Short communication: Optimization of a timed artificial insemination program for reproductive management of heifers in Canadian dairy herds

Abstract

Pregnancy per AI (P/AI) following the use of 1 of 2 timed AI (TAI) protocols and 2 different intervals between TAI and resynchronization were compared in heifers that were inseminated with either conventional or sex-sorted semen. Holstein heifers (n = 317; 527 inseminations) were submitted to a 5-d Cosynch protocol with (+) or without (-) GnRH at the time of controlled internal drug release (CIDR) insertion on d 0, CIDR removal and a single PGF treatment on d 5, and TAI plus GnRH on d 8 (72 h later). Visual estrus detection (ED) was conducted on d 6 in the afternoon and d 7 in the morning and heifers observed in estrus were artificially inseminated on d 7 in the afternoon. Heifers were alternately assigned conventional or sex-sorted semen. Pregnancy was diagnosed by ultrasound 27 and 42 d after AI, and heifers diagnosed as nonpregnant were resynchronized, up to 3 times, starting on d 27 or 34 to provide an interbreeding interval of 35 or 42 d. Overall, TAI protocol had no effect on P/AI at 27 or 42 d after artificial insemination or on pregnancy loss, but P/AI following the first service tended to be higher in the -GnRH TAI group (66.3 vs. 56.8%). Pregnancy per AI at 27 d (61.9 vs. 55.5%) tended to differ between conventional and sex-sorted semen. Heifers artificially inseminated based on ED tended to have a greater P/AI (67.6 vs. 58.2%) and had decreased pregnancy loss (0.0 vs. 4.1%) than those submitted to TAI. A greater number of heifers in the -GnRH TAI protocol were artificially inseminated on ED than the +GnRH TAI protocol (21.5 vs. 13.7%). No difference in P/AI was observed between the 35- and 42-d interbreeding intervals; however, more heifers in the 42-d group were artificially inseminated based on ED than in the 35-d group (22.7 vs. 7.8%). A 5-d Cosynch+CIDR TAI protocol without the initial GnRH and with a single PGF at CIDR removal is an acceptable alternative to achieve high P/AI when either conventional or sex-sorted semen is used in Holstein heifers. Breeding heifers based on detected estrus increases labor, but has the potential to increase fertility.

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

“…En este sentido, Macmillan et al (2017) compararon los protocolos + y -GnRH usando semen convencional o sexado en novillas de leche. Aunque la diferencia no fue estadísticamente significativa, se observó una mayor tasa de preñez en el caso de semen sexado combinado con el protocolo -GnRH en comparación con el protocolo +GnRH (60 vs. 50%, res pec tivamente).…”

“…Por ello, nos hemos planteado la hipótesis de si el uso de una detección corta de celos antes de la IATF para la identifi-cación de animales idóneos para una IA temprana (56-60 horas después de la retirada del CIDR) aumentaría los porcentajes de preñez. En este sentido, Macmillan et al (2017) realizaron una detección de celo a las 36 y 48 horas de la retirada del CIDR. Las novillas que mostraron celo se inseminaron a las 60 horas de la retirada del CIDR, frente a las que no expresaron celo, que se inseminaron a las 72 horas (IATF).…”

“…Tasas de celo y de preñez en novillas de carne, en función del tipo de protocolo (Pr) (Cosynch 5-d modificado vs. J-synch), de la inclusión o no de eCG (eCG) y de la explotación (Ex). En nuestro estudio con novillas lecheras (Macmillan et al, 2017), se compararon 2 protocolos de resincronización con intervalos entre servicios de 35 o 42 días, analizando los protocolos con y sin GnRH en cada inseminación. En este estudio, se obtuvo una tasa de preñez acumulada del 81% después de 2 inseminaciones y del 97% después de 4.…”

Reproductive Performance in a Selected Sample of Dairy Farms in Una-Sana Canton, Bosnia and Herzegovina

“…Accordingly, the improvement of the veterinary advisory service and its structured approach to animals whose indicators suggest a reproductive problem arises as one of the primary goals in the dairy sector in BH. Although not commonly used in BH, timed AI can be introduced as an alternative cost-effective Veterinary Medicine International and viable solution for this group of animals, as previously reported [23,24]. Animals with chronic reproductive problems could also be removed from the dairy herd although farmers reported that reproductive culling is not a common management practice in their farms in Una-Sana Canton.…”

<b>Eficácia do tratamento com antibiótico injetável associado a selante de tetos sobre a saúde do úbere de novilhas com lactações induzidas</b>

“…A média geral em todas as novilhas, independentemente do tratamento foi de 76,2%, o que pode ser considerada uma alta taxa de concepção, por se tratar de novilhas que tiveram a lactação induzida. Além disso, esta taxa de concepção é similar àquela descrita para novilhas nulíparas que não foram submetidas a um PIL em outros estudos: 64,2% com novilhas da raça Jersey, 71,8% da raça Holandesa e 70,4% da raça Jersolando (XU; BURTON, 1999), 68% para novilhas da raça Holandesa (MACMILLAN et al, 2017).Estes resultados sugerem que o presente PIL não afetou a performance reprodutiva das novilhas quando comparado ao de nulíparas não induzidas. Resultados inferiores de 54% de taxas de prenhez acumulada após 5 IATFs foram obtidos em nulíparas não submetidas a indução de lactação antes da primeira prenhez (NORMAN et al, 2010).…”