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Agribusiness News December 2024 – Inputs: Calving Intervals

29 November 2024

Herd Fertility

Suckler cows are the key input in every suckler cow enterprise so managing and improving the fertility of your suckler herd is one of the keyways to improve cow efficiency and herd profitability.  Achieving optimum performance from suckler herds is crucial.  The aim for suckler herds is for each cow to rear (at least) one calf each year, with a calving interval as close to 365 days as possible.  However, the mean calving interval of the Scottish suckler herd in 2021 was c. 400 days, with only 84% of cows and heifers meeting the 410-day threshold.  From 2025, a new calving interval condition of 410 days or less will be applied to the Scottish Suckler Beef Support Scheme (SSBSS).

A further measure of fertility is the number of cows that can get in calf over a short bulling period to achieve a tight calving period.  As well as an indicator of herd efficiency and fertility, a shorter calving interval also has a major influence on the herd’s carbon footprint.  With only a 5-day reduction in calving interval from 400 days to 395 days, greenhouse gas emissions can be reduced by 39.2 kg CO2e per cow.

Reducing your herd’s calving period is beneficial to both cost of production and ease of management.  At the same level of calf performance, reducing the calving period from 15 to 12 weeks can increase sale weights by 10kg and sale age by 9 days, assuming the same sale date.

Herds with extended calving periods are more likely to delay weaning for some of the smaller, later born calves, which results in lighter calves at sale or additional days to finish cattle, therefore reducing the herds profitability.

Advantages of a Short Calving Interval

The industry target for suckler herds is 65% of the herd should calve within the first three weeks, with 90% calving in six weeks.  A shortened calving interval has several advantages besides the obvious benefit of improved herd efficiency and fertility.  Labour requirements can significantly be reduced, with routine tasks such as vaccinating, castration and disbudding, made easier with bigger batches of calves of a similar age and size.

It is easier and more accurate to ration and creep feed youngstock at similar growth stages and allows for improved winter rationing of suckler cows, with cows at similar stages of pregnancy and lactation.

Also, there is less risk of disease spread from older calves to more vulnerable younger calves.  A wide range in age of calves is an important factor contributing to calf health problems.

For herds breeding their own replacements, an increased number of earlier born heifer calves, increases the number of heifers which are more likely to be the correct weight at bulling to calve at two years of age.

Understanding the Reproductive Cycle

Although a longer, extended calving period, may lead to more calves being reared, over time this will lead to the retention of less fertile cows and lower conception rates spread over a longer period.  Also, some cows may not have calved by the time mating starts.

Cows undergo a period of recovery after calving before coming into season.  On average this is approx. 40 days (slightly longer for heifers and considerably longer if there were difficulties at calving).  The following graph shows, the number of heats and therefore mating opportunities for cows calving at different times in the calving period (based on a 12-week mating period), assuming cows are the correct body condition score.

 Source – A Guide to Improving Suckler Herd Fertility

This highlights the advantages of a tight calving period, allowing more time for recovery post calving and increased opportunity for service.

 

Sarah Balfour, sarah.balfour@sac.co.uk

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