Select Sires

Tips for Decreasing Average Age at First Calving - Part 2
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio, Which Aired Oct. 24, 2002
with Dr. Joe Dalton, extension dairy specialist,
University of Idaho

Today’s Reproductive Moment is the second in a series of two with Joseph Dalton, Extension dairy specialist at the University of Idaho. Producers everywhere want to get their heifers to breeding weight as soon as possible. Last week, Joe, you spoke about the importance of setting realistic goals for heifer growth so that people ultimately are satisfied with the average age at first calving in their herds. How should they monitor heifer growth?

Growth monitoring is very critical to the profitability of the dairy farm. We have to remember that if a Holstein heifer weighs 100 pounds at birth, then the animal must gain an average of about 1.8 pounds per day to reach the goals, calving between 1,350 to 1,400 pounds at 24 months-of-age. Average daily gains of greater than two pounds per day before puberty have been shown to lead to increased fat deposition in the mammary glands. This has been shown to lead to decreased milk production when those animals begin lactating. Monitoring growth of heifers can be accomplished with our nutritionist and our veterinarian.

Once heifers reach breeding weight, some producers turn the responsibility for heat detection and breeding over to a herd bull because of convenience, or for clean up. What are some of the risks associated with natural service bulls that can keep herds from seeing a lower age at first calving?

Dairy producers should recognize the limitations and dangers of using natural service bulls. There are costs incurred with the use of natural service. Those costs include: the purchase price of the bull, daily feed costs, veterinary costs, and lost income, because the daughters of natural service bulls produce less milk than the daughters of A.I. sires. Natural service bulls can also introduce venereal disease into a herd, whereas A.I. bulls are free from disease. Another thing we have to consider is that natural service bulls may also suffer from lameness, low libido levels, and/or be sub-fertile. These problems can lead to decreased conception rates and decreased profitability, due in part to an increase in the average age at first calving. My recommendations are to utilize A.I. on your heifers to avoid these problems and realize the financial benefits of genetic advancement made possible by proven A.I. sires.

Joe, you often talk about the importance of early pregnancy checks as a tool to lowering the age at first calving. Why is it so important to pregnancy check heifers before 40 days after an A.I. service?

I am glad you asked this question, Bill. This strategy allows management to focus on heat detection of confirmed open heifers that will be coming into heat in a few days, thus minimizing the potential increase in average age at first calving due to inefficient heat detection. We have to remember that a heifer’s estrus cycle is 21 days and light, and realistically we can palpate heifers after about 32 days. So, if we palpate cows or heifers before 40 days, we are going to have good results and know which ones are open and which animals we should be checking heat on as they return to heat at about day 42.

Thanks, Joe. Joseph Dalton, Extension dairy specialist at the University of Idaho.

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