AI outcome and metabolic indicators in cows: a field study.

Introduction: The AI outcome can be affected by nutritional and metabolic conditions that may disturb either CL function and embryo implantation leading to return to oestrus. In this work, we investigated the relationship between AI outcome, blood metabolites and plasma progesterone from AI to pregnancy diagnosis. Methods: The AI outcome (N=143) performed in 89 cows belonging to 3 herds was recorded for 6 months. The diagnosis of pregnancy was performed by ultrasonography at day 28-34. The outcome of 81 AI was monitored also by PAG measurement in mother blood (RIA) after day 25 to asses embryo viability. Plasma P4, urea, NH3, cholesterol, triglycerides, NEFA, OH-butyrate, and glucose were measured every week from AI to the pregnancy diagnosis. The relationship between AI outcome and metabolic indicators was analysed by ANOVA. Results and discussion: 48.3% of cows became pregnant within 3 AI, 21.3% did not become pregnant after 3 or more AI, and only 3.4% became pregnant beyond 3 AI. 27% of animals did not become pregnant within the end of the experiment. In 14 cases, plasma PAG concentrations measured before a negative ultrasonographic diagnosis of pregnancy were compatible with the presence of a viable embryo thus suggesting a possible embrionic loss. In other 6 cases, plasma PAG were actually decreasing from day 25 onward, indicating that embryo death occurred. Plasma progesterone tended to be lower in negative AI only on day 18. Plasma triglicerydes concentration and NH3/urea molar ratio were slightly but significantly (P<0.05) lower in positive AI. It is unlikely that these differences can affect the establishment of pregnancy “per se”, but they may be the signal of more subtile mechanisms. Measurement of plasma PAG in association with the ultrasonographic diagnosis of pregnancy may be an important tool to identify embryonic death.