B. G. Freitas

Efficacy of a single intramuscular injection of porcine FSH in hyaluronan prior to ovum pick-up in Holstein cattle

Plasma FSH profiles, in vitro embryo production (IVP) after ovum pickup (OPU), and establishment of pregnancy with IVP embryos were compared in untreated Holstein oocyte donors and those superstimulated with multiple injections or a single intramuscular (IM) injection of porcine FSH (pFSH) in hyaluronan (HA). Plasma FSH profiles were determined in 23 heifers randomly allocated to one of four groups. Controls received no treatment, whereas the F200 group received 200 mg of pFSH in four doses, 12 hours apart. The F200HA and F300HA groups received 200- or 300-mg pFSH in 5 mL or 7.5 mL, respectively of a 0.5% HA solution by a single IM injection. Plasma FSH levels were determined before the first pFSH treatment and every 6 hours over 96 hours. All data were analyzed by orthogonal contrasts. Circulating FSH area under curve (AUC) in pFSH-treated animals was greater than that in the control group (P = 0.02). Although the AUC did not differ among FSH-treated groups (P = 0.56), the total period with elevated plasma FSH was greater in the F200 group than in the HA groups (P < 0.0001). However, the F300HA group had a greater AUC than the F200HA group (P = 0.006), with a similar total period with elevated plasma FSH (P = 0.17). The IVP was performed in 90 nonlactating Holstein cows randomly allocated to one of the four treatment groups as in the first experiment. A greater proportion of medium-sized (6-10 mm) follicles was observed in cows receiving pFSH, regardless of the treatment group (P < 0.0001). Also, numbers of follicles (P = 0.01), cumulus-oocyte complexes (COCs) retrieved (P = 0.01) and matured (P = 0.02), cleavage rates (P = 0.002), and blastocysts produced per OPU session (P = 0.06) were greater in cows receiving pFSH, regardless of the treatment group. Cows in the F200HA group had a greater recovery rate (P = 0.009), number of COCs cultured (P = 0.04), and blastocysts produced per OPU session (P = 0.06) than cows in the F300HA group. Similar pregnancy rates were observed 50 to 60 days after transferring IVP embryos from donors in the different treatment groups (P > 0.05). In conclusion, a single IM injection of pFSH combined in 0.5% HA resulted in similar plasma FSH profiles as twice-daily pFSH treatments. Treatment of nonlactating donors with pFSH, with or without HA, resulted in increased IVP over untreated controls. A single dose of 200 mg of pFSH in 0.5% HA resulted in greater IVP than 300-mg pFSH in HA. Finally, pregnancy rates with IVP embryos were similar, regardless donor treatment.

Timed artificial insemination: current challenges and recent advances in reproductive efficiency in beef and dairy herds in Brazil

Beef and dairy productivity depends directly on the reproductive efficiency and genetic gain of the herd, which can be related to the appropriate use of biotechnologies, such as timed artificial insemination (TAI). When considering variations in synchronizations protocols, longer or shorter periods of progesterone (P4) device treatment could provide benefits to fertility. However, our studies evidenced that protocols with six (J-synch), seven, eight and nine days of P4 device treatment had similar pregnancy per AI (P/AI). In cyclic cows, the early prostaglandin (PGF) administration, moving from the day of P4 device removal to two days earlier, which results in four handlings of cows, or the administration of one extra dose of PGF at the onset of the protocol and a single PGF on the day of P4 device removal (three handlings) are both efficient to induce early luteolysis, reducing serum P4 concentrations and, therefore, stimulating LH pulsatility, which improves growth of the dominant follicle and results greater P/AI when compared with protocols with the administration of PGF only on the day of P4 device removal. Resynchronization is another valuable tool to reduce the interval between AI. Traditional Resynch is initiated at pregnancy diagnosis (28 to 32 days after TAI) and the interval between AI is around 40 days; Resynch 22 and Resynch 14 respectively initiates 22 and 14 days after the previous AI in all cows (unknown status of pregnancy) and reduces the interval between AI to 32 and 24 days. The novelty about Resynch 14 is the need to use of Doppler ultrasonography for pregnancy diagnosis [evaluation of corpus luteum (CL) vascularization]. Similar P/AI after Resynch 22 and 14 were found in Nelore cows. In dairy cattle, reproductive management is carried out throughout the year, thus, it is important to adapt the reproductive management to few established days of the week. Therefore, traditional Resynch and Resynch 25 were set to start 32 and 25 days after previous TAI, respectively. The hastening of reproductive age of Nelore heifers aims to reduce age at first calving and increase productivity. Factors such as age, weight, body condition score (BCS), uterine score (USC), average daily weight gain (ADG), withers height/depth of rib relationship (dRIB) and subcutaneous fat thickness (SCFT) were associated with an increase in the success of gestational establishment at TAI and can be used to select the heifers that are more suitable for reproduction. These technologies can contribute to improve the national production of kilograms of meat and liters of milk per hectare, and consequently improve livestock profitability.

