Follicular dynamics, circulating progesterone, and fertility in Holstein cows synchronized with reused intravaginal progesterone implants that were sanitized by autoclave or chemical disinfection

Abstract

This experiment aimed to compare circulating progesterone (P4), follicular dynamics, and fertility during reuse of intravaginal P4 implants that were sanitized by autoclave or chemical disinfection in lactating Holstein cows submitted to fixed-time artificial insemination (FTAI). For this, 123 primiparous and 226 multiparous cows from 2 farms, averaging (mean ± standard deviation) 163.9 ± 141.9 d in milk, 35.7 ± 11.3 kg of milk/d, and a body condition score of 2.9 ± 0.5, were enrolled in the study. Cows were randomly assigned to 1 of 2 treatments using a completely randomized design and each cow received a reused implant (1.9 g of P4; previously used for 8 d) that was either autoclaved (AUT; n = 177) or chemically disinfected (CHEM; n = 172) on d -10. Also on d -10, cows received 2 mg of estradiol benzoate and 100 μg of GnRH. On d -3, cows received 25 mg of dinoprost (PGF). A second PGF was given on d -2, along with 1 mg of estradiol cypionate and P4 implant removal. Cows received FTAI on d 0. A subset of cows (n = 143) was evaluated by ultrasound on d -10, -8, -6, -3, -2, 0, and 5 to identify ovarian structures, and blood was sampled on d -10, -3, and -2 for P4 concentrations by RIA. Pregnancy diagnoses were performed at d 32 and 60. Statistical analyses was performed using PROC-MIXED for continuous variables and PROC-GLIMMIX of SAS 9.4 (SAS Institute Inc., Cary, NC) for binomial variables. The treatments did not differ in circulating P4 on d -10 or -3, but P4 was greater on d -2 in CHEM cows. Ovulation to the treatments on d -10 was associated with lower circulating P4 on d -10 (2.0 vs. 3.1 ng/mL) and resulted in greater P4 on d -3 (4.0 vs. 2.4 ng/mL) and more cows with a corpus luteum on d -3 (100 vs. 40%) than nonovulating cows. Cows that ovulated to d -10 treatments were more likely to have a synchronized new follicular wave (97.9 vs. 63.2%) and had an earlier wave emergence (1.9 vs. 2.6 d), resulting in less cows ovulating a persistent follicle (0.0 vs. 35.7%). Type of P4 implant, corpus luteum presence on d -10, and ovulation to d -10 treatments did not affect fertility (pregnancy per AI; P/AI). However, P/AI on farm A was greater than on farm B at 32 (40.8 vs. 27.8%) and 60 d (35.8 vs. 24.3%), independent of treatment. In conclusion, P4 implants with different P4 release patterns did not produce detectable differences in follicular dynamics, synchronization rate, or P/AI. Nevertheless, presence of corpus luteum or ovulation at the beginning of the FTAI protocol affected reproductive variables, such as timing and synchronization of follicular wave emergence, and size of the ovulatory follicle. Beyond that, more overall synchronized cows became pregnant to the FTAI protocol.

Estrus and pregnancy rate of Simmental-Ongole Crossbred and Ongole Grade heifer after being synchronized and inseminated

“…Intra vaginal progesterone implants that were sanitized in lactating primaparous and multiparous of Holstein cows, affected reproductive variables, such as timing and synchronization of follicular wave emergence, and size of the ovulatory follicle (Melo et al, 2018). Response of estrus synchronization using 50 mg medroxy progesterone acetate in heifers and cows were 91.67% and 65.79% (Sutiyono et al, 2014).…”

Strategies for induction of ovulation for fixed-time AI in lactating dairy cows submitted to a novel presynchronization protocol

“…Weekly, a cohort of cows was submitted to a presynchronization protocol that was the same for all cows. This presynchronization initiated (D-15) with 1.0 g P4 device (Reproneo, GlobalGen, Jaboticabal, Brazil) previously used once or a 2.0 g P4 device (Reprosync, GlobalGen) previously used once, twice or thrice disinfected according to Melo et al (2018) Figure 1).…”

“…South American dairy herds generally utilize protocols based on treatments with estradiol (E2) plus progesterone (P4) sometimes utilizing gonadotropin releasing hormone (GnRH) at the beginning of the protocol and induce final ovulation with estradiol esters (Pereira et al, 2015;Melo et al, 2018). These protocols, however, are not optimized in terms of effectively synchronizing emergence of a new follicular wave or promoting an optimal P4 milieu during development of the preovulatory follicle.…”

“…For instance, cows that started a FTAI protocol with estradiol benzoate (EB) had ~40% luteolysis after D0 of the protocol (Melo et al, 2016). In addition, synchronized emergence of a new follicular wave only occurred in ~60-75% of the cows (Monteiro et al, 2015;Melo et al, 2018), which means that a proportion of cows are ovulating a persistent follicle at the end of the protocol. Melo et al (2016) reported 35% of cows submitted to a E2/P4 based protocol ovulated a persistent follicle at the end of the protocol.…”

“…Melo et al (2016) reported 35% of cows submitted to a E2/P4 based protocol ovulated a persistent follicle at the end of the protocol. In addition, lack of ovulation at the end of E2/P4 protocols occurs in about 20% of lactating dairy cows and this substantially impairs fertility (Monteiro et al, 2015;Melo et al, 2018).…”