Getting cows and heifers pregnant
Early on in my career, I was visiting with a friend of our family. This man was a large hog farmer and he made a statement that I have never forgotten: "If you are going to raise pigs, you have to have pigs." What he was saying was: If you want to sell pigs every week, you have to have pigs born every week, so make sure you do everything to make sure you have enough pregnant sows. Likewise, if you are selling milk, make sure you have enough cows calving every week to average 150 days in milk. As difficult as it can be, that should be the goal on most dairy farms. There may be fluctuations, but the yearly average should be 150. Why 150 days in milk? It is simple math: It is one half of 300 and is basically a midpoint of a 305-day lactation. With a 60-day dry period, this should lead to a 12-month calving interval and keep cows producing at a profitable level.
The fundamental reason most dairy animals exist on farms is to eventually get pregnant so they can have a calf and start to produce milk. By doing so, she is starting to generate income and contribute to the profitability and sustainability of the dairy farm. If a cow does not get pregnant, the animal will be culled. Getting cows and heifers pregnant ultimately drives cash flow on the dairy farm.
The first step in getting cows and heifers pregnant is to decide who is going to be responsible for getting them pregnant. Most likely this is going to be either the owner or the herd manager. It does not work for everyone to be in charge any more than it works for an employee to have multiple bosses. Someone needs to have the responsibility every day, week or month that enough cows are getting bred and enough heifers are also getting pregnant on time to fill in as replacements. Getting cows and heifers pregnant is just as important to the daily operations of the dairy farm as milking and feeding.
What are the top drivers of achieving 150 days in milk? We could discuss each point and diagram out all of the interactions, but fundamentally, it is driven by pregnancy rate of >20% with a goal of >25%. Yes, you can achieve this on your farm. Pregnancy rate is a result of:
- Heat detection in a 21-day period
- Conception rate
What are some other factors that can help to increase pregnancy rate? We know dairy cow fertility has decreased over the last 30 to 40 years as we put greater emphasis on milk production with little regard to health traits. That has changed in the last 10 years as the USDA has been collecting data on health traits in bulls. Are some bulls better at getting cows pregnant than others? Of course, and now we have data to back that up.
If you look at the information provided in the AI bull books, for any given bull there are 15 to 20 numbers listed. In addition to pounds of milk, fat and protein, % test, net merit and other traits, there are values listed for daughter pregnancy rate or DPR, heifer conception rate or HCR, and cow conception rate or CCR. A positive value of 1% DPR means that this bull's daughters will have a 1% improvement in pregnancy rate compared to a bull of 0%. A 1% improvement translates to a decrease of four days open. We do have to realize that heritability of reproductive traits is low and it will take time to see herd wide improvement. But the take home message is that a positive number is better than a negative number and if we consider the difference between a +2% and a -2% DPR bull, this could translate into a difference of 16 days open. If the same choice is repeated on the next generation, we could double the impact of either a positive or negative number. That is why it is best if you use a negative DPR bull in one generation, don't repeat that in the next generation.
We are coming into the most difficult time of getting cows pregnant. Heat stress complicates getting cows and heifers pregnant. Therefore, choosing bulls that excel in CCR and HCR may need greater emphasis at this time of year. It would also be valuable to talk to your semen suppliers for their input on bulls that excel in conception rate that also meet your criteria for net merit or cheese merit or other ranking. Within our many choices of bulls, we can find ones that not only excel in production but also in many health traits, including the ability to get cows pregnant. Good luck with your summer breeding.