|Olson, J - MONTANA STATE UNIV|
|Paterson, J - MONTNA STATE UNIV|
|Funston, R - UNIV OF NEBRASKA LINCOLN|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2003
Publication Date: June 1, 2003
Citation: OLSON, J.L., ROBERTS, A.J., PATERSON, J.A., FUNSTON, R.N. EFFECT OF EXOGENOUS PROGESTERONE BEFORE CALF REMOVAL AND PROSTAGLANDIN F2ALPHA ON ESTROUS RESPONSE AND PREGNANCY RATES IN 3-YEAR-OLD BEEF COWS. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. 2003. v. 81(Suppl. 1). p. 186. Technical Abstract: Objectives for this experiment were to determine effects of a 7-d pretreatment with an intravaginal progesterone insert (CIDR) on estrous response and pregnancy rates in 3-year-old postpartum beef cows synchronized with calf removal and prostaglandin F2alpha. Cows (BW = 488 +/- 7.4; body condition score = 3.8 +/- .07; days postpartum = 58.7 +/- 1.2) were randomly allotted to either control (n = 22; i.m. injection of 25 mg PGF2alpha [Lutalyse®] on d 0) or CIDR treatment from -7 to 0 d preceding, PGF2-alpha injection on d 0 (CIDR; n = 18). All calves were weaned on d 0. Cows were observed for estrus for 120 h after PGF2alpha and inseminated by AI approximately 12 h after the onset of estrus. A bull was placed with cows 12 d after PGF2-alpha and removed 77 d after PGF2alpha. Circulating progesterone (P4) concentrations were determined in blood samples collected on d -7, 0, and 11. Pregnancy status was diagnosed by ultrasonography on d 54 and 145 after PGF2alpha. Synchronization rates were higher (P < 0.05) for CIDR (100%) compared to Control (77%) cows. Time of estrus did not differ (P > 0.10) between Control and CIDR cows (2.41 +/- .15 d). Pregnancy rates by AI were not different (P = .28) between Control (18%) and CIDR (33%) cows. Overall pregnancy rates were higher (P < 0.10) in Control (97%) compared to CIDR (80%) cows. Concentrations of P4 on d -7, 0, and 11 did not influence (P > 0.10) overall pregnancy rates; however, progesterone concentrations were increased (P < 0.05) in CIDR cows on d 0 (5.6 vs. 2.9 ng/ml, for CIDR vs. Control) and d 11 (7.1 vs. 4.8 ng/ml, for CIDR vs. Control). Administration of a CIDR 7 d before calf removal and PGF2alpha increased concentrations of P4 on d 0 and 11, and increased the proportion of cows exhibiting estrus. However, CIDR treatment did not improve conception and pregnancy rates in this study.