Effect of an energy-protein concentrate on the reproductive function of heifers of breeding age

The study aimed to establish the effect of including an energy-protein concentrate from extruded narrow-leaf lupine grain in combination with macro- and microelements in compound feed on the reproductive function of 15-month-old heifers in the Kaliningrad region. Beginning in the second month of the experiment, an asynchronous estrous cycle was observed in three heifers in the control group and one in the Experimental I group. In these animals, estrus manifested itself after sexual arousal and lasted for a long time due to low follicular activity. A longer period of mucus discharge from the genitals was noted in animals of the control group with a synchronous estrous cycle. Rectal examination revealed multiple follicles no more than 0.7 cm in diameter in the heifers, with no corpora lutea in the inhibition stage. In the control group, sexual arousal lasted longer (3.1 and 4.9 hours, respectively) compared to the experimental groups. The manifestation of estrus was shorter (2.2 and 4.6 hours, respectively). Ovulation occurred in the control group after 18.8 hours, and in the experimental groups — after 13.6 and 12.5 hours, respectively. In the experimental groups, follicles with a diameter of 1.5–2 cm were detected, in the control group, follicles of 0.5–0.7 cm. After six to seven days, the heifers of the experimental groups were detected to have corpora lutea measuring 3–4 cm, while in the control group heifers, corpora lutea in the ovaries were either absent or less than 1 cm, with small follicles. In the control group heifers, folliculogenesis ended with follicular atresia without the formation of corpora lutea. In the experimental groups, 90–100% of animals were fertilized with a shorter service period of 26.1–35.3 days and a lower insemination index (by 0.91 and 1.06