Timed Artificial Insemination Protocol Research Articles

Economic viability of using OvSynch and fixed timed artificial insemination protocol in breeding improvement of pastoral herds in the rangelands.

Though using Assisted Reproductive Technologies (ARTs) can improve oestrus detection, conception and pregnancy success, thus benefit breeding program implementation, empirical evidence of their economic viability is lacking to inform investment decisions in pastoral herds. This study assessed economic viability of using OvSynch and fixed Timed Artificial Insemination (TAI) protocol in Sahiwal upgrading breeding program under two hypothetical cases of best and worst in activity-based money allocations when pastoral herds deploy either optimal or low input husbandry practices. From herd owners' assessment of milk production, best-case scenarios attain on average 10 L/cow/day with optimal husbandry and 5 L/cow/day with low input husbandry. The worst-case scenarios attain 5 L/cow/day with optimal husbandry and 1 L/cow/day with low input husbandry. Benefit- Cost Analysis (BCA) estimated Net Present Value (NPV), Benefit-Cost ratio (BCR) and Internal Rate of Return (IRR) to establish economic viability of using OvSynch and TAI Protocol in pastoral breeding programs. Both best-case scenarios retuned positive NPVs (82,028 and 6,912), BCR values (1.68 and 1.08) and IRR (27.46% and 8.08%) while worst-case scenarios returned negative NPVs (-135,855 and -141,025), BCR values of below 1 (0.87 and 0.66) and IRR values below the minimum rate of returns. These economic parameters were sensitive to price changes in inputs and outputs, under both optimal and low input husbandry practices. Results indicate that using OvSynch and TAI Protocol is a profitable and economically viable investment under optimal husbandry practices but not under low input husbandry practices. By implications, use of OvSynch and TAI Protocol in Sahiwal upgrading breeding programs need be accompanied with improved husbandry practices and de-risking pastoral herd owners from price changes in input and output markets.

Timed artificial insemination protocols in dairy cattle: Functioning, shortcomings, and improvements

Oestrus detection is currently at the top of the factors limiting the success of artificial insemination in dairy herds. This limitation becomes more pronounced as milk production increases because of higher metabolic clearance rates of steroid hormones leading to low circulating oestradiol concentration near oestrus. The standard OvSynch has overcome this problem by enabling fixed-time artificial insemination, for it synchronises follicular wave emergence, luteolysis, and ovulation. However, it did not improve fertility compared to cycles with spontaneous ovulation, which motivated the development of “fertility programs”. These later are nothing but improved OvSynch protocol. This article explains what went wrong with the original OvSynch protocol, discusses the improvements made by “fertility programs”, and highlights the advantages and limits of the newly tested molecules.

Use of intravaginal lactic acid bacteria prepartum as an approach for preventing uterine disease and its association with fertility of lactating dairy cows

The objective of this study was to evaluate the effects of the use of intravaginal probiotics prepartum on the incidence risk of metritis postpartum and conception risk after first artificial insemination (AI). A total of 606 Holstein cows were enrolled 3 wk before their expected calving date from 2 farms. Cows were randomly assigned to either receive a 2-mL dose of a combination of 3 lactic acid bacteria (probiotic treatment) washed with approximately 2 mL of a sterile saline solution, into the vaginal canal twice weekly until parturition, or no intervention (control). Metritis diagnoses were carried out on 6 and 12 d postpartum. Vaginal discharge and rectal temperature were assessed, and vaginal discharge was scored on a scale from 1 to 4, where 1 = clear and 4 = fetid, purulent discharge. Metritis was defined as cows having a vaginal discharge score of 4 with or without fever (rectal temperature ≥39.5°C) on either 6 or 12 d postpartum, or both. Cows were bred after a 60-d voluntary waiting period primarily via the detection of estrus using automated activity monitors; cows not found in estrus were enrolled onto timed AI protocols to receive first breeding before 100 DIM. Pregnancy diagnosis was carried out at d 35 ± 7 post-AI on both farms. Data were analyzed via ANOVA using linear mixed regression models and survival analysis using a Cox proportional hazard model. Total incidence risk of metritis was 23.7% and 34.4% on farm A and farm B, respectively. Overall, the incidence of metritis was not different between treatment groups (control: 41.6 ± 3.8%; probiotic: 38.6 ± 4.0%); however, an interaction by farm was detected, where the probiotic treatment reduced metritis on one farm but not on the other. Conception risk after first AI was not affected by treatment. However, we detected an interaction between parity and treatment, where multiparous cows receiving the probiotic treatment were more likely to become pregnant compared with multiparous cows within the control group (hazard ratio: 1.33; 95% confidence interval: 1.10-1.60); no effect of probiotic treatment was found on the hazard of pregnancy for primiparous cows. In addition, the probiotic treatment was associated with an increased proportion of cows being detected in estrus for the first AI postpartum. In conclusion, vaginal probiotic treatment applied during the 3 wk prepartum was associated with a decreased incidence of metritis on one farm but not the other, suggesting that farm management may be a key player influencing treatment efficacy. Overall, probiotic treatment was found to have only limited effects on fertility in the current study.

