The bovine recombinant somatotropin (bST) and the follicular dynamic in dairy cows

Abstract

The aim of the present research was to determine the influence of the recombinant bovine somatotropin (bST) on the reproduction of Black and White Holstein bovine females being evaluated along a complete estrous cycle. The follicular dynamics has been observed in regard to the diameter of the ovaries, number of follicular waves during the estrous cycle, duration of each follicular wave, number and diameter of the recruited follicles. Twelve females were used for the experiment, being six of the control group and six of the treated group, chosen at random. The treatment was carried out by administration of a dose of bovine recombinant somatotropin in the sixtieth day post partum (pp). The ovaries follicular dynamics was followed by daily ultrasound exams starting from the day of the first estrus base (visible estrus, considered the 0 day) post partum, until the animals manifested new estrous. In the 60th day the animals of the treated group received an injection of bST (500 mg, SC) and the animals of the group control, 1,4 ml of physiologic solution (SC), as placebo. For the ovarian monitoring of the animals, ultrasound apparel was used with transducer of 5 MHz. It has been observed that the bovine recombinant somatotropin administered in the 2nd month pp, did not display significant influence on the ovarian activity of the animals, the rate of daily milk production being increased only in 3,5%. The studies on the follicular dynamics and the bovine recombinant somatotropin didnt alter the length of the estrous cycle, the diameter of the ovaries, the number of waves follicular, the length of each wave, the number and the diameter of the recruited follicles.