Randomised controlled trial of the effect of concentration of progesterone before artificial insemination on fertility in ovulatory and anovulatory Bos indicus cattle

Abstract

Manipulating P4 concentrations before AI has the potential to improve pregnancy outcomes to AI in B. indicus females, but treatment may need to vary between animals classified as anovulatory or ovulatory.

A novel strategy for resynchronization of ovulation in Nelore cows using injectable progesterone (P4) and P4 releasing devices to perform two timed inseminations within 22 days

“…The greater accuracy and sensitivity observed for detection of non‐pregnant animals allowed the development of new strategies to reduce the interval between TAI and timed embryo transfer (TEF) to 22–24 days (Baruselli et al, ; Pugliesi et al, ). However, considering that administration of 17β‐oestradiol (E2) esters during the second week of the oestrous cycle may induce CL regression in inseminated dairy cows (Vieira et al, ), the use of increased doses of injectable progesterone (P4) could be an alternative to induce a new follicular wave and avoid the use of E2‐based protocols (Cavalieri, ; Cavalieri, Gaina, & Hepworth, ). In this regard, previous studies (Cavalieri et al, ; Cavalieri, Kinder, & De'ath G, Fitzpatrick L., ; Cavalieri, Kinder, & Fitzpatrick, ) reported that acute administration of P4 might efficiently suppress gonadotropins and induce a new follicular wave in Bos indicus cattle.…”

Effect of the Estrus Expression on Follicular and Luteal Morphofunctional Characteristics and Fertility in Bos indicus females Synchronized for FTAI

“…No presente experimento, o comportamento de estro afetou, também, as concentrações séricas de progesterona. Da mesma forma, trabalhos avaliando a relação entre a expressão do estro e os parâmetros luteais em fêmeas de corte submetidas a um programa de IATF, observaram maiores níveis séricos de progesterona para os animais que demostraram estro antes do momento da inseminação [13,20]. Murdoch e Van Kirk [33] apontaram uma correlação entre maiores concentrações de estradiol e uma maior proliferação das células da granulosa que após a ovulação se tornaram as grandes células lutais, sendo estas responsáveis por 80% da produção de progesterona.…”

“…A junção destas ações, possivelmente, cria um ambiente endócrino favorável à concepção [11,29]. Estudos sobre o impacto da expressão do estro sobre a fertilidade de bovinos de leite, evidenciaram melhores índices de concepção para o grupo com estro em relação aos animais que não apresentaram estro [13]. Em pesquisa com fêmeas de corte submetidas a um protocolo de IATF, foram observados maiores índices de prenhez no grupo de animais que esboçaram estro antes do momento da inseminação artificial propriamente dita [15].…”

In this issue – September 2018: Identification of commercial piggeries using aerial photographs and image analysis • Destruction of foot‐and‐mouth disease virus in carcases in the field • Size of the Australian goat industry • P4 and fertility after AI in extensively managed Bos indicus cattle • Antimuellerian hormone levels not recommended in young bitches • A sarcoma on an echidna beak

“…The first four papers this issue cover a broad range of production animal topics. They include two articles that discuss very different aspects of biosecurity management in the event of an emergency animal disease incursion, a survey that gives new data on the size of the Australian goat industry 3 and a randomised trial on the fertility in Bos indicus cattle …”

“…Results of a study in Bos indicus cattle suggest that increasing the percentage of animals that are cycling before starting treatments, increasing progesterone concentrations in anovulatory animals and decreasing progesterone in ovulatory animals could reduce variability in response to artificial insemination (AI) …”