Effects of early weaning on productive and reproductive performance of Nelore heifers

Abstract We aimed to evaluate the effects of early weaning on the productive and reproductive characteristics of Nelore heifer progeny. Ninety-five calves from primiparous (PRI) and multiparous (MUL) dams were assigned to one of two weaning strategies; 1) early weaning at 150 d (149 ± 1.97) of age (EW; n = 16 from PRI and 31 from MUL); or 2) conventional weaning at 240 d (247 ± 2.41) of age (CW; 16 from PRI and 32 from MUL). All heifers received ~5 g/kg of body weight (BW) of creep-feed as fed from 90 d of age until weaning. After weaning, each group of heifers was transferred to a Brachiaria spp. paddock and received 5 g/kg of BW of a protein-energy supplement until 12 mo of age. Then, heifers were confined and fed a diet with a ratio of 79:31 (corn silage: concentrate) for 4 mo, during which they were submitted to a hormonal protocol to induce puberty and timed artificial insemination (TAI). Reproductive tract score (RTS, 1 to 5 scale: 1 being infantile and 5 being cyclic) and endometrial thickness were determined at 12 mo of age, rump fat thickness (RFT), and BW every 28 ± 4 d through the breeding season, and plasma concentrations of IGF-I were evaluated at 12, 14, and 16 mo. At 15.6 mo of age heifers were submitted to a P4/E2 protocol for TAI at day 0 (D0), and a second TAI was performed at D22 in nonpregnant heifers. Ultrasound was used to determine the presence of corpus luteum on D10 and dominant follicle (DF) diameter and blood perfusion on D2 and D0. Data were analyzed using SAS by ANOVA or logistic regression. Though heifers from EW were lighter (P < 0.05) than CW at postweaning time points and CW presented a greater (P = 0.002) RFT than EW heifers from 11 to 15 mo, weaning strategy did not affect (P > 0.1) body condition score at TAI. Concentrations of IGF-I did not differ (P > 0.1) between heifers weaned at 150 and 240 d. The proportion of pubertal heifers, endometrium tone and thickness, and RTS at 16 mo did not differ (P > 0.1) between EW and CW groups. The diameter of DF on D2 and D0 and follicular blood perfusion on D0 were greater (P < 0.05) for heifers in the CW group than EW group, but P/AI at first and second TAI did not differ (P > 0.1) between groups. In conclusion, early weaning in Nelore heifers moderately reduces postweaning growth but does not affect puberty and reproductive performance before the breeding season when submitted to confinement.

Low versus high antral follicle count on the fertility of timed AI Nelore heifers

This study aimed to determine the effect of antral follicle count (AFC), and pubertal status on the fertility of beef heifers. In this study, 230 Nelore heifers, 20±2 months of age, were subjected to an estradiol progesterone-based timed artificial insemination (TAI) program. On Day 0 of the TAI protocol, the heifers were examined by transrectal ultrasound to record videos of the ovaries. Later, in the darkroom of the laboratory of images, the videos were analyzed for AFC (≥ 3 mm) of each ovary. Females who failed the first TAI were resynchronized with the same hormonal protocol. The pregnancy status was evaluated by ultrasonography 30 days after each FTAI. The general mean of the AFC was 22.0 follicles. Thus, the heifers were divided into 2 groups according to AFC: Low AFC (˂ 22 follicles, n = 114), and High AFC (≥ 22 follicles, n = 116). No differences (P > 0.05) in the pregnancy per AI (P/AI) were observed between the Low and High AFC groups, and between pubertal and prepubertal categories. The P/AI was not different between heifers that displayed or did not estrus (P = 0.2). However, considering the estrus response of each AFC group, High AFC heifers that displayed estrus had greater P/AI (P = 0.01) than High AFC heifers that did not display estrus. In summary, AFC and pubertalstatus did not affect the fertility of Nelore heifers. In contrast, the P/AI of heifers that did not display estrus was lower than heifers observed in estrus only in the High AFC group.

