Fecal Starch Level May Predict Digestibility

By Bill Mahanna, PhD, Dipl. ACAN, Pioneer Global Nutritional Sciences Manager

In early June, I attended the Four-State Dairy Management & Nutrition Conference in Dubuque, Iowa. This conference is organized by cooperative extension from Iowa State University, the University of Illinois, the University of Minnesota and the University of Wisconsin.

I always enjoy interactions at this conference because of the strong attendance by both feed company and independent nutritionists and the excellent speakers that the organizers consistently bring in. The quality of the program was reflected in a record attendance of 436 participants.

The following is a summary of a few presentations.

Fecal Starch Evaluation

Mike Hutjens from the University of Illinois reviewed work from Pennsylvania and Illinois looking at fecal starch as a predictor of total tract starch digestibility.

Earlier research from Illinois indicated a wide range (2-22%) in fecal starch and a relatively poor relationship to production. However, high grain prices appear to be stimulating renewed interest in this analysis when put in context with other cow observations (sorting, manure consistency, rumination, etc.).

More recent research from the University of Pennsylvania suggests that fecal starch level should be less than 5% and that for each 1% increase in fecal starch, there is a potential loss in milk yield of 0.7 lb. per day.

Cumberland Valley Laboratory's results from 1,420 fecal samples showed that 38% contained more than 5% starch. Fecal starch analysis costs $15-20 per sample. It is recommended to collect fecal samples from 10-15 cows and submit one to two cups of pooled sample for analysis.

Having a baseline established for fecal starch levels may help nutritionists quantify the importance of adequate and consistent processing of grain and corn silage.

Dairy Carbon Footprint

Jude Capper from Washington State University presented a strong case for the dairy industry to address environmental concerns with productivity improvements.

While the carbon footprint of an individual dairy cow has doubled from 1944 to 2007, the U.S. dairy industry has reduced its total carbon footprint by 41% for that same time period. This is due to science-enabled productivity such that 59% more milk is produced by 64% fewer cows.

It would benefit the entire dairy industry to keep these facts top-of-mind and use them to explain to consumers that productivity is the only solution to the issue that in the next 50 years, the growth in world population will require 100% more food than is produced today (Simmons, 2010).

HMC Chemistry

Pat Hoffman from the University of Wisconsin described high-moisture corn (HMC) as an enigma due to the lack of homogeneity resulting from wide variations in ensiling moistures/ temperatures, composition (kernels, cobs and husks), various additive treatment options and time in ensiled storage.

Data were presented showing that fermentation of (untreated) HMC is very slow, and chemical alterations occur over an extended (240-day) storage period. There are increasing data to support the belief that traditional laboratory analyses (starch, acid detergent fiber, neutral detergent fiber and crude protein) are not well suited for determining the biochemical factors (such as zein protein degradation) that increase the dry matter digestion of HMC over time in storage.

It will be essential for ration balancing software to begin incorporating algorithms relating ensiling moisture content, kernel particle size and time in fermented storage to the energy availability of HMC (and corn silage).

livestock feeding image

TMR Mixing Uniformity

Tom Oelberg with Diamond V gave a visual presentation on improving feeding consistency through total mixed ration (TMR) audits.

The biggest factors causing TMR variation in more than 135 audits Diamond V has conducted over the past 2.5 years were: overfilling mixers, worn equipment and knives, under-mixing after the last ingredient, under-processing poor-quality hay, improper location of adding liquids to mixers and improper mix order.

Information was presented on a field technique to measure mixer uniformity. Large, easily seen pieces of red licorice can be added as the last ingredient and mixed for 2.5 minutes. It was recommended to add at least 10 pieces of licorice to the mixer for every foot of feed bunk (e.g., for 200 ft. of bunk space fed per mix, add 2,000 pieces of licorice).

One-foot-wide sections of the distributed TMR can be pulled out from the beginning, middle and end of the feed bunk and the licorice pieces counted.

