SYNCHRONIZATION AND INDUCTION OF ESTRUS IN HEIFERS WITH A PROGESTAGEN AND ESTROGEN

Abstract

Estrus has been successfully synchronized in cycling heifers and induced in pre-puberal heifers bw placing of an implant containing 6 mg of y alpha-acetox Y -II -beta-methyl 19 nor preg ene 3 , 2 o dione (norgestomet) in the ear for 9 days and injecting 3 mg of norgestomet and mg of Estradiol Valerate (EV) at time of implantation. In trial 1 50 p. 100 of 14 non-cycling control heifers had been in heat after 45 days of breeding compared to 94 p. I oo of 1 6 treated heifers after days of breeding. After 45 days of breeding p. IOO of the control and 94 p. IOO of the treated heifers were pregnant. In the second trial 3 fS p. ioo of 8 non-cycling control heifers had shown heat after 4 8 days of breeding compared to 79 p. ioo in 79 treated heifers after 4 days of breeding. Pregnancy rates after .1, zi, and 4 8 days of breeding were 4 , 1 and 27 p. I oo in con- tr o l s and 43, 5 8 and 73 p. I oo in treated.