The autumn breeding season is almost upon us and one of the most important jobs prior to breeding is picking replacement heifers.

Decisions made about heifers now is going to have a direct impact on your herd for the next four to eight years as their genetics could remain in the herd for decades to come.

The following are some key points to consider if picking out replacements over the coming weeks. Even if you’re not breeding until next spring, there are some worthwhile points to keep in mind.

How many?

The first thing to consider is how many replacement females you need. The two factors that have the biggest impact on the total number of heifer replacements required are cow longevity (number of calving’s per cow) and age at first calving.

Based on a 50-cow herd, Table 1 shows the number of replacement heifers needed in any one breeding season, as well as the total number of replacements that need to be on the farm at any one time.

Nationally, the average number of calvings per cow is 4.4. Looking at Table 1, this suggests that the average replacement rate each breeding season should be between 20-25%. In a 50-cow herd that’s 10 to 13 heifers per breeding season.

However, it is important to remember conception rate. The aforementioned replacement rates are based on calvings.

When picking numbers prior to breeding, factor in that conception rates are usually only between 85-95% of the total animals bred. In a 50-cow herd, this means letting 12 to 15 heifers to the bull.

Age

Going back to Table 1, it is interesting to see that a farm calving heifers at 36 months of age needs 50% more replacements on farm than those opting to calve at 24 months.

This is the main reason behind calving heifers at 24 months; a reduced stocking rate and at least 10% more productive cows in the herd than when calving heifers at three years of age.

The cost of these extra heifers also can’t be ignored. For a 50-cow herd working off a 20% replacement rate, the difference in calving at 24 months and 36 months is €500/month or €50/heifer/month.

Nationally, only 23% of heifers calved between 22 and 26 months of age in 2018

For those struggling to meet the targets for heifers calving at 24 months, 30 months is also a good option. However, this is only feasible in split-calving herds or on farms that buy-in replacements.

Nationally, only 23% of heifers calved between 22 and 26 months of age in 2018.

Weight

Table 2 shows the minimum target weights for replacement heifers at first service by breed.

The weights are based on a target to breed heifers at 60% of their mature body weight.

Weighing heifers will also show the calf and weanling growth rate. This is a good indicator of the dam’s milking ability and the calf’s genetic potential for growth, and should be considered when picking heifers for the bull.

Visual appearance

While €uro-star indexes have taken the guess work out of picking replacement heifers to a certain extent, the truth is that visual appearance should always be number one.

Visual appearance isn’t necessarily how nice an animal looks, but more so how functional it looks.

Heifers must have sound legs and feet and be able to move well. Take into account the structural soundness of the parents.

Furthermore, temperament is also critical. Do not keep flighty and excitable heifers, or heifers from flighty cows.

€uro-star index

For those looking to go one step further than visual appearance, the replacement index will indicate how successful a particular heifer will be when she calves, based on her genetics.

The replacement index projects how suitable a female will be in terms of calving ability, milk, fertility and ultimately being a low maintenance, functional suckler cow.

Those looking to improve the genetic potential of their herd should be looking towards breeding from four and five-star heifers on the replacement index.

Participants are required to have the equivalent to 50% of their reference number in eligible females on 31 October 2020

For those in BDGP, using the €uro-star index is very important. Participants are required to have the equivalent to 50% of their reference number in eligible females on 31 October 2020.

For BDGP II participants, its 20% in 2020 and 50% in 2022. Eligible females must be over 16 months old at the target date and four or five-star on the replacement index, within or across the breed. Heifers kept as replacements now will play a significant role in meeting these targets later.