From field experience, three scenarios typically exist:

  1. Acceptable uniformity, exhibiting a similar number of licorice from the front, middle and end samplings (e.g., seven pieces from the front, 13 pieces from the middle and eight pieces from the end).
  2. Poor distribution, with licorice counts varying greatly (e.g., 20 pieces from the front, five pieces from the middle and zero pieces from the end).
  3. Poor distribution, with licorice found in all three samples but at very low counts, indicating excessive distribution in some sections of the bunk (e.g., two pieces from the front, three pieces from the middle and three pieces from the end).

There are other approaches to testing mixer uniformity (Herrman and Behnke, 1994) that suggest tracer ingredients such as salt and a goal for the coefficient of variation of less than 10%.

However, despite the labor required, the licorice field method serves to visually convince producers of the importance of mixer reconditioning and/ or adherence to loading/mixing protocols.

It was also suggested to consider the use of a Penn State Separator to monitor particle size consistency and occasionally consider analyzing subsections of the feed bunk for dry matter and protein as another measurement of TMR uniformity.

Feeding Strategy Survey

In another presentation, Hutjens summarized the results of a fi eld survey conducted among nutritionists, veterinarians and educators as to "correct" and "incorrect" dairy management decisions that these advisers saw clients implement during a period of low milk prices in 2009.

The top four correct decisions were:

  1. focusing on forage quality
  2. staying the course
  3. fine-tuning rations
  4. culling strategically

The top four incorrect decisions were:

  1. removing feed 
  2. pulling minerals, vitamins and additives indiscriminantly
  3. not staying the course
  4. feeding low-quality forage

Omega Fatty Acid Nutrition

Tom Jenkins from Clemson University and Bill Thatcher from the University of Florida both addressed omega fatty acid nutrition as part of the Virtus Nutrition LLC pre-conference symposium. They highlighted products containing different levels of omega-6 and omega-3 fatty acids designed specifically for pre-fresh or post-fresh cows.

The three important omega fatty acids are omega-9 (C18:1, oleic), omega-6 (C18:2, linoleic) and omega-3 (C18:3, linolenic). Omega fatty acids all have a double bond at the third carbon-carbon bond from the methyl end of the fatty acid. These can also be converted to other biologically active acids via ruminal biohydrogenation. Examples are the omega-3 metabolites eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6).

It is thought that biohydrogenation is an evolutionary process to protect rumen microbes from the toxic effects of unsaturated fatty acids. Linoleic and linolenic acids cannot be synthesized by body tissues and must be supplied in the diet (essential fatty acids).

The interest in omega fatty acids centers on value-added, health market opportunities for fluid milk ("anti-cancer" conjugated linoleic acid cis-9, trans-11 C18:2) and increasing concentrations in body tissues to improve cow reproduction and immune response.

Research was presented showing that certain omega-3 fatty acids, such as EPA and DHA in calcium salts of fish oil, are absorbed from the gut and preferentially taken up in uterine tissue, where they appear to alter expression of a complement of genes in the uterus to support development and maintenance of pregnancy.

The Bottom Line

Meetings such as the Four-State Dairy Nutrition & Management Conference give nutritionists the opportunity to interact with leading researchers across the country. As we all know, an equal amount of learning is accomplished by talking to colleagues in the hallways and local eating establishments.

The real challenge is coming back home and committing to the implementation of new ideas and products that we believe will help clients become more profi table.


  • Capper, J. 2010. The compatibility between dairy productivity and carbon footprint. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 21-26.
  • Herrman, T., and K. Behnke. 1994. Testing mixer performance. Kansas State University Agricultural Experiment Station and Cooperative Extension Service, bulletin MF-1172.
  • Hoffman, P.C., R.D. Shaver and N.M. Esser. 2010. The chemistry of high-moisture corn. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 84-89.
  • Hutjens, M.F. 2010a. Feeding economics for 2010. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 27-29.
  • Hutjens, M.F. 2010b. Manureology 101. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 59-61.
  • Jenkins, T. 2010. Where do all these fatty acids come from and what do they do to my cow? Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 15-20.
  • Oelberg, T. 2010. Improving feed consistency through TMR audits. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 73-83.
  • Simmons, J. 2010. Food economics and consumer choice. Proceedings Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa. p. 119-122.


© 2010 Feedstuffs. Reprinted with permission from Vol. 82, No. 32, August 9, 2010