How Does Increased Dietary Fat from Traditional DDGS Effect Growth Performance in Dairy Heifers?12 November 2012
Over the last few years, research has been carried out for the South Dakota State University Extension IGrow on a long-term heifer feeding project researching the effects of feeding distillers dried grains with solubles (DDGS) to pre-pubertal dairy heifers.
As part of the experiment, the research measured dry matter intake (DMI), average daily gain (ADG), frame growth, and nutrient digestibility.
Our specific concern with feeding high inclusions (> 30% of the diet DM) of traditional DDGS in dairy heifer diets is that it results in dietary fat concentration of 5% of the diet DM compared to the typical 2-3%. What does that increased dietary fat do to growing dairy heifers? Reviewing the literature left us with more questions, since there has been very little published on this topic.
In recent years, ethanol manufacturers have begun to produce reduced-fat or fat extracted distillers grains, with the goal of using it for biodiesel. Using a reduced-fat distillers grains product combined with ground corn allowed us to formulate diets that were similar in fiber and protein composition. This allowed the reserahcers to finally answer the question of what were the effects of supplying energy from dietary fat from DDGS compared to starch from corn.
Therefore, thesaid they conducted a study with the three treatment diets: 1) control (C) containing ground corn (15.9% of DM) and soybean products (17.9% of a 50:50 mix of soybean meal and Soy Plus®), 2) low-fat distillers grains diet (LFDG) containing a reduced-fat, high-protein distillers dried grains (21.9%) and ground corn (11.9%), and 3) high-fat distillers grains diet (HFDG) with traditional DDGS (33.8%). All diets contained 39.8% grass hay, 24.8% corn silage, and 1.5% vitamins and minerals. Diets were formulated for 16.3% CP (DM basis) and equally balanced for rumen undegradable protein. The HFDG diet was formulated to contain 4.8% fat compared to 2.8% in the C and LFDG diets, which were greater in starch (approx. 8% in HFDG versus 20% in other diets). All diets had a NEg of 1.0 Mcal/kg of DM and were precision fed at 2.45% of body weight. Thirty-three Holstein heifers (11/ treatment) were fed the treatment diets from 4.5 to 10.5 months of age (24 weeks) using a Calan gate system to monitor individual intakes. Heifers were weighed and body frame measurements were taken every 2 weeks. Total tract digestion of nutrients were evaluated by collecting fecal samples and using an external marker during week 16 of the feeding period.
They found that DMI were similar among treatments, indicating that they successfully implemented the precision feeding strategy. Body weights (see figure 1.) were also similar among treatments, as was ADG. Consequently, gain to feed ratios was also similar among treatments. All body frame measurements (hip and wither height, heart girth, and body length) were similar among treatments. Body condition scores were similar among treatments (C= 3.09, LFDG= 3.08, and HFDG= 3.06, SEM=0.02) with limited change over the experiment.
Interestingly, the reserahcers found that total tract digestion of DM (C= 73.7, LFDG= 72.5, and HFDG= 73.4%, SEM=0.65) was similar among treatments. While, digestion of crude protein, neutral detergent fiber, and acid detergent fiber (See Figure 2) was increased for the HFDG diet compared to the C and LFDG diets. This demonstrated that the increased dietary fat from DDGS did not decrease fiber utilization as seen with some other dietary fat supplements.
These results demonstrated that DDGS or reduced-fat DDGS can be used at high inclusion rates in rations for growing heifers and maintain growth performance, as long as dietary energy is balanced to recommended requirements. Using the fat in traditional DDGS as a dietary energy source in replacement of starch from corn did not influence growth performance or nutrient digestion in dairy heifers.
Total Tract Digestion of Nutrients