Associations of Peripartum Health with Fertility in Dairy Cows Managed with Activity Monitors for Estrus Detection
The objective of this thesis was to characterize associations of postpartum health with different aspects of reproductive function in dairy cows primarily managed with estrus detection (ED) for first artificial insemination (AI). We comprehensively assessed markers of clinical and subclinical health variables at multiple time points from 3 weeks before to 9 weeks after parturition and examined their associations with outcomes of reproductive function and performance. Cows with inflammatory disorders marked by elevated haptoglobin (Hp), reproductive tract disease, or metabolic disorders, had reduced odds of ED by 75 d postpartum. Cows with elevated Hp or with multiple clinical diseases also had longer times to first AI and to pregnancy than unaffected cows. After AI, concentrations of progesterone (P4) at d 8 or 12 were lesser in cows that had hypocalcemia, delayed cyclicity, endometritis (ENDO), or any clinical disease. In non-pregnant cows, hyperketonemia or ENDO was associated with lesser expression of interferon-stimulated genes (ISG) in peripheral blood leukocytes at d 19, while in pregnant cows, lameness was associated with greater ISG expression. From d 29 to 40 of pregnancy, markers of metabolic imbalance (elevated non-esterified fatty acids (NEFA) and body condition score (BCS) loss) were associated with lower levels of serum pregnancy-associated glycoproteins (PAG). Uterine diseases were risk factors for decreased pregnancy risk at d 19 (estimated based on ISG expression), and cows affected by metritis or by any clinical disease had increased risk of presumed pregnancy loss from d 19 to 29 and from d 33 to 40 than unaffected cows. Lastly, based on serum P4 profiles measured from 35 to 70 DIM, cows with markers of systemic and uterine inflammation (elevated Hp and ENDO) were more likely to have a prolonged luteal phase (LP) (≥ 21 d) and had lesser P4 concentrations during the LP before first AI than healthy cows. This thesis demonstrates that postpartum health disorders are associated with different aspects of reproductive function and performance in herds primarily managed with ED for first AI.