Preparation of Monoclonal Antibodies Against Bovine Progesterone

Female, 8-week-old BALB/c mice were immunized with the progesterone complete antigen (P4-BSA). Two monoclonal antibodies (MAbs) against P4, named 8G6 and 11A11, were obtained by the lymphocyte hybridoma technique. The titers of the cell culture supernatant and ascitic fluid of MAb 8G6 were 1: 16,000 and 1:512,000, respectively, and the titers of the cell culture supernatant and ascitic fluid of MAb 11A11 were 1: 8000 and 1:256,000, respectively. The subtypes of the MAbs 8G6 and 11A11 were IgMκ. In specific analysis, both of the two MAbs did not react with estradiol. These data demonstrated that the MAbs 8G6 and 11A11 have a potential use for developing diagnostic reagents of progesterone.

Development and application of an ELISA kit for the detection of milk progesterone in dairy cows

Progesterone (P4) is a steroid gonadal hormone that is mainly produced from the corpus luteum and placenta and has various biological functions, especially reproductive regulation. It is important to establish a specific and sensitive P4 enzyme-linked immunosorbent assay (ELISA) for the study of ovary activity and reproductive disorders. Therefore, we prepared a monoclonal antibody (MAb) in a completed antigen (11α-OH-P4-HS-OVA). Based on the MAb and our previously prepared completed antigen, a highly specific and sensitive ELISA was developed. In the present study, a competitive ELISA for the determination of P4 was described in dairy cow milk. It was found that P4 concentration in milk samples from five pregnant cows was significantly higher than that from five estrus cows. The diagnosis rate for pregnancy and non-pregnancy in 54 dairy cows were 93.3% and 95.8%, respectively, at 19 to 23 days after pregnancy by detecting milk P4 concentration. In summary, the developed ELISA is a potential tool for P4 research and offers an alternative, simple, rapid technique for detecting P4, especially in future large clinical investigations on pregnancy identification and reproductive disorders in dairy farms in China.

Gonadotropin-releasing hormone administration to dairy cows without a corpus luteum 4 weeks after calving increases reproductive performance

This field study investigated whether the administration of a single dose of gonadotropin-releasing hormone (GnRH) to dairy cows without a corpus luteum (CL) 4 weeks after calving can improve reproductive performance. Holstein dairy cows underwent ultrasonography to assess the presence of ovarian structures at 29.2 ± 5.2 days post-partum, and cows were divided into two main groups based on the presence (CL group, n = 230) or absence (non-CL group, n = 460) of a CL. The non-CL group was further randomly divided into two subgroups based on the administration of GnRH (non-CL GnRH group, n = 230) or no GnRH (non-CL control group, n = 230). Subsets of cows from non-CL control (n = 166) and non-CL GnRH (n = 175) groups received a second ultrasonography at 44.5 ± 5.4 days post-partum to assess CL formation. The percentage of cows with CL at the second ultrasonography was greater in the non-CL GnRH group (70.9%) than in the non-CL control group (53.0%, p = 0.0006). The hazard of the first post-partum insemination by 150 days in milk (DIM) was higher in the CL group than in the non-CL control group (hazard ratio [HR]: 1.36, p = 0.001). The probability of a pregnancy to the first insemination was higher in non-CL GnRH (odds ratio [OR]: 1.50, p = 0.04) and CL groups (OR: 1.55, p = 0.03) compared to the non-CL control group. Furthermore, the hazard of pregnancy by 210 DIM was higher in non-CL GnRH (HR: 1.30, p = 0.01) and CL (HR: 1.51, p = 0.0001) groups than in the non-CL control group. In conclusion, administration of GnRH to dairy cows without a CL 4 weeks after calving was associated with an increase in ovulation and improved reproductive performance.