What are the factors associated with pregnancy loss after timed-artificial insemination in Bos indicus cattle?

Pregnancy loss (PL) has important impacts on the profitability of livestock production systems, although it is not widely reported, particularly in Bos indicus cattle. The present study retrospectively evaluated PL after timed-artificial insemination (TAI) in Bos indicus (Nelore) beef cows corresponding to several factors, such as parity, body condition score (BCS), presence of corpus luteum (CL) at the beginning of TAI protocols, expression of estrus, and hormonal manipulations during the TAI protocol. Data from two experiments performed during three breeding seasons (BS) were reanalyzed. Both experiments evaluated adding GnRH treatment at TAI in a 7-d estradiol (E2) plus progesterone (P4)-based protocol, with intravaginal P4 implant removal on Day 7 combined with treatment with 0.5 or 1.0 mg E2 cypionate and 300 IU eCG, and TAI on Day 9. In addition, during BS 2 and 3 (Exp 2), cows were randomized to receive or not a PGF treatment on Day 0 (beginning of the TAI protocol). In all BS, presence of CL and BCS were evaluated at the beginning of TAI protocols, follicle size and expression of estrus were evaluated at TAI. The PL was assessed between the first pregnancy diagnosis (∼35d) and parturition. There were no effects of hormonal manipulations within TAI protocols of different BS on PL. There was no interaction between GnRH treatment at TAI and the other variables within BS, and there was no main effect of GnRH treatment on PL (without = 10.1% [102/1007] vs. with = 10.4% [114/1100]). The addition of PGF on Day 0 had no effect on PL (11.5% [102/886] vs. 10.5% [89/850]), as well as EC dose to induce final ovulation (10.8% [89/827] vs. 11.2% [102/909] for 0.5 and 1.0 mg, respectively). Primiparous had greater PL than multiparous cows (14.0% [77/550] vs. 8.9% [139/1557]), and cows not expressing estrus near TAI had greater PL than those expressing estrus (13.5% [57/422] vs. 9.7% [156/1617]). There was no interaction between follicle size at TAI and GnRH treatment on PL. However, probability of PL decreased linearly as follicle size at TAI increased. There were no effects of service number (first TAI or resynchronization), BCS, or presence of CL on D0 on PL. In addition, PL was not affected by sire within any of the BS. In conclusion, some factors that are known to impact pregnancy per AI also influenced PL, such as parity and expression of estrus, although, other aspects such as BCS, number of services, and presence of CL on D0 did not affect PL. Moreover, commonly implemented treatments to increase fertility (e.g., PGF on Day 0 and increasing EC dose to 1.0 mg) did not affect PL. Finally, the GnRH treatment at TAI had no effect on PL and did not interact with any of the variables, an important result, since GnRH at TAI also increases fertility in Bos indicus beef cows.

Machine learning classification of breeding protocol descriptions from Canadian Holsteins.

Dairy farmers are motivated to ensure cows become pregnant in an optimal and timely manner. Although timed artificial insemination (TAI) is a successful management tool in dairy cattle, it masks an animal's innate fertility performance, likely reducing the accuracy of genetic evaluations for fertility traits. Therefore, separating fertility traits based on the recorded management technique involved in the breeding process or adding the breeding protocol as an effect to the model can be viable approaches to address the potential bias caused by such management decisions. Nevertheless, there is a lack of specificity and uniformity in the recording of breeding protocol descriptions by dairy farmers. Therefore, this study investigated the use of 8 supervised machine learning algorithms to classify 1,835 unique breeding protocol descriptions from 981 herds into the following 2 classes: TAI or other than TAI. Our results showed that models that used a stacking classifier algorithm had the highest Matthews correlation coefficient (0.94 ± 0.04, mean ± SD) and maximized precision and recall (F1-score = 0.96 ± 0.03) on test data. Nonetheless, their F1-scores on test data were not different from 5 out of the other 7 algorithms considered. Altogether, results presented herein suggest machine learning algorithms can be used to produce robust models that correctly identify TAI protocols from dairy cattle breeding records, thus opening the opportunity for unbiased genetic evaluation of animals based on their natural fertility.

