Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows1

Abstract

This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.

Estrous Signs and Progesterone Profile of Ongole Grade Cows Synchronized at Different Ages Fed Different Level of Dietary Crude Protein

“…Furthermore, the average percentage of estrous incidence in this study can be categorized as high (more than 70%). As the cows received GnRH and PGF2α synchronization, this number is logical and similar to the previous report showing more than 70% of estrous expression in cows treated with similar synchronization protocol (Rodrigues et al, 2018). The estrous expression is particularly affected by the increasing level of circulating estradiol hormone, which induces the hypothalamic initiation leading to the onset of estrous expression (Silper et al, 2015;Schubach et al, 2017).…”

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

“…Em estudos similares, observou-se a influência do comportamento de estro sobre as dimensões luteais e os níveis séricos de progesterona no período pós-ovulatório, sugerindo, assim, a existência de uma correlação entre expressão do estro e parâmetros morfofuncionais luteais [34,35,43]. Deste modo, a mensuração da vascularização, nesta estrutura ovariana, pode fornecer importantes informações sobre a função luteal e o índice de fertilidade em fêmeas bovinas [8,12,28,48].…”

“…Sá Filho et al [46], buscando avaliar a influência do estro sobre o diâmetro luteal de vacas submetidas a IATF, constatou distinções entre as fêmeas que apresentaram estro e as que não demostraram estro, obtendo média de 22,9 ± 3,0 mm e 20,3 ± 3,9 mm, respectivamente. De forma similar, Rodrigues et al [43] averiguaram que as fêmeas que apresentavam o comportamento do estro antes do momento da inseminação propriamente dita, também, apresentaram maiores dimensões luteais.…”

“…Algumas pesquisas observaram um maior diâmetro folicular e fertilidade nas fêmeas que demonstraram comportamento de estro antes da inseminação artificial propriamente dita [1,5,49]. Estudos recentes sugerem que a expressão de estro pode ser um fator que afeta as características morfofuncionais foliculares e luteais [34,35,43,46]. A junção entre os efeitos do comportamento do estro no período folicular e luteal cria um ambiente endócrino favorável à concepção, devido ao aumento na expressão de fatores responsáveis pela sinalização da gestação para os tecidos maternos [17].…”

Symposium review: Linking activity-sensor data and physiology to improve dairy cow fertility

“…These findings support Løvendahl and Chagunda (2010), who Aungier et al (2012) also found an association between BCS and estrous expression, where a 0.25 increase in BCS was associated with increased physical activity before ovulation. The reduction in estrogen-dependent estrous behavior, caused by a temporary state of negative energy balance, has also been noted in beef cows (Rodrigues et al, 2018).…”