2. Materials and methods
A total of 493 Holstein-Friesian cows from seven
commercial dairy farms in co. Kildare, Ireland, were
enrolled in this study, representing all spring calving cows
in these herds. Mean herd size was 123 animals (range
80–177 animals) and median lactation value was 3 (range
1–11). Cows were housed in free stall–slatted sheds with
cubicles during the winter (November to February) and
were at pasture from March until the end of October.
During the winter, cows received total mixed ration consisting
of grass and maize silage with the supplementation
of concentrates in the parlor. During the grazing season, the
main component of the diet was grass supplemented with
concentrates in the parlor. Cows were milked twice daily.
The mean 305 days predicted milk yield was 6531 L/cow
(range 2878–9863 L). All data were collected during the
spring breeding season of 2014.