Effect of PGF2α treatments during early corpus luteum development on circulating progesterone concentrations and ovulation in breeding-age Holstein heifers

Los procesos reproductivos en vacas y el uso de la ultrasonografía

“…El protocolo OvSynch (PGF2α y GnRH) fue desarrollado y completamente validado para su uso en vacas (Pursley et al, 1995), junto con sus variaciones, este protocolo sigue siendo el protocolo de sincronización de celos más utilizado en la ganadería (Burke et al, 1996;Pursley et al, 1997a;Pursley et al, 1997b;Bisinotto et al, 2014;Tippenhauer et al, 2021), incluso bajo condiciones de estrés calórico (De la Sota et al, 1997;Aréchiga et al, 1998). El tratamiento de vacas que no han sido detectadas en estro, pero que tienen un cuerpo lúteo detectable, se ha centrado principalmente en el uso de PGF2α (Martins et al, 2021;Wilke et al, 2021). En el ganado de carne, una de las características de las vacas anovulatorias es la pulsatilidad reducida de la LH, lo que perjudica el crecimiento del folículo y perjudica el logro o el mantenimiento de la dominancia folicular.…”

Efecto en la eficiente reproductiva mediante el uso de dos protocolos (eCG y Ovsynch) para IATF en ganado bovino tropical

“…Resultados de programas de IATF indican que es posible obtener porcentajes de preñez promedio del 50% a la primera inseminación, tanto en vacas con cría como en novillas; al respecto Bisinotto et al (2022) agregan que existen y se han aplicado protocolos para vacas con cría con los cuales resulta un incremento de los porcentajes de preñez. Los dispositivos intravaginales pueden ser reutilizados debido a que la cantidad hormonal en ellos está dada por gramos y la cantidad que las vacas necesitan para poder entrar en calor es en nano gramos, de esta forma la concentración residual de progesterona de un DIB de tercer uso podría ser capaz de inducir una sincronización de calores con similar tasa de gestación, cuando este se utiliza en novillas (Martins et al, 2021). Los valores aproximados del progestágeno residual en un DIB primer uso (nuevo) es de 1 gr, DIB segundo uso: 0,65 gr, DIB tercer uso: 0,3 gr.…”

Hormonal adjustments for fixed-time artificial insemination and physiologic variables influence in the reproductive performance of >i<Bos indicus>/i< heifers

“…Some studies described the impact of the circulating progesterone (P4) concentration on the largest follicle (LF) diameter at the P4 device removal moment, also at the AI time as Dias et al described in post pubertal Nelore heifers when exposed to a TAI protocol with new P4 device with higher serum P4 concentration two days before the device withdrawal (3.0 ± 1.9 ng/mL) or an already twice times used P4 device (2.0 ± 1.2 ng/mL), finding a difference of almost one millimeter on the follicle diameter at the TAI moment (New device: 10.1 ± 2.0 mm vs. 11.0 ± 2.1 mm) [11] presenting a positive association of a large follicle diameter with the expression of estrus and the pregnancy per artificial insemination (P/AI) in Nelore cows, previously presented by Sá Filho et al study where cows with a follicular diameter at the TAI time over 14.4 mm presented a P/AI of 63.3% compared with those cows with the smaller follicles (>7.5 mm) that achieve just a P/AI of 27.5% [12]. The follicle growth and diameter is controlled primarily by the progesterone regulation function over the LH pulse frequency, presenting a negative feedback on the pituitary LH secretion [13,14] resulting in a negative effect on the follicular diameter at the end of the TAI protocol [15] and a reduce expression of estrus, in a high circulating P4 concentration scenario, described before in Holsteins heifers submitted to four different Ovsynch protocols, reveling a 37% points difference in the expression of estrus between the treatment groups of the highest (8.43 ± 0.39 ng/mL) and the lowest (1.21 ± 0.15 ng/mL) P4 concentration at the first PGF treatment of the Ovsynch protocol (45% vs. 82%, respectively) [16]. It is the reason why, develop strategies to obtain a low circulating P4 concentration during the TAI protocol would be a relevant alternative to improve the follicular diameter at the end of the TAI and potentially improve the P/AI in Nelore heifers.…”

“…The TAI biotechnology has been supported in years of research in different breeds and production systems, leading to the establishment of two main strategies for the TAI protocols, bringing significant advances in the reproductive management of beef herds [12]. One of those strategies is the Ovsynch protocol and the several modifications widely described in literature [13][14][15][16]. On the other hand, an alternative mainly used in South America are the estradiol/progesterone-based TAI protocols, strategy that had different adjustments and alternatives developed in the last years, representing a significant improvement for the fertility results in the breeding herds, opening the possibility of an expressive expansion of the technology application in the field [17][18][19].…”