Effect of nerve growth factor-β administered at insemination for lactating Holstein dairy cows bred after timed-artificial insemination protocol

The objectives of this study were to determine the effects of nerve growth factor-β (NGF), purified from bulls' seminal plasma and administered at the time of artificial insemination (AI), on progesterone post-AI, interferon-stimulated genes (ISG), and pregnancy per AI (P/AI) for lactating Holstein dairy cows enrolled in a timed-AI protocol. We hypothesized that administration of NGF at the time of AI would increase plasma progesterone post-AI, upregulate relative abundance of ISG, and improve P/AI in lactating dairy cows. Holstein cows (n = 557) from a single commercial dairy farm were blocked by parity and randomly assigned to receive an intramuscular injection containing 296 µg of bovine purified NGF at the time of AI, diluted in 2 mL of phosphate-buffered saline (NGF: n = 275), or receive only the 2 mL of phosphate-buffered saline (control: n = 282). Plasma progesterone and corpus luteum size were assessed in a subset of cows (NGF: n = 32; control: n = 36) at d 7, 14, and 19 post-AI. Relative mRNA abundance of ISG (ISG15, MX1, MX2, and RTP4) was assessed in peripheral blood leukocytes on d 19 post-AI. Pregnancy diagnosis was performed at 37 and 65 d post-AI. There was an interaction effect between treatment and parity for plasma progesterone; however, plasma progesterone and ISG did not differ between treatments. There were no effects of NGF for P/AI at 37 d post-AI (NGF = 40.0% vs. control = 41.6%), 65 d post-AI (NGF = 36.0% vs. control = 38.1%), and for pregnancy loss (NGF = 8.4% vs. control = 7.7%). The current study revealed that effects to NGF in lactating Holstein cows were minor and contingent with parity for progesterone, and no improvement in ISG relative abundance and P/AI were observed.

Association between genomic daughter pregnancy rates and reproductive parameters in Holstein dairy cattle

The objective of this observational study was to evaluate the relationship between genomic daughter pregnancy rate (GDPR) with reproduction parameters such as pregnancy at first artificial insemination (AI), pregnancy per AI, and pregnancy losses (PL). A total of 12,949 events from 3,499 Holstein cows were included. Cows were enrolled as nulliparous (n = 1,220), primiparous (n = 1,314), or multiparous (n = 965). Cows were bred either after a timed AI protocol, timed embryo transfer (ET), or spontaneous estrus. Most lactating cows were bred following a timed AI protocol based on estradiol and progesterone, and most nulliparous were artificially inseminated following estrus detection. Hair samples were collected from the tail switch and cows were genotyped using a SNP platform (Clarifide, Zoetis). Cows that were bred by timed AI were evaluated for estrous behavior using tail chalk. Tail chalk was applied on the head of the tail 2 d before timed AI and the chalk was evaluated at AI (no estrus: 100% of chalk remaining or ≥50% of chalk remaining; Estrus: <50% of chalk remaining). Pregnancy diagnosis was performed at d 32 and 60 after AI using ultrasonography, and the presence of a heartbeat was considered a positive diagnosis. Pregnancy loss was defined as a pregnant cow on d 32 that was nonpregnant on d 60. As GDPR increased, the odds of pregnancy at first AI increased [odds ratio (OR) = 1.28, 95% CI = 1.20-1.35], the odds of pregnancy per AI increased (OR = 1.31, 95% CI = 1.25-1.36), and the odds of PL decreased (OR = 0.66, 95% CI = 0.60-0.72). Most cows that were bred on the day of the timed AI demonstrated estrus (n = 6,075; 92.9%). The odds of demonstrating estrus on the day of timed AI increased as GDPR increased (OR = 1.31, 95% CI = 1.17-1.48). There was no interaction between GDPR and parity or breeding management for pregnancy at first AI, pregnancy per AI, and PL. In conclusion, the odds of pregnancy at first AI and pregnancy per AI increased as GDPR increased. Moreover, the odds of PL increased as GDPR decreased. Greater GDPR was also associated with greater occurrence of estrus on the day of timed AI. These results suggest that selecting for higher GDPR could result in better reproductive performance, but this would need to be assessed with additional research.

