Interferon-tau and formation of pregnancy in cows

Abstract

Coordinated action of steroid and peptide hormones and interferons ensure the formation of pregnancy and embryo-fetal development in cows. A special class of such interferons is interferon-tau (INFT) which is synthesized by embryo trophoblast cells. This interferon is responsible for preserving the progesterone synthesis by the ovary yellow body and embryo implantation. This paper is the first in which we report a significance of INFT under impaired embryonic development and data on evaluation of biological and clinical efficacy of bovine recombinant INFT administered to cows after artificial insemination. The aim of this work was to study the dynamics of the blood content of INFT and progesterone (P4) during early pregnancy of Black-and-White cows (Bos taurus taurus) and to identify the possibility of using a bovine recombinant INFT preparation to prevent embryonic losses and to increase the effectiveness of insemination. Recombinant INFT was obtained at the Belarusian State University (V.A. Prokulevich, M.I. Potapovich). Blood content of INFT and P4 was determined by ELISA test using Bovine Interferon-Tau Elisa Kit (USA) and Immuno-Fa-PG (Russia) 7, 14, 21 and 35 days after artificial insemination. Animals with physiological formation of embryos (n = 15) and with embryonic death (n = 3) were tested. The sensitivity of the analyses was 2.9 pg/ml for INFT and 0.4 nmol/l for P4. The phagocytic activity of leukocytes, the content of serum immunoglobulins, and the bactericidal activity of blood serum were also determined. The presence/absence of the embryo in the uterus was judged by the concentration of blood progesterone on day 21 and day 35 and by double ultrasound examination on day 35 and day 50. The evaluation of the efficacy of prescribing different doses and schemes of recombinant interferon to increase the effectiveness of insemination and to prevent delayed embryo-fetal development syndrome was carried out on 87 cows. INFT was administered parenterally once, three times, or five times in doses of 5 and 10 ml from day 12 to day 16 after insemination. Intact animals and those subjected to Progestamage administration were used as control groups. It was found that the blood concentration of INFT increased by 23.2 % from day 7 to day 14, and decreased by 30.8 % on day 35, P4 content increased 32 times from day 7 to day 14 of embryo formation. The concentration of INFT was 7.7 % lower on day 14 and 25.2 % lower on day 35 when the embryo died. The blood P4 level of these animals was 26.5 % lower by day 21 and 9.3 times lower by day 35. This suggests that hypointerfero-nemia and associated hypoprogesteronemia are among the reasons for the delay in the development and death of embryos in the early pregnancy. It was revealed that the optimal scheme of the recombinant INFT use to improve the pregnancy formation in cows is its three-fold parenteral administration in the dose of 5 ml on days 12, 14 and 16 after insemination. As compared to the intact animals, the effectiveness of insemination increased from 38.9 to 75.0 %, or by 36.1 %, and the delayed embryo-fetal development syndrome decreased from 28.6 to 16.7 %, or by 11.9 %. Metric indexes of developing embryos exceeded those of the intact animals by 32.2 % on days 28-30 of pregnancy, and by 55.3 % on days 60-65 of pregnancy, and birth weight of the calves was 14.2 % greater. This occurred along with a 33.9 % increase in INFT blood concentration, and 2.3 times increase in P4. Direct replenishment of progesterone deficiency in animals by Progestamage administration provided 38.1 % increase in preservation of pregnancy. It is also shown that INFT preparation has an immunomodulatory effect on the cows. The phagocytic activity of lymphocytes increased by 8.7 %, phagocytic number by 35.1 %, phagocytic index by 25.1 %, bactericidal activity of blood serum increased by 5.9 %, and immunoglobulin content by 14.3 % after the INFT triple administration. The conclusion is made about expediency of using the recombinant INFT to increase the fertility of cattle pedigree stock.