Synchronization Of Estrus In Cattle Research Articles

Synthesis of Norgestomet and its 17β-isomer and evaluation of their agonistic activities against progesterone receptor

Norgestomet is a synthetic progesterone derivative applied in veterinary medicine to control estrus and ovulation in cattle. Norgestomet has been widely used in the livestock industry to promote the synchronization of estrus in cattle and increase pregnancy rates. However, highly reproducible synthetic methods for Norgestomet have been rarely reported. Here, we described a method for the synthesis of Norgestomet and performed quantitative NMR analysis to determine the purity of the products. Moreover, the agonistic activity of the synthesized compounds against progesterone receptors (PRs) was evaluated using an alkaline phosphatase assay. We synthesized Norgestomet with 97.9% purity that exhibited agonistic activity against PR with EC50 values of 4.5 nM. We also synthesized the 17β-isomer of Norgestomet with 92.7% purity that did not exhibit any PR agonistic activity. The proposed synthetic route of Norgestomet can facilitate the assessment of residual Norgestomet in foods.

Prostaglandin based estrus synchronization in cattle: A review

Reproductive cyclicity provides cattle with repeated opportunities to become pregnant. Understanding the physiology and endocrinology of the estrus cycle gives a great opportunity for reproductive ...

Preparation of TPP-crosslinked chitosan microparticles by spray drying for the controlled delivery of progesterone intended for estrus synchronization in cattle.

Planned reproduction in cattle involves regulation of estrous cycle and the use of artificial insemination. Cycle control includes the administration of exogenous progesterone during 5-8days in a controlled manner allowing females to synchronize their ovulation. Several progesterone delivery systems are commercially available but they have several drawbacks. The aim of the present contribution was to evaluate chitosan microparticles entrapping progesterone as an alternative system. Microparticles were prepared by spray drying. The effect of formulation parameters and experimental conditions on particle features and delivery was studied. A mathematical model to predict progesterone plasma concentration in animals was developed and validated with experimental data. Microparticle size was not affected by formulation parameters but sphericity enhances as Tween 80 content increases and it impairs as TPP content rises. Z potential decreases as phosphate content rises. Particles remain stable in acidic solution but the addition of surfactant is required to stabilize dispersions in neutral medium. Encapsulation efficiencies was 69-75%. In vitro delivery studies showed burst and diffusion-controlled phases, being progesterone released faster at low pH. In addition, delivery extend in cows was affected mainly by particle size and hormone initial content, while the amount injected altered plasma concentration. Theoretical predictions with excellent accuracy were obtained. The mathematical model developed can help to find proper particle features to reach specific delivery rates in the animals. This not only save time, money and effort but also minimized experimentation with animals which is desired from an ethical point of view.

Pregnancy rate evaluation in lactating and non-lactating Nelore cows subjected to fixed-time artificial insemination using injectable progesterone

Most fixed-time artificial insemination (FTAI) protocols utilize progesterone (P4) as a hormonal source to achieve synchronization of estrus in cattle. The use of an injectable P4 source to control estrus would be an interesting pharmacological strategy owing to the practicality of parenteral application. However, the effects of injectable P4 on estrus cycle control in cattle remain poorly studied. In particular, no existing studies have investigated the effect of injectable P4 on the fertility of cows subjected to FTAI. The aim of this study was to evaluate the pregnancy rate of lactating and non-lactating Nelore cows subjected to FTAI with injectable P4. Of the 422 non-lactating cows in this study, 162 (38.3%) became pregnant by 60 days post-FTAI. In the lactating group (n = 516), 166 (32.1%) were pregnant by 60 days after treatment with injectable P4. The proportions of lactating and non-lactating cows becoming pregnant were compared using the chi-square test, adopting a significance level of P < 0.05. It was found that the pregnancy rate of the cows subjected to FTAI with injectable P4 was influenced by lactation status. Lactating cows had lower reproductive performance, possibly because of their higher nutritional requirements. However, the use of injectable P4 shows promising results and may prove to be a useful strategy in large-scale livestock production.