Dynamic changes in gene expression during follicle development and the efficacy of four timed AI protocols in non-suckling female yaks (Bos grunniens)

The objectives of the study were to investigate changes in the mRNA expression levels of five genes during antral follicle development and to assess the efficacy of four timed-artificial insemination (TAI) protocols in female yaks (Bos grunniens). RT-qPCR analysis revealed that expression levels were greater for follicle-stimulating hormone receptor and bone morphogenic protein 15 in the small follicle, luteinizing hormone receptor, and kit ligand in the large follicle, and growth differentiation factor 9 in the medium follicle (p < 0.05). Non-suckling yaks were treated as a 7-d CIDR, and PGF2α + eCG at CIDR withdrawal and TAI with frozen yak semen at 56–58 h after PGF2α (PPe-7d); either a 7-d CIDR (PPG-7d) or a 5-d CIDR (PPG-5d), and PGF2α at CIDR withdrawal and TAI + GnRH at 70–72 h after PGF2α; and GnRH treatment on Day 0, followed by PGF2α on Day 7 and TAI + GnRH on Day 9 (GPG-7d). The results showed that the pregnancy rate (P/AI) was greater in PPG-5d than in GPG-7d (p < 0.05), but the P/AI was not different among the other TAI protocols. In conclusion, the expression levels of these genes in follicles are dynamically changed during antral follicle development in yaks. The PPG-5d protocol achieved a greater P/AI.

The effect of subclinical endometritis on reproductive performance in postpartum Bos indicus multiparous beef cows

The objective was to investigate the prevalence of subclinical endometritis (SE) in postpartum Bos indicus multiparous beef cows using different polymorphonuclear cells (PMN) threshold ratios, and to evaluate the impacts of SE on their reproductive performance. A total of 689 postpartum Nellore cows (45.2 ± 7.8 days postpartum) were submitted to an estrus synchronization protocol + timed-artificial insemination (TAI). Endometrial cytology samples were collected by cytobrush before the beginning of the protocol. Cows were considered positive for SE if: (PMN) ≥ 3% (PMN3), PMN ≥ 5% (PMN5) and PMN ≥ 7% (PMN7). Pregnancy diagnosis was performed at 30 and 100 d after TAI. The prevalence of cows categorized as positive for SE increased (P < 0.05) as the threshold was lowered (PMN7 = 3.9%; PMN5 = 5.5%; PMN3 = 9.1%). Positive SE cows had similar (P > 0.41) BCS, days postpartum, and expression of estrus at TAI compared with negative SE cows. Positive SE cows had decreased (P = 0.04) pregnancy rates compared to negative SE cows in the PMN5 threshold (26.3 ± 8.7% vs 44.5 ± 4.1%); however, no difference (P > 0.45) was observed between positive and negative SE cows in the PMN3 and PMN7 thresholds. Embryonic mortality between days 30 and 100 was not affected by SE (P > 0.16). In conclusion, the prevalence of SE varies based on the PMN threshold used, whereas SE at the beginning of the TAI protocol decreased the pregnancy rates in postpartum Bos indicus beef cows when the PMN5 was used.

Conception rate according to antral follicle count and oestrus expression in Nelore cows submitted to timed artificial insemination

Context Antral follicle count (AFC) has been related to bovine fertility and response to reproductive biotechnologies, but its relationship to oestrus expression during timed artificial insemination (TAI) is not known. Aims This study evaluated the relationship between the AFC and oestrus expression in regard to the conception rate in beef cows that received an ovulation synchronisation protocol for TAI. Methods Multiparous Nelore cows up to 40 days postpartum were evaluated by an ultrasound to determine the AFC, and were classified into low (≤15 follicles; n = 150), intermediate (≥19 and ≤26 follicles; n = 150) and high count (≥30 follicles; n = 150). AFC evaluation was performed on a random day of the oestrous cycle (Day 0). The animals received a conventional TAI protocol based on progesterone and oestradiol benzoate. On Day 8, the animals received cloprostenol, equine chorionic gonadotrophin and oestradiol cypionate, in addition to a painting in the sacrococcygeal region. On Day 10, TAI was performed, and oestrus expression was evaluated and classified as high, low or absent, according to the removal of paint. Pregnancy diagnosis was performed by ultrasound 30 days after TAI. The data were analysed using a generalised linear model and a binary logistic regression model (P &lt; 0.05). Key results Regardless of AFC, a high proportion of cows showed high oestrus expression (low 61.3%; intermediate 67.3% and high 58.7%) at the end of the TAI protocol. The conception rate was influenced by AFC (low 69.3% vs high 56.7%; P = 0.04) and oestrus expression (high oestrus: 67.3% vs no oestrus: 45.4%; P = 0.003). In addition, an interaction (P = 0.008) between AFC and oestrus expression showed that low AFC cows and high oestrus expression had the highest conception rate to TAI. Conclusion AFC and oestrus expression classification influenced the conception rate of Nelore cows in the TAI programme. In addition, the interaction of AFC with oestrus expression revealed that the best conception rate was observed in females with low AFC that expressed high-intensity oestrus. Implications The associated assessment of AFC and oestrus expression represents a strategy to increase the conception rate in TAI programmes in cattle.

