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

Author(s)

Rodrigues, A. D. ^[1] ; Cooke, R. F. ^[2] ; Cipriano, R. S. ^[3] ; Silva, L. G. T. ^[1] ; Cerri, R. L. A. ^[4] ; Cruppe, L. H. ^[5] ; Meneghetti, M. ^[6] ; Pohler, K. G. ^[7] ; Vasconcelos, J. L. M. ^[1]

Affiliation

^[1] Sao Paulo State Univ, UNESP, Sch Vet Med & Anim Sci, BR-18168000 Botucatu, SP - Brazil

^[2] Texas A&M Univ, Dept Anim Sci, College Stn, TX 77845 - USA

^[3] Unisalesiano Auxilium, BR-16016500 Aracatuba, SP - Brazil

^[4] Univ British Columbia, Fac Land & Food Syst, Appl Anim Biol, Vancouver, BC V6T 1Z4 - Canada

^[5] Select Sires Inc, Plain City, OH 43064 - USA

^[6] Zoetis, BR-04711130 Sao Paulo, SP - Brazil

^[7] Univ Tennessee, Dept Anim Sci, Knoxville, TN 37920 - USA

• Document type: Journal article
• Source: JOURNAL OF ANIMAL SCIENCE; v. 96, n. 1, p. 236-249, JAN 2018.
• Web of Science Citations: 3

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 x 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 PGF(2 alpha) 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. indices-influenced cows beef cows. (AU)

• FAPESP's process: 16/18460-6 - Impacts of estrus expression and intensity during estrus synchronization + artificial insemination protocol on parameters associated with fertility and pregnancy establishment in beef females
• Grantee: Rafael Silva Cipriano
• Support type: Regular Research Grants
• FAPESP's process: 16/18216-8 - Collaborating with Oregon State University (USA) on research to enhance reproductive performance of beef females
• Grantee: José Luiz Moraes Vasconcelos
• Support type: Research Grants - Visiting Researcher Grant - International