Growth and estrous behavior of heifers actively immunized against prostaglandin F2 alpha

To determine the effects of active immunization against prostaglandin F2 alpha (PGF) on estrous activity and performance traits of beef heifers, 50 14-mo-old cyclic heifers (358 +/- 3.3 kg) were assigned to two treatments (n = 25 per treatment): 1) heifers (controls) given 3.3 mg of human serum albumin (HSA) on d 0 (primary) and 27 (booster), and 2) heifers (PGF-immunized) given 3.3 mg of PGF-HSA on d 0 and 27. The adjuvant was DEAE-dextran, and the duration of the experiment was 167 d. Plasma progesterone concentrations (every 3 to 4 d) were used to monitor corpus luteum (CL) presence; PGF antibody titers were determined every 2 wk. Heifers were checked twice daily for estrous behavior and were weighed every 2 wk. Data were analyzed using ANOVA. Antibody titers for PGF-immunized heifers increased to a peak (43 +/- 2.9% binding at a plasma dilution of 1:1,250) on d 55 +/- 4.6. Antibody titers were greater (P = .02) in PGF-immunized than in control heifers by d 15 and remained elevated (P < or = .001) throughout the experiment. Twenty-four of 25 PGF-immunized heifers formed persistent CL with a mean duration of 129 +/- 6.4 d. The mean number of estrous period per heifer were less for PGF-immunized (1.5 +/- .27) than for control heifers (7.0 +/- .32). Mean daily live weight gain of the PGF-immunized heifers was decreased (P < .05; .75 +/- .024 kg) compared with that of controls (.83 +/- .014 kg), largely due to a 31.5% decrease during the 28-d period after booster.(ABSTRACT TRUNCATED AT 250 WORDS)