Suckling as a regulator of postpartum rebreeding in cattle: a review.

Abstract

An extended and variable period of anovulation and anestrus occurs in suckled beef cows following parturition. This imposes both biological and economic constraints on the efficiency of beef production. A large body of knowledge has linked these phenomena to an attenuation of neuroendocrine signals that subserve gonadal function. During late gestation, high concentrations of placental estrogen inhibit the synthesis of LH, and pituitary stores of LH are depleted at parturition. Maximum pituitary stores of LH, releasable pools of LH and the ability of hypothalamic centers to respond to positive feedback effects of estradiol occur within 3 to 4 wk after calving in suckled cows. However, the requisite pattern of pulsatile LH secretion, which accompanies similar changes in nonsuckled cows within 2 to 3 wk after calving, occurs in only 30 to 50% of suckled animals. The period of acyclicity that continues in the remainder is exacerbated by poor body condition and may persist in some females for periods exceeding 100 d. Utilizing data from the cow, as well as other species, a model for suckling-induced inhibition of pulsatile LH release is proposed. The biological and economic impact of current and future techniques for controlling suckling-induced anestrus also is considered, including a conceptual analysis of nonbiological limitations.

Minimizing cows’ stress when calves were early weaned using the two-step method with nose flaps

“…In this context, suckling managements can be used to stimulate ovulation and consequently early pregnancy rate in beef cows (Quintans et al, 2009 and. In extensive grazing systems in which cows usually have a low body condition after calving due to the high dependence on native pastures, early weaning has been developed as an alternative that provided good results to farmers by advancing postpartum rebreeding and increasing pregnancy rates (Williams, 1990;Arthington and Kaimbacher, 2003;de Castro et al, 2006;Vaz and Lobato, 2010).…”

Management factors associated to the duration of postpartum anoestrus interval in Brown Swiss and Pirenaica beef cows

“…El aumento de la frecuencia de amamantamiento, asociado a un retraso en la reactivación ovárica postparto (Williams, 1990), podría desencadenar también un mayor crecimiento del ternero (Osoro y Wright, 1992). En este trabajo ni el peso del ternero al nacimiento, ni su ganancia media diaria estuvieron vinculados a la duración del APP, de acuerdo con el trabajo de Revilla y Blasco (1993).…”

“…La crianza del ternero puede retrasar la reactivación ovárica postparto de la vaca, a través de la inhibición de la liberación pulsátil de LH (Williams, 1990). Se han practicado diversos manejos del ternero con el fin de reducir el efecto negativo de la crianza sobre la actividad reproductiva; por ejemplo, la restricción del acceso del ternero a la madre a uno o dos breves periodos diarios (Bluntzer et al, 1989;Stagg et al, 1998).…”

Desempenho reprodutivo de vacas de corte em lactação e solteiras submetidas à indução/sincronização de estro

“…A lactação é um estado dominante sobre outras atividades fisiológicas, fazendo com que a vaca priorize a produção de leite para o terneiro em relação à atividade reprodutiva (SHORT et al, 1990;BAUMAN, 2000). Sendo assim, vacas com baixas reservas nutricionais e afetadas negativamente pela presença do terneiro levam um maior tempo para retomar a atividade ovariana normal pós-parto, não concebendo dentro de períodos de acasalamento restritos (HOUGHTON et al, 1990;WILLIAMS et al, 1990;WETTEMANN et al, 2003). Esta categoria de fêmeas que falha em conceber e permanece na propriedade até o próximo acasalamento é denominada de "vaca solteira".…”