Effect of galectin-1 administration on pregnancy rate and its economic viability in TAI procedures in beef cattle

The purpose of this work is to demonstrate the reproductive efficacy and the economic impact of a complementary tool to the TAI (timed artificial insemination) protocols - the administration of a single dose of recombinant human galectin-1 (rHGAL1) during the insemination procedure. GAL-1 can be considered as a modulator of the pregnancy development process. Reproductive efficacy was verified through the pregnancy rate in the first service, by ultrasonography (at 28-35 days) in contemporary groups (YG) of cows subdivided into 02 experimental groups (Control Group, composed of cows inseminated in a conventional and Treated group, composed of cows inseminated with rHGAL-1 administration following the deposition of the semen dose). Ninety YG were formed, grouping cows under identical conditions (inseminator, farm/lot, breed, animal category, semen/bull variables). The experiment was conducted in 15 farms, with 3,125 cows (Nellore and crossbred), all multiparous and with calf at foot (from 60 to 100 days old) and who maintained a body score (BSC) between 3.5 and 2.5 in the act of the TAI protocol and in the pregnancy diagnosis. It was demonstrated, by the proposed statistical method, that the “rHGAl-1 dose” effect was significant, increasing the probability of obtaining pregnancy by 8.38 percentage points (p &lt; 0.0001). Based on the construction of a hypothetical model, the economic profitability that can be obtained were compared. Using the average increase obtained by 8.38 percentage points more in the pregnancy rate, it was possible to increase productivity, adding, almost U$ 2 thousand to profitability for each 100 cows worked.

Follicular dynamics, luteal characteristics, and progesterone concentrations in synchronized lactating Holstein cows with high and low antral follicle counts

We performed two experiments in high milk-producing Holstein cows. First, we evaluated the repeatability of the antral follicle count (AFC) – where all follicles were ≥2 mm in diameter – during the days of the ovulation synchronization protocol for timed artificial insemination (TAI) in dairy cows (n = 20). In the second study we investigated the follicular dynamics and Doppler ultrasonography in cows with low (≤15 follicles, n = 9) and high (≥25 follicles, n = 9) AFC, and measured progesterone (P4) concentrations during CL evaluation. In addition, the diameter of the preovulatory follicle, area of blood flow of the preovulatory follicle, CL area, and CL blood flow were compared between groups with high and low AFC. Ultrasound examinations were performed during the days of the protocol and 10 days after ovulation to assess the CL. The constancy of the AFC was analyzed by calculating the repeatability. Parametric variables were analyzed using the t-test, and nonparametric variables were analyzed using the Mann-Whitney test (P ≤ 0.05). The repeatability of the AFC on different days of the protocol was 0.98. Cows with low AFC showed a greater diameter of the preovulatory follicle (16 ± 0.3 vs. 15 ± 0.4 mm), blood flow area of the preovulatory follicle (17.3 ± 2.3 vs. 8.1 ± 3.2 mm2), CL area (579.1 ± 16.9 vs. 405.8 ± 21.2 mm2), area of CL perfusion (97.1 ± 9.4 vs. 68.3 ± 5.2 mm2), as well as higher P4 levels (3.1 ± 0.2 vs. 2.2 ± 0.2 ng/mL). In high milk-producing Holstein cows, the AFC has high repeatability on different days of the TAI protocol, and cows with a low AFC show larger preovulatory follicles and CLs with greater perfusion, in addition to greater P4 concentrations in comparison to those cows with a high AFC.

