Effect of somatotropin on survival and diameter of bovine preantral follicles

The effect of bioidentical nanostructured progesterone in the in vitro culture of preantral follicles and oocyte maturation

This study evaluated the effects of bioidentical nanostructured progesterone alone or in association with human chorionic gonadotropin (hCG) on the in vitro survival and development of preantral follicles (experiment 1) and oocyte maturation (experiment 2). Bioidentical hormones have a molecular structure identical with that of endogenous hormones; nanostructured substances refer to those reduced to a nanoscale. In experiment 1, fragments of goat ovarian tissue were cultured for 7 days in α-MEM⁺ alone or supplemented with nanoprogesterone (MEM⁺ + P4) or P4 and hCG (MEM⁺ + P4 + hCG). In experiment 2, two mediums of oocyte in vitro maturation (IVM) were compared. Medium 1 consisted of TCM 199⁺ + LH, and medium 2 consisted of TCM 199⁺ with nanoprogesterone and hCG. The MEM⁺ + P4 + hCG treatment showed the lowest percentage of follicular survival after 7 days of culture. MEM⁺ + P4 and MEM⁺ + P4 + hCG treatments showed higher percentage of follicular activation than MEM⁺. In experiment 2, there were no differences between mediums 1 and 2 for all endpoints evaluated. In conclusion, the addition of nanoprogesterone is advisable for in vitro culture of preantral follicles and oocyte maturation. However, the association of nanoprogesterone with hCG causes the cellular death of initial follicles but shows efficacy in IVM.

Recombinant bovine somatotropin in the synchronization of ovulation in crossbred dairy cows (Bos taurus indicus × Bos taurus taurus)

Aim:

The aim of this study was to evaluate the effects of the administration of recombinant bovine somatotropin (rbST) at the moment of implementation of the timed artificial insemination protocol, on follicular dynamics and pregnancy rate in crossbred cows.

Materials and Methods:

A total of 346 cows were used in two experiments with a factorial 2×2 design. The cycling cows (Tcycling) and the anestrous cows (Tanestrous) were considered as factor 1 and the administration of rbST (TrbST) or not (Tcontrol) as factor 2. The experimental protocol: (1) Tcontrol – day 0 (D0), insertion of a progesterone-release intravaginal device (PRID) plus 2 mg of estradiol benzoate (EB); D8, PRID removal, plus 0.150 mg of prostaglandin F_2α, and 400 IU of equine chorionic gonadotropin; D9, 1 mg of EB; and with artificial insemination at day 10; (2) TrbST – similar to Tcontrol plus 500 mg of rbST on D0. In experiment I, ultrasound examinations were performed in all treatments. In experiment II, the cows’ pregnancy rate was evaluated. Data were analyzed with 5% probability.

Results:

There was no effect of the protocols on cows cyclicity or follicular growth rate (p>0.05). There was no interaction of the effects, administration of rbST, and the cyclicity of cows on the pregnancy rate. The total pregnancy rate observed was 49.0%. The pregnancy rate in cows receiving rbST was lower for anestrous compared with cycling cows (p<0.05).

Conclusion:

The administration of rbST did not alter the patterns of follicular dynamics nor the ovulation rate. However, cows in anestrous that received rbST had lower pregnancy rates than cycling cows.