Cows crave consistency. Milking time, udder prep, feed delivery, animal care and handling, reproduction and the nutrients delivered in the ration should be the same day in and day out.

Brown tim
Director of Technical Support / Dairy Nutrition Plus

This focus on consistency – doing everything right every time – has helped increase milk production per cow by 35 percent in 20 years. According to USDA data, annual milk production per cow was just 16,871 pounds in 1997, compared with 22,774 pounds per cow in 2016. Many elite herds achieve 30,000-plus pounds per cow today.

Lactating cows are analogous to elite athletes. They both need a structured routine for activities and precise nutrition to maximize performance and health. Consistency of feed ingredients plays a big role. About five years ago, Normand St-Pierre and Bill Weiss at Ohio State University conducted a large survey to quantify the inconsistency in feed ingredients and to help producers and nutritionists learn how to minimize variability in order to feed a more uniform diet.

“The amount of variation in the nutrient composition of a feed can affect diet formulations strategies, the economic value of the feed, the sampling and analysis schedule for the feed, and possibly the productivity and health of the cows,” said Bill Weiss at the 2012 Mid-South Ruminant Nutrition Conference.

Diets are formulated, in part, to minimize the risk of an adverse health event and to allow cows to achieve their genetic potential. Variability in quality, digestibility and nutrient content of feed ingredients can negatively impact animal performance, most noticeably, reducing milk production.


Take for example, research with distillers grains conducted by Weiss et al., 2013. All cows were fed a diet that contained the equivalent of 25 percent distillers grains, but with varying amounts of long-chain fatty acids (LCFA). When the change in LCFA was moderate, 5.4 percent to 6.4 percent, there was no change in dry matter intake (DMI) or milk yield. But when the variation in LCFA was greater, 4.8 percent to 7 percent, cows had lower DMI and milk production. The range of variation in LCFA in the distillers grain used in this experiment would all fall in the “normal” range but deliver different results unless the diet is reformulated.

Diets are no longer balanced for just crude protein. Instead they are balanced for metabolizable protein (MP), amino acids (AA), rumen degradable protein (RDP) and rumen un-degradable protein (RUP). Products such as bypass protein and rumen-protected amino acids deliver nutrients beyond the rumen to the intestine. The amount of crude protein formulated into diets of lactating dairy cows has declined from 18 percent or higher to around 16 percent today. Milk production has increased and environmental risk from the excretion of excess nitrogen has declined.

Formulating diets for MP, RDP, RUP and AA instead of crude protein makes minimizing inconsistency of feed ingredients even more critical. In the “100-year Review of Protein and Amino Acid Nutrition in Dairy Cows,” it states that “the commercial production of high-quality rumen-protected AA supplements is difficult. ... Current products are far from being created equal and users should not use products that have not undergone rigorous, documented and transparent evaluations of how much of the contained AA gets absorbed.” In 2012, St-Pierre stressed that purchasing commercial feeds from a manufacturer with an effective quality control program is one of the cornerstones for reducing feed variation, which can lead to lost productivity and lost profitability.

Take for example, bypass protein. It’s a premium ingredient that delivers known results. But if the percentage RUP in a protein supplement is lower than expected, you could lose milk production. If the percentage RUP is greater than expected, you could short the cow on RDP and lose milk. With consistent ingredients, you can formulate close to the cow’s needs, maintain production and save money. Unless you purchase bypass protein from a manufacturer that guarantees a consistent nutrient profile, the only way to know what you get is to test it yourself. Nutritionists have been routinely testing forages for years in order to account for obvious variability in nutrient content. But concentrate feeds can vary too.

High-producing dairy cows, like top-performing athletes, need precision in their diets. As such, variability in ingredients can have noticeable effects. The care and feeding of dairy cows has changed a lot over the years. It will continue to evolve as researchers find new tools to help account for variability in feeds, improve efficiency and improve the overall health and productivity of cows.  end mark

Tim Brown
  • Tim Brown

  • Director of Technical Support
  • SoyPlus and SoyChlor
  • Dairy Nutrition Plus

PHOTO: Variability in quality, digestibility and nutrient content of feed ingredients can negatively impact animal performance and reduce milk production. Photo by Mike Dixon.