Designing a management decision tool to identify cows at risk of failing to maintain a pregnancy seven days after artificial insemination

Abstract

Limited data has been published concerning embryonic losses in the pastoral based dairy industry in New Zealand compared to Northern hemisphere data published. This study was conducted as a part of a bigger trial investigating conception losses in New Zealand dairy cattle. In this study, the possibility of using as single progesterone (P4) concentration measured seven days after artificial insemination (AI) as an indicative tool to identify cows at risk of failing a pregnancy is investigated. Non-synchronised dairy cows of an average dairy farm in New Zealand were allocated into four groups; uterine flushing for embryo recovery at D7 with blood samples taken at D0 and D7 (Group 1; n=131), uterine flushing for embryo recovery at D15 and blood samples taken at D0, D7 and D15 (Group 2; n=111), pregnancy diagnostics by using ultrasound scanning at D28 and D35 with a blood sample taken at D0 and D7 (Group 3; n=92) and a routinely managed control group where no experimental interventions were performed (n=109). No data available of this group and therefore not discussed in this study. The hypothesis tested in this study defined that there was no significant difference between mean D7 P4 values (ng/ml) of cows recorded as pregnant and cows recorded as not pregnant. By conducting a two-sample t-test mean D7 P4 values were compared. If significant difference between mean D7 P4 values of pregnant and non-pregnant cows would be calculated, a single P4 measurement at D7 after AI could be used as a predictive value for maintaining pregnancy further on. Two sample t-test values of 0.28, 1.89 and 0.13 with a corresponding critical value of 1.97, 1.97 and 1.99 (P =0.05) were calculated for Group 1, 2 and 3 respectively. Comparing mean D7 P4 values of pregnant and non-pregnant cows of all three groups combined resulted in a t-test value of 1.40 with a corresponding critical value of 1.96. No significant difference between mean D7 P4 values of pregnant and non-pregnant cows was calculated in all three groups and a total combined group, and therefore a single P4 measurement seven days after AI could not be used as a predictive value for pregnancy.