Association between Cow Reproduction and Calf Preweaning Growth Traits and ELISA Sample-to-positive (S/P) Ratio Scores for Paratuberculosis in a Multi-breed Herd of Beef Cattle

Abstract

Paratuberculosis is caused by Mycobacterium avium subspecies paratuberculosis (MAP). The disease remains in a subclinical stage for a number of years before animals show clinical signs of diarrhea, weight loss, lower milk production, and eventually death. The serum ELISA test is a commonly used method to detect subclinical paratuberculosis; it is a serological test that detects antibodies to MAP in the serum of exposed animals. The ELISA is primarily used as a herd-screening tool that can detect approximately 50% of infected animals. Despite its low sensitivity, evidence suggests an association between ELISA sample-to-positive (SIP) ratio scores and various cow and calf traits. The objective of this study was to assess the association between four cow reproductive and weight traits, and three preweaning calf traits and ELISA SIP ratio scores for paratuberculosis (0 = negative, 1 = suspect, 2 = weak-positive, and 3 = positive) in a multi-breed herd of cows ranging from 100% Angus (A) to 100% Brahman (B). In addition, potential economic losses associated with ELISA scores were explored using prospective cow and calf market prices.