16 after insemination would be greater in heifers with increased numbers of antral follicles. Heifers classified with either increased or diminished antral follicle counts were artificially inseminated following the CO-Synch protocol (d0). On d16 after insemination, reproductive tracts of heifers were collected at an abattoir to retrieve conceptuses to determine pregnancy. Uterine luminal fluid was collected, endometrium was biopsied, total RNA was extracted and glucose transporter transcript abundances were determined. Data were analyzed using the MIXED procedure of SAS with antral follicle group, pregnancy status, and the interaction as fixed effects. Glucose concentrations in ULF were greater in heifers with increased antral follicle numbers. Glucose ULF concentrations increased in pregnant heifers. Facilitated glucose transporter member 1 (SLC2A1) transcript abundance was increased in the endometrium of pregnant heifers but was not different due to antral follicle number or the interaction. Differences in uterine concentrations of glucose associated with antral follicle number could be due to another mechanism, since glucose transporters were not different between antral follicle numbers. Therefore, heifers with increased number of antral follicles have increased energy availability in the uterus to support trophoblast proliferation and function.

PSXII-20 Ovarian dynamics and fertility in beef cows administered a 5-day or 6-day CO-Synch protocol for timed artificial insemination

Abstract The 5-day CO-Synch is an extensively used TAI protocol; however, it requires multiple administrations of prostaglandin F2α (PGF). The objective of the present study was to evaluate the effect of increasing progesterone (P4) device insertion from 5 to 6 days during a TAI protocol on ovarian dynamics and fertility in beef cows. Suckled beef cows (n = 867) at six locations were randomly assigned to either a 5-day or 6-day CO-Synch. Cows received an intravaginal P4 device (CIDR, Zoetis) and 100 µg of gonadorelin acetate (GnRH, Parnell) on d-9 (6-day) or d-8 (5-day). On d-3 CIDR’s were removed, an estrus detection patch applied (Estrotect, Rockway Inc.) and either one (6-day) or two (5-day) doses of PGF (500 µg of cloprostenol sodium, Estroplan, Parnell) was administered. On d0 (72 h after CIDR removal) all cows received 100 µg of GnRH, estrus expression was evaluated, and AI was performed. Pregnancy was determined by ultrasonography 34 days after TAI. Ovarian dynamics were evaluated in a subset of animals (n = 20) between d-3 and d7 to determine preovulatory follicle size, time of ovulation and corpus luteum (CL) size. Data were analyzed using generalized linear mixed models (SAS 9.4). Cows in the 6-day group tended (P = 0.09) to have a larger maximum follicle diameter (16.2±0.4mm) than cows in the 5-day group (15.0±0.6mm). In addition, CL volume on d7 was greater (P = 0.01) in the 6-day (4302±495mm3) than 5-day (2406±455mm3) group. There were, however, no differences (P = 0.15) in the interval between CIDR removal and ovulation. Cows assigned to the 6-day group had greater (P &amp;lt; 0.05) estrus expression [56.1% (215/385) vs 41.5% (161/388)] and pregnancy rate [54.6% (236/438) vs 47.4% (207/435)] than cows in the 5-day group. In conclusion, extension of the period of P4 device insertion in a prolonged proestrus protocol increases preovulatory follicle size, estrous expression, and fertility to TAI.

244 Fertility Outcomes Associated with Reproductive Tract Cytokines and Microbiota in Postpartum Beef Cows

Abstract Local immune activity in the reproductive tract is crucial in the response to uterine diseases, normal reproductive functions, and establishing pregnancy. Few studies have evaluated the influence of the local immune environment of the reproductive tract on fertility outcomes. The objectives were to 1) evaluate reproductive cytokine concentrations in postpartum cows undergoing estrus synchronization followed by timed artificial insemination (TAI) and 2) correlate reproductive bacterial communities with cytokine concentrations. Angus cows (n = 20) were subjected to a 7-Day Co-Synch protocol with pre-synchronization beginning 21 days prior (d -21) to TAI (d 0). Uterine and vaginal flushes were collected on d -21 and -2. Pregnancy was determined by transrectal ultrasound on d 30. Bacterial community profiling and analyses were conducted targeting the V1 to V3 hypervariable regions of the 16S rRNA gene. Cytokine concentrations for interleukin (IL)-1b, IL-6, IL-10, and transforming growth factor beta (TGF-β) were determined by commercial ELISA kits. Concentration data were analyzed using PROC MIXED and correlations using Pearson correlation in SAS. No differences were detected in vaginal samples (P &amp;gt;0.05). No differences in IL-10 or IL-1b concentrations were detected in uterine samples (P &amp;gt;0.05). Uterine TGF-β concentrations were greater in resulting pregnant than non-pregnant cows (44.0 ± 13.4 pg/mL vs 14.7 ± 4.9 pg/mL; P = 0.05). Uterine TGF-β was negatively correlated with the relative abundance of genera Treponema (r = -0.668; P = 0.05) in resulting non-pregnant cows on d -21. Uterine IL-6 concentrations were greater in resulting non-pregnant than pregnant cows (198.7 ± 21.8 pg/mL vs 144.3 ± 16.1 pg/mL; P = 0.05). Uterine IL-6 and the relative abundance of genera Butyrivibrio were positively correlated (r = 0.742; P = 0.02) in resulting non-pregnant cows on d -21. These results suggest possible relationships between uterine bacterial communities and cytokines prior to TAI that may ultimately affect fertility outcomes in beef cattle.