The aim of the study was to conduct an ultrasound analysis of quantitative parameters of the corpus luteum (CL) in recipient heifers on days 6-8 after oestrus, and to compare reproduction potential of both types of CL in those females. Analyses were performed on 300 heifers, synchronized with two injections of cloprostenol. Clinical and ultrasound examinations of ovaries were performed and measurements of the CL were recorded. The blood samples were taken to determine progesterone level. Pregnancy examination was conducted after 6-8 weeks from the ET. Cavitary CL was found in 32.7% heifers In 48.0% of the cavitary CL, its luteal tissue area was reduced by 14.3% compared to the compact CL, while 16.3% of the CL had luteal tissue reduced by more than 33.8%. Progesterone level in blood serum was higher in heifers with the cavitary CL (p < 0.001). Pregnancy rate was higher for females with a cavitary CL (52%) than those with compact ones (33%, p < 0.05). The ultrasound assessment of luteal tissue should be included in the evaluation of the functional status of the CL in ET-recipient heifers. The cavitary CL presence may indicate a higher potential of the recipient in maintaining the pregnancy.
Keywords: cavitary corpus luteum; compact corpus luteum; corpus luteum; embryo transfer; heifers; ultrasound examination.