Editor's note: The following column appears in the July 2014 issue of Dairy Herd Management.
Any good coach knows the best strategy is not just to have all the positions filled, but to have them filled with the best possible players. That same strategy applies in a dairy herd.
Making sure all of your stalls are filled with productive cows “pulling their weight” is a priority. With producers currently enjoying both high milk prices and high beef prices, carefully evaluating when to cull and when not to needs to be part of every manager’s game plan.
Dairy farmers make culling decisions either directly or indirectly every day, with the most common decision being the default – keeping the cow. However, the bottom line is that a cow should be culled when a replacement offers greater economic rewards. This will ensure that every stall is occupied by the most profitable animal.
When major factors such as disease or injury hamper production and the prognosis of recovery is poor, culling the animal is an obvious decision. More challenging is when a combination of subtle factors, such as production level, age, or reproductive status is in play.
How often does a 10-year-old cow go down and the farmer is left thinking, “I wish I would have culled her last lactation.” Making good culling decisions before the choice is obvious would reduce the chance for on-farm loss.
Models using an economically weighted aggregate of determining factors have been developed to estimate a cow’s value. You can also use models to estimate the value of the average replacement animal. The difference between these two estimates is called the “Retention Pay Off” or RPO. So, when the estimated future value of a cow and its replacements is greater than the value of the replacement animal and her replacements, the cow should be kept, because the RPO is positive. When the RPO is negative, the replacement animal offers a better opportunity, and the cow should be culled.
Retention Pay Off = Estimated Value of Existing Animal & Her Replacements
– Estimated Value of Replacement Animal and Her Replacements
A cow’s future value is a function of her attributes (production level, days in milk), her reproductive status (open, bred, pregnant), and her lactation number and age. It is constantly changing, influenced by management practices that can enhance or restrict her productive capacity. A cow becomes more valuable when she is bred. Her value increases even more when she is confirmed pregnant. A higher producing cow is more valuable than a lower producing cow with the similar age and reproductive status, giving her a higher RPO.
Often culling decisions are integrated with breeding decisions. A cow with a negative RPO, or even a very low RPO, should be evaluated as a possible “do not breed.” Low RPO cows with health events that require high treatment costs, such as mastitis, should also be identified as potential culls.
Since the value of the cow is contrasted against the value of the replacement, the assumption is there is a replacement animal available, and there is competition for stall space. If either of these factors change, that increases the RPO of the current animal.
Current culling models always contrast the current cow against a replacement cow as the alternative decision. However, future models could expand the concept and evaluate other alternative investment opportunities beyond replacement animals. For example, current models assume maintaining the cow would not impair the productive capacity of other animals. However, certain disease conditions, like mastitis, directly challenges this assumption. It’s important to look at all factors involved when considering when to cull an animal and when to maintain her in the herd.
Producers have several options to investigate the potential opportunity of strategic culling. Dairy Comp 305 has a culling model integrated within the record system. Dr. Caberra, at the University of Wisconsin-Madison, also has a RPO model, allowing users to input herd data to calculate the retention payoff values of cows. That model can be found at: http://dairymgt.uwex.edu/tools/rpo_calc/.
Dr. David Galligan is a professor of animal health economics within the University of Pennsylvania’s School of Veterinary Medicine. He is the director of the Center for Animal Health and Productivity. “Dairying on the Offense” is a joint initiative of University of Pennsylvania and the Center for Dairy Excellence.