The objectives of this study were to evaluate the length of the estrous cycle, duration of estrus, time of ovulation and progesterone patterns during prostaglandin F (PG)-synchronized (PG-S) and natural estrous cycles in Brown Swiss (BS) and Simmental (SIM) heifers reared in the Peruvian Highland (elevation 4250 m). Two- to three-year-old Brown Swiss (n = 8) and SIM (n = 4) heifers that had shown at least three estrous cycles were synchronized with two injections of Tiaprost (150 mg per 5 ml) 11 days apart. The same heifers were evaluated during their third estrous cycles after PG synchronization, which were considered natural cycles. Progesterone concentrations were determined in serum collected at daily intervals; estrus was detected visually. The ovaries of each heifer were examined 30 h after onset of PG-S and fourth estrus following PG treatment to determine the occurrence of ovulation. Percentages of BS and SIM heifers that exhibited a decrease in progesterone concentrations to levels lower than 1 ng ml-1 and behavioral estrus after PG treatment (responding heifers) did not differ (P > 0.10). The interval from PG injection to the onset of estrus and progesterone concentrations for 4 days after PG for responding heifers did not differ (P > 0.10) between breeds. The duration of estrus did not differ (P > 0.10) between breeds or type of cycle. More (P < 0.05) ovulations occurred after 30 h from the onset of estrus than before 30 h. Estrous cycle lengths were longer (P < 0.05) in PG-S heifers compared to their natural cycles (21.8 and 20.7 days, respectively). Breed, type of cycle (PG-S or natural) or interaction of breed by type of cycle did not influence (P > 0.10) progesterone patterns during estrous cycles. However, there was an interaction (P < 0.05) of day by type of cycle for progesterone concentrations on Days 3-10, indicating that corpus luteum function was delayed during PG-S cycles in heifers of the Peruvian Highland.
ASJC Scopus subject areas
- Animal Science and Zoology