Fig. 4

Venn diagram of the count of candidate genes identified based on a heat stress (HS) time-periods and b environmental gradient class. The four potential HS time-periods throughout the day were defined as (1) from 23h00 to 06h30, representing when vaginal temperature (T_V) starts to decrease with decreased ambient temperature (T_a) and with relatively more comfortable environmental conditions; (2) from 06h30 to 09h30, representing T_V maintained at a relatively low level when environment is not too hot for the sows; (3) from 09h30 to 18h30, representing the time in which T_V starts to increase with increasing T_a; (4) from 18h30 to 23h00, representing T_V maintained at a relatively high level when T_a is usually above thermoneutral conditions. Each two standardized Dew point units was considered as an environmental gradient class (no to mild HS: − 3.5 to 1.5; moderate HS: − 1.5 to 0.5; severe HS: 0.5–2.5)