23 February 2025

Data on calving times

Noeleen Brereton, Mark Mcgee, Peter Doyle and Bernadette Earley of the Animal & Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co. Meath report on the calving times of suckler cows over a 16-year period.

At Teagasc Grange, the calving times of 1,535 spring-calving suckler cows were recorded over 16 individual herd-years. The suckler cows were accommodated indoors each year and generally offered moderate DMD grass silage ad libitum (straw included occasionally) with a mineral and vitamin supplement daily pre partum. Feeding generally took place in the morning. One to seven days before calving the cows were moved into individual straw-bedded pens to calve.

Calving times were recorded hourly over the ‘24-hour’ day. Mean hourly percentage (%) of calvings ranged from 2.7 to 5.3, with large variation evident within hours. When categorised according to springtime ‘daylight’ (8.00am-4.00pm) and ‘darkness’ (4.00pm-8.00am) hours, the mean hourly percentage of calvings was 4.1 and 4.4, respectively, corresponding to a distribution of 65% and 35% for those time periods. When the daily calving pattern was divided equally into three eight-hour periods: ‘night’ (11.00pm-7.00am); ‘morning-day’ (7.00am-3.00pm); and, ‘evening-day’ (3.00pm-11.00pm), the mean distribution of calving times was 33%, 35% and 32%, respectively, albeit with large variation within each period (21-46%, 27- 46% and 22-46%, respectively) across the herd-years.

Cow breed type, calf sex, calf birth weight and calving difficulty did not appreciably influence the distribution of calving.

Assisted and unassisted calvings were also evenly distributed throughout the day. It was concluded that, on average, the time of calving for spring-calving suckler cows was relatively evenly distributed throughout the 24-hour day, albeit large variation is evident across individual herd- years. Farmers managing suckler cows should be prepared for calving at any time and maintain regular checks, especially as the calving season draws near.