Luteolytic effectiveness of Preloban® or Croniben® products in holstein heifers

The objective was to evaluate the effect of intramuscular injection of two different commercial products of cloprostenol (Preloban® or Croniprest®) on luteal regression of Holstein heifers. On a random day of the estrous cycle, 36 heifers were synchronized with an estradiol-progestin-PG-estradiol treatment. Twelve days after withdrawal of progestin, heifers were randomly divided into 3 groups of 12 animals. Groups 1 and 2 received the equivalent of 150 µg of d-cloprostenol of Croniben® or Preloban® products, while group 3 received 2 ml of saline. Estrus was detected with the aid of the dispositive Estrotec® on the following five days, and heifers that expressed estrus were inseminated. Blood samples were collected daily during the periods of 0, 24, 48 and 72 hours after the injection of d-cloprostenol for measurement of plasma progesterone by radioimmunoassay. Pregnancy diagnosis was performed by ultrasonography 40 days after insemination. The interval between the manifestation of estrus and the Croniben® or Preloban® injection was 68.4 ± 4.4 and 63.3 ± 4.6 hours, respectively (P&gt;0.05). The distribution of estrus occurred in the period of 36 to 108 hours. With the exception of two heifers with incomplete luteolysis, all animals treated with d-cloprostenol showed complete luteolysis. The conception rate was 50.0% and 54.5% for Preloban® and Croniben® treatments, respectively (P &gt; 0.05). We conclude that Preloban® and Croniben® products have similar effectiveness to induce luteolysis and and to synchronize the estrus of Holstein heifers. Thus, producer may choose any one of them without risk of compromising reproductive performance.</span