02 April 2025

Getting suckler cows bulling earlier

In advance of the suckler breeding season, Catherine Egan, Beef Specialist at Teagasc, and Prof. David Kenny, Head of the Teagasc Animal and Bioscience Research Department, look to Teagasc research to find solutions to get cows bulling earlier this spring.

Nationally, the calving-to-calving interval is currently 397 days for suckler cows – 32 days longer than the target required for efficient and profitable suckler systems. Contributing to this is the delay in the resumption of oestrous cycles post calving – in other words, the length of time it takes a cow to come bulling after calving. 

Studies conducted at Teagasc have recorded average intervals from calving to first ovulation or heat of 50 to 55 days in beef cows, which is almost twice as long as the interval for dairy cows. For first calving beef cows, this interval is usually 10 to 15 days longer than for mature cows.

There are a number of factors influencing this post-calving period of inactivity, including cow-calf bonding and nutrition.

Cow-calf bonding

The predominant reason for long anoestrous intervals in suckler cows is the strong maternal-offspring bond that exists between the dam and her calf. This bond is predominately affected through sight and smell.

Teagasc studies have shown the ‘cow-calf bonding effect’ is further compounded by having beef cows in a low body condition score (BCS) at calving. The effect of low BCS at calving are only partially reversed by increasing the feed allowance of the cow after calving.

Where the interval from calving to first heat extends beyond 55 days in duration, the cow has only one opportunity to become pregnant and calve again within a 12-month period. 

One way of avoiding cows having delayed resumption of normal heat cycles after calving is to implement short-term restriction of access of the calf to the cow (ideally out of sight and sound) in the form of a twice-daily suckling regimen from when the calf is one month old.

This practice has been proved to result in 85 to 90% of cows exhibiting a fertile heat within 18 to 22 days. About 10 to 15% of cows fail to ovulate in response to calf separation and these cows are typically those in poor BCS. It is unlikely that these cows will respond to synchronisation either until such time that their body condition score (BCS) is improved.

Calf separation is particularly applicable to autumn-calving cows, early spring-calving cows and first-calvers, and additionally facilitates the use of AI in such cows, though it does entail some additional labour and logistical challenges.

The role of nutrition

From published research studies, it is clear that:

1. Energy is the primary nutrient regulating reproduction in female beef cattle and inadequate dietary energy during mid-to-late pregnancy delays the resumption of subsequent heat activity, even when dietary energy is adequate during lactation;
2. A BCS of 2.5 to 3.0 (scale 0-5) at calving will ensure that body reserves are adequate for post-partum reproduction;
3. Fluctuations in feed supply should be avoided during the breeding season, as even short term deficits in feed intake can lead to drastic reductions in pregnancy rate.

The key objective is to calve cows in moderate-to-good condition but not overly fat. Target BCS for cows calving at different times of the year are outlined in Table 1. One BCS unit (0-5 scale, where 0 or 1 is emaciated and 5 is obese) is equivalent to approximately 70kg of bodyweight in a moderate-sized cow.

Table 1: Target body condition score (BCS; 0-5 scale) at key reproductive events for spring and autumn calving sucker cows

More breeding tips and advice

In order to prepare suckler farmers for the upcoming breeding season, the Teagasc Future Beef Programme hosted a series of webinars focusing on: pre-breeding essentials; breeding the ideal suckler cow; and the latest technologies and how to use them properly.

As part of the webinar series, experts shared tips on: heat detection and the use of teaser bulls; bull management; bull selection criteria to improve genetics; understanding the role of myostatin; and synchronisation, sexed semen usage and embryo transfer in beef cattle.

Find out more and re-watch the webinar series on the Future Beef webpage here.