2.6 Data analysis
The percentage (with 95% CI) of the results was calculated. Based on age, cows were divided into three age groups: 1–5 years, 6–10 years, and > 10 years. Fisher’s exact test was used to compare the age and pregnancy status of the cows with neutralising antibodies. The correlation between antibodies analysed and age was evaluated via Pearson correlation analysis using GraphPad Software InStat 3, (San Diego, CA). P values less than 0.05 were considered statistically significant.