June 21 2023 09:50 AM

Provided by Gavin Staley, Ruminant Technical Specialist with Diamond V

The information below has been supplied by dairy marketers and other industry organizations. It has not been edited, verified or endorsed by Hoard's Dairyman.

Improving herd productive life raises average milk production, improves feed efficiency, increases beef cross opportunity, lowers heifer inventory, and helps reduce greenhouse gas. Many attractive positive outcomes. Accomplishing this goal requires converting “Platinum Heifers” to “Golden Girls”! Elite herds have the ability to create and retain healthy mature cows!

Platinum heifers are healthy, well-grown heifers that reach the lactating herd at a size and weight that is on target to achieve mature body weight in the 3rd lactation. These heifers achieve higher milk production than immature herd mate heifers and are more likely to pay back their rearing costs sooner.

The typical break-even point on a dairy, when cows have created enough value from milk production to offset their heifer rearing costs, is sometime early in their second lactation. Since the average lactation of many dairies is just over 2 lactations it follows that many cows barely pay off their heifer rearing costs before they leave the herd. If these cows stay healthy, continue with high production, and breed back in a timely manner, the longer they stay in the herd the better. These older mature cows are the dairy’s “Golden Girls”.

So how do we make sure our heifers turn into long-living cows? Firstly, we need to consider what the ideal herd should look like. A model developed by Dr. Albert de Vries at the University of Florida shows the 5 key factors influencing herd demographics (Journal of Dairy Science, 2020, Vol. 103, No. 4). They are as follows:

  • Calf value opportunity cost: young herds have lower beef cross opportunity
  • Aged cow cost: older herds need to take greater care of older cows that are more disease prone
  • Lack of maturity cost: young herds have more lactating animals that are still growing
  • Herd replacement cost: young herds need large heifer inventories to support high replacement rates
  • Genetic opportunity cost: young herds have better genetics

The number of older cows we have in the herd has a direct effect on herd dynamics. The more cows we have in lactation 3 and older, the fewer cows we need in lactation 1. So, let’s say more than 40% of our herd is lactation 3 and older. That means the dairy needs only 30-35% for lactation 1, which means the replacement rate will be 30-35% and the replacement rate/culling rate will also be 30-35% (assuming a stable milking herd). This is an important observation because the replacement rate requirements/culling rate directly impacts the number of heifers you will need as replacements. Lower replacement rate means lower heifer inventory required.

Here are a few factors to consider as you consider the ideal herd demographic:

  • Reduce Days in Milk (DIM): This shifts the herd towards peak production and increases average herd milk production: The goal is to hit an annual herd average DIM of 160 with an annual variability of only +/- 6 DIM (difference from average DIM to peak and nadir). This reduces “calving slugs” and associated higher culling rates
  • Optimize reproduction: Reproduction must be outstanding e.g. 21-day pregnancy rates of at least 25, and many herds are now 30%. Herds with low DIM (and low culling) must have outstanding herd reproduction success. Poor reproduction increases DIM, drops milk production, and increases cows culled for low production/reproduction.
  • Manage heat stress: Elite herds mitigate heat stress well. Dramatic seasonality (calving “slugs”) due to heat puts stress on cow health, reproduction, and transition management.
  • Limit involuntary culling: Obviously if a cow needs to be culled, she must go, regardless of parity, reproductive status, or DIM. Nonetheless, outstanding dairies limit involuntary culls and tend to create more voluntary culls (animals that could stay). Remember, all culls, except “deads” are actually voluntary culls (management makes a decision), BUT some animals have so many issues that they move from voluntary to involuntary.
  • Mitigate the four main reasons (the four “Horsemen of the Apocalypse”) why cows leave: Mastitis, transition disorders, lameness/injury, and reproduction/low production failures. Investigate why these diseases are causing more cows to leave than desired, and then take steps to mitigate.
  • People: Elite herds require elite people. If productive life is the desired outcome, make sure the right people are involved with daily management and that the right training processes are in place.

It is possible for dairies to shift the demographics to a more mature herd and graduate more cows to the next lactation. This requires an intentional change in management and a careful scrutiny of culling practices including who makes culling decisions.