Three experiments were conducted to evaluate methods of immunization against GnRH on antibody titer, luteal activity, and pregnancy in beef heifers. Experiment 1 evaluated the efficacy of adjuvants with 30 heifers. Control heifers were immunized against human serum albumin (HSA) emulsified in Freund's complete adjuvant (FCA). The other 4 treatments contained GnRH conjugated to HSA (HSA-GnRH) emulsified in FCA, Freund's incomplete adjuvant (FIA), DEAE dextran (DD) + mineral oil (MO), or DD+FIA. Treatment was in the mammary gland for all experiments. Titers against GnRH for heifers immunized against HSA-GnRH with FCA, DD+MO, or DD+FIA were greater than titers for HSA-GnRH with FIA or control heifers (P < 0.01). Body weight was reduced (P < 0.05) in control and FCA heifers compared with FIA, DD+MO, and DD+FIA heifers. Heifers immunized with DD+MO and DD+FIA had fewer granulomas in mammary glands than heifers treated with FCA (P < 0.01). In Exp. 2, 36 heifers were used to determine the effect of the protein conjugated to GnRH on titers against GnRH. Heifers (6/treatment) received a primary immunization against GnRH conjugated to HSA (HSA-GnRH), ovalbumin (OA-GnRH), or keyhole limpet hemocyanin (KL-GnRH), or heifers were immunized against each carrier protein. Antigens were emulsified in DD+FIA. Immunization of heifers against OA-GnRH, KL-GnRH, or HSA-GnRH suppressed luteal activity (P < 0.01) for 23, 16, and 12 wk, respectively, and antibody titers against GnRH were greater (P < 0.01) for 19, 5, and 7 wk, respectively, compared with heifers immunized against the carrier proteins. In Exp. 3, 90 heifers were used to determine the effect of immunization against GnRH on ovarian activity and pregnancy rate. Heifers (30/treatment) received a primary and 2 or 3 booster immunizations against GnRH conjugated to OA, and controls received a primary and 2 booster immunizations against OA. All antigens were emulsified in DD+FIA. At 8 wk after primary immunization, heifers were exposed to fertile bulls for 24 wk. Pregnancy rate was less (P < 0.01) for 3-booster heifers (13%) compared with control (83%) and 2-booster (62%) heifers. We conclude that immunization against GnRH, conjugated to OA and emulsified in DD+FIA, does not influence ADG and produces sufficient titers against GnRH to prevent estrous cycles with few mammary granulomas. Immunization against GnRH with 3 booster immunizations prevented luteal activity and pregnancy in most beef heifers for more than 4 mo.

Abstract. Rapid screening of large numbers of swine sera for antibody is an essential element in the current eradication program for pseudorabies in the United States. We evaluated a recently introduced commercial semiautomated latex agglutination test (LAT) kit for pseudorabies antibody. A total of 1,191 swine sera were tested using the new procedure and 3 established tests: the manual LAT, the serum neutralization test (SNT), and an enzyme-linked immunosorbent assay (ELISA). There was close agreement among results of semiautomated LAT, the manual LAT, and ELISA but less agreement between semiautomated LAT and SNT. Overall, the sensitivities of the 4 tests were as follows: semiautomated LAT = manual LAT > ELISA > SNT. For 74 samples of known pseudorabies antibody status, the overall specificities were as follows: semi-automated LAT = manual LAT = SNT > ELISA. Because of its relative insensitivity, the SNT should no longer be considered the official "gold" standard for pseudorabies testing in the on-going eradication program. However, because no single test was perfect for all samples, a scheme including 3 tests in the following sequence is recommended: 1) screening using semiautomated LAT or ELISA and 2) confirmation testing of positives by manual LAT and SNT, with any sample that tests positive by any 2 tests being regarded as true positive. Pseudorabies is caused by the pseudorabies virusRecently, the same principle used in the manual LAT (PRV), 4 an alphaherpesvirus, and is an economically (i.e., agglutination of PRV antigen-coated latex partiimportant viral infection of swine in the United States cles in the presence of specific PRV antibody) was and many other countries. The economic impact of applied to the development of a semiautomated latex pseudorabies on the US swine industry is estimated to agglutination assay. b In the study described here, we be $21 million per year (Hallam JA et al., unpublished evaluated the ability of the semiautomated LAT to data). Swine constitute the main host and natural res-detect PRV antibody in field sera submitted for PRV ervoir of PRV. Pigs can become latently infected and diagnosis and in negative and positive control laboperiodically shed infectious virus particles into the en-ratory sera. The semiautomated LAT results were vironment; other species such as cattle, sheep, goats, compared with results from 3 other PRV antibody tests dogs, and cats that are susceptible to PRV usually ac-(manual LAT, ELISA, SNT) using the same sera. All quire a lethal infection and are therefore dead-end 4 tests are approved by the USDA for official pseuhosts. 4 dorabies testing. Strategies adopted for the control of pseudorabies rely on the knowledge that any pig that has contracted Materials and methods a primary infection can become latently infected and Serum samples. The 1,191 serum samples tested (Tables must therefore be considered a potential source of 1, 2) included 1,117 samples randomly selected from field transmission of infectious virus. Working on that sera submitted to...