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Methods to Increase Reproductive Efficiency in Cattle
Department of Animal and Food Sciences
Need: Reproductive efficiency continues to be a major problem in lactating dairy cows. Improved procedures for estrous synchronization in heifers and lactating dairy cows will increase farm income by increasing milk production, through reduced days open and genetic improvement (widespread use of artificial insemination). The increase in milk production is conservatively valued at $100/cow.
Accomplishments/Outputs: The effect of reproductive status on the metabolic clearance of progesterone was clearly demonstrated in our preliminary research. This needs to be verified. Using CIDRs to deliver the progesterone allowed us to show that the concentration of progesterone maintained in lactating dairy cows is remarkably low and approaches the threshold required for effectiveness as an estrous synchronization tool. Our results suggest that estrous synchronization protocols utilizing these devices in lactating dairy cows may require the use of multiple CIDRs or a reformulation of the device by the manufacturer to increase the rate of progesterone release. Future work will be conducted to determine concentrations of progesterone maintained by multiple CIDRs in lactating dairy cows.
2010 Project Description
We have examined the temporal relationship between core body temperature, accelerometer measurements of motion, expression of estrus behavior, secretion of LH and ovulation. Fifty cows were used in an experiment to determine if a rise in body temperature is a reliable predictor of time of ovulation in lactating dairy cows.
Cycling cows were presynchronized beginning 45-70 days postpartum. Cows received an injection of prostaglandin (PG) F2α (25 mg). Two days later, cows received an injection of GnRH (100 ug). Six days after the GnRH injection, an Ovsynch protocol (Pursley et al., 1995) was initiated. Cows received an injection of GnRH, then 7 days later an injection of PGF2α. The day of PGF2α injection was designated day 0 of the experimental protocol. Another injection of PG F2α was administered 12 hr later to ensure that luteolysis is complete.
Beginning on day 0, cows were ultrasounded daily to determine the location and size of the 3 largest ovarian follicles. On day 1, a jugular vein of each cow was cannulated for the collection of blood samples. Temperature sensing boluses (SmartBolus, TenXsys Inc., Eagle, ID, USA) were inserted into the reticulum and vagina. Temperature data from the boluses was recorded at 30 min intervals beginning immediately after insertion. Accelerometer data were collected at hourly intervals. Beginning at 8:00 AM on day 2, jugular venous blood samples were collected at 2 hour intervals to determine the concentration of LH. These samples were used to precisely determine when the preovulatory surge of LH occurred in each cow. As blood samples are being collected, rectal temperature was determined using a thermometer.
Immediately after collecting blood samples and temperatures, cows were moved to a dirt lot for estrus detection. Cows were observed for 30 minutes for signs of estrous behavior (being mounted by other cows, mounting other cows, genital sniffing, head resting, bawling; etc.). All behaviors were recorded. Onset of estrus was defined as the time of the first heat check period when a cow stands to be mounted at least two times. Heat checking continued until a cow failed to stand to be mounted for 3 consecutive heat check periods. Blood samples for LH and temperatures were collected until 12 hours after the onset of estrus. Beginning 12 hours after the onset of estrus, the frequency of ovarian ultrasound was increased to every four hours. This was done so as to precisely determine the time of ovulation.
Ultrasound was continued until it is clear that at least one of the 3 largest follicles is no longer visible by ultrasound for two consecutive ultrasound checks. The experiment was conducted in 8 or 9 replicates of 6-8 cows per replicate. Data are currently being analyzed.
Improved efficiency of estrus detection will increase farm income by increasing milk production, through reduced days open, and genetic improvement (widespread use of artificial insemination). The annual increase in milk production is conservatively valued at $100/cow.
King, S.S., B.L. Douglas, J.F. Roser, W.J. Silvia and K.L. Jones. 2010. Differential luteolytic function between the physiological breeding season, autumn transition and persistent winter cyclicity in the mare. Animal Reproduction Science 117:232-240.