title: Corpus luteum development and function after supplementation of long-acting progesterone during the early luteal phase in beef cattle.
abstract: Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4-containing supplement has not been determined for beef cattle. Effects of supplementation of long-acting progesterone (P4) on Days 2 or 3 post-ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4-based protocol and treated with 150 or 300 mg of long-acting P4 on Day 2 or 3 post-ovulation (6-7 cows/group). Colour-doppler ultrasound scanning and blood sample collection were performed from Day 2-21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5-5.5 in the Day 2-treated groups and from Day 3.5-5.5 in the Day 3-treated cows than in the control group. CL area and blood flow during Day 2-8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non-treated and 150 mg-treated cows. The interval from pre-treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4-treated groups than in the control cows. In conclusion, was showed for the first time that long-acting P4 supplementation on Day 2 or 3 post-ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.
authors.affiliation: Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo, Pirassununga, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Pugliesi
authors.forename: M L
authors.initials: ML
authors.lastname: Oliveria
authors.forename: S C
authors.initials: SC
authors.lastname: Scolari
authors.forename: E
authors.initials: E
authors.lastname: Lopes
authors.forename: F V
authors.initials: FV
authors.lastname: Pinaffi
authors.forename: B T
authors.initials: BT
authors.lastname: Miagawa
authors.forename: Y N
authors.initials: YN
authors.lastname: Paiva
authors.forename: J R G
authors.initials: JR
authors.lastname: Maio
authors.forename: G P
authors.initials: GP
authors.lastname: Nogueira
authors.forename: M
authors.initials: M
authors.lastname: Binelli
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D005260:Female; D008183:Luteal Phase / Q000502:physiology*; D003341:Luteolysis / Q000187:drug effects; D010060:Ovulation; D011374:Progesterone / Q000008:administration & dosage* / Q000097:blood; D013997:Time Factors; D018615:Ultrasonography, Doppler, Color / Q000662:veterinary
chemical_list: D011374:Progesterone