Synchronization of Estrus in Cattle: A Review

Numbers of estrus synchronization programmes are available in cattle based on the use of various hormones like progesterone, prostaglandin F2a and their various combinations with other hormones like estrogen and Gonadotrophin Releasing hormone (GnRH). Selection of appropriate estrus synchronization protocol should be made on the basis of management capabilities and expectations of the farmer. Synchronization of oestrus can be accomplished with the injection of prostaglandin F2a alone, but it needs proper detection of the ovarian status of the cows as prostaglandin F2a is active in only functional corpus luteum in between 8 to 17 days of estrous cycle. Progesterone may reduce fertility up to 14 percent, but short time progesterone exposure (less than 14 days) is beneficial. Addition of GnRH in the Progesterone or Prostaglandin based synchronization programme is helpful for more synchrony in estrus as GnRH may be helpful to synchronize the oestrous cycle in delayed pubertal heifers and post partum cows (Post partum anoestrum) and further a single, timed artificial insemination is possible with this method. New methods of synchronizing estrus in which the GnRH-PG protocol is preceded by progesterone treatment offer effective synchronization of estrus with high fertility.

Application of knowledge about corpus luteum function in control of estrus and ovulation in cattle

Understanding corpus luteum (CL) function has led to development of methods of estrus synchronization in cattle that either extend the estrous cycle by administration of exogenous progestins or shorten the cycle by induction of luteolysis. Both methods have limitations, which have been reduced or overcome through sequential or combined treatment with progestin and luteolytic drugs. Future improvements in estrus synchronization methodology are most likely to come from achieving more synchrony between the development of a highly fertile ovulatory follicle and control of luteal function.

Failure of the LH-releasing hormone agonist, deslorelin, to prevent development of a persistent follicle in heifers synchronized with norgestomet

The use of exogenous progestagens for estrus synchronization in cattle can result in a persistent dominant follicle which is associated with reduced fertility. We examined whether the LHRH agonist, deslorelin, would prevent the formation of a persistent follicle in heifers synchronized with norgestomet. The estrous cycles of heifers were synchronized with cloprostenol, and on Day 7 of the ensuing cycle the heifers received one of the following treatments for 10 d: Group C (n = 5), untreated control; Group N (n = 6), injection of a luteolytic dose of cloprostenol on Days 7 and 8 and implant of norgestomet from Day 7 to Day 17 (i.e. typical 10-day norgestomet implant period); Group D (n = 6), injection of cloprostenol on Days 7 and 8 and implants of deslorelin from Day 7 to Day 17; Group ND (n = 6), injections of cloprostenol and both norgestomet and deslorelin implants as above. Follicle growth was monitored using ultrasonography. Group-N heifers showed continued follicle growth and had larger follicles on Day 17 of the cycle than Group-C heifers (16.8 ± 1.6 and 10.4 ± 1.6 mm). Follicle growth for Group-D and ND heifers was similar and variable, and seemed to depend on follicle status at the initiation of treatment. Heifers with follicles of 5 to 10 mm (n = 9) in diameter either showed no follicle growth ( 2 9 ) or developed large follicles ( 7 9 ), while heifers with follicles approximately 12 mm (n = 3) in diameter showed follicle atresia with no further significant growth. On Day 17, size of the largest follicle was similar for Group-ND (14.3 ± 2.9) and Group-D (16.8 ± 1.6) heifers. Heifers in Group N showed estrous behavior 1.8 ± 0.2 d after treatment, whereas heifers in Groups D and ND did not show estrus for 2 to 4 wk. The results show that combined treatment with progestagen and an LHRH agonist does not consistently prevent the development of a persistent dominant follicle and that return to estrus can be delayed after treatment with an LHRH agonist.

Estrus synchronization in cattle with estradiol-17β and CIDR-B vaginal devices

Estrus synchronization in cattle with estradiol-17β and CIDR-B vaginal devices

The development and marketing of estrus synchronization in cattle in Australia using prostaglandins