Impact of progesterone and estradiol treatment before the onset of the breeding period on reproductive performance of Bos indicus beef heifers.

The present aimed to develop a hormonal therapy based on the insertion of a progesterone (P4) insert (PI) during 10 d plus an estradiol injection (E2) at PI removal before the onset of breeding of beef heifers. In Exp. 1, the plasma P4 profile of prepubertal heifers showed that the insertion of a PI or 24 d previously used P4 insert (UPI) sustained plasma P4 above 1 ng/mL for at least the first 7 d of the treatment. In Exp. 2 there was no positive effect of additional estradiol benzoate (EB) administered at the insertion of UPI on the proportion of heifers with a corpus luteum (CL/Treated) 30 d after UPI removal [UPI + EB = 85.3%(a) (n = 134); EB + UPI + EB = 80.8%(a) (n = 125)]; however, both were greater (P < 0.0001) than the Control group [60.3%(b) (n = 129)]. In Exp. 3, a positive effect (P=0.01) of UPI treatment and both E2 supplementations [EB and estradiol cypionate (EC); P = 0.10] at the UPI removal was observed on CL/Treated [Control = 42.5%(b) (n = 94); UPI = 58.5%(a) (n= 130); UPI + EB = 64.0%(a) (n = 128); UPI + EC = 67.2%(a) (n = 128)]. However, greater pregnancy per treated heifer (P/Treated) following artificial insemination (AI) upon estrus detection was achieved when EC was applied [Control = 20.2%(b); UPI = 29.2%(ab); UPI + EB = 26.6%(b); UPI + EC = 36.7%(a)]. In Exp. 4, the treatment prior to the timed AI (TAI) tended to improve pregnancy per TAI [P/AI; Control 43.6% (n = 298) vs. UPI+EC 51.9% (n = 342); P = 0.08], but increased P/Treated [26.5% vs. 43.3%; P < 0.001]. Thus, UPI + EC treatment were efficient in increasing the CL/Treated, tended to improve the P/AI and consequently enhanced P/Treated of zebu beef heifers.

Hormonal strategy to reduce suckled beef cow handling for timed artificial insemination with sex-sorted semen

Two experiments were conducted to assess a hormonal strategy developed to reduce animal handling for timed artificial insemination (TAI) with sex-sorted semen. Four-hundred ninety-one (491) suckled beef cows received a progesterone (P4) intravaginal device and 2 mg intramuscular (im) injection of estradiol benzoate (EB) on a randomly chosen day of the estrus cycle (Day 0) in Experiment 1. Cows were treated with 500 μg of sodic cloprostenol (PGF2α) and with 300 IU of eCG at P4 device removal (Day 8); these cows were also randomly assigned to receive 1 mg of estradiol cypionate (EC) administered at P4 device removal (treatment EC-0h) or 1 mg of EB 24 h after P4 device removal (treatment EB-24h). Both treatments were timed inseminated (TAI) with sex-sorted semen 60 h after P4 device removal. Cows treated with EC-0h presented higher pregnancy rate per AI (P/AI) [45.0% (113/251)] than the ones treated with EB-24h [35.4% (85/240); P = 0.03)]. A subset of cows (n = 26) were subjected to ultrasound examination every 12 h after P4 device removal for 96 h in the row in order to determine the time of ovulation. Similar interval between device removal and ovulation was recorded for EB-24h = 70.0 ± 2.9 h vs. EC-0h = 66.0 ± 2.8 h (P = 0.52). Five-hundred ninety-one (591) cows were subjected to the same synchronization protocols and treatments (EC-0h or EB-24h). In addition, they were randomly assigned to a 2 × 2 factorial arrangement aiming at determining the effects of treatment with estradiol (EC-0h vs. EB-24h) and of semen type (Sex-sorted vs. Non-sex-sorted semen). All animals were timed inseminated 60 h after P4 device removal. There was no interaction (P = 0.07) between the ovulation inducer and semen type. The EC protocol led to greater P/AI than EB (P = 0.03). Greater (P = 0.01) P/AI was achieved through treatments with non-sex-sorted semen rather than with sex-sorted semen [sex-sorted (EB-24h = 49.0%; EC-0h = 51.0%) vs. non-sex-sorted semen (EB-24h = 52.4%; EC-0h = 68.2%)]. Therefore, EC administered at P4 device removal resulted in greater P/AI. Furthermore, the EC-0h protocol allowed reducing suckled beef cow handing for timed artificial insemination with sex-sorted semen.