Association of Mycobacterium avium paratuberculosis serostatus with age at first calving, calving interval, and milk production in dairy cows

• Published in: Journal of dairy science 2024-06, Vol.107 (6), p.3916-3926
• Main Authors: Martins, Elisabete, Oliveira, Pedro, Correia-Gomes, Carla, Mendonça, Denisa, Ribeiro, João Niza
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Cattle Diseases - microbiology; Female; intercalving interval; Lactation; Milk; milk per day of productive life; milk production and reproduction; Mycobacterium avium ssp. paratuberculosis; Mycobacterium avium subsp. paratuberculosis; Paratuberculosis; Pregnancy; Reproduction
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2023-23516

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of bovine paratuberculosis, also known as Johne's disease. This infection is responsible for negative effects, ranging from reduction of milk production to reproductive compromise and increased susceptibility to other diseases such as mastitis. Contradictory information on the association between this infection and reproductive performance has been reported in dairy cows. The aim of this work was to investigate associations between individual cow MAP seropositivity and lifetime reproduction and production performance. The MAP serum ELISA (IDEXX MAP Ac) results from all the 13,071 adult cows present on 191 farms and corresponding birth- and calving-date records obtained from the National Association for Genetic Improvement of Dairy Cattle were used. Cows and farms were classified as positive or negative, based on ELISA results. Outcomes assessed were age at first calving (AFC), intercalving intervals (ICI) from first to fourth interval, and average milk production per day of productive cycle (Milk-305/ICI, a ratio between 305-d corrected milk production and the number of days of the respective calving interval). Multilevel mixed models were used to investigate the association of cow MAP status with AFC, ICI, and Milk-305/ICI. Three levels were considered in the models: “measurement occasion,” the first level, was nested within cows and cows were nested within farms. The “measurement occasion” is the time point to which all the observed measures (between 2 successive parturitions, such as milk production and somatic cell count) were referred. Our results indicate that MAP-positive cows have a significantly lower 14-d mean AFC than MAP-negative cows. The overall average ICI in our study was 432.5 d (standard deviation: 94.6). The average ICI, from first to fourth, was not significantly affected by MAP seropositivity. No significant effect of MAP positivity was found on the overall ICI. In relation to Milk-305/ICI, MAP-positive cows did not produce significantly less milk than negative cows across their productive lifetime. We observed higher but nonsignificant Milk-305/ICI (kg/d) in MAP-positive cows. In our study, the proportion of MAP-positive cows within lactations remained similar across all lactations, suggesting that seropositivity did not in