Are efficient producers less fertile?
1 May 2020
It’s a known fact that cows bred for very high milk yields are less fertile – but is this a problem in New Zealand? DairyNZ’s Samantha Tennent finds out what you need to know.
The dairy sector can be quick to blame increasing production levels for poor reproductive performance. When talking to farmers, we regularly hear them say that cows are ‘milking off their back’ and it causes the animals’ reproductive performance to suffer. Let’s explore how the modern cow performs.
Measuring production levels
We do know that if cows have been bred for high milk yields – for example, with North American or Dutch genetics – they struggle to get in calf. But in our New Zealand systems, we have different breeding objectives. We want cows that are efficient at converting feed into milk and are sustainable in the herd.
Milksolids production alone doesn’t consider how much volume a cow produces, the quality of her milk and what her maintenance requirements are, which all lead to how profitable she is. Therefore, we use production worth (PW) to indicate which are the most efficient, or best producers, in our herds.
PW is calculated from these traits: fat, protein, volume, somatic cell count (SCC), and liveweight. PW is a prediction of a cow’s lifetime performance and is comparable across all herds, ages and breeds.
With PW, we can compare how a cow performs with her peers managed under the same conditions and same feeding system, then rank them on their efficiency at converting feed into milk.
When we are measuring production, we also have the lactation worth (LW). It can show us how profitable and efficient a cow will be within the current season.
If we break down dairy statistics data into quartiles based on PW (see table below) and compare the reproductive performance, we see no major differences.This indicates that production doesn’t impact reproduction.
Usually, our early calvers have the best reproductive performance, as they have the most time to recover before getting back in calf. These cows also commonly have the highest milksolids production, as they have more days in milk. This counters the production argument if measuring on yield, and is shown in the LW (as it is the current season’s performance).
A good cow is a good cow across all areas. She can breed profitable youngstock, produce well within the current season and through her lifetime, and get in calf and back in calf reliably – as long as her other management needs are being met.
Myth: Effecient producing cows are less fertile
Busted: Reproductive performance is now affected by efficient production