Search

The capacity of recipients to support transferred embryos is a challenge for dairy cattle production systems. This review explores methods for increasing P4 to improve early pregnancy establishment in dairy cattle. A key aspect of P4 supplementation during the critical first weeks of pregnancy is its correlation with successful embryo elongation. Moreover, P4 was correlated to an increased chance of embryo survival after maternal recognition of pregnancy. Internal releasing devices increase circulating P4 concentrations but may negatively impact fertility possibly due to unwanted health pathologies such as vaginitis and the still undefined mechanism of haste luteolysis. The accessory corpus luteum (CL) induction in recipient dairy cattle increases endogenous P4 output increasing circulating P4 concentrations. Two ovulatory inducers are commonly used: gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG). Despite their distinct structures, GnRH and hCG are equally capable of inducing ovulation in cattle. The P4 supplementation by an accessory CL formation was widely used in fixed-time artificial insemination breeding programs, but still not exhaustively studied in embryo transfer (ET) programs. The induction of an accessory CL in ET programs has yielded inconsistent results depending on parity, embryo type production, embryo stage of development, and type of hormone used. Although maternal physiological mechanisms support the idea of increasing P4 for higher fertility and better embryo development, the actual results in creating a high-P4 maternal environment are still uncertain., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Effects were evaluated in Bos indicus cows of eCG and FSH on follicular growth, estrous expression, and pregnancy per artificial insemination (P/AI) as a result of fixed-time artificial insemination (TAI). In Experiment 1, extent of timing-of-ovulation synchronization among cows was evaluated after imposing an estrogen/progesterone-based treatment regimen. At progesterone device removal (D8), cows were administered: eCG, or FSH or served as untreated Controls. In Experiment 2, percentage of cows P/AI was evaluated when the Experiment 1-treatment regimen was imposed. On D10, all cows were artificially inseminated. In Experiment 3, cows were assigned to two treatment groups (Control and eCG) on D8 to evaluate percentage of cows P/AI and estrous expression. In Experiment 1, follicular dynamics were similar among treatment groups. In Experiment 2, follicular growth was greater (P =  0.0001) with the eCG treatment. There was an interaction of treatment × parity (P =  0.007) on percentage of cows P/AI. There was a greater percentage of primiparous cows P/AI in the eCG-treated than Control and FSH-treated cows. There was a greater percentage of eCG-treated multiparous cows pregnant as a result of TAI than Control cows. There was an interaction of treatment × parity (P =  0.005) on P/AI in Experiment 3, in which the eCG effect was more pronounced in primiparous cows. Treatment with FSH, therefore, was not as effective as eCG in stimulation of follicular growth or enhancing percentage of cows pregnant as a result of TAI. Physiological effects of eCG, however, were also more evident in primiparous cows., (Copyright © 2021 Elsevier B.V. All rights reserved.)

It was hypothesized that Brahman cows have greater in vitro embryo production than Simmental cows, and that regardless of breed, antral follicle count (AFC) and vulvar width (VW) are positively associated with oocyte quality, embryo number and pregnancy rate. Brahman (Bos taurus indicus, n = 184) and Simmental (Bos taurus taurus, n = 99) cows were classified as having a large AFC (Brahman: ≥50, Simmental: ≥25); intermediate AFC (Brahman: >30 and ≤49; Simmental: >16 and <24) and small AFC (Brahman: <30, Simmental: ≤15). The VW was considered to be large (Brahman: >123 mm, Simmental: >80 mm); intermediate (Brahman: >102 mm and ≤123 mm; Simmental: >65 mm and ≤80 mm) and small (Brahman: ≤102 mm and Simmental: ≤65 mm). For each group of cows, ovum pick up, oocyte in vitro maturation, fertilization and embryo culture were performed. Embryo transfers were subsequently performed and pregnancy rate was evaluated. Brahman cows had a larger number of viable oocytes, greater efficiency of embryo production and greater pregnancy rate (P < 0.05) than Simmental cows. Pregnancy percentages in Simmental cows with a small AFC were greater than those cows with an intermediate and large AFC. With the Brahman cows, there was no difference in pregnancy rate among the cows with different AFC classifications. In contrast to Simmental cows, Brahman cows with an intermediate VW had a greater pregnancy percentage than those with a small and large AFC. In conclusion, Brahman cows have a larger AFC, number of viable oocytes, and pregnancy rate than Simmental cows., Competing Interests: Declaration of Competing Interest There was no conflict of interest that could be perceived as prejudicing the impartiality of the research reported., (Copyright © 2020 Elsevier B.V. All rights reserved.)

