In recent years, a great amount of discussion has surrounded the determination of optimal stocking density based on economic and health-related measures. Research has pointed to ideal stocking densities ranging from 80 to 140 percent, depending on stage of lactation and facility.
Again and again, on-farm monitoring finds some herds are very successful at high-stocking densities while others are better off at much lower rates.
What causes that wide divide?
According to The Miner Institute’s Mac Campbell, stocking density should be viewed as a subclinical stressor on farms. “Stocking density is a big problem when there are other secondary stressors present,” he shared at the recent Cornell Nutrition Conference.
One of the most prominent secondary stressors is feeding environment. Research at the Miner Institute found that ruminal pH is a strong indicator of this interaction between stocking density and nutrition. The study measured the severity of subclinical ruminal acidosis (ruminal pH below 5.8) in a herd stocked at 100 percent versus 140 percent and fed a diet with or without straw.
Cows that were on the lower fiber diet (without straw) and exposed to greater stocking density tended to have ruminal pH values below 5.8 pH for a longer amount of time than those that were fed high-fiber diets (straw) and stocked at a lower stocking density.
When separated by causative factors, stocking density had more of an effect on ruminal pH time below 5.8. Cows stocked at 100 percent spent 1.4 hours less time below the 5.8 ruminal pH threshold than cows stocked at 140 percent. Meanwhile, the ration played a much smaller role with cows on the high-fiber diet spending 0.9 hour less below 5.8 ruminal pH than cows on the low-fiber diet.
Perhaps stocking density isn’t the biggest issue on your farm, but when compounded with other stressors, it may be the one that’s holding your operation back.