Short communication: Characterization of early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry

The objective of this study was to describe early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry. Cows (n=50) were continuously monitored for behavioral estrus with a radiotelemetric system, HeatWatch II (CowChips LLC, Manalapan, NJ), from d 14 to approximately d 49 postpartum. Blood collection for analysis of progesterone and ovarian ultrasonography were performed once weekly starting on d 14. First ovulation was associated with behavioral estrus in 5 cows and occurred at 28.2±10.8d (mean±SD; range 17 to 40d). The average duration of estrus was 6.0±4.9h (range 3 to 12.2h), and the mean number of standing events was 18.4±8.9 (range 4 to 26). Based on progesterone concentrations of ≥1ng/mL, estimated first postpartum ovulation occurred at 25.1±10.4d (range 10 to 49d) for 38 animals without evidence of behavioral estrus. The interval to estimated first ovulation without behavioral estrus was not different from the interval to first ovulation associated with behavioral estrus. Level of milk production and body condition score loss did not affect the interval to estimated first ovulation without estrus or first ovulation associated with estrus. Six animals did not show evidence of ovulation based on progesterone concentration, whereas 1 cow showed evidence of estrous behavior on the day before removal from the study. The majority of first postpartum ovulations (38/43; 88.4%) were not associated with behavioral estrus

Evaluation of reproductive and economic outcomes of dairy heifers inseminated at induced estrus or at fixed time after a 5-day or 7-day progesterone insert-based ovulation synchronization protocol

The objectives of the current experiment were to evaluate the reproductive performance and economic outcome of 3 synchronization strategies for first artificial insemination (AI) of dairy heifers. Holstein heifers from 2 herds (site A, California, n=415; site B, Idaho, n=425) were assigned to 1 of 3 treatments. Heifers assigned to the AI on estrus (AIE) treatment received an injection of 25mg of PGF2α at enrollment (d 0) and every 11 d thereafter until AI occurred. Heifers assigned to the CIDR5 treatment received a controlled internal drug release insert (CIDR) containing 1.38g of progesterone, which was removed 5 d later concomitantly with an injection of 25mg of PGF2α, and received fixed-time AI (TAI) concomitantly with an injection of 100μg of GnRH 53 to 60 h later. Heifers assigned to the CIDR7 treatment received a CIDR insert, which was removed 7 d later concomitantly with an injection of 25mg of PGF2α, and received TAI concomitantly with an injection of 100μg of GnRH 53 to 60 h later. Heifers were observed for estrus and inseminated up to 98 and 73 d after enrollment in sites A and B, respectively. Thereafter, heifers were moved to pens with bulls and considered failure to conceive to AI if still not pregnant at the end of the observation period. Economic outcomes were based on cost of synchronization protocol (CIDR treatment=$11, PGF2α or GnRH treatments=$2.5/treatment, estrous detection=$0.80/heifer per day), rearing cost ($2.75/heifer per day), and economic loss if a heifer did not conceive to first AI ($150). Input cost of the reproductive programs=synchronization protocol cost + semen cost + rearing cost + replacement cost. Pregnancy per AI (P/AI) 38±3 d after first AI was greatest for AIE heifers (61.1$67.1±4.4 and −$107.1±7.0, respectively) were reduced compared with CIDR5 ($86.9±5.1 and −$143.4±8.1, respectively) and CIDR7 ($98.3±5.1 and −$156.5±8.2, respectively) heifers, but no differences were observed between CIDR5 and CIDR7 heifers

Short communication: Characterization of early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry

The objective of this study was to describe early postpartum estrous behavior and ovulation in lactating dairy cows using radiotelemetry. Cows (n=50) were continuously monitored for behavioral estrus with a radiotelemetric system, HeatWatch II (CowChips LLC, Manalapan, NJ), from d 14 to approximately d 49 postpartum. Blood collection for analysis of progesterone and ovarian ultrasonography were performed once weekly starting on d 14. First ovulation was associated with behavioral estrus in 5 cows and occurred at 28.2±10.8d (mean±SD; range 17 to 40d). The average duration of estrus was 6.0±4.9h (range 3 to 12.2h), and the mean number of standing events was 18.4±8.9 (range 4 to 26). Based on progesterone concentrations of ≥1ng/mL, estimated first postpartum ovulation occurred at 25.1±10.4d (range 10 to 49d) for 38 animals without evidence of behavioral estrus. The interval to estimated first ovulation without behavioral estrus was not different from the interval to first ovulation associated with behavioral estrus. Level of milk production and body condition score loss did not affect the interval to estimated first ovulation without estrus or first ovulation associated with estrus. Six animals did not show evidence of ovulation based on progesterone concentration, whereas 1 cow showed evidence of estrous behavior on the day before removal from the study. The majority of first postpartum ovulations (38/43; 88.4%) were not associated with behavioral estrus