To evaluate the effects of moderate dietary restriction and lipid supplementation on ovarian follicular development, hormonal and metabolic profile, thirty-five prepuberal ewe lambs were blocked by body weight and randomly assigned to treatments: ALUS (control) - unsupplemented-diet ad libitum (3.5% ether extract, n = 9); R-US - intake restricted to 85% of the ALUS diet (n = 9); AL-LS - lipid-supplemented-diet ad libitum (9.8% ether extract, n = 8); R-LS - intake restricted to 85% of the ALLS diet (n = 9), from 95 ± 8 days of age until estrus or 7 months of age. Lipid supplementation did not reduce dry matter intake. Daily weight gain was greater in lambs fed ad libitum. Plasma glucose was greater in the RLS treatment group, while serum insulin was less with lipid supplementation. There was a treatment by age interaction on total cholesterol, HDL cholesterol and triglyceride serum concentrations. Estrus was detected in 43% of the animals and the overall ovulation rate was 60%. The number of follicles, diameter of the largest follicle, body weight, age and serum progesterone at puberty did not differ among treatment groups. The mean diameter of the largest follicle was greater in lambs having than in those not having ovulations and increased with age in both groups. There was an interaction between the effects of occurrence of ovulation and age on the number of follicles between 3 and 5 mm and > 5 mm. Lipid supplementation and dietary restriction altered the metabolic profile in ewe lambs with no concomitant changes in values for reproductive variables., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The intense selection of characteristics related to animal performance may affect the reproductive efficiency of beef cows negatively. Selection for fertility along with production traits is, therefore, readily justifiable. The objective of the present study was to evaluate possible relationships among AFC, serum AMH concentrations and external morphometrics with reproductive efficiency in Tabapuã (a Brazilian Bos indicus beef breed) females. Antral follicle counts and external morphometrics were measured in nulliparous (n = 162), primiparous (n = 80) and multiparous (n = 351) cows, from four farms. Age at first parturition (AFP), parturition interval (PI), maternal ability (MA), precocity, rusticity and survival (PRS) and overall reproductive efficiency (RE) were evaluated according to the Brazilian Association of Zebu Breeders (ABCZ) data bank indexes. A single blood sample per animal was collected at random stages of the reproductive cycle from a subset of animals (nulliparous = 84, primiparous and multiparous = 136) to determine serum AMH concentrations. The AFC classes were defined as lesser (<28), intermediate (28-50) and greater (>50). Correlations between all variables and the effects of parity and AFC on reproductive traits, AMH and external genitalia size were analyzed by the PROCORR and by the PROCGENMOD procedures of SAS ® (SAS, Cary, NC, USA), respectively. Antral follicle count did not differ (P = 0.71) among nulliparous (38.6 ± 23.96) primiparous (47.54 ± 26.16) and multiparous (41.08 ± 25) cows and was negatively correlated with pregnancy interval (PI), such that, as PI decreased (r = -0.28; P < 0.005), AFC increased. Vulva width was not affected (P = 0.08) by parity and was larger (P < 0.05) for females in the greater AFC class (8.81 ± 0.12 cm) compared with the intermediate (8.42 ± 0.11 cm) and lesser (8.38 ± 0.13 cm) classes. As vulva width increased, parturition interval decreased (r = -0.15; P < 0.005) and overall reproductive efficiency increased (r = 0.17, p < 0.005). Thoracic depth was associated with greater AFCs (r = 0.10; P < 0.001). Anti-Müllerian hormone concentrations were greater (P < 0.05) for animals in the greater AFC class (1.15 ± 0.09 ng/mL) compared with the lesser (0.44 ± 0.02 