PSXII-22 - Relationship between beef cow fertility and Maternal Immunity

Immunity plays important role in reproduction. There is evidence that maternal immunity changes from a type 1 to a type 2-biased during pregnancy and lack of such a shift may contribute to unsuccessful pregnancy in animals. The objective of the study was to examine the relationship between relative balance between type 1 and type 2 and fertility in suckled beef cows by characterizing relative quantity ratio of IgG 1 and 2 subclasses (IgG₁/IgG₂). Angus-Hereford cows (n = 394) were synchronized (d0) with a 5-d CIDR protocol. Estrous behavior was monitored using estrus detection aids and visual observation from d5 until AI (d8). On d8 all cows were inseminated at a fixed time and blood samples were collected form to be examined for type1/type/2 ratio and progesterone (P4). A new rapid blood test (D2Dx) was used to assess the type 1/type 2 immunity balance by measuring the relative quantity ratio of IgG1 and IgG2. Pregnancy was determined by ultrasound 48 to 63 days after AI. Overall pregnancy per AI was 51%. Mean relative quantity of IgG1/IgG2 was different (P < 0.05) between non-pregnant and pregnant cows. There was negative relationship between relative IgG/IgG2 ratio and probability of pregnancy to AI (P < 0.05). As IgG1/IgG2 ratio increased, probability of P/AI decreased. Mean relative IgG1/IgG2 ratio was lesser (P < 0.05) in cows detected in estrus vs non-estural cows. There was no correlation between serum P4 concentrations and IgG1/IgG2 ratio. The results indicate that blood IgG₁/IgG₂ at the time AI has a potential to be used as a marker for pregnancy prediction in beef cows.