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

• Published in: Journal of animal science 2018-02, Vol.96 (1), p.236-249
• Main Authors: Rodrigues, A D, Cooke, R F, Cipriano, R S, Silva, L G T, Cerri, R L A, Cruppe, L H, Meneghetti, M, Pohler, K G, Vasconcelos, J L M
• Format: Article
• Language: English
• Subjects: Administration, Intravaginal; Animals; Cattle - physiology; Dinoprost - administration & dosage; Dinoprost - pharmacology; Estradiol - administration & dosage; Estradiol - analogs & derivatives; Estradiol - pharmacology; Estrus - drug effects; Estrus Synchronization - methods; Female; Fertility Agents, Female - administration & dosage; Fertility Agents, Female - pharmacology; Insemination, Artificial - methods; Insemination, Artificial - veterinary; Ovarian Follicle; Pregnancy; Progesterone - administration & dosage; Progesterone - blood; Progesterone - pharmacology; Reproduction
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/skx043

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.