08 February 2023

Night or day? Timing of calving within the suckler herd

With 80% of the national suckler herd expected to calve in the springtime, a successful calving season – where both mortality and morbidity is minimised and health and safety is prioritised – is critical.

Teagasc research indicates that livestock account for 65% of all on-farm injuries and that 35% of fatal accidents are from attacks by ‘cow with calves’. Calving is an exceptionally busy and labour-intensive period, and working with calving cows, especially at night, can pose an increased safety risk to farmers. As part of a larger project at Teagasc Grange investigating the development of the cow-calf maternal bond, Teagasc researchers Noeleen Brereton, Bernadette Earley, Colin Byrne, Peter Doyle and Mark McGee, looked at the factors influencing time of calving in suckler cows.

The research examined 15 different herd years from Teagasc Grange, involving 802 beef x beef cows and 509 beef x dairy cows; 45% of which were first-calvers. The cow breeds included: Charolais; Limousin; Hereford; Aberdeen Angus; Belgian Blue; Salers; Simmental; and Friesian. The calves were sired by: Aberdeen Angus; Blonde d’Aquitaine; Belgian Blue; Charolais; Hereford; Limousin; and Simmental bulls.

Like commercial suckler farms, the cows were offered moderate dry matter digestibility grass silage ad-lib prior to calving. In occasional years, straw was included in the diet during the weeks immediately prior to calving, while cows were offered minerals daily and had unrestricted access to fresh water. In addition to the time of calving, the level of assistance was also recorded.

Key findings

Calving times were expressed hourly over the 24-hour day. To define daily calving pattern, each 24-day was divided equally into three 8-hour periods defined as ‘night’ (23:00-07:00), ‘morning-day’ (07:00-15:00) and ‘evening-day’ (15:00-23:00). Substantial variation was evident across the years studied. However, the overall mean percentages of cows calving in those three periods were 32%, 36%, and 32%, respectively. The mean percentage of ‘assisted’ and ‘unassisted’ calvings over 15 herd years during the ‘night’, ‘morning-day’ and ‘evening-day’ was similar.

A further categorisation representing spring-time ‘daylight’ (08:00-16:00) and ‘darkness’ (16:00-08:00) hours was also evaluated. When daily calving pattern was divided on the basis of ‘darkness’ and ‘daylight’, the mean percentage of cows that calved during those two periods was 64% and 36%, respectively.