CALF_News_April_May_2018

39 CALF News • February | March 2018 • www.calfnews.net L ab analysis is an essential tool for managing livestock nutrition. Laboratories have many different methods to evaluate the different fractions of various feedstuffs and forages. Some are simple; some are complex. Analyzing moisture content seems simple, but may not be considered as important as other feed analyses. The non- moisture dry matter content of a sample contains the nutrients of interest like protein, fiber and minerals. Accurate moisture analysis is essential for proper feeding management. The National Forage Testing Association lists 12 different methods for dry matter determination in forage samples. Most of these methods determine moisture content by heating a sample to remove water from the sample and identifying the change in sample weight. It’s actually not only water. There are other non-water volatile compounds that may be driven off during heating – like fatty acids, waxes and other natural compounds – that are included as “moisture.” There are specialized methods for fats, oils, fermented samples, etc., using toluene or other solvents that only remove the water from the sample. Drying technique is also critical. A sample that’s heated for too long or at too high a temperature may drive off more than water and normal volatiles. A portion of the plant tissue in the sample may be heated to the point where it cooks off and is lost by volatilization. This may overestimate the moisture con- tent and underestimate the nutrient content, leading to errors in feeding management. It’s easy to underestimate the potential impact of moisture content. Here’s an easy little illustration that I use with stu- dents during our lab tours. I ask them to assume they are now in charge of buying silage. The purchase basis is $25 per ton for 60-percent moisture silage. I tell them I want to sell some silage at 80-percent moisture. Then I ask them what they will pay me for this silage. The students often try to calculate some ratio between 60 and 80, and then multiply that by the $25 base price. There are always some surprised and puzzled faces when I tell them my silage is only worth $12.50. I go through the math as follows: A ton of silage weighs 2,000 pounds. At 60 percent moisture, there are 1,200 pounds of water in that ton (2,000 lbs. x 60 percent = 1,200 lbs.) This means there are 800 pounds of dry matter in that ton (2,000 –1,200 = 800). The 80-percent moisture silage has 1,600 pounds of water per ton (2,000 lbs. x 80 percent = 1,600 lbs.). There are only 400 pounds of dry matter – half the dry matter of the 60 percent silage. Half as many nutrients, half the dollar value because the animal digestive system doesn’t necessarily care if the water comes from the feed or from the waterer. Just because “it’s NOT only water,” accurate moisture analy- sis is crucial to good livestock nutrition.  It’s Only Water By Fred Vocasek Senior Lab Agronomist, Servi-Tech Laboratories “The Insectary”