Relationship between beef cow fertility and maternal immunity

Objective There is evidence that maternal immunity changes from type 1 (cell-mediated response) to predominantly type 2 (antibody-mediated immune response) during pregnancy. Lack of this shift in maternal immune response may contribute to unsuccessful pregnancy in animals. Changes in estradiol and progesterone during the estrous cycle affect immune function and potentially change the type 1–type 2 balance. The objective of this study was to examine the relationship between relative balance of type 1 and type 2 immunity at the time of insemination and fertility in beef cows, using a nanoparticle probe-enabled blood test. Materials and Methods Angus-Hereford cows (n = 394) were synchronized with a 5-d CO-Synch controlled internal drug release (CIDR) fixed-time AI protocol. Estrus behavior was monitored using estrus detection aids and visual observation from CIDR removal until the day of AI. At the time of AI, a blood sample was collected from all animals to determine relative ratio between type 1 and type 2 and serum progesterone concentrations. A rapid blood test (D2Dx; Tsai et al., 2021 ) was used to assess the type 1–type 2 immunity balance. Pregnancy was determined by ultrasound 48 to 63 d after AI. Results and Discussion Overall pregnancy per AI (P/AI) was 51%. Mean relative type 1–type 2 immunity balance as determined by the D2Dx immunity test was different (P Implications and Applications The results indicate that the measurement of the relative type 1–type 2 immunity balance at the time of AI may be used as a potential marker for pregnancy prediction in beef cows.