This week I had one conversation with someone who waits 80 days after calving to start breeding cows and another conversation with someone was considering starting 45 days after calving. That’s quite a range. Who was right? And, does the right answer have anything to do with whether or not cows are milked in robots?
The voluntary waiting period (VWP) is the time we allow between calving and the first insemination. It allows the cow, and specifically the uterus, to recover from calving before another pregnancy. Dairy Records Management Systems reports the average VWP is 60 days with a minimum of 35 and a maximum of 90. Again, that’s a wide range. 68% of farms have a VWP between 53 and 67 days. That’s a little narrower. In very simple terms, choosing a voluntary waiting period depends on 2 things: when you want cows to be pregnant? And, how long it takes cows to become pregnant? If a cow becomes pregnant at 100 days in milk, with 281 days gestation, and a 60-day dry period, she will milk for 321 days.
When do you want cows to be pregnant?
This answer might depend on whether cows are milked in robots. On one hand, lactations over 365 days result in lower lifetime production regardless of the milking system. This is even more true in robotic systems because late lactation cows lose the will to come to the robot. They become chronic fetch cows or we simply accept less frequent milking. On the other hand, robot cows in general, and especially first lactation robot cows, produce more milk per day in later lactation than their parlor counterparts. Drying off high producing cows is difficult and that may prompt a longer VWP. Start with a goal of getting cows pregnant before 150 days in milk. Adjust it longer only if high producing late lactation cows prove that it is necessary.
How long does it take to get cows pregnant?
A strict estrus synchronization program may mean that all cows are inseminated withing 7 days after the end of the voluntary waiting period. In that case, an 80-day VWP results in all cows being inseminated by 87 days in milk. A program that depends on natural heats will probably take over 40 days, or 2 cycles, for all the cows to be inseminated. With the same 80-day voluntary waiting period it will take until 120 days in milk for all cows to receive their first insemination. Either program can be effective. Remember that at least half of the cows will require more than one service in most herds. The longer it takes to inseminate cows after the VWP, and the more inseminations it take to make a pregnancy, the shorter the VWP should be.
The wrong reasons
Some suggest that low first service conception rates can be fixed by delaying first breeding. That may be worth a look if the VWP is less than 60 days. Review the transition cow program if the VWP is greater than 60 days and first service conception rates are below the average for all services. Others suggest a shorter VWP when production drops too quickly after peak. Review the ration and the feed tables to determine why cows are not more persistent before adjusting the VWP.
Avoiding long lactations is an important part of maintaining cow flow in a robot barn. The right voluntary waiting period is an important part of avoiding long lactations. Let me use my experience in robotic milking and reproductive management to help determine the right VWP for your farm, and the right protocols to achieve the optimum calving interval.
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