Feed Strategy - March 2018 - 48
48 ❙ FeedStrategy
REDUCE MILK FAT DEPRESSION
How to formulate poultry, swine diets with modern
their dairy cattle diets. In another survey
on the use of distillers grains sent to 10
nutritionists specializing in dairy cattle, their high fat
content was the main reason why distillers grains inclusion was restricted in dairy diets.
Half of those surveyed (5 out of 10) agreed that the
high concentrations of unsaturated fatty acids in distillers grains reduced fat content in milk. Nine out of 10 of
the dairy consultants indicated that the level of distillers
grains inclusion in diets could be increased if a portion of
the fat in distillers grains was removed.
Inception of low-fat distillers grains
In recent years, there has been growing interest by many
ethanol plants to extract a portion of the oil from distillers
grain or other process streams as a means of increasing plant
profitability. When part of the oil is removed, the fat content
decreases and the rest of the nutrients are concentrated proportionately. These distillers grains are, in general, called
low-fat distillers grains. Different commercial processes have
been developed to extract the oil from thin stillage, semiconcentrated stillage and even condensed solubles.
DISTILLERS GRAINS USE
RATES were 30 percent for
dairy and 44 percent for
beef cattle in 2016.
Most of the methods are based on physical separation
techniques, using different separation columns or centrifuges. Another possibility is the chemical extraction of
the oil in distillers with solvents. The final fat content in
the co-products is variable, depending on the method used
by each company, and it ranges between 2.5 and 7.5 percent dry matter (DM).
Dry mill ethanol plants extracted roughly 2.9 billion
pounds of corn distillers oil in 2016. This oil is generally sold
as a feed ingredient or as a feedstock for biodiesel production.
Analysis of the effects of fat composition
The fat in distillers grains is mainly composed of unsaturated fatty acids. Linoleic (C18:2) and oleic (C18:1),
are the most abundant fatty acids, with an average of
almost 50 percent and 25 percent of the total fatty acids,
respectively. The high concentration of unsaturated fatty
acids, together with high free fatty acids content, can
sometimes lead to milk fat depression in dairy cows fed
diets that include high levels of distillers grains.
Researchers from the University of Nebraska compared conventional with low-fat dried distillers grains
with solubles (DDGS) as the main protein supplements
in lactating dairy cow diets. The diets consisted of 35.6
percent forage as DM basis and included 29.2 percent (17.1
pounds) of either conventional (12.0 percent fat and 29.1
percent protein in DM basis) or low-fat DDGS (6.6 percent
fat and 31.5 percent protein). Fat and polyunsaturated fatty
acid contents averaged 5.8 and 2.78 percent in the conventional, and 4.2 and 2.16 percent of DM in the low-fat
DDGS diet, respectively.
The results, published in the Journal of Dairy Science,
showed milk fat depression in the conventional DDGS diet.
Although DM intake (58.5 pounds/day), milk production (76.2
pounds/day), and protein concentration and yield (3.22 percent
- 2.44 pounds/day) were not affected by diet, milk fat yield
(2.50 vs. 2.75 pounds/day) and content (3.27 vs. 3.65 percent)
were lower in the cows fed regular DDGS.
Using values from September FMMO Advanced
Component prices (fat US$3.03/pound), the economic impact of milk fat depression in the regular DDGS diet was
76 cents per cow per day or US$277 per year. ■
References available upon request.
Fernando Diaz works as a dairy nutrition and management consultant at Rosecrans Dairy Consulting, LLC. He can
be reached at email@example.com.
www.WATTAgNet.com ❙ March 2018