CDCB communicates about seasonal trend in fertility evaluations, April 2019

April 5, 2019



Last year, the April 2018 evaluations showed a larger-than-expected variation in CDCB fertility traits (daughter pregnancy rate {DPR}, heifer conception rate {HCR} and cow conception rate {CCR}). AI bulls in all breeds showed a reduction in their traditional Predicted Transmitting Abilities (PTA), the effect being more accentuated among young bulls. When comparing April 2018 to the previous run (December 2017), the individual bull rankings were stable with high correlations (0.98) between consecutive runs. CDCB and AGIL staff investigated this result and discovered that the exceptionally large fluctuation was associated to the way year-groups were accounted for in the evaluation model. The yearly grouping strategy was revised and the new model produced fertility PTAs in August 2018 that compared more favorably with PTAs from December 2017. After August 2018, the December results for fertility traits did not show any trend fluctuation. The revised model was expected to prevent significant variation in fertility traits. However, a larger than expected decrease in the average PTA for fertility traits reoccurred in the April 2019 results. 

CDCB explains the effect on the current evaluations here: