Economics are based upon three basic principles: time, income over cost, and number of units.
As we try to improve herd management and increase profits, we can evaluate common practices on the dairy with these principles in mind.
Consider income over feed cost: Even if we maximize all our breeding parameters, there will be some cows near the end of their lactation with low production. To be fair, a low producer does not eat as much as a high producer, so let us say our low cows are costing about $4.50 in feed per day. If our average feed cost for the herd is $7 a day, we know we are losing money on the low producers. At $0.30 per kg of milk, then for every day she is producing less than 15 kgs of milk, the dairy loses money. Standard practice is to get her out of the milking herd and feed a cheap ration in the dry pen or cull her if she is open.
Culling open cows with low milk production is a good decision. From this point forward the cow cannot produce more milk than feed cost and she is losing money. If she is pregnant and there is only room for one animal on the dairy, replacing her with a new animal that could produce 35 kgs of milk is the right decision.
If we have room for both cows, should we keep both in the milking herd? 
*Dry Cow milk evaluations
Why would we keep her in the milking herd when we can reduce feed costs from $4.50 a day to $2.50 a day by moving her to the dry lot? The simple answer is income. A dry cow produces no milk and no income over feed costs. A milking cow is still producing some income as long as she is milking. The difference between dry cow feed and milk cow feed is $2.00 a day. Can she produce more than $2.00 of milk? At $0.30 per kg, any milk production above 6.7 kg a day will generate income when compared to drying her off.
In addition to the profitability calculation, the health risk associated with extending the dry period past 60 days must be evaluated. Considering income over feed cost helps maximize production compared to the feed inputs for every dairy. Remember, the example above was about maximizing income in a losing situation. Moving forward, we need to determine why we have animals in this group and make changes to our processes so that cows do not enter these low production periods.
First lactation cows that are dry for long periods of time (target 40-70 days dry) seem to have fewer problems than older cows. Older animals with long dry periods have a couple of issues: lower production and reduced longevity. Dr. Chad Dechow of Penn State University estimates that long dry period costs include a 10% decrease in milk production for the following lactation and about a five point higher culling risk in the first 60 days post calving.
This all adds up to confirm that long dry periods are a poor economic decision and put the welfare of the cow at risk. This decision is easier if you are replacing the animal with a higher producing animal. However, our focus should be on improving our dairy reproduction and management so decisions about length of dry period are not required.
The Genetic Connection to Economics
We need to focus on the animals that get pregnant at the right time. The number one reason cows are considered for an early dry off is delayed conception. Fertility is a key component in this equation, influencing a cow’s ability to maintain a productive cycle. To address conception rates, today, consider selecting bulls with higher Sire Conception Rate (SCR) values, which indicate superior fertility. For the future, place emphasis on traits like Fertility Index (FI), which incorporates multiple fertility measures including: Daughter Pregnancy Rate (DPR), Cow Conception Rate (CCR) and Heifer Conception Rate (HCR). Although these traits are lower in heritability, continued emphasis can drive improvement over time.
Herd Health Profit Dollars® (HHP$®) and Dairy Wellness Profit Index® (DWP$®) both place a strong emphasis on fertility, with HHP$ attributing 9% and DWP$ 12% of their evaluations to fertility traits, primarily DPR and CCR. Additionally, DWP$ benefits from incorporating Zoetis fertility traits, which include factors such as resistance to twinning, cystic ovaries, and abortion. Using these indexes as a selection tool can aid in addressing delayed conception, preventing early dry-off, and improving overall efficiency and profitability.