What should you do about LDAs?

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Remember your first car? and the lengths you would go to keep it running because you couldn’t afford to trade it in on a different vehicle? Then, as your earning power improved so did your ability to trade up rather than try to keep your less-than-reliable transportation running.

The same scenario often applies to your cows, says Michael Overton, dairy production medicine specialist at the University of California Veterinary Medicine Training and Research Center. When milk prices are low and cash flow is tight, you often do what you can to keep every cow in the herd. However, as income increases, so does your opportunity to “trade up” when health problems arise. Such is the case with the occurrence of a left displaced abomasum. You have options.

A new software tool developed by Overton can help you decide whether to treat that LDA; if surgery is your best option, or if you should trade up and replace the cow with a fresh heifer. The entire process will be published in the coming months. Meanwhile, here’s a sneak peek at using the decision-tree approach to LDAs.

1. Describe the problem.

First, define the situation. Have your veterinarian confirm the diagnosis of an LDA. Determine the age of the cow (with regard to parity) and where she is in her lactation.

2. Identify possible solutions.

In the event of an LDA, you have three main options:

  • Laparotomy correction (surgery).
  • Roll-and-toggle correction.
  • Market the cow for beef.

3. Assess the probability of each outcome.

On average, according to published research, about 85 percent to 90 percent of cows have a successful outcome following surgery, as compared to  70 percent to 75 percent following a roll-and-toggle procedure. These percentages depend on the skill of your veterinarian and herdsman, as well as the condition of the cow when the DA is diagnosed. The success rate will vary somewhat between farms. However, these ballpark figures give you a place to start.

Furthermore, about 15 percent to 25 percent of cattle culled following an LDA are condemned at the slaughterhouse or die before they get there. That takes some of the luster off the third option — culling the animal.

4. Calculate the payoff.

Your next objective is to determine the marginal return for your decision, or which treatment option will best optimize projected income over feed cost.

Overton’s computerized decision-tree program, which runs in an Excel spreadsheet, can forecast up to three potential lactations into the future.

When milk prices are high, it makes sense to market (cull) more LDA cows, the computer model shows, because higher cash flows make it easier to replace the animal with a heifer replacement.  Conversely, when milk prices are low, it takes much more marginal milk from the newly acquired replacement to pay her way, and more LDAs should be corrected.

To determine the best solution for your situation, the program asks you to provide several pieces of data. Then it uses built-in equations to help you make the best management decision.

For instance, you provide:

  • The number of lactations the cow has had.
  • The relative value of the cow in your herd. For example, if she is an average cow, then her relative value is 100 percent.
  • Herd milk production.
  • Lactational culling risk.
  • Several other herd-specific data like dry period length, milk price and average replacement heifer cost.

The tool then estimates the probabilities and cost associated with each of the treatment options, including:

  • Predicted income-over-feed value after surgery.
  • Milk loss following surgery.
  • Amortized replacement cost for healthy and poor market cows.

How it works
“Under the assumptions in the model, surgical laparotomy correction and the roll-and-toggle approach often offer similar values, once the cost of the procedure, follow-up, and expected returns are considered,” notes Overton. Your final choice is impacted by parity, relative value of the cow, current milk price, replacement cost, and of course, the probability for success.

For example, assume you have an LDA cow that is less than 30 days into her second-lactation. She’s an average cow, so her relative value is 100 percent in a herd that is averaging 24,000 pounds per year. Using a current replacement value of $2,000, a cull-cow price of $500.85 and milk price of $13.50 per hundredweight, as well as the base assumptions included in the program, surgery results in a projected income over feed cost value of $2,255, just edging out roll-and-toggle at $2,241.  (Note: the projected income over feed cost is not to be confused with profit.  It is merely a way of establishing projected marginal returns when considering milk production and feed costs.)

You can easily change the data that you input in order to assess other situations. Therefore, you can determine the best course of action for each cow and your business as conditions change. 

This is not the first LDA decision-tree ever developed. Pam Ruegg, University of Wisconsin extension veterinarian and milk-quality specialist, published a similar decision-tree in the Aug. 15, 1989, Journal of the American Veterinary Medical Association.

For more information about this latest tool, e-mail Overton at: moverton@vmtrc.ucdavis.edu



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