Estrus synchronization using prostaglandins was applied to a well-developed system of AI in beef cattle. Cows and heifers were selected to be free from infectious disease. Cows were run at pasture in a single group and estrus was detected visually twice a day without the use of any aids. Estrous cows were removed from the group each morning. Cows detected in estrus in the morning were inseminated that afternoon and cows detected in the afternoon were inseminated the next morning. The AI program ran for 25 to 42 days and was evaluated by rectal pregnancy palpation about 42 days after the last insemination. Calves were produced at an average cost of $26. The only management systems of synchronization using prostaglandins that could match this cost was the 10 day program with one treatment of 10 or 12.5 mg prostaglandin F2α on day 5. Management systems using two treatments of PGF2α, 12 days apart, increased calf costs to $160, $100, and $45, respectively, with two or one timed insemination or insemination after detection of estrus. The most significant efficiency factor was the ratio of the number of cows inseminated to the number of cows put into the AI program and this ratio was statistically the same in normal AI (72%) and AI with synchronization and detection of estrus (74%). About half of the cattle not inseminated had ovarian activity, palpable follicles or corpora lutea but had not yet come into estrus. Pregnancy rates per insemination and the number of cows pregnant per 100 cows in an AI program were the same but the labor input was reduced by synchronization. Responses to prostaglandin F2α treatment were the same over the range of dose rates from 8 to 20 mg. The 10 day AI program with a single treatment of 10 or 12.5 mg PGF2α has been used commercially in Australia for 6 years with other management systems being tailored to particular needs.

Synchronization of estrus in cattle for embryo transfer

Two groups of donors (31 animals) receiving 2,000 to 3,000 IU of PMSG followed by 30 to 33 mg of prostaglandin F 2α-THAM salt 48 hours later showed an average interval to estrus of 44 ± 2.7 and 51 ± 5.7 hours after prostaglandin treatment. Three groups of donors (32 animals) receiving the above treatment plus 500 μg estradiol 32 to 38 hours after prostaglandin showed an average interval to estrus of 50 ± 1.0, 36 ± 1.6 and 48 ± 5.2 hours after prostaglandin. One group of recipients (16 animals) receiving prostaglandin during the mid luteal phase of the cycle showed an average interval of 78 ± 9.2 hours to onset of estrus while a comparable group treated with estradiol 32 hours after prostaglandin had an average interval of 52 ± 5.0 hours to estrus. One group of recipients (15 animals) treated with prostaglandin during the late diestrous or early proestrus phase of the cycle had an average interval to estrus of 41 ± 3.7 hours and two groups of recipients (27 animals) treated at the same stages of the cycle and receiving estradiol had an average interval to estrus of 47 ± 2.0 and 48 ± 5.2 hours, respectively.

Estrus synchronization and conception rate in dairy cattle treated with progestin-impregnated vaginal sponges

Twelve Israeli-Friesian heifers and cows were treated for estrus synchronization with intravaginal sponges impregnated with 250 mg. medroxyprogesterone acetate (MAP) for a period of 14 days. All sponges were retained throughout the treatment period and 100% of the animals came into estrus 3–7 days after sponge removal. Conception rate from insemination at the synchronized estrus was 60%. It is concluded that further investigation is justified regarding the value of progestin-impregnated sponges as a practical means of estrus synchronization in cattle.

Estrus Synchronization in Cattle Following Feeding Six Progestogens

The oral effectiveness of six progestogens in synchronizing estrus was determined in dairy heifers. The hormones were fed in a concentrate ration twice daily for 17 or 18 days. Four progestogens effectively synchronized estrous cycles at the levels studied. Progestogen 1 (6α-methyl-4-pregnen-17-Ol-one acetate) synchronized estrus at minimum effective levels of 80 and 90mg daily. Fertility at the synehronized estrus after Progestogen 1 feeding was depressed, as only 24.1% of the heifers conceived compared with conception in 48.5% of the controls at first service. After two services the conception rates were 65.5 and 69.7% for treated and control heifers, respectively. Progestogen 2 (6-methyl-3,5-pregnadien-17 α-Ol-20-one-3-β-acetylthioethoxy acetate) was effective in controlling the estrous cycle at 30mg daily. Increased levels of this compound up to 90mg daily did not increase the interval to estrus after the end of treatment. The minimum effective doses of Progestogen 3 (3-aza-A-homo-6α-methyl-4α-pregnen-17α-Ol-4-one acetate) and Progestogen 4(6α-methyl-4-pregnen-17α-Ol-3,20-dione-3-ethylene thioketal acetate) were 45 and 90mg daily. Progestogen 5 (6-α-methyl-4-pregnen-17α-Ol-3,20-dione-3-oxime acetate) and Progestogen 6 (17α-ethynyl-19-norandrost-4,6-diene-3-one-17β-acetate 3-oxime) were ineffective in controlling estrous cycles at the highest levels tested (90mg).

Synchronization of estrus in cattle with an oral progestational agent and an injection of an estrogen.

Synchronization of estrus in cattle with an oral progestational agent and an injection of an estrogen.