The relationship between estrogen pretreatment and route of administration of cloprostenol on progesterone concentrations and farrowing in sows
Roy N. Kirkwood, DVM, PhD; Frank X. Aherne PhD
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Objective: To test the effect of preinduction estradiol treatmentand route of cloprostenol (PGF) administration on the farrowing and endocrineresponses of sows.
Methods: Sows were allocated in a 2 x 2 factorial arrangementto receive 3 mg estradiol at 112 days versus no injection, and to subsequentlyreceive 175 µg PGF either intramuscularly or perianally on day 113of gestation. Sows were blood sampled at the time of PGF injection, andat 12, 18, and 24 hours after PGF injection and at farrowing. Plasma sampleswere assayed for progesterone.
Results: There was no effect of estradiol pretreatment or routeof administration of PGF on farrowing responses. Blood samples were successfullycollected from nine of 10 sows with an interval between PGF injection andfarrowing of >= 48 hours. Progesterone profiles indicated that in fiveof these nine sows, PGF failed to cause luteolysis. However, the other foursows had clear evidence of PGF-induced luteolysis but still had a prolongedinterval between PGF injection and farrowing.
Implications: Estradiol pretreatment does not improve the predictabilityof farrowing in response to PGF. Further, luteolysis does not occur in allsows after PGF injection and not all sows farrow promptly after luteolysis.