Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Master of Science (MS)

Department

Animal Science

First Advisor

Julie Walker

Second Advisor

George Perry

Keywords

gestation, lateral flow, postpartum, pregnancy test, pregnancy-associated glycoproteins, ruminant pregnancy test

Abstract

Transrectal ultrasonography is known as the gold standard for pregnancy detection but requires costly equipment and technical skill. Access to a cheaper and more user-friendly method with similar accuracy to transrectal ultrasonography would be beneficial to individual cattle producers and to the cattle industry as a whole. Pregnancy diagnosis by detection of pregnancy-associated glycoproteins (PAGs) has the ability to accurately determine pregnancy in ruminants, however, usually requires specialized equipment for the assay. Pregnancy-associated glycoprotein pregnancy tests are gaining in popularity due to their ease of use and the unique feature of not requiring specialized training. Recently, a new lateral flow test (Alertys OnFarm Pregnancy Test) that does not require special equipment has been developed. A downside to blood pregnancy tests is they only provide an answer as to whether an animal is pregnant or nonpregnant. In addition, PAGs have a long half-life (80 to 100 d) in the maternal blood supply and can cause a false positive result. Thus the objectives of these studies were to determine whether a commercially available blood pregnancy test could be modified to detect differences in PAG concentrations to determine fetal age in cattle (study 1, chapter 2) and to determine factors that impact clearance of PAGs in postpartum beef females (study 2, chapter 2) and also, to compare the accuracy of the IDEXX lateral flow, IDEXX Alertys Rapid Visual, and IDEXX Alertys Ruminant Pregnancy Test to transrectal ultrasonography (study 1, chapter 3) and to determine how many days postpartum (dpp) is necessary for the clearance of PAGs from the previous pregnancy to avoid false positives when utilizing the lateral flow test (study 2, chapter 3). In chapter 2, previously identified pregnant Bos taurus females from six different herds and postpartum females from one herd were utilized: (n = 1,753; study 1) between d 28 and 285 of gestation and (primiparous n = 418 and multiparous n = 657; study 2) once a week for up to 12 weeks after calving. In study 1, procedures were adapted to allow PAG concentrations to fall within the detectible range of the assay. Data were analyzed using the MIXED procedure of SAS with parity and gestational age (also divided into four gestational groups: 1) < 30 d; 2) 30-90 d; 3) 91-180 d; 4) > 180 d) in the model and then analyzed further using the REG procedure in SAS within gestational age group. In study 2, data were analyzed as repeated measure using the MIXED procedure of SAS with parity, days postpartum (dpp), and parity by dpp in the model, then data was analyzed further using the REG procedure in SAS. In study 1, there was a significant effect of gestational age and a parity by gestational age interaction (P < 0.01) as well as a tendency of parity (P = 0.08). Among nulliparous and multiparous females, serum PAG concentrations did not differ between gestational age groups 1 and 2 (P > 0.84); however, PAG concentrations differed between groups 2 and 3 (P < 0.0001) and 3 and 4 (P < 0.0001). There was a positive correlation between gestational age and PAG concentrations (P < 0.01; r2 = 0. 2604). In study 2, there was a significant effect of dpp (P < 0.01) on PAG concentrations; however, PAG concentrations were not influenced by parity (P = 0.73) or parity by dpp (P = 0.55). Concentrations of PAGs rapidly decreased from d 0 to 50 postpartum and then continued to gradually decrease (P < 0.01; r2 = 0.8083). Prior to 42 dpp, PAG concentrations were sufficiently elevated which resulted in false positive readings. In chapter 3, blood samples were collected from six different Bos taurus herds between day 27 and 285 of gestation (nulliparous n = 1,205 and multiparous n = 1,539; study 1). Additional blood samples to determine PAG clearance interval were collected weekly postpartum for up to 12 weeks (primiparous n = 418 and multiparous n = 657; study 2). Serum was tested using the lateral flow test and were read by two technicians who were blind to animal pregnancy status. Level of agreement between the different methods of pregnancy detection was determined by Pearson’s correlation and Kappa scores. The MIXED procedure of SAS was used to evaluate the effect of dpp and parity (primiparous or multiparous) on clearances. In study 1, there was a positive correlation between transrectal ultrasonography and the lateral flow test (r = 0.77; P < 0.01), and agreement between the two tests was good (Kappa = 0.84). Of the animals that were diagnosed nonpregnant by transrectal ultrasonography, 5.61% were called pregnant by the lateral flow test. Of the animals diagnosed pregnant by transrectal ultrasonography, 2.00% were called not pregnant by the lateral flow test. Thus, a 92.38% agreement occurred between the two methods. In study 2, for postpartum samples, there was no effect (P = 0.21) of parity, but there was an effect of dpp (P < 0.01) and a tendency for a dpp by parity interaction (P = 0.06). All animals were still considered pregnant from the previous pregnancy through 35 dpp (100 ± 2.58%). The percentage of females receiving a false positive test result further decreased with time postpartum, by 77 dpp there were 13.72 ± 3.16% of the females positive for pregnancy and at 84 dpp there were 4.11 ± 4.39% positive for pregnancy detection. In conclusion, there is very good agreement between transrectal ultrasonography and the lateral flow PAG test, but if the test is used at less than 40 dpp the likelihood of false positive result is extremely likely. Thus, the test should be utilized at least 42 dpp to prevent gaining false positive results.

Number of Pages

105

Publisher

South Dakota State University

Available for download on Friday, December 15, 2023

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