Endocrine and metabolic differences between Bos taurus and Bos indicus cows andimplications for reproductive management

Abstract

Based on the considerable differences in ovarian morphology and function, as well as circulating hormones and metabolites between Bos indicus (B. indicus) and Bos taurus (B. taurus), researchers are using this acquired knowledge to optimize protocols for fixed-time artificial insemination (FTAI), and production of in vivo derived embryos by multiple ovulation or by in vitro embryo production (IVP). In B. indicus, at the time of follicle deviation, the dominant follicle is smaller and acquires ovulatory capacity at a smaller diameter than B. taurus. Moreover, despite ovulating smaller follicles and having smaller corpora lutea (CL), circulating concentrations of estradiol (E2) and progesterone (P4) are greater in B. indicus than B. taurus. These physiological differences may be related to greater circulating cholesterol, insulin and IGF1 in B. indicus than in B. taurus. For both genetic groups there is a negative relationship between circulating P4 and ovulatory response to the first GnRH treatment of a fixed-time AI (FTAI) protocol. Moreover, despite lower clearance rates of steroid hormones in B. indicus than B. taurus, the dose of 2 mg estradiol benzoate seems to be the most effective either for Nelore (B. indicus beef), Angus (B. taurus beef), or Holstein (B. taurus dairy) cows at the initiation of an E2/P4-based FTAI protocol to optimize synchronization and pregnancy per AI (P/AI). Several studies have shown that only one recommended dose of PGF2α at a FTAI protocol may be insufficient for adequate luteolysis in B. indicus and B. taurus. When submitted to multiple ovulation and embryo transfer, B. indicus cows and heifers need less FSH than B. taurus to achieve superovulation. Moreover, IVP has been more successful in B. indicus than B. taurus due to greater antral follicle count and anti-mullerian hormone, and better oocyte quality.

Comparison of three doses of estradiol benzoate for synchronization of follicular wave emergence in suckled Bos indicus beef cows

“…This divergence between the previous and present results may be related to several factors affecting circulating E2 concentrations at the time of EB treatment, as the size of DF and the liver clearance of steroid hormones. According to Sartori et al (2016), Bos indicus cows have a slower metabolism of steroid hormones, compared to Bos taurus cows. In addition, increased clearance of steroid hormones is directly correlated with high dry matter intake and lactation (Sangsritavong et al, 2002).…”

Effect of single dose follicle stimulating hormone on follicular aspiration, in vitro fertilization and pregnancy rate

“…Physiological differences between bovine breeds (cows) are widely described in the literature. These particularities may have implications for the success of treatments that manipulate follicular development (Bó et al, 2003;Sartori et al, 2016). However, more studies are necessary to evaluate synthetic cows (crosses between Bos indicus and Bos taurus) as donors of oocytes with the application of FSH and OPU, especially for the Brangus breed.…”

Estradiol and GNRH on Ovulation Induction for Estrus Synchronized Crossbred Cows1

“…Additionally, other inducers have been effectively used, such as estradiol cypionate (EC) in Bos taurus indicus (SÁ FILHO et al, 2009;MENEGHETTI et al, 2009;SÁ FILHO et al, 2010;SARTORI;MONTEIRO JR.;WILTBANK, 2016) and gonadotropin releasing hormone (GnRH) in Bos taurus taurus. EC can be used at the same time as the removal of the progesterone device and the GnRH can be administered during AI (GOTTSCHALL et al, 2012;ALMEIDA et al, 2016a).…”