Hibernate + Postgres: simple query with bad performance - performance

Question

In my JavaEE webapplication, I am querying a postgres database to get the data of an employees holidays.
The table holiday has the following columns:
id bigint NOT NULL
start timestamp without time zone NOT NULL
end timestamp without time zone NOT NULL
employee_id bigint (FK referencing PK of table employee, indexed)
some other columns that do not seem to be related to my issue. Not much data in here.
Goal: Find any holiday entry of a specific employee concerning a given time interval (not necessarily completely, i.e. a holiday from 2009-12-30 to 2010-01-05 is a valid result when searching for holidays from 2010-01-01 to 2010-01-31).
That said, my named Query is:
SELECT
h
FROM
Holiday h
WHERE
h.employee.id = :employeeIdParam
AND (
h.end BETWEEN :fromParam AND :toParam
OR
h.start BETWEEN :fromParam AND :toParam
)
Query execution using hibernate takes ~400ms, resulting in 100 selected rows out of only 2000 rows in total. Much too long, isn't it?
(Using pgAdmin, it takes ~12ms.)
What's the issue here?
(Running on local machine - it's not a connection problem)
Using Wildfly 9.0, Postgres 9.4, Hibernate 4.3.1.
Update
Database Log:
select holiday0_.id as id1_70_, holiday0_.end as end3_70_, holiday0_.employee_id as emplo10_70_, holiday0_.start as star6_70_
from holiday holiday0_ where holiday0_.employee_id=$1 and (holiday0_.end between $2 and $3 or holiday0_.start between $4 and $5)",
"Parameter: $1 = '2757', $2 = '2003-07-01 00:00:00', $3 = '2015-08-11 23:59:59', $4 = '2003-07-01 00:00:00', $5 = '2015-08-11 23:59:59'"