by Amanda Smith, Associate Editor
Despite our best efforts, we will never create a ration our cows won't try to sort. Even when we put together a great ration on paper, these diets don't always perform the way we expect or want them to.
"We need to look beyond the printout of our cow's dietary recipe and consider the ration that is delivered, consumed and ultimately digested by the cow," noted Trevor DeVries, University of Guelph-Kemptville, at the Mid-South Ruminant Nutrition Conference.
In a study conducted by DeVries' group on Canadian dairies, the average TMR exceeded the paper formulation for energy (NEl, nonfiber carbohydrates, acid detergent fiber and calcium). On the same token, crude protein, neutral detergent fiber and sodium were underfed.
Ensuring that the feed both delivered and mixed is what you formulated for is the first step to optimizing your ration's potential. In the above study, conducted over two, seven-day periods, there was wide variability in the percent of long and fine particles or physical structure of the ration. For each 5-point gain in long particles, a 2.6-pound-per-day drop in milk yield was seen.
A 0.15 percent milkfat drop was seen for every 10 percent refusal of long particles. Additionally, every 2 percent refusal of long particles was correlated to a 2-pound-per-day drop in 4 percent fat-corrected milk.
As the diet's energy content went up, the lower the cow's dry matter intake went. For each 0.5 point raise in NEl variability, there was a 7.1-pound-per-day drop in milk yield.