A comparison of the reproductive performance in primiparous sows following two timed artificial insemination protocols

Timed artificial insemination (TAI) is an efficient reproductive technology in batch farrowing production that aids management in pig farms. However, the effect of TAI on the reproduction performance is still controversial. This study aimed to evaluate the effects of two TAI protocols on the reproductive performance of primiparous sows. A total of 332 weaned sows were randomly allocated into three treatments. Sows assigned to Control (n = 110) were untreated and inseminated on each day in oestrus after weaning. Sows assigned to eG-TAI (n = 112) received equine chorionic gonadotropin (eCG) 24 h after weaning and gonadotropin-releasing hormone (Gonadorelin: GnRH) at oestrus, and were inseminated at 8 and 32 h later if oestrus at 0800, or 16 and 40 h later if oestrus at 1600. Sows assigned to 2e-TAI (n = 110) received eCG and GnRH 24 h and 96 h after weaning, respectively, and were inseminated 16 and 40 h after GnRH administration. Sows showing oestrus at GnRH administration or 64 h after were inseminated immediately, for a total of three inseminations. Ultrasonographic evaluations were performed to determine the follicular diameter and time of ovulation. Most sows in the 2e-TAI and eG-TAI groups ovulated 0–48 h after the GnRH injection. Our results indicated that oestrus rate within seven days after weaning in the experimental groups was higher, and weaning-to-oestrus interval was shorter than in the control group (99.3 h vs 113.5 h, P < 0.05). The breeding and farrowing rates in the experimental groups were significantly higher than in the control group (P < 0.05), while the numbers of total born, live-born and stillborn were not different among the three groups (Control: 12.7, 11.6 and 1.1; 2e-TAI: 12.4, 11.3 and 1.0; eG-TAI: 12.0, 11.4 and 0.4, respectively). These results indicated that TAI could ensure a high farrowing rate in primiparous sows under batch farrowing management.

GnRH34: An alternative for increasing pregnancy in timed AI beef cows

Two experiments evaluated the effects of gonadotropin releasing hormone (GnRH) treatment on fertility of suckled Nelore beef cows treated with an estradiol/progesterone (P4)-based protocol for timed artificial insemination (TAI). Experiment 1 was designed to determine the effect of GnRH administered 34 h after P4 insert removal (GnRH34) on time of ovulation. Suckled cows (n = 34) were treated with 2 mg estradiol benzoate (EB) and an intravaginal insert containing 1.9 g of P4. Eight days later, P4 inserts were removed, and all cows received 150 μg of d-cloprostenol (prostaglandin F2 alpha analogue), 300 IU of eCG, and 1 mg of estradiol cypionate (ECP). On Day 9 (05:00 p.m.), cows were randomly distributed, according to the diameter of the pre-ovulatory follicle, in two treatments: 1) GnRH (n = 17) cows that received 10.5 μg of buserelin acetate, or 2) no further treatment (control, n = 17). Cows treated with GnRH 34 h after P4 insert removal ovulated earlier (P = 0.02) than control cows (66 ± 0.0 and 77.2 ± 4.3 h). Experiment 2 was designed to determine the effect of GnRH34 on the fertility of suckled beef cows. Nelore cows (n = 506) were treated as Experiment 1. On Day 8, cows were painted in the sacrocaudal region to identify cows that displayed estrus. On Day 9 (05:00 p.m.), cows were randomized to receive same treatment as Experiment 1, control (n = 252), or GnRH (n = 254). All cows were TAI 48 h after P4 insert removal. At TAI, estrus was evaluated, and deemed to have occurred in cows without a tail-head chalk mark (>75% paint loss). Cows treated with GnRH 34 h after P4 insert removal had greater (P = 0.01) pregnancy per AI (P/AI) than cows that only received ECP (63.0% and 50.4%). No difference (P = 0.5) was observed in the proportion of cows that displayed estrus between treatments. Furthermore, cows that displayed estrus had greater (P < 0.01) P/AI than cows that did not. Treatment with GnRH, given at 34 h after P4 insert removal, increased (P < 0.05) P/AI in cows that did not show estrus at TAI. In summary, treatment with GnRH 34 h after P4 insert removal was associated with earlier ovulation and resulted in greater P/AI in suckled Nelore cows treated with an estradiol/P4-based protocol for TAI.

Controlled breeding in dairy cows. Part 2: selection and ethical implications

Background: Controlled breeding programmes describe timed artificial insemination (TAI) protocol choice and a strategy for their implementation, encompassing when they will be used and which cattle will be enrolled. A holistic approach to the reproductive management of every dairy herd, tailored to meet the requirements and expectations of the individual client, is essential if success of a controlled breeding programme is to be maximised.Aim of the article: This article, the second of a two‐part series, describes strategies for implementation of controlled breeding programmes on dairy farms. It considers factors aside from the TAI protocol that are essential for the success of any programme, as well as the ethical implications of hormone use in dairy cattle. The first part, published in last month's issue of In Practice, discussed common TAI protocols, how they manipulate ovarian activity and how to optimise protocol selection.

