Effects of Method of Presynchronization and Source of Selenium on Uterine Health and Reproduction in Dairy Cows

Diagram of presynchronization treatments. Cows in the Presynch treatment received 2 injections of 25mg of PGF_2a on study d 37 and 51. Cows in the CIDR-PS received a controlled internal drug releasing insert (CIDR) containing 1.38g of progesterone for 7 d and aninjection of PGF2a on the day of insert removal. All cows received AI at a fixed time on study d 72 after completion of the Ovsynch protocol starting at 12 or 3 d after the presynchronization with the Presynch and CIDR-PS protocols, respectively. Ovsynch=injection of 100μg of GnRH, followed 7 d later by an injection of 25mg of PGF_2a, and a second injection of 100μg of GnRH 48h later; PGF=25mg of PGF_2a; TAI=timed AI 12h after the second GnRH injection of the Ovsynch protocol; US=ultrasound examination of the ovaries.

Temperature-humidity index (THI; NOAA, 1976) during the different months of the study. Mean THI post=mean daily THI in the postpartum pens; Mean THI pre=mean daily THI in the prepartum pens; Max THI post=maximum daily THI in the postpartum pens;Max THI pre=maximum daily THI in the prepartum pens. Mean and maximum daily THI differed (P<0.01) among weeks of the study for the pre- and postpartum periods, but not among pens (P>0.05). Cows were exposed to heat stress during the months of July and August based on mean daily THI ≥72 (dashed line indicates THI=72).

Relationship between ovulatory follicle diameter and estradiol concentrations at the final GnRH of the Ovsynch protocol in cows presynchronized with 2 injections of PGF_2a 14 d apart, with the second injection given 12 d before the Ovsynch (Presynch), or with a controlled internal drug releasing insert (CIDR) for 7 d and PGF_2a at CIDR removal, with the Ovsynch starting 3 d after CIDR removal (CIDR-PS). Estradiol, pg/mL=0.7029 + 0.2591×follicle diameter, r²=40.2% (P<0.001).