Replacement heifers: Management benefits the bottom line


As we transition into summer, our to do list seems never ending. If the spring continues to stay wet and cold, we may still be trying to plant and start making hay at the same time.

With all of that weighing on our minds, we still can’t forget about planning ahead and making a strategy for the breeding season. Reproduction is the most influential factor contributing to the profitability of a cow calf producer.

Reproduction means profit

If for some reason we have poor conception rates, the annual revenue of the operation will drastically decrease, likely inhibiting profitability. While there are several reasons that contribute to this happening, we need to manage our risk to ensure that we give our cows an opportunity to be successful. Replacement heifers and first calf heifers are among the most difficult to manage as they have greater nutritional and management needs.

The first thing to remember is that cows are long term investments, and the cow usually has to wean six calves before she pays for herself and begins generating a profit. Often this group gets blended in with the mature cows, and as a result they may not get the feed and attention they need to ensure that they are around for a long enough period of time to become profitable. These groups benefit a great deal when separated so that they are not competing with mature cows for feed, and so that you may supply them with better quality forage that is too expensive to feed mature cows.

Body weight

Traditional margins require heifers to calve at two years of age; otherwise, they usually do not recapture the financial investment placed in them. In order for this to take place, they need to be bred by 15 months of age and reach puberty between 12 and 14 months of age.

An animal’s ability to reach puberty is partly due to age and genetics, but more dependent on their plan of nutrition. As a result, we have typically recommended that heifers be bred when they reach 65% of their mature body weight. You can estimate mature weight by surveying the cow herd that the heifer derived from. If the cows are an average weight of 1,200 pounds, then it is probably a fair assumption that the heifers will be that size when they reach maturity. That will require the heifers to average 780 pounds at breeding.


It is important to realize that there is a great deal of opportunity for error in this group, so we need to manage these groups to the best of our ability. One possible opportunity to decrease the age in which puberty is reached is to utilize ionophores. Research has shown that by including ionophores in the diet of developing heifers, it will slightly decrease the age in which heifers reach puberty. This is especially true when feed resources are limited or marginal. It is important to remember that this does not replace the need for a good plain of nutrition, just helps to better utilize feed resources for positive results.

Sophomore slump

Typically, the hardest group to breed is two year old first calf heifers. This may be referred to as the “sophomore slump,” as they are heifers that are still growing, raising a calf and are being asked to re-breed.

In order for cattle to have a calf every 365 days, they need to re-breed — 80 days post-partum. Usually, these groups of “sophomores” need an additional two to three weeks post-partum to begin cycling than mature cows due to their added stress and nutritional needs.


To help ensure that they do not conceive late in the breeding season or fail to breed, it may be a good idea to breed your yearling heifers two to three weeks before the cows to help compensate for this additional stress. This may be the place where synchronization can help. By incorporating a synchronization protocol that allows more heifers to be bred at the beginning of the breeding season, it ensures that they have more time to begin cycling after their first calf. There are additional benefits to using this management strategy as well.


If heifers have not yet reached puberty, a synchronization protocol that utilizes progesterone may cause them to begin cycling.
Additionally, this option may allow you to utilize artificial insemination to ensure that your heifers are bred to proven calving ease sires. Cows that calve at the beginning of the calving season are more likely to continue to calve at the beginning of the season. In turn, they will have older calves that will weigh more at weaning, increasing your revenue. This is also a great group to select replacements from as they are the oldest heifers in the group and should be heavier and reach puberty earlier than their younger contemporaries.

As you can see, utilizing a few simple technologies can have multiple positive effects on your operations productivity and bottom line. For more information, consult your extension educator for additional resources and insight on how to implement practices that best suit your operation and goals.

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