Four trials were conducted to evaluate the effectiveness of Melegestrol
Acetate (MGA ®) and prostaglandin (PGF) in inducing and synchronizing estrus.
In trial 1, treated heifers were fed MGA for 7 days and given a PGF
injection on either the first or last day of MGA feeding. The 7-day estrus response
was higher (P<.01) for treated heifers than untreated controls.
In trial 2, treated cows were fed MGA for 7 days and given a PGF
Injection on the last day of MGA feeding or 13 days after the last day of MGA
feeding. The 7-day estrus response was also higher (P<.01) in treated cows.
In trial 3, 59 cows were fed MGA for 7 days followed by a PGF injection,
and exposed to bulls for 66 days. The MGA-PGF treatment was ineffective in
synchronizing estrus and hastening conception.
In trial 4, feeding MGA for 7 days successfully synchronized estrus in.
cycling cows, but first service conception rates were reduced by 10% in the
Kansas study and by 16% in a four state study.