Estrus expression and pregnancy rates in heifers primiparous and multiparous Nelore cows subjected to timed artificial insemination with strategic use of gonadotropin-releasing hormone

We evaluated the effects of nulliparous, primiparous, and multiparous conditions on the estrus and pregnancy rates in females that did not show estrus but were treated with gonadotropin-releasing hormone (GnRH) at the time of timed artificial insemination (TAI). Nelore females (n = 531) were allocated according to the following categories: nulliparous (n = 144), primiparous (n = 132), and multiparous (n = 255). The animals received a conventional TAI protocol, and estrus expression was identified by the absence of paint in the sacrococcygeal region on the day of TAI. Females that did not show estrus were treated with 10 μg of GnRH together with insemination. The rates of estrus and pregnancy were analyzed using a logistic regression model (P &lt; 0.05). The estrus expression was lower (P = 0.006) in the primiparous (61.36%) group than in the nulliparous (76.39%) and multiparous (75.69%) groups. Similar pregnancy rates were observed in females that showed estrus (nulliparous 84.54%, primiparous 86.42%, and multiparous 80.31%; P = 0.39) and in females that did not show estrus and received GnRH (nulliparous 41.18%, primiparous 56.86%, and multiparous 58.06%; P = 0.24). The total pregnancy rates were also similar (P = 0.98) among the categories (nulliparous 74.3%, primiparous 75.0%, and multiparous 74.9%). The primiparous females had a lower rate of estrus, and the pregnancy rates were similar among the categories that received GnRH.

Controlled breeding in dairy cows. Part 1: bovine oestrus cycle and synchronisation

Background: Timed artificial insemination (TAI) as part of a controlled breeding programme is a reproductive strategy that eliminates the requirement for oestrus detection, guarantees the submission of enrolled cows and attempts to optimise the timing of insemination relative to ovulation. However, the success of TAI requires careful cow selection, diligent herd management and the selection of an appropriate synchronisation protocol.Aim of the article: This article, the first in a two‐part series, outlines the key ovarian follicular wave dynamics in the bovine oestrous cycle and the key goals of any synchronisation protocol. It describes the most commonly used drugs, their actions and how they can be combined into effective synchronisation protocols. The second part of the series, to be published in a subsequent issue of In Practice, discusses how to implement controlled breeding strategies on farms and considers factors aside from the TAI protocol that are essential for the success of any programme.

Vaginal parameters during the 24-hour preceding insemination in Bunaji cows under three standard synchronization protocols

Introduction: The criticalness of the point at which inseminations are carried out at breeding stations to pregnancy rates perhaps contributed to the emergence of timed artificial insemination (TAI) protocols. Methods: Vaginal mucus resistivity (VMR), temperature (VT) and cytology (VC) were investigated using cows (Bunaji, n = 75, &gt;2 parities) that were equally randomized to TAI protocols: CoSynch (100µg Gonadotropin-Lecirelin® IM on d0, d10; 500µg Clorprost 1® IM on d7), OvSynch (100µg Le-cirelin® on d0, d9; 500µg Clorprost 1® on d7) and Prostaglandin (500µg Clorprost 1® on d0, d11). VMR, VT and VC (superficial-epithelia-cells %) were monitored on d9, d10 (Gonadotropin-group) and d13, d14 (Prostaglandin-group) using Draminski® bovine Estrous probe, SK-SKATO® thermometer and standard procedures, respectively. Results: From d9 to d10, VMR declined by 22.40% to 260.06±44.27Ω (range 250-270), VT rose by 1.43% to 35.50±0.71°C while VC declined by 69.57% to 14% for CoSynch-group. Similarly, VMR declined by 13.04% to 245.12±12.91Ω (range 240-250), VT rose by 2.86% to 36.00±0.00°C while VC increased by 52% to 52% for OvSynch-group. From d13 to d14, VMR declined by 2.90% to 335±28.87Ω (range 330-340), VT rose by 1.43% to 35.50±0.71°C while VC declined by 76% to 0% for Prostaglandin-group. These findings suggest that the 24-hour preceding insemination were associ-ated with VMR: 240 to 270Ω, VT: 35 to 36°C, VC: 14 to 52% and VMR: 330 to 340Ω, VT: 35 to 35.5°C, VC: 0% for Gonadotropin-based and Prostaglandin protocols, respectively. Significance: Vaginal-mucus resistivity, temperature and cytology are thus described to better define insemination time and improve pregnancy rates at cattle breeding stations.