BCS at mating & its impact on repro

Based on data recorded in MINDA, LIC were able to look at the BCS of nearly 200,000 cows prior to mating, and how they got back in calf.

Here are 6 take away points and tips to consider in the lead up to mating:

1. Why is BCS important?

Body condition score (BCS) is a measure of a cow’s fat reserves and is a good indicator of energy balance. The fat reserves on animals are important in early lactation, buffering the peak in energy demand and milk supply against feed shortages. A rapid drop in BCS can increase the time for a cow to resume cycling again, reduce the conception rate and increase the risk of reproductive disorders and health problems like metabolic diseases.

2. What are the BCS targets?

DairyNZ has BCS targets for cows at both calving and mating. At time of calving, 2-year-old and 3-year-old cows (first- and second-calvers) have a target BCS of 5.5, while older cows have a target of 5. Between calving and mating, cows should not lose more than 1.0 BCS. This translates to a target BCS at mating of 4.0 or greater for older cows and 4.5 for 2-year-old and 3-year-old cows. In addition, DairyNZ advises no more than 15% of animals to be above the target, as well as no more than 15% being below the target.

3. What BCS are our cows achieving?

On average, 4-8 year-old cows are hitting their mating BCS target, with an average BCS of 4.38, with only 7% below target. The 2-year-olds are also, on average, meeting target with an average BCS of 4.51, however, 28% of them were below target. In addition, 3-year-olds are falling short of the target, with an average BCS of just 4.34, with 44% of them being below target.

4. How does BCS relate to reproduction?

Cows at the recommended BCS just before mating (4.5 for 2 and 3-year-olds, and 4.0 for 4-8 year-olds) or half a condition score greater, have a higher 6-week in-calf rate and a lower not-in-calf rate. Thinner cows will take longer to get in-calf, meaning a later calving date next year, or they may not get in-calf at all. These results support the importance of meeting BCS targets.

5. When to condition score?

DairyNZ recommends condition scoring regularly, with emphasis on late lactation, pre-calving, pre-mating and at the end of mating.

6. What can we do to minimise BCS loss?

One strategy that can be used now is preferential treatment, such as reduced milking frequency in early lactation. Reducing the cows’ energy requirements to better match her energy intake can help mitigate some effects of not reaching calving BCS targets. This strategy can be used for the whole herd or to target at-risk cows.

Prevention is better than a cure, so setting up the cows well before calving, will mean that we aren’t trying to stop BCS loss to keep the cows in the right range, rather ensuring they don’t lose too much. Prevention strategies are better implemented at the end of the season, these strategies for managing BCS include:

Monitor the weights of heifers as well-grown heifers tend to meet condition score targets at calving.
Dry off first calvers ahead of the mature cows to give them more time to reach their higher target as a 3-year old.
Dry cows off based on BCS and expected calving date.

For more information or help with body condition scores, contact your local Franklin Vets clinic.

This analysis is based on individual BCS data recorded in MINDA®. This data is from 199,724 cows calving in spring 2019 with an individual BCS recorded, at most, 50 days before mating start date, and only from herds which produced a detailed fertility focus report. A detailed fertility focus report requires accurate calving dates and early aged pregnancy data (between 35 and 122 days of pregnancy).