A transgenerational study on the effect of granddam conception month on granddaughter test day records for milk production traits in Italian Simmental cattle

The consequences of climate change are becoming a relevant issue also for the livestock industry in temperate countries. Transgenerational studies outlined the effect of the ancestors' calving season, considered as an indicator of the period during which pregnancy occurs, on their female progeny performance. The aim of this study was to evaluate the effect of great granddam (F0) calving month on their great granddaughters (F3) Test Day (TD) records for milk production. A total of 414,069 TD records of milk, fat, and protein yields from 27,224 Italian Simmental F3 cows was analysed with a mixed linear model with year of calving, parity, age at parity, F0 calving month, days in milk class, the interactions between DIM and F0 calving month and between parity and F0 calving month, F3 calving date and the random effects of herd-test date and animal. The F0 calving month significantly influenced F3 performance for the three considered traits; largest F3 TD records were obtained for F0 calvings occurring in October, smallest for February. The largest milk production of F3 cows were observed when their F1 conceptions occurred in winter. Results were confirmed by a further analysis considering the calving seasons of F0, F1 and F2. The effect of F0 calving month (associated with the conception of F1) on milk production decreased as F3 parity increased. Results of this study suggest that the period of ancestor pregnancy and conception affects milk production traits of further generations also in temperate climates.