EVALUATION OF LUTEOLYSIS AND ESTROUS SYNCHRONIZATION USING A PROSTAGLANDIN ANALOG (PROSOLVIN) IN BORAN X FRIESIAN CROSSBRED HEIFERS IN ETHIOPIA

Luteolysis, oestrus synchrony and subsequent fertility were evaluated in 32 Boran x Friesian heifers after treatment with a prostaglandin an alog, Prosolvin. Heifers were assigned to receive 1 ml Prosolvian (ful l), two injections of 0.5 ml each at 24 hour interval (split) or to se rve as untreated controls. Treated heifers were mated on induced oestr us and control heifers were mated over a 21-day breeding period Blood samples were collected from all heifers at the time of treatment, at 1 2 hour intervals for 72 hours after treatment and every three days for five weeks after onset of oestrus. Plasma samples were used for deter mination of progesterone levels. Oestrus response did not differ betwe en heifers that received either full or split dose (90 vs 73%), while all heifers in the control group (100%) showed oestrus during the 21-d ay period. Mean (+/- SEM) oestrus response intervals did not differ be tween heifers that received full (86 +/- 27 h). and split (76 +/- 29 h ) dose, but were shorter (P<0.001) than in the control group (262 +/- 25 h). Both full and split doses resulted in luteolysis as indicated b y a significant decline (P<0.001) in progesterone concentrations to 10 % of the pretreatment levels at 48 hours after treatment. Progesterone levels after induced oestrus in heifers which received full and split doses revealed the subsequent formation of functional corpora lutea. Pregnancy rates were 60, 73, and 91% for heifers that received full an d split dose, and for the control group, respectively. It was conclude d that although luteolysis and oestrus synchrony were similar in heife rs treated with either full or split dose, the earlier resulted in a h igher oestrus response and minimized handling of animals.