Priming pheromones from oestrous cows increase synchronization of oestrus in dairy heifers after PGF-2 injection

Abstract

Post-pubertal Holstein heifers with palpable corpora lutea were injected i.m. with 25 mg PG[prostaglandin]F-2.alpha. to bring all animals to the follicular phase of the estrous cycle. After 3 oronasal treatments with secretions from estrous cows or water, heifers were observed for estrus and inseminated about 12 h after the onset of estrus. In experiment I, heifers were treated with water or a mixture of urine and cervical mucus from estrous cows at 6, 30 and 56 h after the PGF-2.alpha. injection. The percentage of heifers in estrus within 72 h after PGF-2.alpha. was 86% for urine + cervical mucus-treated heifers and 60% for water-treated heifers and (P > 0.05). Days to estrus and conception rate after artificial insemination did not differ between the treatments. The degree of synchrony of estrus after PGF-2.alpha. was significantly greater (P < 0.05) in the animals receiving urine + mucus treatment. In experiment II, urine and cervical mucus from estrous cows were separately tested in comparison to water. Test substances were applied at the time of PGF-2.alpha. injection, and 6 and 30 h later. The percentage of heifers in estrus within 72 h after PGF-2.alpha. (100%) was highest (P < 0.05) in the cervical mucus-treated heifers, but the conception rate (24%) was the lowest. The days to estrus did not differ among groups, but the degree of synchrony of estrus after PGF-2.alpha. was greatest (P < 0.05) in animals treated with cervical mucus. A priming pheromone in the cervical mucus of estrous cows can affect the ovarian function of herdmates and improve synchrony of estrus after PGF-2.alpha. injection.