Evaluation of a modified GnRH-based timed-AI protocol associated with estrus detection in beef heifers inseminated with sex-selected or conventional semen

Abstract

The main objective was to compare pregnancy per AI (P/AI) between sex-selected and conventional semen in cyclic beef heifers subjected to a 5-day Co-synch plus CIDR protocol and evaluated the usefulness of an estrus detection (ED) aid to identify heifers that were most likely to conceive. This study also determined if the expression of estrus before timed-AI (TAI) would be associated with increased P/AI in acyclic heifers inseminated with conventional semen. Heifers (n = 1690; 320-523 kg of body weight, and 13-15 mo of age) at three locations over 2 years were scanned by ultrasonography to determine cyclicity (presence of luteal tissue) and reproductive tract normalcy. Cyclic heifers (n = 1331) received a progesterone releasing device (CIDR) on Day 0, CIDR removal and 500 μg of cloprostenol (PGF) on Day 5, and 100 μg of GnRH along with TAI on Day 8. Acyclic heifers (n = 275) received the same treatment with the addition of GnRH on Day 0. On Day 5, all heifers received ED patches (Estrotect™) that were scored from 0 to 3, based on color change between initial application and Day 8; 0 = unchanged, 1 = ≤ 50% color change, 2 = > 50% color change, 3 = missing. Estrus was defined to have occurred when an ED patch was scored 2 or 3. Cyclic heifers were inseminated with either frozen-thawed sex-selected or conventional semen from either of three sires available commercially (two per year). Acyclic heifers were inseminated with conventional semen. Pregnancy diagnosis was performed by transrectal ultrasonography 28 or 48 d after TAI, depending on management. The percentage of cyclic heifers was 83.9% and the average estrus response was 63.8%. P/AI was greater (P < 0.01) in cyclic compared to acyclic heifers (53.3 vs. 36.0%) and tended to be greater (P = 0.07) for conventional semen (52.3 vs. 47.6%), despite all acyclic heifers being inseminated with conventional semen. Heifers with an ED patch scored 2 (61.1%) or 3 (58.6%) had greater (P < 0.01) P/AI than those scored 0 (31.8%) or 1 (33.1%), regardless of semen type. Pregnancy per AI was greater (P < 0.01) for heifers detected in estrus (60.6 vs. 32.3%). In cyclic heifers that did not exhibit estrus, P/AI was lower (P < 0.01) in those inseminated with sex-selected semen (27.8 vs. 45.9%), while in heifers that exhibited estrus, P/AI only tended to be lower (P = 0.08; 56.7 vs. 65.5%). In summary, P/AI was greater in cyclic heifers, in those inseminated with conventional semen and in those exhibiting estrus before TAI. The ED patches were considered useful to identify animals for TAI with sex-selected semen and could be used to increase the adoption of this technology in beef herds.

Effect of delaying the time of insemination with sex‐sorted semen on pregnancy rate in Holstein heifers

“…However, the results in the presented study were not consistent with the previous studies (Colazo et al, 2018;Hall et al, 2017;Sá Filho et al, 2010;Thomas et al, 2019), and the possible reason may have been due to the fact that at least 200-300 inseminations are required to assess the fertility of a sire (Amann & DeJarnette, 2012). In addition, there was a tendency between the technician, time of the AI and sire in terms of all two-way and three-way interactions.…”

Revisión de los programas de sincronización ovárica basados en el uso de hormona liberadora de gonadotropinas y prostaglandina F2α para novillas de leche y de carne

“…Además, no se observaron diferencias significativas debidas a la GnRH inicial sobre la tasa de preñez (68 vs. 71%, para los lotes +GnRH y -GnRH, respectivamente). Estos resultados se han confirmado en estudios posteriores, aplicando el mismo protocolo en novillas de leche y de carne (Mac millan et al, 2017;Colazo et al, 2018a;Tabla 2). En otro estudio reciente, realizado en novillas de car ne (López-Helguera et al, 2018), tampoco encontramos diferencias significativas en la tasa de preñez a la IATF debidas al uso de la dosis inicial de GnRH (56 vs. 55%, para los lotes +GnRH y -GnRH, respectivamente), en línea con las tasas de preñez obtenidas por otros equipos en novillas de carne, al estudiar la inclusión o no de la GnRH al inicio de un protocolo de sincronización (51 vs. 55%) (Cruppe et al, 2014).…”

“…Al final de la época reproductiva (tras 2 rondas de IA y servicio natural durante 45 días más), la proporción de novillas vacías fue mayor dentro del grupo de las que no estaban ciclando al inicio del protocolo de sincronización (7 vs. 3%). En novillas lecheras se han obtenido resultados similares, observando mayores tasas de preñez si las novillas estaban cíclicas al inicio de un protocolo Cosynch 5-d modificado (35 vs. 59%, para acíclicas y cíclicas) (Colazo et al, 2018a). En la misma línea, los resultados de varios estudios realizados en Canadá, que aglutinan datos de más de 4000 IATF en novillas sometidas a un protocolo de sincronización de estradiol más progesterona de 7 días, mostraron que la fertilidad obtenida en la IA inicial fue un 10-15% inferior en las novillas acíclicas en comparación con las que estaban cíclicas al inicio de los tratamientos (Colazo, Resultados no publicados).…”

“…En otro estudio, realizado en novillas de carne (Colazo et al, 2018a), se utilizaron parches Estrotect™ (colocados en la base de la cola, que indican que la novilla fue montada por otras novillas si la superficie plateada aparece raspada y pasa a tener un color visible) para detectar celo entre la retirada del CIDR y la IATF, aunque todas las novillas recibieron una IATF a las 72 horas de la retirada del CIDR. En función de la superficie de Es-trotect™ frotada, se asignaba una puntuación a los parches de 0 (sin cambio de color), 1 (≤ 50% de cambio de color), 2 (>50% de cambio de color) y 3 (perdido).…”

Nutrient requirements in Hanwoo cows with artificial insemination: effects on blood metabolites and embryo recovery rate

“…Heat detection was conducted every morning and afternoon for 30 min from February 21, 2019 to April 29, 2019. To define heat estrus, estrus detection patches (Estrotect™, Rockway, Spring Valley, WI, USA) were applied about mid-way between the hip and tail head as previously described [ 22 ]. To determine the estrus cycle in Hanwoo cows, the follicular wave, ovulation, and corpus luteum formation were examined twice each week (Monday and Thursday) by ultrasonography with 7.5 MHz probe (NL/MyLab, Esaote, Genova, Italy).…”