Fixed-time artificial insemination protocols on brazilian locally adapted breed gilts on ovulatory response and embryo production

Abstract

The aim of this study was to use estrus synchronization protocols to favor fixed-time artificial insemination and consequently fixed-time embryo collection, and increase embryo production using eCG, in gits. In a cross over design, nine Piau breed gilts were subjected to 18 days of oral progesterone; P4 group did not receive any further; GnRH group received 25µg of GnRH 104 hours after the final application of P4; and eCG+GnRH group received 1000IU of eCG 24 hours after the final P4 in addition to GnRH for subsequent embryo collection, that was performed six days after first AI, by laparotomy. Artificial insemination was performed after 12 and 24 hours of estrus in P4 group, and 128 and 144 hours in GnRH and eCG+GnRH groups. The number of CL (8.6±3.9; 8.3±2.1; 26.7±15.0) and anovulatory follicles (4.3±3.7; 3.9±3.9; 17.2±9.5) was higher in the eCG+GnRH gilts (P<0.05). However, the use of 1000 IU of eCG reduced (P<0.05) the number of total structures (5.2±3.6; 5.1±3.1; 1.7±2.7), viable embryos (5.0±3.5; 4.8±3.3; 0.4±0.7), freezable embryos (3.6±3.4; 3.3±3.8; 0.1±0.3) and recovery rate (63.7±38.9; 58.6±24.7; 5.38±9.5). P4 and GnRH protocols were effective in the production and recovery of embryos. However, the use of 1000 IU of eCG, 24 hours after P4, was not effective in promoting the production of embryos, although the animals had superovulated.

The neuroendocrine pathways and mechanisms for the control of the reproduction in female pigs

“…Estradiol has a biphasic effect in pigs, inhibiting basal LH pulses via negative feedback then stimulating an ovulatory surge of LH through positive feedback (Ieda et al, 2014;Thorson et al, 2017). When sexually mature OVX gilts were given a dose of estradiol sufficient to stimulate an ovulatory surge of LH, the expression of Kisspeptin in the PeV was upregulated compared with control OVX gilts (Tomikawa et al, 2010;Silva et al, 2021). It is inferred that separate populations of Kisspeptin neurons in the ARC and the PeV of gilts mediate negative and positive estrogen feedback for the control of tonic and surge LH secretion, respectively.…”