ng/mL) and intermediate (0.73 ± 0.05 ng/mL) classes. Vulva width, AFC, external morphometrics and AMH concentrations were moderately associated, considering the low heritability of fertility traits, and should be studied further to be considered in the selection for fertility in Bos indicus cattle., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The objectives were to evaluate the effects of the administration of either eCG or progesterone (P4) alone or combined on endogenous P4 concentrations and pregnancy per AI in lactating dairy cows. Cows received a P4-releasing intravaginal device (PRID) and estradiol benzoate on D-8. The PRID was removed and a PGF2α injection was given on D-3. An estradiol cypionate was given on D-2 and TAI was performed on D0. On D-2, cows were randomly allocated to treatments in a 2×2 factorial design: Control-saline solution on the D-2 and D+3 (n=104), eCG - 400IU eCG on D-2 (n=93), P4 - 600mg of P4 on D+3 (n=106), and eCG+P4 - 400IU eCG on D-2 and 600mg of P4 on D+3 (n=95). Blood samples were collected on days three, four, and thirteen and pregnancy diagnoses were performed at 32 and 46 days after AI. There was no interaction between eCG and P4 injection. Cows treated with eCG and with P4 injection had higher serum P4 on Day +4. On Day +13 serum P4 was lower in eCG-untreated primiparous cows (Interaction eCG×parity). Cows with serum P4<4.57ng/mL on Day +13 had lower probability to be pregnant on day 32. P/AI on days 32 and 46 and embryonic losses were not influenced by eCG and P4 injection. In conclusion, the addition of 400IU of eCG on D-2 and/or 600mg of P4 on D+3 to the present TAI protocol did not increase P/AI., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The hypothesis was that the intramuscular injection (i.m.) of beta-carotene associated to tocopherol improves cow (n=86) and heifer (n=91) embryo production and quality. Time of estrus was synchronized in animals with an ear implant with 3 mg of norgestomet associated with an i.m. injection of 6 mg of norgestomet and 10mg of estradiol valerate (CRESTAR, Intervert International B.V., Boxmeer, Holland) and superovulated by 8 i.m. FSH/LHp injections (400 IU-heifers and 500 IU-cows) in decreasing concentrations at 12h intervals. Animals were inseminated 12 and 24h after observed onset of estrus and embryos recovered 7 days later. Animals were randomly allocated to one of three treatments: (1) vegetable oil vehicle (control), (2) 800 mg of beta-carotene and 500 mg of tocopherol (T800) and (3) 1200 mg of beta-carotene and 750 mg of tocopherol (T1200). Supplemental injections were given at the day norgestomet implants were inserted and at first superovulatory injection. An index (Embryo Quality Index or EQI) was proposed to more precisely evaluate embryo quality (excellent*1 + good*2 + regular*3 + poor*4 + degenerate*5 + unfertilized ova*5)/total. There was an interaction between physiological stage (heifer or cow) and treatment on EQI (P=0.01) and on the proportion of viable embryos (P=0.03), where both variables were improved in T1200 cows, but not in heifers. The average EQI for heifers and cows in control, T800 and T1200 were 2.6+/-0.3 and 3.6+/-0.3; 2.5+/-0.3 and 3.6+/-0.3; 2.9+/-0.3 and 2.7+/-0.3, respectively. The average total number of viable embryos was greater (P=0.01) in supplemented cows (3.5+/-1.1; 5.4+/-1.4 and 7.5+/-1.2 in control, T800 and T1200, respectively), but less (P=0.01) in heifers (7.5+/-1.2; 5.6+/-1.2 and 4.0+/-1.1 in control, T800 and T1200, respectively). Supplementation injections of beta-carotene associated to tocopherol improved embryo quality in superovulated Holstein cows, in the present experimental conditions and may be advantageous in similar embryo production systems. However, at dosages applied in the present experiment, this treatment should not be recommended for nulliparous heifers.